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TexAQS II Support Forecasts by Texas A&M
Forecast made Wednesday, October 11, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: Pacific cold front moves through East Texas today followed by a polar cold front tomorrow.
Today: Flow today across East Texas should be mainly northwesterly with mostly clear conditions across all of East Texas once morning clouds and fog in the Houston area erode as it looks like first surface front has already pushed through SE Texas. Weak high moves through SE Texas behind this front bringing a period of stagnation this evening before return to southerly flow for tonight in Houston area. Clean background behind this first front will make an exceedence unlikely in East Texas.
Thursday, October 12: Second cold front pushes through East Texas during the day bringing strong northerly flow in its wake. With return flow ahead of front could see some convective activity accompanying frontal passage but severe weather seems unlikely. The front should be offshore by tomorrow evening which is a bit slower than the models were showing yesterday so expect southerly flow in the Houston area for the majority of the daytime hours. Skies should clear out in the Dallas area behind the front but it looks as though clouds and chances for precipitation will linger behind the front in SE Texas.
Friday, October 13: The Dallas area should see mostly sunny skies and light winds with high pressure in place but with surface temperatures struggling to reach 70 degrees and clean background, ozone formation should be minimal. Forecast is a bit trickier for Houston but it looks as though the high pressure will move eastward instead of pushing further south, meaning clouds and rain are likely to stick around the Houston area with easterly flow.
A Look Ahead: Onshore flow will bring moisture into East Texas this weekend meaning unsettled weather will be a good possibility.
Evaluation of Tuesday, October 10 Forecast
Timing of the cold front pushing through on Thursday looks slower than expected yesterday and easterly movement of high behind the front looks likely.
Forecast made Tuesday, October 10, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Two cold fronts moving through Texas during next couple of days.
Today: Multicell convection affecting parts of southeast Texas may not reach the Houston area today, but isolated, disorganized convection is already present. Cloudy, with occasional thunderstorms. Winds generally from the south and southeast except in convective outflows.
Tomorrow, October 11: Pacific cold front should move through eastern Texas overnight. Behind the front, partly cloudy skies and winds from the west and northwest at 5-10 kt. Clean background and no stagnation, so ozone levels will stay fairly low, with only possibility of exceedance along the shore of Galveston Bay. Sea breeze development will be very late in the day and limited to coastal areas. Isolated showers possible in mid to late afternoon.
Thursday, October 12: Arctic cold front will move through the area between midnight and noon. Non-severe thunderstorm activity may accompany frontal passage in some areas. Winds from the north to northeast at 20 kt. Low stratus likely behind the cold front in southeast Texas; Dallas area will probably be clear by midday. Clear skies possible in afternoon in Houston too, but I expect clouds to linger.
Friday, October 13: Uncertain movement of high pressure system leads to widely divergent forecast possibilities. High may stall over Texas, leading to regional stagnation and mostly clear skies, but fairly clean background and temperatures in the 70s would prevent rapid ozone formation. If high remains to the north and easterlies set up across northern Gulf of Mexico, thick mid-level clouds are likely for southeast Texas with occasional rain, mostly stratiform but with some chance of convection. Dallas would remain clear with light winds under either scenario.
A Look Ahead: Scenario for weekend depends on Friday setup, but no new cold fronts expected.
Evaluation of Monday, October 9 Forecast
Timing of first cold front more clear and quicker than expected.
Forecast made Monday, October 9, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: Cold front currently positioned in the Texas panhandle will push through East Texas sometime during mid-week with the best guess being that the front will push off the coast by Wednesday afternoon with a reinforcing front bringing in cooler air and strong northerly winds on Thursday.
Today: Generally a weak easterly (SE Texas) to southeasterly (NE Texas) flow by this afternoon across East Texas with a seabreeze developing along the SE Texas coast bringing southeasterly flow to the Houston area. Look for mid/upper level cloudiness across East Texas with afternoon cumulus developing at lower levels. Background ozone levels high in the Dallas (50-55ppb) and Houston areas (60-65 ppb) though no exceedences are expected and highest one-hour concentrations likely in the Tyler-Longview area. Precipitation in East Texas should be confined to a bit of afternoon convection along the SE Texas coast with a 20-30% chance at a given location in the Houston area.
Tuesday, October 10: Overnight transport winds generally out of the southeast in the Houston area where precipitation is possible overnight transitioning to easterlies near Dallas. During the day tomorrow, models are in agreement about southerly flow across East Texas but disagree a bit on the setup for precipitation. Severe weather may be a possibility across the northern half of East Texas with a greater than 50% chance of precipitation across all of East Texas. Background ozone should still be high across East Texas but clouds and precipitation will make any ozone exceedence very unlikely.
Wednesday, October 11: The main issue on Wednesday is the timing of the front pushing through which we should have a better grasp on tomorrow. Ahead of the front expect southwesterly flow transitioning to northwesterly flow behind the front, which should be clear of the Dallas area by the late morning hours on Wednesday. The NAM model is a bit faster than the GFS in bringing northerly flow to the Houston area, but these winds should be in place by . Looks like a slight chance of precipitation before noon in the Dallas area with clouds decreasing in the afternoon, while Houston will have a 30-40% chance of convection with a bit drier air in place than Tuesday. The air behind the front the front is cleaner, with no ozone exceedences expected in East Texas.
A Look Ahead: Thursday will see a reinforcement of northerly flow and a taste of fall entering East Texas during the day with surface high temperatures in the 60’s in the Dallas area.
Evaluation of Sunday, October 8 Forecast
Winds have a bit more of an easterly component than expected but otherwise today's forecast looks good. A bit more confidence that front will push through on Wednesday with secondary front on Thursday.
Forecast made Sunday, October 8, 2006 11:00 AM
by James Tobin
Synopsis: Gradually veering winds and high regional background pollution will persist until unsettled weather arrives in advance of a strong cold front mid-week.
Today, October 8: East to southeasterly winds in southeast Texas, southeast to southerly winds in northeast Texas. Scattered mid to upper level clouds this afternoon especially across southeast Texas. A weak sea breeze will develop along the coast with a very slight chance of convection along the sea breeze. Ozone exceedance probable downwind of ship channel as background remains high and conditions favor high local contributions.
Monday, October 9: Continued light, generally southeasterly winds across east Texas. Increasing background pollution in the Dallas area as Houston background/plume finally begins to be advected in that direction. Winds may be easterly or calm early in the day in southeast Texas. Continued mid-upper level clouds with another weak sea breeze directly along the coast in the afternoon. Chance of precipitation in southeast Texas increasing but still small.
Tuesday, October 10: Similar winds to Monday, except stronger southeasterlies should begin to pick up across southeast Texas as the approaching storm system begins drawing moisture from the Gulf. Mid-upper level clouds still present with scattered to widespread afternoon cumulus possible. First day with appreciable chance of convection in advance of the next cold front. Best day for an ozone exceedance in northeast Texas if appreciable cloud cover or precipitation do not interfere as Dallas background will be the highest it has been during the current regional background event.
A Look Ahead: Regional event should come to an end as unsettled weather moves in ahead of the next front. Some disagreement on the initial wind shift between models with one placing it on Wednesday and the other on Thursday. Either way this wind shift will clear out the background pollution that had been building up across east Texas for the past few days and scattered showers and thunderstorms are expected on Wednesday whether the wind shifts that day or not.
Evaluation of Saturday, October 7 Forecast
Winds may become southeasterly in southeast Texas sooner as models, though in some disagreement, seem to be shifting the high out of our region a bit quicker. Otherwise forecast is on track.
Forecast made Saturday, October 7, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Gradually veering winds as high pressure drifts farther to east.
Sunday, October 8: Continued northeasterly or easterly winds in southeast Texas, southeasterly in northeast Texas. Houston plume will remain over land. Probable broken to overcast cirrus deck, and a very slight chance of convection. A weak sea breeze will develop along the immediate coast.
Monday, October 9: Generally light winds from the east and southeast. Continued cirrus. Continued moderately dirty background from the east. Chance of precipitation again very small.
Tuesday, October 10: Light winds from the southeast, possibly stagnant during the morning. Mostly cloudy with an increasing chance of convection or rainfall, especially in the afternoon or evening.
A Look Ahead: Unsettled weather mid-week in advance of a powerful cold front scheduled to arrive late Wednesday or Thursday.
Evaluation of Friday, October 6 Forecast
Minor ozone exceedance south of Houston and southeast of Ship Channel. Forecast good.
Forecast made Friday, October 6, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: Weak stationary front in the Houston area now, but high pressure centered to the northeast will provide little to no cloud cover and dominate the large scale winds in the forecast period.
Today: High pressure will provide mostly sunny conditions across East Texas with just a few scattered afternoon cumulus. Winds in the Dallas area look to be light easterlies with a bit stronger northeasterly flow of 5-10 kts in the Houston area. Seabreeze looks to form in the afternoon bringing a slight chance of convection to the SE Texas coast but looks like best chances are to the SW of Houston. The weak front cleared out much of the background ozone across East Texas so don’t expect an exceedence in Dallas. In Houston however, the afternoon seabreeze may cause a convergence of the urban plume with the dirtier air over the Gulf.
Saturday, October 7: Overnight transport winds will be easterlies across East Texas with a magnitude of 15-20 kts at 300m and lighter at the surface. Tomorrow’s winds should be a light northeasterlies in the Houston area and light easterlies in the Dallas metroplex. Surface temperatures only expected to reach into the middle 80’s across East Texas and may be a limiting factor in an otherwise favorable setup for local ozone buildup. Again, slight chance of seabreeze convection along the SE Texas coast. Though background ozone may begin to build due to regional contributions exceedences appear unlikely across East Texas.
Sunday, October 8: Overnight transport winds should get a bit more of a southerly component with easterlies in the Houston area transitioning to southeasterlies in the Dallas area. Again mostly clear skies across East Texas with a light easterly to southeasterly flow as the high dominating the weather weakens a bit. Background ozone should be higher across all of East Texas but it looks now that an exceedence is unlikely in both Houston and Dallas.
A Look Ahead: Expect Monday to be similar to this weekend but high looks to break down by Tuesday and a system bringing increased cloudiness and rain chances may reach East Texas by Wednesday.
Evaluation of Thursday, October 5 Forecast
Forecast right now looks on track through the forseeable future.
Forecast made Thursday, October 5, 2006 11:00 AM
by James Tobin
Synopsis: After a weak front passes high pressure will quickly begin to dominate again, bringing northeasterly to easterly winds throughout the weekend.
Today: Northwest winds across the region are already having a slight cleaning effect, and since Houston's maximum 8-hr ozone was only 81 ppb yesterday it is not likely there will be an exceedance anywhere in SE Texas today with the highest ozone along the coast south and southeast of Houston. No exceedance in Dallas either. Partly sunny skies with less chance of convection than in previous days due to the northerly flow; convection is only slightly possible right along the seabreeze. Winds will strengthen and become northerly later in the day in northeast Texas; remain weak and potentially stagnant along the seabreeze in southeast Texas.
Friday, October 6: Increasing northeast flow overnight (15-20 knots), weakening to 5-10 knots again in the afternoon. Partly to mostly sunny with just a few low AM clouds and scattered afternoon cumulus. Less than 20 percent chance of convection along seabreeze, none elsewhere. Most interesting feature is the remnants of this past week's ozone episode, which should be sitting over the Gulf with ozone values up to 65 ppb possible just offshore. The onset of a seabreeze against the weak northeasterly flow would create a stagnant convergence zone where the Houston plume and the ozone over the Gulf could meet, which if this happens would make an exceedance quite possible south or southwest of Houston. No exceedance in Dallas.
Saturday, October 7: Light, generally easterly winds (ranging from northeast to southeast) will continue as high pressure continues to weakly control our weather. Only scattered afternoon cumulus except along the seabreeze where cumulus may be more widespread. Background may begin to build up but an ozone exceedance is only slightly probable in southeast Texas and not likely at all in Dallas.
A Look Ahead: High pressure will remain in control through at least Monday, with a regional ozone event possible for Sunday-Monday.
Evaluation of Wednesday, October 4 Forecast
Adjusted today's winds due to the timing of the front and removed mention of exceedance in Dallas due to lower than anticipated background levels.
Forecast made Wednesday, October 4, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: Flow around high pressure will continue to bring background air with higher levels of ozone to East Texas.
Today: Fog present across much of SE Texas this morning should burn off by noon. Models in agreement that light easterlies will be in place across the Houston area and a southerly flow will be present in the Dallas metroplex this afternoon. Skies should be partly cloudy in the Houston area with fewer clouds to the north. With ample moisture in the air, an isolated shower isn’t out of the question but not likely. Background levels a bit higher in the Houston area so an exceedence is possible to the west of town while Dallas is unlikely to see an exceedence today.
Thursday, October 6: Overnight it looks as though a front pushes toward the Red River and then dies out through the morning hours tomorrow. A bit of disagreement as to the timing but winds across East Texas will be transitioning from southerly overnight to a northerly flow during the day on Thursday as high pressure to the north strengthens its grip. Higher background levels will be in place across all of East Texas with likely stagnation in the Dallas area and possibly in the Houston area during the day on Thursday. By the afternoon it looks like northerly flow transitioning to more of a northeasterly flow.
Friday, October 7: Overnight, looks like weak northerly flow in SE Texas transitioning to a bit stronger northeasterly flow in NE Texas. As high pressure continues to dominate the weather in East Texas, it looks a bit stronger NE flow across all of East Texas on Friday. With fairly high background levels in place across all of East Texas, an exceedence is likely in both the Dallas and Houston areas on Friday.
A Look Ahead: High pressure will dominate the weather across East Texas through the weekend.
Forecast made Tuesday, October 3, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Persistent anticyclonic flow around high pressure produces transport from southern United States.
Tuesday, October 3: Onshore southeasterly flow will persist throughout the day, preventing ozone buildup or sea breeze surge. Partly cloudy skies, with some lingering chance of convection.
Wednesday, October 4: Stagnation appears unlikely tomorrow as well, as winds take on more of an easterly component. Possible high background could lead to an 8-h exceedance west-northwest of Houston. Isolated convection possible. Sea breeze surge unlikely. Winds in Dallas are light from the south, probably not light enough for an exceedance, but from this day forward the Houston plume could contribute to the Dallas background.
Thursday, October 5: High ozone likely in Dallas and East Texas as high background ozone (partly from southeast Texas) combines with probable stagnation. Too early to tell whether stagnation will occur in Houston, but afternoon and evening transport will most likely be toward the west or northwest.
A Look Ahead: A new high pressure system builds into the eastern United States sometime Thursday or Friday, dominating Texas weather through the weekend.
Evaluation of Monday, October 2 Forecast
Ozone exceedance today very unlikely, and wind speed model forecasts are erratic.
Forecast made Monday, October 2, 2006 11:00 AM
by James Tobin
Synopsis: High pressure will dominate the area throughout the week with light to moderate south to southeasterly flow and only a slight chance of rain today with the passage of an upper level disturbance and a very slight chance along the seabreeze each day.
Monday, October 2: Light southeasterly winds around Houston, stronger south to southwesterlies in Dallas. Scattered to widespread cumulus but only a slight chance of convection in southeast Texas, clearing skies in northeast Texas. An ozone exceedance is possible but not likely in Houston, and unlikely in Dallas due to the high wind speeds.
Tuesday, October 3: Similar pattern with winds veering just a bit, becoming more southeasterly in Houston and southerly in Dallas. Scattered cirrus but only isolated cumulus, mostly along the seabreeze. Background ozone and aerosol levels on the increase, especially across southeast Texas where winds will be lighter. Ozone exceedance probable northwest of Houston, still unlikely in Dallas due to high winds.
Wednesday, October 4: Lighter winds across all of east Texas, with wind directions still predominantly south to southeasterly, possibly easterly in southeast Texas. Background levels continue to increase, especially if winds turn easterly, bringing Lake Charles plume to Houston. Decrease in wind speeds and advection of Houston plume into the Dallas area will make an ozone exceedance possible in Dallas, while one is likely in Houston.
A Look Ahead: No change in the significant weather pattern through Friday, with ozone exceedances likely in both Dallas and Houston as regional background continues to build throughout the week.
Evaluation of Sunday, October 1 Forecast
Forecast basically on track, with some adjustments to the cloud cover as a result of modified timing of the upper level disturbance.
Forecast made Sunday, October 1, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Stationary high pressure over the southeastern United States leading to reduced precipitation chances and increased background pollution.
Sunday, October 1: Near-stagnation today with winds strengthening out of the south during the afternoon. Scattered boundary-layer cumulus dissipating by late afternoon. Small chance of convection. Background ozone levels over 40 ppb, but winds probably too strong to permit an exceedance. Moderate sea breeze surge inland during the evening, overdone by MM5.
Monday, October 2: Slight veering of large-scale wind will lead to southeasterlies during the day. Stagnation possible but not probable in the morning. Urban plume transport toward the north-northwest. Dallas winds steady from the south. Chances of precipitation a bit higher with a weak upper-level disturbance approaching, but rain at any given point unlikely. Ozone exceedance in Houston will depend upon morning winds.
Tuesday, October 3: Continued veering of the wind means transport from more distant areas in the southeast. Continued increase of background ozone and aerosol levels. Large-scale pressure gradient may allow stagnation in the morning, but afternoon winds will most likelyl be from the east-southeast or southeast. Ozone exceedance likely because of further increases in background levels. Winds in Dallas remain from the south, but light winds in northeast Texas make exceedances possible all along the Louisiana border.
A Look Ahead: Weather pattern locked in through Saturday. Regional ozone episode likely.
Forecast made Saturday, September 30, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: High pressure settling in to the southeastern United States for the next week.
Sunday, October 1: In Houston area, light SW-W winds in morning will become very light around noon and then strengthen from the south during the afternoon. Scattered to broken boundary layer cumulus likely, with some isolated thunderstorm activity likely in the area. Chance of precipitation at any given point 10%-20%. Ozone exceedance possible, depending on amount of stagnation. Farther inland, wind will generally be from the south and southwest with no precip chances.
Monday, October 2: In Houston area, stagnation possible in late morning, with winds becoming southeasterly in the early afternoon. Gradual increase in background ozone levels makes exceedance a bit more likely than Sunday; location would be over downtown and NW of city if wind forecast is correct. Still 10%-20% chance of thunderstorm activity. Transport farther inland will be from the south. Winds remain too strong for exceedance in Dallas, but lighter (with higher background) in NE Texas.
A Look Ahead: Stable weather pattern throughout the week with dominant wind direction E-SE in Houston and SE-S in Dallas. Progressively drier and dirtier airmass with very high regional ozone levels possible toward the end of the week.
Evaluation of Friday, September 29 Forecast
Thundershowers affected the southwest half of the Houston metropolitan area around sunset. Remainder of forecast still looks reasonable, depending on precip outcome.
Forecast made Friday, September 29, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: Cold front has pushed off Southeast Texas coast bringing cooler and drier air to all of East Texas. Expect onshore flow to resume in East Texas tonight on into Saturday.
Today: NAM seems to have better handle on today’s situation than GFS so will use for wind forecast today. Expect a southeasterly flow in the Dallas area this morning to turn to the SW this afternoon and easterlies in the Houston area transitioning to a more southeasterly onshore flow by this afternoon and evening. A bit more cloudiness in the Houston area than previously expected with mostly cloudy skies in the morning giving way to partly cloudy skies by the afternoon. The Dallas metroplex should remain almost cloud free throughout the day today but will see a few more clouds creep in by the late evening hours. Given the low background levels of ozone behind the front, more cloud cover than expected in the Houston area, and a quicker return of moderate winds to the Dallas area, an ozone exceedence is not expected across East Texas.
Saturday, September 30: Models come into agreement for overnight winds in East Texas with a fairly uniform southerly flow. By tomorrow morning, these winds look to shift slightly to the SSW across all of East Texas. During the day tomorrow, the winds should stay relatively consistent out of the S-SSW bringing in moisture, clouds, and a chance of precipitation (20-30% at any given location) to SE Texas. Skies should be partly cloudy in NE Texas with precipitation chances being slim to none and winds shifting to the SW. It appears as though a weak trough will be in place across Central Oklahoma but shouldn’t provide much more than a few added clouds to North Texas. The return of onshore flow will bring back the low background ozone air behind the front to East Texas on Saturday and combined with other factors makes any ozone exceedence highly unlikely.
Sunday, October 1: Overnight winds look to become uniform southerly across all of East Texas again adding a weak westerly component by the early morning hours. By Sunday it looks as ridging at upper levels will dry out the atmosphere and make rain an unlikely proposition across all of East Texas. Winds across all of East Texas look to be southerly with a small added easterly component heading through the afternoon and evening hours. A surface high pressure area off to the east looks to act as a block to a low pressure area and trailing cold front that will be off to the northwest. Winds on Sunday should be strong enough to keep chances of an ozone exceedence minimal.
A Look Ahead: A mid/upper level ridge will establish itself over the Southern half of the country early next week keeping southerly winds and onshore flow in place. Warmer than normal temperatures expected with little to no chance of precipitation though dewpoints should be fairly high in SE Texas.
Evaluation of Thursday, September 28 Forecast
High pressure area moved off to the east a bit quicker than expected and took more of an ESE track than a SE track which may have slowed frontal passage through the Housron area. Long term forecast probably overemphasized the daily rain chances as they now seem to be slim to none.
Forecast made Thursday, September 28, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: Cold front pushing through East Texas with northerly flow behind and a few showers along and ahead of the front.
Today: The major weather maker in East Texas is a cold front that was located near College Station at 12Z and should continue to push south through the day. Mostly cloudy skies in the morning in the Houston area will give way to partly cloudy skies in the afternoon with a 20-30% chance of precipitation through this evening. Dallas skies should remain clear with northerly flow through the evening hours. Houston winds will transition from a SW-W type of flow to northerly flow as the front passes through. The front should clear the SE Texas coast during the afternoon hours. Chances of an ozone exceedence are small in the Houston area and negligible in the Dallas area today.
Friday, September 29: Winds should transition to a NE flow, a bit stronger in the Houston area than Dallas, by midnight with a surface high pressure centered somewhere in Eastern Oklahoma. By tomorrow morning there should be a return of light southerly flow to the Dallas area as high pressure moves to the southeastward with the best guess being somewhere near Shreveport, LA bringing a bit stronger E-NE flow to the Houston area. All of East Texas should have mostly clear skies through the day on Friday. The wind forecast gets a little tricky because of model divergence in the location of the stagnant winds associated with high pressure. Best guess is a transition to a light southerly flow in the Houston area by tomorrow afternoon with SW winds in the Dallas area. With a clean background, ozone exceedences are not expected across East Texas.
Saturday, September 30: Clouds should develop in the Houston area in the evening hours Friday night into early Saturday with the return of onshore flow. With high pressure moving well to the east, wind forecast becomes more unanimous with southerly flow through all of East Texas. May or may not be a trough developing in West Texas by Saturday with again some model divergence in the winds. GFS is wettest with a S-SE flow during the day in the Houston area with MM5 having more of a S-SW flow and drier conditions. Will go with a chance of showers in SE Texas with partly to mostly cloudy skies and S-SW winds across the rest of East Texas. By evening, it looks like southerly flow will predominate, with the chances of an ozone exceedence minimal across all of East Texas during the day.
A Look Ahead: Looks like a pretty consistent weather pattern setting up across East Texas for the next several days with southerly flow and a daily small chance of showers in the Houston area.
Evaluation of Wednesday, September 27 Forecast
Forecast is generally on track. Rain chances maybe a bit higher than expected and frontal progression slower than forecasted yesterday.
Forecast made Wednesday, September 27, 2006 11:00 AM
by James Tobin
Synopsis: Mostly clear with high ozone in southeast Texas today but a front is on its way for tomorrow.
Thursday, September 28: Main feature is the arrival of the cold front, which should begin moving through north Texas Wednesday evening and be offshore south of Houston by noon on Thursday. A few clouds are possible along the front with just an isolated shower or two, mainly in far southeast Texas toward Beaumont Thursday morning. Behind the front skies should be mostly clear with just a few lingering cirrus clouds over southeast Texas. Winds will generally be from the north at 5-10 knots near the surface and 15-20 knots in the free boundary layer, and will be stronger in northeast Texas than in southeast Texas. No ozone exceedances expected.
Friday, September 29: Overnight transport is from the northeast at 5-10 knots in northeast Texas, 15-20 knots in southeast Texas. Winds will be light as the ridge axis arrives. Winds will become southwesterly by noon in northeast Texas and southerly or southwesterly across all of east Texas by late Friday afternoon. Some cirrus or isolated cumulus possible after the wind shift but otherwise skies should be mostly clear. Background is clean, no ozone exceedances expected.
Saturday, September 30: Models really begin to diverge beyond Friday based on intensity and placement of high pressure to our east and next incoming system to our west. Winds will be roughly southerly in southeast Texas and southwesterly in northeast Texas. Scattered clouds are possible and there is a slight risk for afternoon showers in southeast Texas. Texas A&M wins by 3, Texas by 52.
A Look Ahead: Similar conditions should exist in southeast Texas through Sunday. Model divergence makes it difficult to say anything about northeast Texas at this time.
Evaluation of Tuesday, September 26 Forecast
There is a bit more cloud cover than previously expected today but not enough to affect yesterday's air quality forecasts. Have also introduced a slight chance of rain with frontal passage especially in southeast Texas. Forecast is generally on track.
Forecast made Tuesday, September 26, 2006 11:00 AM
by James Tobin
Synopsis: Generally clear skies, high pressure, and local ozone buildup.
Today, September 26: Forecast from yesterday is pretty much on track except PBL heights in southeast Texas are now expected to be a bit lower, enhancing the possibility of an ozone exceedance southwest of Houston. The wind reversal sending the Houston plume back over Houston, or just to the west of Houston, late tonight still appears quite plausible.
Wednesday, September 27: Some cirrus possible, otherwise mostly clear. Winds will be from the southwest across all of east Texas, stronger in northeast Texas (10-20 kt) and weaker in southeast Texas (5-10 kt). Boundary layer heights will be below average for this time of year and background ozone will be high. A seabreeze will set up along the coast turning winds there more southerly and producing just a few isolated cumulus, if anything. An ozone exceedance is likely in Houston and possible in far northeast Texas where yesterday's Houston plume ends up. Winds should be too strong to permit enough local contribution for an exceedance in Dallas, but one is not out of the question.
Thursday, September 28: Models are in good agreement on frontal passage through Texas beginning overnight into Thursday in far north Texas and moving offshore by Thursday afternoon. A few clouds are possible along the front but the passage should be dry in terms of precipitation. Moderate north-northwest winds will usher in cooler and much cleaner air across east Texas. At this time it appears the timing of the front will prohibit any ozone exceedance in east Texas but one right along the coast in the Galveston area is not out of the question if the front slows just a tad.
A Look Ahead: Winds will likely shift back to the south or southwest across all of east Texas by Friday afternoon, but due to the strength of the front the first day or so of this renewed southerly flow will be of clean continental origin. A weak front appears across west Texas by Saturday but the models currently keep the front stationary at least through Sunday. A few clouds are possible this weekend but precipitation should hold off until the next front decides to move into east Texas.
Evaluation of Monday, September 25 Forecast
Models are in much better agreement about the position of the critical high 24 hours later so more certainty has been expressed in the forecasts for Wednesday and Thursday. Ozone probabilities are a bit higher today as PBL heights appear they will be lower than previously forecasted. Forecast is generally on track.
Forecast made Monday, September 25, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Generally clear skies, high pressure, and local ozone buildup.
Tuesday, September 26: Mostly clear skies. Winds light and variable in central Texas and 5-10 kt from the northeast in southeast Texas. Deep boundary layer and relatively cool temperatures should work against ozone exceedance, but highest ozone levels will be found south and southwest of Houston. Wind reversal possible Tuesday evening that may bring interesting aged pollution to monitoring sites.
Wednesday, September 27: Some cirrus possible, otherwise mostly clear. Winds will be from the southwest in northern and central Texas in advance of Pacific cold front. Winds will be light and generally southerly in southeast Texas, but specific direction depends on track of surface high. A sea breeze will develop along the coast in the afternoon. Possible shallow mixed layer due to inversion aloft. Ozone exceedance probable in Houston.
Thursday, September 28: The Pacific cold front will be reinforced by an Arctic cold front and advance through the state, with northerly winds behind it. The frontal passage will be mostly dry. Timing in southeast Texas uncertain, and one more day of light winds and high ozone possible in Houston.
A Look Ahead: Behind the front, northerlies veering to northeasterlies veering to southeasterlies over the weekend. Precipitation possible.
Evaluation of Sunday, September 24 Forecast
Clouds cleared out earlier than expected today. PBL on Tuesday likely to be deep rather than shallow. High pressure ridge moving faster than expected, but track (and winds Wednesday) uncertain. Southwesterly winds possible. All in all, lots of reevaluation.
Forecast made Sunday, September 24, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: High pressure dominates the weather for the next several days, and regional ozone gradually builds up.
Monday, September 25: Mostly clear skies and northerly winds at 5-15 kt throughout Texas. Midlevel clouds likely from the Houston area south in the morning. Clean continental background.
Tuesday, September 26: Winds will be northeasterly at about 10 kt in the Houston area and points east. Winds in Dallas and along the I-35 corridor will be fairly light, with stagnation likely in late morning or afternoon. The PBL should be fairly shallow. Few low clouds, but some cirrus possible from a weakening upper-level trough to the west.
Wednesday, September 27: Winds mostly southerly at about 10 kt in the Dallas area. In Houston and southeast Texas, the surface ridge moves past and winds will be fairly light. Directions from NE, E, or SE are possible. Mostly clear skies and shallow PBL. Significant ozone buildup likely in Houston.
A Look Ahead: Southerly flow (but still mostly clear skies) in the Houston area on Thursday, with land breeze stagnation possible in the morning and winds strengthening in the afternoon. A cold front will move south across Texas on Thursday and Thursday night.
Evaluation of Saturday, September 23 Forecast
Accurate except that the squall line was a few hours ahead of schedule.
Forecast made Saturday, September 23, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Cold front sweeping through Texas today and overnight, with clear skies to follow and light winds by mid-week.
Sunday, September 24: Main focus of forecast is NASA Calypso flight early Sunday morning. Patchy mid-level clouds are likely in Nebraska and central-northern Kansas. Clear skies at all levels across Oklahoma. Both anvil cirrus and low-level stratus likely in southeast Texas as cold front and probable squall line (with some intense convection) is in the vicinity of Houston. Heavy weather should be long gone by midday. Low-level stratus will probably hang around until mid-afternoon in the Houston area; winds will be 15-20 kt from the north.
Monday, September 25: Generally clear skies with scattered to isolated boundary layer cumulus in southern areas. Winds will be from the north at 10-15 kt across eastern Texas, possibly lighter in the Dallas area. Air mass origins in central Canada so fairly low background aerosol and ozone content.
A Look Ahead: Mostly clear skies continue as high pressure moves across area and an upper-level ridge builds to our west. Very light winds likely Tuesday in Dallas and Wednesday in Houston, depending on timing of motion of surface ridge axis. Because the cold front will push most of the way across the Gulf of Mexico, the onshore southeasterly flow that will set up around Thursday will be nearly cloud-free, something we haven't seen yet this field program. Background ozone levels will steadily increase.
Evaluation of Friday, September 22 Forecast
The forecast still looks good.
Forecast made Friday, September 22, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: Cold front expected to sweep through North Texas on Saturday afternoon and through the SE Texas coast Sunday morning.
Today: Expect partly cloudy skies today in both the Houston and Dallas areas for today with fewer clouds around than yesterday. There is a stationary frontal boundary in place between Dallas and Lubbock with a bit of a temperature contrast across it. A dryline ahead of the front looks to push across North Texas today bringing a chance of storms, with the best chance off to the East of the metroplex with the deeper moisture. In the Houston area isolated storms are possible this afternoon, especially toward the coast. Winds will continue to be strong out of the S to SSW during the daytime hours around 15-20 kts in the Houston area to 20-25 kts in the Dallas area. With these strong winds and a clean background, an ozone exceedence will not occur in the Dallas and Houston areas today. However, the strong southerlies will likely bring in particles from a Saharan dust cloud.
Saturday, September 23: Overnight winds across East Texas will remain strong out of the south becoming more southwesterly in North Texas ahead of the front. By tomorrow morning, the stationary front mentioned yesterday should get moving through East Texas as a cold front pushing from the NW to the SE throughout the day. Winds ahead of the front will remain strong out of the south veering to the southwest just before frontal passage and behind the front, winds will transition to a northwesterly flow. All of East Texas will be mostly cloudy and with abundant moisture and lift with the front, severe weather is a good possibility across all of East Texas on Saturday. Otherwise, precipitation will be possible throughout the day on Saturday across all of East Texas, possibly tapering off in the Dallas area by the afternoon hours. By the evening hours, expect the front to be located roughly halfway between Houston and Dallas.
Sunday, September 24: Overnight winds will be determined by the frontal position with continued strong southerly flow ahead of the front and strong northerly flow behind the front. There is a bit of disagreement as to the propagation of the front, but it should be somewhere near the SE Texas coast by Sunday morning. As the front pushes off the coast, it looks like northerlies across East Texas between 10-20 kts with a more northeasterly flow toward the coast. With the front pushing through the Dallas area, expect partly to mostly sunny skies and more clouds hanging around in the Houston area. There will still be a good shot of precipitation near the SE Texas coast until the front has pushed offshore. With clean background air pushing in behind the front an ozone exceedence is not expected in East Texas. However, there may be some smoke filtering in from California fires behind the front.
A Look Ahead: Looks like high pressure building in early next week with winds decreasing in intensity and may lead to increased background levels of ozone by the middle of next week and possible exceedences. An upper level trough across the central United States looks firmly entrenched and should continue to bring periods of unsettled weather for the foreseeable future.
Evaluation of Wednesday, September 20 Forecast
Yesterday's forecast looks to be on track.
Forecast made Thursday, September 21, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: A strong low pressure system located now on the lee side of the Rockies will be the major player in our weather today and for the next couple of days.
Today: The wind field in all of East Texas today will be dominated by the large scale southerly flow associated with the tightening pressure gradient with the low pressure area. Expect the surface winds to intensify throughout the day with 15-20 kt winds in the Dallas area and 10-15 kt winds in the Houston area by afternoon. Afternoon storms are a possibility in the Dallas area with a dryline that looks to push through. A warm front in the Houston area and fairly high PW values will make precipitation a possibility, with better chances toward the coast. Skies should be partly to mostly cloudy in the Houston area and mostly cloudy in the Dallas area for today. An ozone exceedence today is very unlikely given the strength of the winds, clouds, and precipitation forecasted.
Friday, September 22: Overnight winds are forecasted to be very strong at lower levels out of the south at Houston and veering slightly to the SW in the Dallas area. Expect partly cloudy skies in the Dallas area tomorrow and partly to mostly cloudy conditions in the Houston area for tomorrow. Looks like chances for precipitation in the Dallas area are minimal tomorrow, but winds will be very strong out of the S to SSW (possibly >20 kts) which will prevent an ozone exceedence. PW values will still be high enough in the Houston area tomorrow to leave in a chance of precipitation but only around the 20-30% range for a given location in SE Texas. Winds will be strong out of the south between 15-20 kts which combined with the cloud cover will prevent an ozone exceedence. However, it looks like with the strong southerly flow, some Saharan dust may be entering SE Texas which may raise particulate levels.
Saturday, September 23: The major player for the forecast on Saturday will be a developing cold front that will be just to the northwest of Dallas in the morning hours and will push southeast throughout the day and should be located somewhere around the Waco to College Station vicinity by Saturday evening. There should be a great deal of cloudiness in East Texas through the day on Saturday with precipitation a good possibility with the front. Precipitation chances are in the 30-40% range in Dallas and a bit higher in the Houston area with more moisture to work with. Winds will be gusty out of the S to SW ahead of the front between 10-20 kts with higher gusts possible near areas of convection. Behind the front in North Texas, expect a transition to a weaker northerly flow by the evening. Ozone production is not favorable on Saturday.
A Look Ahead: By Sunday the cold front looks to push through all of East Texas and there is the possibility elevated smoke levels with diffusion from California wild fires behind the front. It looks like the front will still bring a chance of rain to SE Texas during the first part of the day before pushing completely offshore later in the day. Looks like northerly flow and clean background air behind the front will be in place across all of East Texas by late on Sunday.
Evaluation of Wednesday, September 20 Forecast
Forecast looks pretty good for today but no mention of morning rain in SE Texas, though North Texas convection is occurring. Rest of forecast looks consistent with today's forecast.
Forecast made Wednesday, September 20, 2006 11:00 AM
by James Tobin
Synopsis: Southeasterly winds are returning to east Texas and will become quite gusty tonight as a strong low pressure center passes north of the region.
Thursday, September 21: Strong southerly flow across all of east Texas early in the day except near the coast where there will be moderate southeasterly flow. Winds will stay fairly strong throughout the day becoming more southwesterly in northeast Texas and southerly near the coast. Scattered afternoon cumulus are expected along with a slight chance for convection along the seabreeze. An organized convective line expected to develop ahead of the trough overnight may clip northern Texas early in the day as well. 8-hr ozone exceedances are not expected due to the gusty winds and chance of precipitation.
Friday, September 22: Very strong southwesterlies in northeast Texas overnight weakening just a bit during the day; strong southerlies most of the day across southeast Texas, possibly southwesterly overnight. Scattered cumulus with convective activity possible, especially in far eastern Texas and along the coast. No ozone exceedances expected due to strong winds, chance of precipitation, and clean background.
Saturday, September 23: Moderate to strong southwesterly winds expected across most of east Texas with southerly winds near the coast. Front will begin to pass through Texas from northwest to southeast and will probably make it through at least the northern two-thirds of east Texas during the day on Saturday. Clouds and convection are expected along the front and will likely also develop in southeast Texas ahead of the front.
A Look Ahead: Front will finish moving offshore during the day on Sunday with clouds and convection in southeast Texas and clearing skies in northeast Texas. A day or two of northerly flow will follow the front.
Evaluation of Tuesday, September 19 Forecast
Trends between yesterday's forecast and today's forecast include slightly increasing wind speeds on Thursday and Friday across east Texas and a slight acceleration of the next frontal passage. The general features of the 19 September forecast are on track.
Forecast made Tuesday, September 19, 2006 11:00 AM
by James Tobin
Synopsis: Mostly clear conditions are expected today and tomorrow with northerly winds today becoming southeasterly by tomorrow afternoon.
Wednesday, September 20: Light southeasterly winds are expected in northeast Texas by daybreak and will become more southerly by afternoon. Light east or northeasterly morning winds in southeast Texas will become southeasterly by afternoon. A period of nearly calm winds, especially near the surface, is possible in the Houston area. Skies will be mostly clear but there will be more afternoon boundary layer cumulus than today, particularly in the Dallas area and right near the coast. Relatively clean background will make an 8-hr ozone exceedance in the Dallas area unlikely. Ozone exceedances in Houston are quite possible, most likely in the Galveston area but also quite possibly west or northwest of the city.
Thursday, September 21: The southerly flow across east Texas should strength overnight as a strong low pressure system passes north of the region. Winds overnight and during the day on Thursday will be very strong and southerly, possibly becoming southwesterly on Thursday afternoon. Scattered boundary layer cumulus are expected with a very slight chance of afternoon convection, mostly in far north Texas or right along the coast. Wind speeds should be too strong to support any 8-hr ozone exceedances in Houston or Dallas.
Friday, September 22: Moderate south to southwesterly wind across all of east Texas. Scattered afternoon clouds with just a slight chance of afternoon convection, particularly near the coast and in far northeast Texas.
A Look Ahead: Generally southerly flow to continue on Saturday with an increasing risk for clouds and convection. Next possible frontal passage will be on Sunday.
Evaluation of Monday, September 18 Forecast
Lingering clouds moved offshore quicker than previously expected, supporting quicker timing on wind shift advertised by all models for today's forecast. Otherwise general features of the September 18 forecast are on track.
Forecast made Monday, September 18, 2006 11:00 AM
by James Tobin
Synopsis: Clearing will begin later this afternoon in northern Texas while Houston will remain cloudy and wet until the front finishes moving across the state late tonight, leaving clear skies and light northerly winds across east Texas tomorrow.
Tuesday, September 19: Northerly winds will prevail across east Texas in the morning with speeds ranging from light in northeast Texas to moderate in southeast Texas. Winds will turn more northeasterly and weaken slightly in the afternoon across all of east Texas. A few clouds may linger early in the day in the Houston area but otherwise skies will be mostly clear across all of east Texas, except perhaps for a few clouds across extreme east Texas (in places like Texarkana or Beaumont) and some very isolated shallow boundary layer cumulus near the coast (more likely offshore) in the afternoon. Surface winds may become nearly calm and variable in northeast Texas late in the afternoon with 5-10 kt northeasterly flow just aloft (~300m). Peak 8-hr ozone across all of east Texas will likely occur near the coast south-southwest of Houston at around 70 ppb.
Wednesday, September 20: Light northeasterly winds across east Texas will gradually become southeasterly, early in the day in north Texas and by late afternoon in the Houston area. Background ozone will begin to build up in both Dallas and Houston and combined with mostly clear skies and a shallow (about 1500m) afternoon boundary layer this may lead to an 8-hr ozone exceedance, especially west or southwest of Houston. Only cloud cover expected is from isolated boundary layer cumulus, which will be possible across all of east Texas.
Thursday, September 21: Southeasterly flow is expected across all of east Texas. Boundary layer cumulus will become a bit more prevalent and there is a slight chance of afternoon convection along the seabreeze. Convection is also possible in northeast Texas as the next cold front begins to threaten the area, though it will be more of a risk on Friday and Saturday. A period of stagnation in the Houston area is possible in the morning; if one develops and lasts a few hours an 8-hr exceedance will be likely in the Houston area. Otherwise an ozone exceedance is possible due to increased background but does not appear particularly likely at this time.
A Look Ahead: Chance of showers and Thunderstorms as the next front approaches on Friday/Saturday, followed by at least one day of northerly flow Saturday or Sunday.
Evaluation of Sunday, September 17 Forecast
Forecast is on track.
Forecast made Sunday, September 17, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: After cold front and rain push through Houston on Monday, clear skies and light to moderate winds will dominate the middle of the week.
Monday, September 18: Heavy rain likely in the Houston area in the morning as exceptionally high precipitable water values encounter an approaching cold front. Rain may clear out by sometime in the afternoon, leaving moderate northerly winds. Dallas will be clear with northerlies all day.
Tuesday, September 19: Light northeast wind in Dallas, moderate northeast wind in Houston. Mostly clear skies all day. Possible smoke/dust behind front and moderate tropopause folding event aloft, but ozone background levels at surface will be low.
Wednesday, September 20: Winds turning to southeasterly in Dallas and remaining light, with possible regional background buildup but no major exceedance. In Houston, light northeast winds will linger, possibly turning to southeasterly during the afternoon. Continued mostly clear skies and shallow PBL may allow for ozone exceedance downstream (SW-W) of Houston.
A Look Ahead: Moderate southeasterlies likely in both Dallas and Houston, with possibility of stagnation in Houston during the morning. The next synoptic-scale disturbance brings back chance of rain on Friday.
Evaluation of Saturday, September 16 Forecast
Latest forecasts have extended range evolving slightly slower than before.
Forecast made Saturday, September 16, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: A hurricane, a cold front, and heavy rain ... what more is there to ask for?
Sunday, September 17: Satellite overpass in Louisiana at 08Z will have patchy convection in the Gulf and occasional thin cirrus from Hurricane Lane (presently approaching the Gulf of California) or its remnants. Best bet for clear skies is within 150 mi of the Louisiana coast. During the day, strong southerly winds will continue, with scattered unorganized showers in the Texas coastal plain. Meanwhile, a cold front will be approaching the Dallas area, and there will be widespread organized convection along and ahead of the front with possible heavy rain and severe weather. Air is clean and ozone levels will be low.
Monday, September 18: The cold front will move through the Houston area during the afternoon or evening. Widespread heavy rain likely in the Houston area at times during the day, with some flash flooding possible. The rain will have ended in Dallas, and winds there will be moderate from the N or NW with cirrus likely in the morning and early afternoon.
Tuesday, September 19: Winds in Houston will be from the N or NE at 5-10 kt. Moderate ozone production in a shallow PBL may allow for fairly high ozone south of Houston along the coast and offshore. Dallas is likely to have very light winds as winds shift from N to SE during the period, and ozone buildup is possible there as well. Skies should be generally clear in both places.
A look ahead: Continued dry continental airmass advected from SE US over Gulf to Houston. Possible light wind/high ozone event on Wednesday as high pressure moves past.
Evaluation of Friday, September 15 Forecast
Nothing approaching high ozone anywhere in the state on Friday. Otherwise, weekend forecast still looks reasonable.
Forecast made Friday, September 15, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: Looks like onshore flow and increasing cloud cover with chances of precipitation in the Houston area through the weekend. With an approaching low pressure area and tightening pressure gradient, the Dallas area will see an increase in the strength of southerly flow through the weekend and a chance of precipitation by Sunday.
Today: Winds offshore and at the Laporte profiler are out of the SSE while onshore winds are generally out of the ESE. Expect winds to have a general ESE-SE heading by early afternoon in the Houston area. This onshore flow should be enhanced along the SE Texas coast during the afternoon and further inland by the early evening hours. The Dallas area should see pretty consistent SSE flow during the daytime hours today, picking up in intensity a bit by the early evening hours. Expect partly cloudy skies across all of East Texas with more clouds in SE Texas than in NE Texas. Precipitation should remain confined to SE Texas with around a 30% chance at any given location in the Houston area. With higher background levels, an ozone exceedence is possible in the Dallas and Houston areas. The limiting factors will be the clouds and precipitation in the Houston area and stronger than normal winds in the Dallas area.
Saturday, September 16: A chance of showers will linger into the late evening hours in the Houston area but should go away with loss of daytime heating. Winds overnight will be fairly uniform across East Texas out of the SSE with stronger winds in the Dallas area (around 10 kts) than in the Houston area (around 5 kts). By morning, expect a similar wind regime to Friday morning along the SE Texas coast with an easterly flow toward Beaumont becoming more southerly heading down the coast. During the day, expect onshore flow in the Houston area with partly to mostly cloudy skies and a good chance of precipitation (40-50% point chance). The Dallas metroplex should remain dry with partly cloudy skies and fairly strong southerly flow with a tightening pressure gradient with a low pressure to the NW of town. the chances of an ozone exceedence are minimal in both the Houston and Dallas areas as background air from the Gulf of Mexico should be cleaner.
Sunday, September 17: The best bet for winds overnight on Saturday night into Sunday morning is a pretty strong southerly flow across all of East Texas, though the 12Z NAM has a dofferent viewpoint. With the approaching cold front expect winds across all of East Texas to remain southerly through the day on Sunday with considerable cloudiness. There is a better than 50/50 shot of precipitation for a given location in SE Texas while in NE Texas, chances of precipitation will increase throughout the day. Localized winds may deviate from southerly with convection in the area. Chances for an ozone exceedence in both the Houston and Dallas areas appear to be slim to none at this point.
A Look Ahead: Severe weather may be a possibility in East Texas on Monday with the cold front pushing through. The front should push through the Dallas area by Monday evening and the Houston area by Tuesday afternoon. There should be northerly winds behind the front which may usher in air with increased particulate from wild fires burning in the northern Rockies.
Evaluation of Thursday, September 14 Forecast
So far, no major changes to the forecast from yesterday. Increased the chances of precipitation for the day on Saturday.
Forecast made Thursday, September 14, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: Clear skies across most of East Texas today. Will increase moisture the next few days with return of onshore flow to SE Texas tomorrow, bringing back a chance of precipitaiton to the Houston area. Should hold off on rain in the Dallas area until Sunday with an approaching cold front.
Today: The Dallas area should see light southeast winds during the day today picking up to around 10-15 kts by the evening hours. Winds in the Houston area should be predominately light easterly to ENE throughout the day until a seabreeze front expected to form pushes onshore. Winds associated with this front will turn the winds to the southeast and create convergence along a boundary and an increase in clouds, though no precipitation is expected. The large scale winds in the Houston area should turn to the east by evening. NE Texas is extremely dry so conditions should be clear for the entire day with mostly clear conditions expected across SE Texas aside from the seabreeze front. An ozone exceedence not out of the question in both the Houston and Dallas areas for today, though background levels are still fairly low in the Houston area.
Friday, September 15: Overnight, winds in East Texas will be affected by a seabreeze jet expected to form, the typical southerly jet off to the west and large scale winds associated with high pressure to the northeast. This setup looks to put a bit stronger SE winds in the Dallas area (15-20 kts) and lighter SE winds in the Houston area (5-10 kts). By morning expect a S-SE flow in the Dallas area and easterlies in the Houston area. Southerly flow seems a good bet in the Dallas area with ESE winds in the Houston area. This onshore flow should be enhanced by a seabreeze jet expected to form in the afternoon, which could bring a chance of showers (20-30%) near the SE Texas coast. With increased moisture across East Texas expect a few more clouds in both Houston and Dallas in the form of partly cloudy skies. An ozone exceedence is a bit more likely than today in the Houston area and likely in the Dallas area, depending on the strength of the southerly flow, with increasing background levels and higher temperatures.
Saturday, September 16: Overnight winds in the Dallas area look to be strong out of the south (20-25 kts at 300m) and fairly strong out of the SE in Houston (10-15 kts at 300m). It looks like by midday on Saturday there is a fairly strong southerly flow ahead of a front in the Dallas area and a moderate onshore flow in the Houston area. Skies should be partly cloudy across all of East Texas during the day with a 30-40% chance of precipitation at any given location in the Houston area. At this point, an exceedence does not seem to likely in Dallas because of the stronger winds expected and not likely in the Houston area because of increased cloud cover and precipitation.
A Look Ahead: Precipitation looks to be widespread across all of East Texas during the day on Sunday with onshore flow and a front approaching from the northwest. The rainy weather looks to continue for Monday as the front pushes south through Texas. The best bets for frontal passage look like Monday afternoon in the Dallas area and Tuesday morning/midday along the SE Texas coast.
Evaluation of Wednesday, September 13 Forecast
Forecast looks pretty good with SE winds in Dallas area a bit earlier than expected at Cleburne profiler, but otherwise still on target.
Forecast made Wednesday, September 13, 2006 10:00 AM
by Brent Mc Roberts
Synopsis: Front will have pushed through all of East Texas by early this afternoon bringing northerly winds and mostly clear skies.
Today: Winds in both the Dallas and Houston areas today will be out of the north around 5-10 kts, turning more northeasterly along the SE Texas coast in the afternoon hours. NE winds should be predominate across East Texas by the evening hours. A very slight chance of precipitation near the coast in the morning but PW values will decrease in SE Texas during the day so precipitation will not be a threat after noon across all of East Texas. Clouds should be at a minimum across all of East Texas with a few fair weather cumulus clouds developing in the afternoon and a few associated with a weak upper level trough. Lower than normal high temperatures and clean background air with frontal passage make an ozone exceedence unlikely across East Texas today.
Thursday, September 14: Overnight, winds in the Dallas area are expected to turn from the NE in the evening to easterly overnight to a light southeast flow by sometime tomorrow morning, with the best bet around 15Z. In the Houston area, NE winds should be around 10-15 kts overnight diminishing by sunrise and turning to the east by morning. Looks like winds during the day should be light southeasterly for the entirety of the day in the Dallas area and easterly in the Houston area switching to a light SE wind by the evening hours. Skies should be mostly clear across all of East Texas with a few scattered fair weather cumulus developing in the afternoon. MM5 developing a seabreeze front in the afternoon hours so this is a possibility along the SE Texas coast and may increase cloudiness. Ozone exceedences are possible in both the Dallas (N and NW of town) and Houston (W of ship channel) tomorrow with increasing background levels.
Friday, September 15: Overnight winds across East Texas look to start off southeasterly turning to the south in the Dallas area by morning and to easterlies in the Houston area. There should be a few more clouds across all of East Texas during the day on Friday with increasing moisture levels. Higher precipitable water and onshore flow in SE Texas on Friday make precipitation a possibility in the Houston area with a point chance around 20-30%. The seabreeze effect may enhance the SE winds near the coast in the afternoon hours along the SE Texas coast. Winds in the Dallas area look to stay out of the south during the day turning slightly to the SSE by sunset. Higher background levels of ozone will make an exceedence likely in Dallas and in Houston, if convection doesn’t hamper local contributions.
A Look Ahead: Looks like precipitable water values will remain high across SE Texas and increase in the Dallas area by this weekend. Pretty good chance of convection in the Houston area on both Saturday and Sunday with predominately southerly flow across all of East Texas through the weekend. Dallas rain chances should hold off on Saturday but may need to be introduced by Sunday afternoon.
Evaluation of Tuesday, September 12 Forecast
Forecast for today looks on track though the front was maybe a bit slower than expected. Looks like the forecast for tomorrow is good as well but went with a bit of different timing for the SE wind shift in both NE and SE Texas.
Forecast made Tuesday, September 12, 2006 11:00 AM
by James Tobin
Synopsis: A cold front currently draped across central Texas will finish moving through tonight signaling a brief return of northerly flow to east Texas.
Tomorrow, Sept. 13: Skies should be mostly clear across all of east Texas except for scattered afternoon cumulus and perhaps a few morning clouds right along the coast. Winds will be out of the north at 10-15 knots to start the day but will slow to 5-10 knots and become more northeasterly later in the afternoon. Background ozone levels are not particularly high behind this front, thus the only 8-hr ozone exceedance is expected to be in the Gulf of Mexico south of the ship channel.
Thursday, Sept. 14: Skies should be mostly clear across all of east Texas except for scattered afternoon cumulus. Winds will be northeasterly from 5-10 knots in northeast Texas to 10-15 knots in southeast Texas overnight, gradually diminishing and becoming light southeasterly winds by around midday in northeast Texas and late afternoon in southeast Texas. Localized seabreeze effects are likely in winds near the coast. These light, turning winds in conjunction with the return of the prefrontal background ozone and slightly warmer than yesterday's surface temperatures will make 8-hr ozone exceedances a possibility in both Houston and Dallas.
Friday, Sept. 15 and Saturday, Sept. 16: Southeasterly flow should continue across all of east Texas, and as a result precipitable water amounts in southeast Texas should be on the increase. A few more clouds are possible on Friday in southeast Texas, and a few more clouds are possible across all of east Texas on Saturday. Convection is possible in southeast Texas on Friday and there is an even better chance on Saturday. However, if the coverage and intensity of any convection that does develop is not enough to wash out the entire region ozone exceedances will still be likely both days as background ozone levels will be high.
A Look (Farther) Ahead: No significant changes in the weather pattern across east Texas are expected through Sunday.
Forecast made Monday, September 11, 2006 11:00 AM
by James Tobin
Synopsis: Widespread clouds and showers will start the week, with clearing and moderate offshore flow across all of east Texas by Wednesday.
Tomorrow, Sept. 12: Partly to mostly sunny in northeast Texas where the front will pass overnight tonight. Winds in the Dallas area should be northerly at 10-15 knots. Another day of widespread clouds and showers across southeast Texas before the front finally pushes offshore in the evening. Precipitation will likely start offshore, moving onshore in the afternoon, with a chance for organized and possibly isolated severe convection with the frontal passage in the late afternoon. Winds will be light from the northeast where not influenced by convection and may even be calm for several hours near the coast during the late morning, before becoming northerly at 10-15 knots overnight into Wednesday after the front passes. Possible smoke above 15 kft, especially in northeast Texas.
Wednesday, Sept. 13: Scattered low clouds may linger in southeast Texas Wednesday morning, otherwise skies will be mostly clear with scattered cumulus developing during the afternoon. Winds are expected to be 10-15 knots from the north across all of southeast Texas, slowing to 5-10 knots in the afternoon across northeast Texas. Winds may possibly be disrupted by seabreeze circulation and an ozone exceedance is possible near the coast. Background pollution levels will be elevated. Possible smoke above 10kft, especially in northeast Texas.
Thursday, Sept. 14 and Friday, Sept. 15: Winds will become southeasterly on Thursday and remain generally easterly (far SE Texas) to southeasterly (northeast Texas) across all of east Texas through Friday. Mostly clear skies other than scattered afternoon cumulus and a few morning clouds near the coast. High ozone is possible in both Houston and Dallas on both days.
A Look (Farther) Ahead: Moisture and a chance of afternoon convection will return to southeast Texas on Saturday. Next mid-latitude system is forecast for this weekend but model guidance currently suggests it will not reach southeast Texas, and it may be a coin flip right now as to whether it affects northeast Texas. If this system passes north of Texas, no sign of this flow pattern changing at least through Sunday.
Forecast made Sunday, September 10, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Wet pattern disrupted by cold front sweeping through state Monday-Tuesday, followed by brief spate of dry weather.
Tomorrow, Sept. 11: Another convective blowup overnight along the near offshore, followed by morning towering cumulus and afternoon convection over land within 120 miles of the coast. Winds generally light and easterly but with land/sea breeze cycle superimposed. Prefrontal or frontal squall line likely in the afternoon in North Texas.
Tuesday, Sept. 12: The front should be well past Dallas, so mostly clear skies and moderate NNW flow likely there. In southeast Texas, the cold front will most likely come through sometime during the day. Winds will be light in the morning, becoming weak northerly ahead of the front and strong northerly behind it. Precip forecast depends on outcome of previous day's convection, but most likely is widespread offshore convection early in the morning, morning cumulus, scattered afternoon showers, and organized deep convection during frontal passage. Possible smoke above 15K ft.
Wednesday, Sept. 13: Mostly sunny skies. Winds probably light and from the northeast in Dallas, light to moderate and from the northeast in Houston. Scattered to broken boundary layer cumulus will develop in the afternoon. Possible smoke above 5-10K ft. Increasing background ozone.
Thursday, Sept. 14: Continued sun (except for afternoon scattered cumulus) in Dallas. Winds there generally light and probably from the southeast. In Houston, forecast less certain, but most likely scenario is very light winds in the morning and strengthening easterlies or southeasterlies in the afternoon. High ozone levels expected under this scenario. High background ozone. Precipitation unlikely, but boundary layer cumulus will form in late morning.
A Look (Farther) Ahead: Moisture will return to Texas, probably by Friday, but unorganized (scattered showers offshore in the morning, over land in SE TX in the afternoon). Winds E-SE in southeast Texas, SE-S in northern Texas.
Evaluation of Saturday, September 9 Forecast
Forecast mostly accurate, except background levels in Dallas were 10-15 ppb lower than yesterday and no exceedances occurred.
Forecast made Saturday, September 9, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: A generally cloudy and wet pattern for Texas coastal areas, but day-to-day details remain difficult to forecast, and operations plans may wish to allow for the possibility of breaks in the weather.
Today: Broken to overcast conditions will persist in Houston with occasional showers, and winds will be moderate from the east or southeast during the day. Shower activity offshore will taper off later in the day. Dallas may receive yesterday's Houston plume; ozone formation will depend on location of cloud edge in North Texas. Boundary layer cumulus likely in central and north Texas, developing around noon between breaks in the mid-level clouds and becoming more widespread in the afternoon.
Tomorrow, September 10: More offshore convection likely overnight and beyond, and scattered showers likely over southeast Texas during the day. Dallas will be partly cloudy to cloudy, and light winds (southerly in morning, easterly in afternoon) and possibly high background (depending on precip today) imply a good possibility of Dallas and NE Texas exceedances. Houston winds will remain moderate and generally from the east. A convergence zone may form 50-150 km offshore with southerly flow farther offshore. Boundary layer cu forecast same as today.
Monday, September 11: Weather remains unsettled in the Houston area. A good drenching is likely sometime Monday or Tuesday. The next cold front approaches Dallas from the north and convective activity (possibly evolving into a squall line) is likely for North Texas.
A Look Ahead: The front is currently forecast to stall in the vicinity of the Gulf Coast, keeping conditions unsettled in the Houston area. Dallas will probably dry out, and higher aerosol and photochemical activity are likely by Wednesday or Thursday.
Evaluation of Friday, September 8 Forecast
High background helped produce 8-h exceedances in Dallas but not Houston where wind speeds and cloud cover hindered local formation. Showers moved in overnight ahead of schedule. Extensive cloud cover across Houston today.
Forecast made Friday, September 8, 2006 10:00 AM
by Brent Mc Roberts
Synopsis:
Today: Winds in the Houston area should remain generally easterly and decrease in intensity a bit by midday while a seabreeze develops along the coast in the early afternoon hours and pushes onshore in SE Texas. This will switch winds to the SSE, which will converge to create a small chance of precipitation. Winds in the Dallas area were generally out of the south this morning and should turn to the SE by afternoon and decrease a bit in intensity. A storm system off to the west will bring high cloudiness to most of East Texas but still remains far enough away to be of concern for precipitation. Given the high background concentrations of ozone in both Houston and Dallas, exceedences are likely. The highest concentrations in the Houston area look to be to the west of the city and in Dallas to the north of the city.
Saturday, September 9: Overnight should bring SE flow to the Dallas area and lighter southerly flow with the seabreeze jet to the Houston area, while NE Texas should have easterlies. In the Houston area, it looks like onshore SE flow during the day and increasing chances of precipitation tomorrow, though it is possible that the localized winds fields may be affected by convection. This onshore flow should be enhanced by seabreeze flow in the afternoon hours. With continued higher background levels of ozone, an exceedence is possible NW of Houston where rain chances are smaller and transport of ship channel emissions is expected to end up. The rain should hold off in the Dallas area with another day of southerly flow which will transport ozone points north of town. An exceedence is possible in the Dallas area if the cloud cover from the approaching low pressure system does not inhibit photochemical processes.
Sunday, September 8: Overnight model winds in the Houston area show a strong seabreeze signal with southerly winds in the evening turning to the east by Sunday morning. In the Dallas area, the forecast is a bit tricky because of the seabreeze jet to the south and east and the normal southerly jet to the west. It appears that flow overnight will be anywhere from the between E and SW though a transition from E flow in the evening to southerly flow by morning appears to be the most likely scenario. Onshore flow should return to the Houston area during the day on Sunday, with an exceedence is not likely in the area with the increased cloud cover and precipitation in the area. We should see southerly flow again in the Dallas area but with an increase in cloud cover and moisture. It is a bit too far out to know the timing, but a cold front is expected to push through early next week and could bring a chance of precipitation to Dallas on Sunday. There could be an ozone exceedence in Dallas on Sunday if the cloud cover is not extensive and the rain holds off.
A Look Ahead: A cold front should push through North Texas sometime on Monday and it looks like all of East Texas will have a pretty good shot of rain. This front should clear the SE Texas coast by Wednesday bringing a northerly component to the flow and likely drag more continental air with higher background levels of ozone.
Evaluation of Wednesday, September 6 Forecast
The forecast for today still looks on track and the forecast for Saturday is roughly the same forecast as the one made yesterday.
Forecast made Thursday, September 7, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: NE flow today across East Texas turning to a more SE flow the next couple of days. Looks like a strong seabreeze pattern setting up in SE Texas over the next few days.
Today: Models are in pretty good agreement that a general ENE flow will be established by mid morning in SE Texas around 5-10kt weakening a bit by early afternoon. A seabreeze regime expected to shift winds to a SE flow along the coast penetrating inward as the day progresses. Flow in Dallas a bit more uncertain and dependent on location of a high pressure system with general easterlies, with models disagreeing on the northerly component to this wind. A very slight chance of precipitation near the coast in SE Texas but for the most part all of East Texas with mostly clear skies throughout the day with a few clouds in the afternoon. Ozone exceedences in both Dallas and Houston are likely with continental air and higher background levels in place along with favorable conditions combining together.
Friday, September 8: Overnight, pretty high confidence that winds overnight will turn to the SE across the Dallas area. Winds in the Houston area are a bit trickier but it looks like the best guess is a light S to SE flow turning easterly by tomorrow morning. Winds tomorrow in Dallas look to be light southeasterly throughout the day on Friday and likely in the Houston area as well, though the models disagree a bit on the southerly component. Expect a fairly extensive seabreeze pattern with S to SE winds to develop along the SE Texas coast and push inward through the afternoon hours. With increasing temperatures and light flow, expect an ozone exceedence in both the Dallas and Houston areas tomorrow, though there is a slight chance of precipitation with the afternoon onshore flow in SE Texas.
Saturday, September 9: Overnight it looks like large scale SE winds across all of East Texas associated with the high pressure area off to the northeast. However, it looks as though the overnight seabreeze jet will add more of a southerly component to the wind in SE Texas. S to SE winds seem to be the consensus across all of East Texas for the day on Saturday with a bit more of an easterly component towards the Houston area. Increasing precipitable water and a strong onshore flow look to make precipitation an more likely proposition across SE Texas during the day on Saturday (30-40% at any location), with outflow from convection disrupting the large scale wind field. With the dirty air in place, ozone exceedences are likely in Dallas while in the Houston area, an exceedence will be likely in areas that remain precipitation free for most of the day.
A Look Ahead The pattern for Sunday looks similar to that on Saturday but with a bit more moisture in SE Texas. It looks like the beginning of next week could be wet across all of East Texas with a low pressure system forecasted to come across South Texas early next week.
Evaluation of Wednesday, September 6 Forecast
Forecast for today looks on track by the look of things currently.
Forecast made Wednesday, September 6, 2006 11:00 AM
by James Tobin
Synopsis: Although there is some uncertainty it appears that the return of onshore flow to east Texas is near.
Today: Mostly clear across all of east Texas except in the immediate vicinity of the coast. North-northeast winds at 5-10 knots. Seabreeze-related wind reversal possible only within a couple miles of the coast and ozone exceedances are not expected anywhere besides these immediate coastal areas.
Thursday, Sept. 7: Mostly clear across all of east Texas, a few afternoon cumulus possible in southeast Texas along the seabreeze. Winds will be light and generally northeasterly across east Texas with a seabreeze wind shift to southeasterly likely near the coast in the afternoon. Ozone exceedances are possible in both Houston and Dallas due to the low wind speeds though surface air temperatures will not have completely rebounded from the frontal passage.
Friday, Sept. 8: The large scale winds will gradually become southeasterly overnight and into Friday morning, beginning in the western and southern parts of east Texas. An added jolt of overnight southerly flow is possible from the seabreeze jet. Winds will be light and southeasterly during the day, possibly more southerly in western portions of east Texas, and will pick up from the south-southeast in the afternoon in southeast Texas as the seabreeze kicks in. With the onshore flow resuming there is a very slight chance of afternoon convection in southeast Texas. Ozone exceedances are possible in both Houston and Dallas and likely even more probable than on Thursday as surface temperatures and background pollution levels continue to increase.
A look ahead: Transport winds will be south (over northern east Texas) to southwest (over southern east Texas) Friday night with southeasterly flow once again during the day on Saturday. Light winds and an increasingly dirty background will make ozone exceedances in both Houston and Dallas possible through Sunday. Increasing precipitable water with the onshore flow will also cause an increasing chance of afternoon convection this weekend, especially in the southern half of east Texas.
Evaluation of September 5 Forecast
Forecast is on track.
Forecast made Tuesday, September 5, 2006 11:00 AM
by James Tobin
Synopsis: Cold front has moved through with disturbed weather behind the front about to reach the Houston area.
Today: Cloudy across most of east Texas with clouds moving into currently clear areas near the coast by noon and clearing skies in roughly the northern third of east Texas later this afternoon. Scattered showers are likely in the southern half of east Texas along with an isolated thunderstorm or two near the coast. Winds will be out of the north to northeast across all of east Texas at 5-10 knots in the north and 10-15 knots in the south.
Wednesday, Sept. 6: Lingering clouds near the coast in the morning will give way to partly sunny skies by afternoon; partly to mostly sunny across the rest of east Texas. Northerly to northeasterly winds will decrease to 5-10 knots across east Texas in the afternoon on Wednesday. No wind reversal is likely on Wednesday afternoon. Little chance of rain or ozone exceedances anywhere in east Texas.
Thursday, Sept. 7: Light northeasterly flow overnight will become more easterly during the day on Thursday across most of east Texas and possibly even southeasterly along the coast during the afternoon. A wind reversal is possible near the coast. Skies will be mostly clear except for a few scattered cumulus near the coast. An ozone exceedance is possible in both Houston and Dallas as background ozone and its precursors will increase, especially near the coast in southeast Texas where stagnation may occur.
A Look Ahead: Models are still suggesting a "dirty" (continental-based) onshore flow will set up perhaps late Thursday across southeast Texas but by Friday for all of east Texas. This pattern is expected to continue throughout the weekend but as PW values increase a slight chance of seabreeze-fired thunderstorms must be added to the southeast Texas forecast beginning on Saturday.
Evaluation of September 4 Forecast
Widespread convection did not occur as expected, and once again a front passed through southeast Texas with little "weather" ahead of it. Aside from these problems with yesterday's nowcast, the forecast from yesterday is still on track.
Forecast made Sunday, September 3, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Continued predominantly easterly flow and mostly clear skies for the next two days before disturbed weather on Tuesday.
Today: Mostly clear skies, some boundary layer cumulus late in the day. Winds NE in late morning, E during afternoon with southeasterly sea breeze in afternoon. No ozone exceedance expected. Most of Houston plume will stay over land, but offshore transport from S Louisiana likely. Highest ozone levels will be offshore.
Monday, Sept. 4: Land breeze along coast. Light winds from the northeast in morning, strengthening from northeast or east in afternoon. Mostly clear skies likely, unless frontal clouds invade area from the north. Showers likely in central and north Texas and near Victoria/Corpus Christi. Continued offshore transport from S Louisiana. Outside chance of transport from N during afternoon if biased model verifies. Highest ozone levels will be offshore.
Tuesday, Sept. 5: Clouds at various levels likely as cold front moves across southeast Texas. Dallas will probably be clear under moderate northerly winds. Winds in Houston will be from the west, northwest, and north.
A Look Ahead: Clear skies likely on Wednesday under northeasterly flow conditions. High pressure will move eastward, setting up onshore flow with continental dirty background advected across Gulf to Houston late in the week.
Evaluation of September 2 Forecast
Showers verified west of Houston; mostly clear skies in Houston proper. Cold front is slower in models today, so one more day of dirty background in store for southeast Texas.
Forecast made Saturday, September 2, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Light northerly to easterly winds will dominate the next couple of days, with somewhat cleaner background arriving sometime Monday.
Today, Sept. 2: Light northerly winds this morning will evolve to very light northeasterlies and easterlies during the day, with a sea breeze developing along the coast. Thunderstorm activity is likely in mid to late afternoon, mostly west of Houston. The highest ozone should occur near and west/southwest of Houston. Nighttime transport will be toward the west and northwest, probably contaminated by shower activity that should die away in the evening.
Tomorrow, Sept. 3: Situation apparently very similar to today. Winds should be very light in the morning, out of the northwest or north, before developing a more northeasterly component during the afternoon and a sea breeze along the coast. Precipitation chances appear similar to today as well. Stagnation possible but a bit less likely than the past few days.
Monday, Sept. 4: A cold front front will move through Dallas and approach southeast Texas. The lifting associated with the front and a large upper-level cutoff over the north-central United States will lead to likely showers in the afternoon and evening with probable middle and high clouds during the day as well.
A Look Ahead: Transport will be from the north rather than the northeast for a few days beginning on Tuesday, and clouds and precipitation chances will decrease.
Summary of Friday Sept. 1 Event (JD 243)
A more typical high ozone event in Houston than occurred yesterday. Winds were light from the west in the morning, stalled around noon, and developed from the east and southeast during the afternoon. The lightest winds coincided with maximum ozone production. 8-h ozone exceedances were observed at numerous sites, mostly around and north of the Ship Channel, with the highest value being 121 ppb at Deer Park. Background ozone levels were around 65 ppb.
Dallas experienced another significant exceedance as well, with an 8-h maximum of 102 ppb at Denton and 11 sites violating the standard. Southerly morning winds gave way to very light winds during the afternoon, making the event a repeat of yesterday.
Elsewhere in the state, exceedances occurred at Tyler and Sabine Pass.
Forecast made Friday, September 1, 2006 11:00 AM
by Brent Mc Roberts
Synopsis: Land breeze developed this morning between Galveston and Beaumont and is very noticeable on visible satellite. Winds at Laporte shifted from southerly to westerly by this morning. Expect light northerly winds to develop in the Houston area by late morning and early afternoon with a period of stagnant winds possible. A seabreeze front will likely develop in the early afternoon hours pushing onshore especially SW of town changing the winds along the coast to a southeasterly direction. Expect another day with less than average cloudiness though clouds will be more likely near the coast due to convergence from the sea breeze front. A one-hour ozone exceedence will occur with the most likely region just to the south of the Ship Channel. Winds in Dallas look to be easterly pushing plumes west toward the Fort Worth area.
Saturday, September 2: Overnight, the models show a marked transition zone between strong southerlies associated with a jet setting up to the west and easterlies to the north of Houston. Again a zone of lighter winds is expected to set up somewhere near the Houston area overnight. Expect another land breeze to develop tomorrow morning with winds near the coast out of the W or NW. Tomorrow, expect generally light E to NE with a period of stagnation possible in the early afternoon if we have a transition for westerlies to easterlies. The sea breeze front developing tomorrow my penetrate further inland with a very slight chance of precipitation. Expect a one-hour ozone exceedence SW of the Houston area tomorrow with continental background flow and possible recirculation of ozone with the sea breeze expected to develop.
Sunday, September 3: The large scale flow overnight should turn to easterlies in the Houston area with the strength of these winds and overnight transport a bit uncertain and dependent on the location of an easterly jet expected to set up. During the day, the Houston area should see fairly light winds throughout the day, with the chances of precipitation making their way back into the picture.
Monday, September 4: Precipitation looks like a possibility in both Houston and Dallas for the day on Monday. The wind forecast is difficult because of the convection fired up by the GFS and the outflow created by these storms.
Evaluation of Thursday, August 31 Forecast
As has been the case the past few days, we have overestimated the northerly component of the wind in the forecast, so we have adjusted today’s forecast accordingly to compensate for this model bias.
Summary of Thursday, August 31 (JD 242) Weather
by John Nielsen-Gammon
Profiler winds in the morning were from the northeast at 0-5 kt. By noon, the LaPorte? winds had developed a slight southeasterly component, but they remained unusually light, below 5 kt, throughout the day. All available mesoscale models had forecasted more of a northerly component to the winds, but in this situation (high pressure to the north, clear skies), the mesoscale models have consistently overdone the northerly winds. The mixing height in Houston, according to UH soundings, was 1.6 km. The sea breeze did not affect the Houston area until 5-7 PM.
Background ozone levels were 55-60 ppb. Ozone first became unusually high at Park Place (CAMS 416), just south of the I-45/I-610 interchange south of Houston, downwind of the Ship Channel according to morning winds, and about 8 miles south of the Moody Tower site. The hourly average ozone there was 94 ppb at 11AM (all times are CDT) and 126 ppb at Noon. Hourly ozone remained above 110 ppb through 6PM.
Almost all stations southwest, west, and northwest of Park Place exceeded the 8-h standard. A total of 16 monitors exceeded the 8-h standard of 84 ppb, led by Houston Westhollow (CAMS 410), which had an 8-h average of 126 ppb and a 1-h maximum of 147 ppb. The nearby long-term station at Bayland Park (CAMS 53) was not far behind, with an 8-h average of 124 ppb.
Many high ozone events in Houston are associated with a few hours of stagnation, producing a concentrated blob of ozone that then advects past surface monitors, producing rapid increases and decreases of ozone levels. This event was more like a typical high ozone day in the eastern United States, in which winds remain light throughout the day. The high ozone was broadly distributed and remained high for several hours at each site, leading to exceptionally high 8-h ozone values.
In Dallas, overnight winds at the Cleburne profiler were light from the southeast in the evening and stronger (15-20 kt) from the south during the predawn hours. It is possible that part of yesterday's Houston ozone plume moved into the Dallas area overnight, but profiler trajectories do not show this. For whatever reason, the background 8-h ozone level in the DFW metropolitan area was 70 ppb, unusually high for that location. Background levels in East Texas were only 50-60 ppb.
After sunrise, the winds gradually decreased, becoming very light at 1 PM and remaining light through the rest of the afternoon. This allowed local sources to contribute strongly to ozone levels, resulting in what, like Houston, was the dirtiest day of the field program so far. Eight monitors exceeded the 8-h standard, led by Frisco (CAMS-31) at 101 ppb.
Across the rest of Texas, a marginal 8-h exceedance occurred in Austin and a near-exceedance in Corpus Christi.
Forecast made Thursday, August 31, 2006 12:15 PM
by Brent Mc Roberts
Synopsis: Flow at Laporte this morning has been easterly, and is expected to mix with winds aloft that are NE to turn winds this afternoon over the Houston area to the NE. A seabreeze is expected to develop, most prominent to the SW of Galveston Bay but its penetration onto land will be limited.
Friday, September 1: Overnight transport in Houston a bit tricky because of a region of very light winds the models set up between the typical southerlies associated with the jet to the west and high pressure flow from the NE. Because of this regime, little ozone that forms in the Houston area will leave. Again, clouds will be minimal with the very dry air in place behind the frontal passage. Light easterlies in the morning will turn to the NE during the middle of the day, but exact evolution of winds relies heavily on the behavior of the surface high pressure building in behind the front. Very high levels of ozone are likely to the south of Houston as very light winds will allow for local buildup. Seabreeze formation expected in the afternoon and looks to make it a bit further onshore.
Saturday, September 2: Overnight winds in the Houston area should be fairly close to what is forecasted for overnight tonight. Looks like an increase in cloud cover of Southeast Texas for Saturday with higher relative humidity values aloft though convection should not be a problem in the Houston area. There is a bit of uncertainty in the wind forecast for Saturday but the best guess is a similar scenario to that on Friday with winds perhaps a bit stronger around 5-10kt. Seabreeze front may be accompanied by precipitation as we return moisture levels to more typical levels for this time of year. Convection looks to threaten Dallas with a front approaching the area.
Sunday, September 3: Models are showing convection forming during the day on Sunday with onshore flow in Houston. Convection in Dallas will be a good bet with a light northerly flow, though the heaviest precipitation should remain to the west of the metro area.
Evaluation of Wednesday, August 30 Forecast
Northerly component of wind forecasted did not pan out as expected with the steady easterly winds at the profiler sites in the Houston area.
Forecast made Wedneday, August 30, 2006 11:00 AM
by James Tobin
Synopsis: Mostly clear and less humid conditions are expected behind the cold front that moved through overnight, with pollution events becoming a significant issue beginning tomorrow.
Today, August 30: Mid-high level clouds should clear by mid afternoon with only a few cumulus remaining. A seabreeze reversal of the winds just along the coast may cause high ozone to be reported in Galveston today, but otherwise high ozone is not expected anywhere inland.
Thursday, August 31: Transport overnight will be from the north-northeast at about 10 knots in southeast Texas, weaker and becoming easterly overnight in northeast Texas. Winds out of the north-northeast will become more northeast decreasing to 5-10 knots over southeast Texas with winds becoming light and variable over the Dallas area as a weak, broad area of high pressure moves in. A seabreeze event will be likely along the coast during the mid-late afternoon hours in southeast Texas with winds becoming light out of the southeast or south. An ozone exceedance is likely in the Houston area south of the city; an exceedance in Dallas will depend on the timing and duration of stagnation associated with the light and variable winds. Cloud cover will be minimal across east Texas once any low morning clouds burn off.
Friday , September 1: Overnight transport will be weak and southeasterly in Dallas becoming stronger from the south as the seabreeze jet kicks in, and weak and easterly in southeast Texas. Should be a pretty close repeat of Thursday except winds in southeast Texas will remain more easterly than northerly. A seabreeze event and an ozone exceedance are both likely in southeast Texas, with the exceedances likely both south and west of Houston.
Saturday, September 2 Yet another repeat of the past two days is expected. Models suggest flow across southeast Texas may become southeasterly but will remain light. There is a slight chance that convection may threaten the northern 2/3 of east Texas in the afternoon, otherwise skies will be mostly clear once again. Ozone exceedances are once again likely in southeast Texas.
Evaluation of Tuesday, August 29 Forecast
Front slowed down across central Texas as expected but nothing else fired up convection across southeast Texas as forecasted. Thus there was no convection associated with the frontal passage and a distinct seabreeze recirculaton was allowed to take place, recirculating Houston's own emissions blown offshore by morning convective outflow back into Galveston Bay. One and eight hour exceedances almost occurred southeast of Houston but neither threshold was actually reached.
Forecast made Tuesday, August 29, 2006 11:00 AM
by James Tobin
Synopsis: Front coming later tonight will spread northerly flow across east Texas on Wednesday.
Today, August 29: Scattered cu developing around Houston with convective initiation likely within the next couple hours as outflow from earlier convection approaches, followed later tonight by the front. Widespread convection is likely in the Houston area later today and tonight with the passage of the front.
Wednesday, August 30: Lingering overcast conditions and scattered convection near the coast in the morning moving completely offshore by afternoon. Winds across east Texas will be generally out of the north at 10-15 knots and too strong to permit any stagnation in conjunction with the seabreeze along the coast. Saharan dust will also be cleared out by the frontal passage and the primary aerosol over east Texas will become sulfates from continental U.S. sources. Moderately dirty background will move in from central U.S. but will do more to set the stage for ozone tomorrow, when winds will be weaker. Ozone exceedance possible near the coast south of Houston depending on when convection ends, I would not consider an exceedance likely.
Thursday , August 31: Transport overnight will be from the north at 10-15 knots pushing the Houston plume well offshore. Winds will weaken and become northeasterly in the morning, followed by a turn to the east with possible stagnation in the Dallas area. Stagnation will also be possible along the coast in conjunction with the seabreeze. Ozone exceedances will be likely in both locations due to these light winds. Cloud cover in southeast Texas is expected to follow the typical pattern of low broken clouds early giving way to scattered cu later in the day, with mostly clear skies in northeast Texas. Precipitation is not expected.
Friday, September 1 Transport overnight will be light from the northeast. The general consensus among the models is for a return of southeasterly flow during the day on Friday, particularly in the southern half of east Texas. Exact details such as wind speeds and the potential for recirculation are still uncertain. Winds should not be too strong and with light transport from the night before a second straight day of ozone exceedances in both Houston and Dallas are likely. This is a departure from what the models were saying 24 hours ago so for the time being it should be taken with a grain of salt.
Evaluation of Monday, August 28 Forecast
Convection initiated earlier in Houston than expected. Clues that this was going to happen could have been taken from satellite and radar data that showed both convective boundary layer rolls and several outflow boundaries in southeast Texas before 11 am. Convection will likely initiate earlier than previously expected today as well (see discussion above). Otherwise the forecast is on track.
Forecast made Monday, August 28, 2006 11:00 AM
by James Tobin
Synopsis: Saharan dust plume has arrived...deep convection along a surface boundary in north-central Texas...front still poised to arrive tomorrow in northeast Texas and Wednesday in Houston.
Today, August 28: It appears winds in southeast Texas will be slightly stronger than previously forecast, out of the south at 10-15 knots this afternoon. In northeast and central Texas an area of deep convection that developed overnight along a surface convergence zone has contaminated the low-level wind field. The resulting outflow boundary may influence parts of southeast Texas north and west of Houston much later this afternoon by weakening winds and triggering showers and thunderstorms.
Tuesday, August 29: Strong south-southwest transport winds overnight will carry the Houston plume into northeast Texas tomorrow where it will likely be picked up by the cold front moving through. Winds will weaken and become more southwesterly by late morning. Light west to southwest winds will then persist until the arrival of the cold front. A few scattered clouds/towering cu are expected by late morning with scattered convection holding off until late afternoon or early evening when the front approaches. Scattered storms are also expected in northeast Texas along and ahead of the cold front with strong northerly winds and mostly clear skies behind the front. Background ozone levels will be slightly higher behind the front, but the bulk of the pollution from central U.S. emissions sources will not reach Dallas until Wednesday or Houston until Thursday.
Wednesday , August 30: Moderate north winds are expected immediately behind the cold front giving way to lighter northeasterly winds. Front may just be passing through Houston in the morning but will definitely be through Dallas. Continental background building into northeast Texas and light northeast winds will make an ozone exceedance a possibility in Dallas on Wednesday. Houston will not be as likely to see an exceedance Wednesday with lingering convection possible in the morning and the dirtiest continental air not reaching southeast Texas until Thursday.
Thursday, August 31 Light northeasterly winds are expected with a wind reversal possible in the vicinity of the coast where the sea-breeze will come in. A broken low cloud deck is possible near the coast early, and scattered cu are possible throughout the day but precipitation is not expected. Ozone exceedances will be possible in both Houston and Dallas.
A Look Ahead: No change from the post-frontal conditions are expected in the next 4-5 days.
Evaluation of Sunday, August 27 Forecast
Cu field seems to be a bit more widespread, likely due to the combination of relatively high PW values and the Saharan dust plume. Convection may be an issue in the northern 2/3 of east Texas this afternoon since a convective complex fired up in north-central Texas overnight. Winds overnight were stronger than predicted but over the past few hours have been closer to yesterday's forecast. Otherwise forecast was on track.
Forecast made Sunday, August 27, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Saharan dust plume almost here; gradual shift from southerly flow to northerly flow during the next several days.
Monday, August 28: Clean marine air mass except for dense Saharan dust plume. Winds will be southwesterly in the morning, turning to westerly by late morning, weakening, and increasing from the south in the mid afternoon. Stagnation is possible in early afternoon. Convection will likely be suppressed by the dry air aloft. High dewpoints will lead to morning low clouds, becoming broken by 10AM, but becoming sparser in the afternoon with mostly clear skies by late afternoon. Best chance for towering cumulus may be midday. Dallas will have southwesterly winds with deep convection and thunderstorms threatening from the northwest in the afternoon.
Tuesday, August 29: First light wind day in a while. Tropical air with Saharan dust plume probably still in place; same cloud forecast as Monday. (If Monday's forecast is wrong, Tuesday's forecast will be similarly wrong.) Light winds and recirculation almost guaranteed, but details up in the air. Most likely scenario calls for northwest winds (5 kt) in the morning turning to northerly by middday, northeasterly in midafternoon (5-10 kt), and easterly by late afternoon. Significant ozone buildup in Houston possible if morning northwest winds are light; transport will keep air cleaner if morning winds are stronger but that scenario would allow Houston emissions to be advected offshore. Cold front will move through Dallas area, with northerly winds behind front. Isolated thunderstorms possible along front, which may be approaching Houston by the evening.
Wednesday, August 30: Generally northerly and northeasterly winds of 5-10 kts throughout most of the day, possibly turning to easterly by late afternoon with a sea breeze along the immediate coast. This air will be post-frontal and higher in background ozone, but air from central US emission sources will not yet have arrived. Drier air mass means clouds will not form until later in the morning, say around 11AM. Similar conditions (but sunnier) in Dallas.
A Look Ahead: Continued transport from central and southeastern United States will lead to continental background throughout Texas for several days. High ozone levels will depend upon strength of wind, which is presently uncertain.
Evaluation of Saturday, August 26 Forecast
Forecast on track.
Forecast made Saturday, August 26, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Clean air and showers will give way to Saharan Dust Plume Sunday/Monday with reduced clouds and major change in weather regime Tuesday.
Tomorrow, August 27: Continued moderate southerly flow and very moist airmass will cause scattered thunderstorms in southeast Texas and prevent stagnation anywhere in eastern Texas. Urban plumes not disrupted by convection will extend northeast of urban areas in morning and early afternoon, north of urban areas in late afternoon. Saharan dust cloud expected below 3km to arrive in Houston area from the south, probably in late afternoon.
Monday, August 28: Saharan dust cloud will still be present; associated warm/dry air aloft will likely prevent widespread convection offshore in early morning and over land during the day. Expect morning boundary layer cumulus to become broken early, around 10AM, but mixing of dry air aloft should lead to mostly clear skies in the afternoon. Winds will be lighter than the past few days, so there is about a 30% chance of land breeze transport in the morning, stagnation around noon, and southerly transport in the afternoon. If light winds do not materialize, transport will be toward the northeast in morning and toward the north or northwest in the afternoon. Ozone levels will depend on the wind details but will probably be higher than during the past few days.
Tuesday, August 29: Strong southerly flow will be over, and stagnation or morning offshore transport is likely in the Houston area. Dallas will be affected by a cold front approaching from the north; winds and thunderstorm activity will depend on timing of front.
A Look Ahead: Beginning Wednesday, several days of northeasterly winds and transport from the continental United States are likely. Usually cloud coverage and precipitation chances decrease dramatically with such a weather regime. Current TS Ernesto is expected to undergo steady strengthening, but the forecast track beyond 72 hours is very uncertain as the storm approaches the Gulf of Mexico.
Evaluation of Friday, August 25 Forecast
Wind forecast on track, but considerable convection present already along the coast in the morning.
Forecast made Friday, August 25, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Continued clean background and afternoon showers, with recirculation unlikely.
Saturday, August 26: Winds will be moderate from the southwest in the morning, decreasing in intensity and then picking up from the southeast late in the day, with wind speeds higher in Dallas than Houston. Low clouds will form between 9AM and 10AM and become broken, with isolated showers probably forming by noon and becoming more widespread in the afternoon. A widespread convective event along the coast is an outside possibility. Convection is unlikely from Conroe north.
Sunday, August 27: The forecast for Sunday is identical to the forecast for Saturday, except that a Saharan dust plume will be in the southern Gulf of Mexico by then.
A Look Ahead: The current weather regime will end early next week, and the chances are better than 50% that we will see our first predomantly northeasterly wind event. Ernesto may be a concern but is not worth worrying about until Monday when it may be approaching the Gulf of Mexico.
Evaluation of Thursday, August 24 Forecast
Precipitation formed much later than forecasted and was not widespread. Consequently, near-stagnant conditions in the morning allowed ozone in Houston to build up to moderate levels in the Ship Channel before drifting north of Houston.
Forecast made Thursday, August 24, 2006 11:00 AM
by John Nielsen-Gammon
Synopsis: Widespread afternoon precipitation, moderate southerly winds, and clean background make pollution buildup impossible for the next several days.
Tomorrow, August 25: Winds will generally be southerly across Texas, specifically S-SW in the morning and SE in the afternoon. Wind speeds will be 5-15 kt, too strong for coastal stagnation. Scattered thunderstorms are likely. Low clouds will develop around 9-10 AM and some will evolve into cumulonimbus around 11 AM to noon. The initial convection is most likely 0-20 km inland from the coast and it will spread farther inland during the aftern