Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 4

[DoctorMu]

Wow, Uncertainty with the models is leaning more and more West, with the consensus leaning towards the euro (Mobile) and GFS (near Slidell).

http://www.sfwmd.gov/sfwmd/common/images/weather/plots/storm_09

We've got spotty showers and a sea breeze the next few days. Will the ridge indeed build and force Isaac east?

[msp]

got a nice downpour driving home from mass today. central college station got soaked while the house on the south side of town missed out on almost all of it.

hoping for a continued west trend on isaac

[Ed Lizard]

I reject the 12Z GFS slow Westward crawl as seeming unlrealistic, especially the part the storm maintains intensity half on land, but it is interesting to note it would bring hurricane force winds to about half the HGX CWA.

[DoctorMu]

I reject the 12Z GFS slow Westward crawl as seeming unlrealistic, especially the part the storm maintains intensity half on land, but it is interesting to note it would bring hurricane force winds to about half the HGX CWA.

Just about to post this Holy ****

It's all about whether the ridge builds back or not...The GFS has this puppy at the Texas coast within 96 hrs.

[DoctorMu]

18Z GFS for Isaac not quite as strong on land and about 50 mi east...still that's a significant impact on east Texas in this model

[Srain]

Update from Jeff:

No major track shifts have occurred since the 400am advisory. The landfall of tropical storm force winds on the MS River Delta is about 30-36 hours away. The 12Z GFS this morning has trended slightly eastward and a general model consensus is found over SE LA with the GFDL and GFS on the western side of the guidance clustering and the ECMWF, CMC, UKMET on the eastern side (more aimed toward MS).

On the intensity side of things, East Gulf Buoy went very near the center this morning and recorded a pressure of 987mb (now down to 984mb per recon) and sustained winds of around 40-45mph. Dry air has wrapped into the east side of the circulation this morning and weak ENE wind shear is pushing the main convective mass to the WSW side of the circulation. While conditions are generally favorable for development, Isaac still has some issues to overcome and has yet to develop an inner core/eyewall. If the inner core can develop Isaac could make a run at a moderate to strong category 1 hurricane prior to landfall, but the window for intensification is shrinking.

Note: Isaac is a large tropical cyclone with tropical storm force winds extending outward over 200 miles to the east of the center. It is important to not focus on the exact point of landfall and instead the overall range of impacts to the entire area.

Storm Surge:

Do to the large size of the circulation, Isaac will be very capable of moving a large amount of sea water toward the US Gulf coast. Significant storm surge flooding is likely along the MS and SE LA coasts including Lake Pontchartrain. The below listed values are currently forecast on the current forecast track. The exact track of the center is important when dealing with storm surge as the worst of the surge will be near and just east of where the center crosses the coast. Additionally, given the current track, Isaac’s SE wind flow on the eastern side of the circulation will pile water into the concave shape of the coast of SW MS into Lake Pontchartrain. At this time, the current forecasted surge values are below the top limits of the levees protecting SE LA and the City of New Orleans.

Surge Ranges (above sea level):

SE LA (from the mouth of the MS River west to near Houma): 6-9 ft

SE LA (from the mouth of the MS River to the LA/MS state line): 7-11 ft

SE LA (Lake Pontchartrain): 5-8 ft

MS coast: 8-12 ft

AL coast: 6-10 ft

FL panhandle: 3-6 ft

Winds:

Tropical storm force winds are likely from the western FL panhandle to the central Louisiana coast. Hurricane force winds are likely over SE LA and coastal MS. Tropical storm force winds will onset over the lower MS delta around midday Tuesday and spread into metro New Orleans and coastal MS by early evening. Hurricane conditions will spread NW from the mouth of the MS River Tuesday evening into SE LA and coastal MS late Tuesday through Wednesday morning. Due to the large size of tropical storm force winds, adverse conditions will last for hours.

Generally winds will average 60-80mph over the MS delta into New Orleans and the coast of MS with gust to near 90-100mph. Tropical storm force winds will spread well inland over central and eastern Louisiana and much of southern and central Mississippi including Baton Rouge. Main impact from these winds will be downed tree and tree limbs along with power lines and power outages and damage to carports, and siding. Near the coast of SE LA and MS winds may be strong enough to cause minor roof damage. All mobile homes in the hurricane warning area should be evacuated!

Rainfall:

Rainfall amounts are expected to average 8-12 inches near and to the right (east) of where the center crosses the coast or across SE LA and much of MS and AL. Isolated rainfall amounts of 15-20 inches will be possible over extreme E Louisiana into all of MS, AL, and the FL panhandle.

Tornadoes:

As always tornadoes will be possible in the feeder bands of any land falling tropical system. The best tornado potential is usually to the right of the center and can extend well inland and well away from the center. The tornado threat remains highest today across the FL peninsula in the SSE to NNW moving feeder bands and this threat will be shifting toward the MS, AL, and GA area over the next 24-48 hours. Tropical cyclone tornadoes are usually fast moving and brief.

Actions:

The time for action is now in the hurricane warning area…preparations to protect life and property should be rushed to completion and all preparations completed by noon Tuesday. Residents outside of hurricane protection levees and low lying areas and those under evacuation orders should evacuate immediately. Follow all recommendations and advice from local officials.

[DoctorMu]

Very cool interaction with the periphery of Isaac, a sizeable storm, helping to trigger a few local showers...heading southward towards CLL and Houston.

http://www.goes.noaa.gov/GSSLOOPS/ecwv.html

[DoctorMu]

rur roh. The Euro just went waaaaaaay West.

[msp]

rur roh. The Euro just went waaaaaaay West.

we've got a game to play in shreveport on thurs. bummer.

[DoctorMu]

GFS has this puppy hugging the coast west all the way to the TX line.

[msp]

GFS has this puppy hugging the coast west all the way to the TX line.

question is whether we can get anything more than gusty winds. 20% pops seems a bit low, but we are on the left side.

[DoctorMu]

Westward bound now

http://tinyurl.com/bwr7us2

[Srain]

Morning e-mail from Jeff:

Hurricane Isaac pounding SE LA and MS with storm surge, strong winds, and flooding rainfall.

Flash Flood Emergency for Plaquemines Parish (east bank). A levee on the E side of the MS River is being overtopped and water levels have rapidly risen to the rooftop of homes from Braithwaite to White Ditch.

Very strong winds currently affecting metro New Orleans with frequent gust to 70mph or greater.

Discussion:

Based on radar the center of hurricane Isaac is on the coast over extreme SE LA just SE of Houma near Terrebonne Bay and is moving WNW at maybe 4 mph…and this may be generous. With the center moving more parallel to the coast than inland, the hurricane has not weakened much overnight and is only expected to slowly weaken given the marshy flat land areas along the southern LA coast. A very slow WNW motion is expected today into tonight has high pressure over the central US builds north and then NE of Isaac blocking its northward motion and trapping the system in weak steering currents. After 36 hours, this high pressure cell should move far enough ESE to allow Isaac to turn toward the N and move toward NW LA and AR.

Based on this thinking Isaac will continue to pound the LA and MS coast for the next 24-30 hours with strong winds, heavy rains, and storm surge. Heavy flooding rainfall and strong winds will spread well inland along the track of Isaac and will begin to affect Baton Rouge later this morning.

Winds:

Some locations on the SE LA coast have now had sustained TS force winds for over 12 hours and another 12-16 hours of strong winds is likely. 300,000 SE LA residents are now without power and expect this will continue to rise as Isaac moves slowly inland. The constant battering of 60-80mph winds for hours and hours will result in somewhat greater damage than usual from a category 1 hurricane especially as the ground saturates allowing trees to up root and topple. 700am winds:

N.O. Airport: 44g67

N.O. Lakefront: 51g64

Slidell: 28g49

Boothville: 43g59

Belle Chase: 36g62

Baton Rouge: 41g58

Gulfport: 35g46

Houma: 39g62

Biloxi: 29g44

Bayou LaBranch: 46g63

Waveland, MS: 46g62

Storm Surge:

Forecasted storm surge values are verifying in the impact area currently.

Listed below are the 630am water levels:

Shell Beach: 10.16ft

Rigolets: 6.40 ft

West End: 5.40 ft

New Canal: 5.04 ft

NO Lakefront: 4.35 ft

Waveland, MS: 7.79ft

As winds turn toward the SE this morning on the east side of SE LA, the storm surge that has piled into Lake Borgne will begin to shift toward the north coast of Lake Borgne and SW MS. Additionally surge will be increasing on the W and N sides of Lake Pontchartrain. Large and dangerous battering waves will accompany the storm surge. Given the large size of the wind field, the storm surge will be slow to recede.

Rainfall:

Radar suggesting 5-7 inches of rain has fallen over SE LA overnight and with the very slow forward motion an additional 10-15 inches of rainfall can be expected. Some total could be as high as 20 inches along and to the right of where the center tracks. Significant potentially life threatening inland freshwater flooding is likely.

Local Impacts:

With the slight westward track overnight, this may bring TS force winds closer to the TX/LA border this afternoon. Expect winds to increase into the 15-25mph range east of I-45 this afternoon with gust to near 30mph. A few feeder bands may rotate westward and impact our area tonight into Thursday as Isaac moves slowly into SC Louisiana.

Current Wind Field:

[Ed Lizard]

12Z GFS impressive with the drier cooler airmass of the first real cold front of Autumn, but not super impressive with rain accompanying it...

[Srain]

Morning e-mail from Jeff:

Summer heat will make a stand this week with high pressure in control both aloft and at the surface. Upper ridge will build into the area from the NW producing subsidence across the region and eliminating any chance of rainfall. At the surface high pressure centered over the Gulf of Mexico will continue to pump in a humid southerly flow keeping dewpoints on the high side. Lack of significant cloud cover will allow afternoon temperatures to top out in the 97-102 range each afternoon this week. High dewpoints and surface RH will result in afternoon heat index values at or above 105. Only relief will be a slight SSW to SW surface flow in the 10-15mph range. No chance of rainfall is expected through Thursday.

Toward the end of the week into the weekend, the ridge over the western US amplifies allowing a deep trough for this time of year to develop across the eastern US. Cold air for early September standards will begin to move southward down the plains this week and a cold front will arrive into TX by Friday/Saturday. Upper pattern looks fairly favorable for the first cold frontal passage of the upcoming fall/winter season in the Saturday time period. Moisture does begin to pool along and ahead of this boundary late Friday into Saturday, but GFS guidance is not overly impressive on rain chances (30-40%). This is still several days away, and better dynamics and moisture may be found over the next few days to raise rain chances. Bigger news will be the much drier and yes “cooler” air mass that will move into the area. Not ready to go as cool as some of the guidance as it is still early and such fronts tend to look stronger in the extended range only to show up in a much weaker state. For now will go with the front pushing off the coast late Saturday or early Sunday with gusty NW winds in its wake. Low temperatures look to fall into the low to mid 60’s for Sunday morning into early next week with high temps in the lower 90’s, could see cooler highs in the 80’s if the thrust of the cooler air is more southward than SE.

TS Leslie:

Large tropical storm continues to sit and spin over the open Atlantic waters north of the Leeward Islands. Leslie has been undergoing NW shear for the past 3 days which has continued to remove the thunderstorm activity to the south of the center of circulation. Leslie is also caught in a region of very weak steering with a trough bypassing her to the NNE and high pressure building down from the E coast of the US over the top of the system blocking any northward motion. In fact there is likely to be little motion over the next 3-4 days until the central/E US trough that drives the cold front into TX this weekend begins to affect the system by Day 5. At that time Leslie should begin to move at a slightly faster speed to the NNW or NW ahead of this approaching trough. The large wind field and slow storm motion will produce increasing swells along the entire US east coast over the next 5-7 days.

[Ed Lizard]

Sure, the climatological window (except we'll always have October 1949) starting to close, but Euro holds out slim hope tropical season 2012 hasn't quite passed Texas by yet...

[Srain]

Morning e-mail from Jeff:

Tropics remain very active with another tropical storm forming over the Atlantic Ocean.

Leslie:

TS Leslie remains a sheared system with WNW to NW wind shear affecting the circulation as it remains nearly stationary 490 miles SSE of Bermuda. Leslie is trapped in a region of weak steering as high pressure builds to the north of the system for the next 48 hours. After that the high pressure will shift eastward and a trough will approach the US east coast, with Leslie turning northward and increasing in forward speed. On this track the system will pass near Bermuda as a large hurricane. Conditions looks favorable for intensification as the ongoing shear weakens allowing thunderstorms to develop near the center. The current NHC forecast makes Leslie a 75mph hurricane in 36 hours and a 105mph hurricane in 120 hours.

Michael:

New tropical storm forms over the far eastern Atlantic 1190 miles WSW of the Azores Islands. This tiny tropical storm has shown a mass of deep convection to the NE of the low level center suggesting SW wind shear is affecting the system. Condition should gradually become more favorable for development as the shear relaxes and Michael is forecast to become a hurricane in about 3 days as it drifts toward the NNW and then NW on the south side of high pressure passing to its north. Michael is currently no threat to land.

90L:

An area of surface low pressure is currently moving off the coast of the FL panhandle and AL this morning with a large area of showers and thunderstorms noted over the northern Gulf of Mexico from south of Pensacola to just east of New Orleans. A weak, ill defined circulation is noted in coastal radar images south of Pensacola and Mobile. While one could possibly trace this system back to the remains of Isaac, the official word from NHC is that if development does occur it will be a name (Nadine) as the surface low associated with Isaac appears to have dissipated over KY yesterday. This system is drifting toward the S or SSW at 5-10mph and will be over very warm waters and under light shear for the next 36-48 hours. Some development is possible over the next 48 hours and NHC gives the system a 20% chance of developing into a tropical cyclone. While the area will drift southward, steering currents are very weak as the system is located between building high pressure over TX and a trough along the US east coast. By late Friday into this weekend building of the ridge across the western US will favor a deep and strong downstream trough over the E US and this will swing anything that develops over the NC Gulf toward the NE or ENE toward the west coast of FL. There is marginal model support for this system.

[wxmx]

90L has been forecasted to move a little farther SSW before being picked by the longwave trough in 3-4 days. Synoptic setup is such, that a stronger/deeper system than forecasted could eventually turn towards MX or TX as the ridge that is currently expanding over TX is stronger with height. 12z GFS even decouples the mid and low level vortices, with the former going SW, while the latter gets picked up by the trough.

Edit: Actually the low level vortex gets left behind, since the trough doesn't dig as deep...but it's still in the westerlies flow.

[Srain]

Morning e-mail from Jeff:

High pressure remains in control of the weather over the state.

High pressure aloft to the WNW of the area and at the surface over the central Gulf of Mexico is resulting in very warm conditions. Afternoon high temperatures have been topping out in the upper 90’s to low 100’s and this will continue for today and Friday. Cold front is still slated to cross the area on Saturday as the western US ridge amplifies and deepens the trough over the eastern US. The front with a significantly drier air mass will cross the area from Saturday morning through early evening. Moisture profiles increase ahead of the boundary, but model trends over the past 24-26 hours have been for less and less rainfall potential. This potential seems even more reasonable if a tropical system forms in the central Gulf of Mexico over the next 48 hours producing northerly flow ahead of the boundary. Still think there may be a think band of showers or an isolated thunderstorm along the front Saturday afternoon, but chances of widespread wetting rains is decreasing.

Front will be of the coast Sunday morning with a much drier air mass in place. Dewpoints should fall well into the 50’s at most locations giving the area its first reprieve from the summer humidity. High temperatures on Sunday will be 10-12 degrees cooler than Friday (the upper 80’s) and lows on Monday morning under clear skies and calm winds will fall into the low 60’s and upper 50’s. SE winds begin to return moisture to the area by Tuesday of next week with a gradual warming and moistening trend.

Fire Weather:

Lack of widespread rainfall over the past several weeks and intense heat has allowed vegetation to dry. Incoming frontal boundary this weekend will spread gusty winds and a drier air mass over the region. KBDI values range from 500-750 across many of the SE TX counties suggesting fire weather conditions could be near critical under the right weather conditions. For now it does not appear that wind speeds will reach Red Flag criteria on Saturday or Sunday and the onset of the drier air mass does not happen until after the stronger post frontal winds decrease. With that said, wildfire danger will be elevated from Saturday-early next week.

90L:

Weak low pressure is located over the northern Gulf of Mexico south of the AL/MS coast this morning. Numerous thunderstorms have develop well to the S and SW of this feature over the north-central Gulf of Mexico. This system is along the far SE edge of the ridge of high pressure over W TX which is producing a degree of N/NE wind shear across the system and preventing much development. Global models are in some agreement that the system may attempt to develop into a tropical cyclone as it moves southward and then ENE or NE this weekend ahead of the incoming frontal boundary across the western Gulf of Mexico. At this time, this system poses no threat to the TX coast.

[Srain]

The pre frontal trough should sweep through most of the area in the early morning hour of Saturday. It appears the actual front will lag behind by about 6-8 hours. Increasing northerly winds and drier air should be the theme for the weekend and a few spots could see some lows in the low 60’s Monday morning. The front will not linger, so enjoy the weekend.

Looking ahead to later next week, the GFS and Euro are very suggestive of deep tropical moisture pooling across the Western Gulf as a return flow from the Gulf becomes re established. If guidance is correct, rain chances could increase by next Friday as an inverted trough/weakness develops across the Southern half of the Lone Star State and may well bring some badly needed rainfall to the area once again.

[Ed Lizard]

^^

Euro AccuWx PPV indeed also has front retreat with moisture heading back into Texas mid and late week. Best rain along the coast and offshore. It'd be worth watching even though it is starting to get late in the tropics game for the NW Gulf, but then the most massive trough of the young Fall season blasts through to the North of us. Cold front with that trough not as impressive as the trough (with a cutoff developing by Day 10), 850 mb temps don't seem to get any cooler (a shade below 15ºC) than with the next front.

GFS ensembles seem to support a deep trough centered East of here day 10, or Northwest flow aloft. GFS 500 mb Spaghetti isn't too messy on day 10, but gets completely deranged after. Perhaps the sign of a pattern shift.

[patrick7032]

The pre frontal trough should sweep through most of the area in the early morning hour of Saturday. It appears the actual front will lag behind by about 6-8 hours. Increasing northerly winds and drier air should be the theme for the weekend and a few spots could see some lows in the low 60’s Monday morning. The front will not linger, so enjoy the weekend.

Looking ahead to later next week, the GFS and Euro are very suggestive of deep tropical moisture pooling across the Western Gulf as a return flow from the Gulf becomes re established. If guidance is correct, rain chances could increase by next Friday as an inverted trough/weakness develops across the Southern half of the Lone Star State and may well bring some badly needed rainfall to the area once again.

Yeah I totally agree with you and hope the models don't change. There's a nice theata surge ahead of the front....and like you said we need the rain. Some communities in my CWA have less than 180 days of water left....with the community of Lawn having less than 45 days from what they said. Another nice thing to see on the long long range models is the southern jet stream getting more active over the state. We mentioned the same thing regarding later next week and mentioned it in our AFD. Below are a few pictures from the area and long range forecast.

000

FXUS64 KSJT 092102

AFDSJT

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SAN ANGELO TX

402 PM CDT SUN SEP 9 2012

.LONG TERM...

GFS AND EC MODELS CONSISTENTLY INDICATING WIDESPREAD SHOWERS AND

THUNDERSTORMS THURSDAY INTO FRIDAY. COLD FRONT IN 12Z GFS MODEL

MOVES IN SLIGHTLY EARLIER...THURSDAY AFTERNOON IN THE BIG COUNTRY

AND CONCHO VALLEY. FRONTAL TIMING ON THE EC MODEL IS SLOWER...

MOVING IN THURSDAY NIGHT. LOCALLY HEAVY RAINFALL AMOUNTS OF 1 INCH

PLUS STILL INDICATED. CROCKETT COUNTY AND WESTERN SECTIONS OF THE

CONCHO VALLEY MAY SOME OF THE HEAVIER AMOUNTS WITH A STRONGER 30

KT 850 MB LLJ OVER THE FRONT THURSDAY NIGHT. THERE ARE NEGATIVES

FOR HEAVIER RAINFALL HOWEVER...MODELS HAVE A BIAS FOR BRINGING IN

MOISTURE LOW LEVEL MOISTURE TOO QUICKLY... ESPECIALLY WHEN

CONDITIONS HAVE BEEN DRY IN SOUTH TEXAS. ALSO MAY SEE DRIER AIR

ADVECT IN FROM THE MID LEVELS WEST OF THE 500 MB TROUGH.

HOWEVER...WITH CONSISTENCY BETWEEN THE MODELS AND MODEL

RUNS...INCREASED POPS TO 30 PERCENT THURSDAY NIGHT.

THE EC MODEL SPINS OFF A CUTOFF UPPER LOW IN THE PANHANDLE FRIDAY

NIGHT WHICH PROGRESSES SLOWLY EAST ACROSS OKLAHOMA NEXT WEEKEND.

THIS IS SUPPORTED BY 2 MEMBERS OF THE GFS ENSEMBLE. WILL NOT ADD

RAIN CHANCES IN FOR SATURDAY OR SUNDAY AT THIS TIME...BUT BEARS

WATCHING. THE GFS MODEL IS DRY THIS WEEKEND WITH THE UPPER TROUGH

TO THE EAST AND DRY NORTHWEST FLOW FOR WEST CENTRAL TEXAS.

OTHERWISE DRY FOR TUESDAY INTO WEDNESDAY THIS WEEK...WITH UPPER

RIDGING. LOW LEVEL MOISTURE RETURNS WEDNESDAY.

04

&&

.PRELIMINARY POINT TEMPS/POPS...

ABILENE 57 92 61 93 66 / 0 0 0 0 0

SAN ANGELO 56 93 59 95 66 / 0 0 0 0 0

JUNCTION 54 93 58 94 65 / 0 0 0 0 0

&&

.SJT WATCHES/WARNINGS/ADVISORIES...

NONE.

&&

$$

04

[Srain]

Morning e-mail from Jeff:

A refreshing change to the local weather this weekend as a cold front moved across the area Saturday.

Cool and dry morning in progress with lows into the upper 50’s and 60’s across the area under calm winds. Surface high responsible for the break in the late summer heat will be shifting eastward allowing onshore (ESE) winds to return by late Tuesday. Deep tropical moisture is lurking over the southern Gulf of Mexico and will make a return to the area starting on Wednesday. Noticeable change will be the increase in humidity and cloud cover followed by increasing rain chances. GFS 00Z run from yesterday evening has come in wetter in the Thurs-Fri time period with rain chances in the solid 40-50% range.

Another upper air trough and cold front will swing toward the area this next weekend, but the push behind this feature looks weaker than the one that just passes on Saturday. Still with tropical moisture in place, showers and thunderstorms should continue along and ahead of the slowing boundary into at least the first half of the weekend. While moisture and humidity will be returning by mid week, high temperatures do not warm much with lowered mid level heights and increasing cloud cover. We might just be done with the really oppressive heat of the summer…highs near 100.

[Srain]

The 12Z suite of guidance still suggests some differences, but rain chances still look like a good bet beginning Wednesday and increasing into Friday. The GFS is the most aggressive with bringing a weak frontal boundary through SE Texas and stalling it offshore and remains rather wet. The Euro is still much slower with that boundary and virtually stalls it on top of SE Texas and keeps rain chances going throughout the coming weekend. The differences appear to be just how strong the short wave diving S from the Northern Plains will be as well as any meso features that cannot be determined at this range. What is interesting is the GFS suggests a rather wet pattern becoming established that may last until the end of September. We’ll see how all this shakes out over the next couple of days as the GFS Ensembles are rather suggestive of a general 1-2 inch rainfall with some potential for isolated higher amounts closer to the Coast. It is also noteworthy that the GFS and the Euro both agree that some areas of the Lone Star State that have been rather dry will have a fairly good chance of receiving some very beneficial rains.

[DoctorMu]

POPS have increased up to 40% Wed-early Friday with the arrival of the front. GFS has a lot of Gulf moisture stacked up for its arrival

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX

329 PM CDT MON SEP 10 2012

.DISCUSSION...

TONIGHT SHOULD BE ONE OF THE LAST COOL NIGHTS FOR THE NEXT FEW

DAYS ACROSS SE TX. MIN TEMPS SHOULD DROP INTO THE LOW/MID 60S. SFC

HIGH PRESSURE OVER THE MIDWEST EXTENDING INTO TX SHOULD MOVE

TOWARDS THE MID ATLANTIC TONIGHT INTO TUE MORNING. THIS SHOULD

TURN WINDS MORE TO THE E AND SE BUT STILL SHOULD BE RATHER LIGHT

WITH GENERALLY PARTLY CLOUDY SKIES.

MOISTURE RETURN SHOULD SET UP TOMORROW BUT BE FAIRLY WEAK. MODELS

HAVE BEEN FAIRLY CONSISTENT WITH BRINGING BETTER MOISTURE INTO THE

COASTAL AREAS WED AND THEN INTO SE TX THU/FRI. THERE IS SOME

QUESTION AS TO THE QUALITY OF MOISTURE SINCE THE NAM ONLY HAS

ABOUT 1.5 INCHES OF PRECIP WATER WHERE THE GFS BRINGS CLOSER TO 2

INCHES OF PW INTO THE UPPER TX COAST BY THU MORNING. FORECAST WILL

STICK CLOSER TO THE GFS AND GO WITH 30/40 POPS THUR. THINK THERE

SHOULD BE PLENTY OF MOISTURE FOR SCT SHOWERS AND THUNDERSTORMS.

EXTENDED FORECAST STILL IS A BIT MUDDLED BUT MAY BE COMING MORE

IN LINE. MODELS STILL HAVING SOME ISSUES WITH THE UPPER LOW OVER

CANADA AND MOVING IT EAST. BY FRI MORNING ALL 3 OF THE

GFS/ECMWF/CANADIAN BRING AN UPPER LOW INTO IOWA ALL WITH ABOUT THE

SAME AMPLITUDE. GFS/ECMWF BOTH SLOWLY BRING THE UPPER LOW EAST

INTO THE GREAT LAKES SAT/SUN. CANADIAN STILL SLOWER. THERE SHOULD

BE ENOUGH UPPER LEVEL SUPPORT FOR THE COLD FRONT TO PUSH INTO THE

AREA. GFS PUSHES IT THROUGH AND OFF THE COAST SATURDAY BUT

POSSIBLE FOR IT TO HANG UP ALONG THE COAST. HIGHER RAIN CHANCES

ARE IN THE FORECAST FOR FRI WITH 40 POPS BUT KEEP SOME 20/30 POPS

ALONG THE COAST FOR THE WEEKEND. WEEKEND FORECAST STILL RATHER

UNCERTAIN GIVEN THAT THE FRONT WILL LIKELY BE IN THE AREA AND

COULD BE THE FOCUS FOR RAIN CHANCES UNTIL IT DISSIPATES.

[Srain]

There still remain some differences between the overnight guidance, but the trend is looking a bit more favorable for rain chance increasing Thursday and extending into the weekend. The GFS and Euro are in some what better agreement regarding the potent short wave and mid latitude trough diving SSE into the Eastern US on Friday. A strong 500mb upper low develops over the Ohio Valley and the attending ‘cold front’ drops S into the Lone Star State. The potent short wave drops S into Texas and slowly meanders E providing lift in an unstable air mass with increasing moisture as the Gulf opens with a return flow. The fly in the ointment will be just where this boundary stalls. Another new wrinkle is a potential surface low developing in the Western Gulf that the Canadian, and to a weaker extent, the Euro are ‘sniffing’. The GFS does not show this feature, but does suggest lowering pressures in the Gulf, so that bears watching as well. All in all it does appear that some beneficial rains are ahead and we’ll need to monitor for any potential development in the Gulf. Stalled boundaries and lowering pressures in the Gulf always raise an eyebrow or two when we enter the month of September.

[Srain]

Morning e-mail from Jeff...he must have been reading my mind...

Nice and dry weather of late will be ending over the next 24 hours as Gulf moisture returns.

Stalled frontal boundary over the Gulf of Mexico is washing out and dissipating this morning as surface high pressure moves to the eastern US. This will allow ESE to SE winds to begin to return deep tropical moisture to the region starting late today and in earnest on Wednesday. Not sure how quickly the air mass will modify, but suspect dewpoints will rebound into the lower 70’s south of I-10 on Wednesday and showers/thunderstorms may affect the coastal counties by Wednesday afternoon.

Moisture begins to surge northward on Thursday as a trough deepens over the high plains. Expect scattered showers/thunderstorms as deep SSE wind flow pumps moisture into the region. Friday appears to be the wettest day with deep moisture in place and increasingly large scale lift from an approaching cold front. Front does not look to plow through the area like the last front, but slow and possibly stall either along the coast or offshore. Rain chances will continue into the weekend (especially Saturday) with the boundary in the area.

CMC and ECMWF try and develop a broad surface low over the central/western Gulf of Mexico late this weekend/early next week. This low could help drive the front further offshore. CMC drifts the low over the western Gulf while the ECMWF has the feature caught up in the trough and pulled toward Louisiana. GFS does not show this feature as much and is not nearly as well defined as the CMC and ECMWF.

With deep tropical moisture returning, scattered rainfall amounts of 1-2 inches will be possible Thursday-Saturday. Would not be surprised to see a few higher totals (3-5 inches) under areas of more organized convection. Dry spell of late with high KBDI values suggest this rainfall should be easily handled.

[Ed Lizard]

Little enthusiasm for anything tropical-ish in NW Gulf as long as GFS, which has been the model of choice, doesn't start to see it.

But, who needs the stinking tropics?

[DoctorMu]

GFS and GGEM getting in on the action as well. I accidentally left the sprinklers on last night (oops!), so we're due for a drenching!

[Srain]

The overnight guidance continues to paint a wet picture for our area and most of Lone Star State. The HPC 5 Day QPF Forecast has increased the rainfall potential to a general 1-2 inch rainfall with isolated higher amounts nearing the 4 inch mark for a lucky few. Those totals may be a bit too low as the frontal boundary stalls along Coastal Texas and a surface wave of low pressure develops and rides the boundary ENE. Again, the fly in the ointment will be just where that boundary actually stalls as the guidance has been flip flopping with the upper air disturbance developing across Texas and just how quickly or slowly it translates E.

Another interesting turn of events is a tropical system that some of the models have been ‘sniffing’ developing in the Bay of Campeche early next week. The GFS finally latched on to that idea overnight and brings that disturbance N to near the SE Texas/SW Louisiana Coast as the boundary washes out and yet another perhaps stronger cold front dive S into the area and finally picks up that disturbance and clears us out. There are also hints of yet another area of disturbed weather developing in the Western Caribbean later next week that begins to lift NW further complicating things. All in all it truly appears we are entering a more active period and showers/storms chances will become the theme and an active flow that we tend to expect in late September with fronts progressing S and plentiful tropical moisture available. We will see.