August 2014 - Showers/Storms Possible To End The Month

[srainhoutx]

Update from Jeff regarding the increasing rain chances...


Pattern change in store for the region as early as late Monday.

 

Vertically stacked high pressure ridge over the middle MS Valley will be moving slightly eastward allowing a tropical wave/upper level trough over the NE Gulf of Mexico/FL to move westward along the US Gulf coast and landfall along the TX coast Tuesday. Water vapor and visible images show the upper trough over the NE Gulf starting to progress westward. On its SW flank a ball of deep convection has developed today over the NC Gulf of Mexico…but appears to be weakening early this evening.

 

Forecast models bring the entire system and its associated deep tropical moisture (PWS greater than 2.0 inches) into the area late Monday evening. Short range meso models show thunderstorms blowing up over SC LA Monday afternoon and tracking WSW into E TX during the late afternoon hours as large scale lift and moisture increase from the east and upper level ridging breaks down. Not sure how far west these storms will make it as they will be fighting drier air over most of SE TX still in place on Monday.

 

The upper level trough weakens into an inverted trough axis or shear axis along the TX coast on Tuesday. Forecast models are quite aggressive in pegging a fairly significant convective event over the nearshore waters Tuesday possibly spreading inland to the first tier coastal counties. Such patterns with high PWS air masses tend to focus heavy rainfall near the coast/offshore in the early morning hours and this may be what the models are attempting to resolve.

 

Feel the best rain chances will be from late Monday-Wednesday mainly south of I-10 where potentially waves of rainfall will advance inland from the Gulf. Drier air mass and more ridging may limit the northward extent of the showers and thunderstorms across the northern portions of the region. Rainfall amounts of 1-2 inches appears possible along the coast with lesser amounts north of I-10. Rainfall gradient looks fairly impressive with much more significant accumulations possible over the Gulf waters off the TX coast. Given the incoming tropical air mass and PWS pushing over 2.0 inches high hourly rainfall rates will become more common from Tuesday onward.

 

For what it is worth as couple short range models and the NAM have off and on been trying to develop a surface reflection along the backside of the inverted trough axis over the central or western Gulf. The convective “bombs” being shown in the meso guidance suggest there will be some significant thunderstorm activity offshore over the NW Gulf which could result in some lowering of the surface pressure or the formation of a weak low pressure center. There is currently very little support for anything tropical to develop with this feature, but extensive convection over the warm Gulf waters in late August does bear watching at the least.

 

By late in the week a slow moving upper level trough will approach TX from the WNW. This will keep an onshore highly moist flow in place and help aid in preventing upper level ridging from returning. Rain chances look to remain in the forecast for the next several days with potentially higher chances again from Friday into next weekend as the upper trough over W TX slowly moves eastward.

[Ptarmigan]

Nice to see more rain coming back for a change.

[Ptarmigan]

Levi Cowan of Tropical Tidbits think something could brew in the Gulf of Mexico. The same system that is forecasted to give us rain this week.
https://twitter.com/TropicalTidbits

Levi Cowan @TropicalTidbits · 5h
The back-door front bringing me rain right now needs to be watched next 3 days in GOM, despite no model support (yet)



Levi Cowan @TropicalTidbits · 4h

HWRF parent domain for Cristobal illustrates how something could get going in the gulf. Never trust a front in August

[srainhoutx]

Early morning water vapor imagery suggests the inverted trough/shear axis currently along and S of the Central Gulf Coast should edge closer to SE Texas/SW Louisiana bringing tap idly increasing PW's of 2+ inches across the Upper Texas Coast later today. Showers and storms should begin to increase this afternoon across Coastal SW Louisiana and spread W this evening. PW's increase tomorrow and may near the 2.5 Inch mark. These higher PW's will likely increase storm chances across the Coastal waters and along the Coastal tier of Counties S of I-10. The Euro as well as the short range high resolution guidance suggest things may dry out a bit on Weednesday.

As we near the long Labor Day Holiday Weekend, showers/storms increase area wide as a trough edges closer with a weak frontal boundary. The inverted trough across the Coastal waters in tandem with the slow sagging boundary look to increase rain chances Thursday into Sunday. It is almost September and perhaps someone would like to start a new Ttopic as we begin the march toward Fall and possibly more rain chances from the N as well as the Western Caribbean and Gulf...

[Portastorm]

FWIW, JB is tweeting this morning that from midweek on, the place to watch in the tropics will be the NW Gulf. Said piece of Cristobal moved into gulf and that'll be a part of what to watch.

[srainhoutx]

FWIW, JB is tweeting this morning that from midweek on, the place to watch in the tropics will be the NW Gulf. Said piece of Cristobal moved into gulf and that'll be a part of what to watch.

The 06Z GFS is 'sniffing' an area of potential weak low pressure near the Lower/Middle Texas Coast and as we know, our Gulf Coast waters are very warm and favorable for developing a disturbance IF storms persists for any length of time beyond 24 hours. The NW Caribbean and Gulf are certainly conducive for tropical mischief over the next 15 or so days.

[tireman4]

From Dr. Masters blog:

Keeping an eye on the Gulf of Mexico
In the Gulf of Mexico, a weak cold front is kicking up some heavy thunderstorms in the Louisiana coastal waters. This activity will spread to the Texas coastal waters by Wednesday. With wind shear a moderate 10 - 20 knots, we should monitor this area for development. About 1/3 of the 20 members of the 06Z Monday GFS model ensemble showed some development in the Gulf on Thursday or Friday. (The GFS ensemble is a set of 20 runs of the GFS model done at lower resolution with slightly different initial conditions to generate an uncertainty "plume" of model runs.) The preferred track of the system was to the west towards Texas.

[srainhoutx]

Pressures are not as high as what we witnessed back in August of 1983 when Alicia formed from a Mesoscale Convective Complex that dropped S from Mississippi/Alabama into the Central Gulf. Some of the higher resolution rapid refresh models are also 'sniffing' they potential for a weak surface low to develop as it gets a bit closer to the Texas Coast Wednesday into Thursday. That said winds offshore from the various buoy sites suggest a general WNW to NW flow at the surface across the Western Gulf with and NE to ENE surface flow across Coastal SE Louisiana back to the Panhandle of Florida. The front that dropped S across the Eastern US has pulled up stationary near the mouth of the Mississippi River. A surface trough or wave of low pressure is forecast to develop tomorrow S of Louisiana. Typically the global guidance do not handle these feature very well, so if convection continues...all eyes will turn to the Gulf.

[srainhoutx]

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1224 PM EDT MON AUG 25 2014

VALID AUG 25/1200 UTC THRU AUG 29/0000 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...


12Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.

WEAK CYCLONE MOVING THROUGH THE GULF OF MEXICO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: UKMET/ECMWF COMPROMISE
CONFIDENCE: ABOVE AVERAGE

MOST OF THE GUIDANCE TRACKS A WEAK LOW OFF THE TAIL END OF A
FRONTAL BOUNDARY ACROSS THE GULF OF MEXICO TO THE EAST SIDE OF A
WEAK UPPER LEVEL LOW, WITH THE 00Z CANADIAN PRODUCING TWO FOR THE
PRICE OF ONE -- ITS USUAL SPECIAL WITH POSSIBLE
TROPICAL/CONVECTIVE LOWS. SINCE THE NATIONAL HURRICANE CENTER IS
NOT DISCUSSING THIS SYSTEM, PREFER TO DOWNPLAY ITS PREFERENCE. A
COMPROMISE OF THE 00Z UKMET/00Z ECMWF IS PREFERRED HERE WITH ABOVE
AVERAGE CONFIDENCE CONSIDERING CANADIAN/NAM STRENGTH BIASES ALOFT.

[JamieP]

Is it just me, or does anyone else see a small circulation forming just south of Alabama in that last frame?

http://www.ssd.noaa.gov/goes/east/gmex/flash-vis.html

[Rip76]

Sort of looks like some outflow to me.

A few more frames and you may be able to tell.

[unome]

from the 2pm discussion http://www.nhc.noaa.gov/text/refresh/MI ... WDAT.shtml?

GULF OF MEXICO...
AN UPPER RIDGE COVERS THE NE GULF AND SE CONUS WITH THE WEAK
SURFACE RIDGE BRIDGING A STATIONARY FRONT THAT EXTENDS FROM THE
W ATLC ACROSS CENTRAL FLORIDA JUST S OF TAMPA BAY ALONG 28N88W
TO THE COAST OF LOUISIANA NEAR GRAND ISLE. SCATTERED SHOWERS/
THUNDERSTORMS W ACROSS THE N GULF N OF 26N BETWEEN 84W-92W. AN
INVERTED UPPER TROUGH EXTENDS FROM NEAR VERACRUZ MEXICO ALONG
26N91W TO 29N87W. THE DIFFLUENT FLOW ALOFT BETWEEN THESE UPPER
FEATURES IS ENHANCING THE THE ACTIVITY ASSOCIATED THE FRONT
ABOVE. A SECOND UPPER RIDGE IS ANCHORED OVER THE FAR SE GULF
NEAR 23N83W AND EXTENDS S OVER THE W CARIBBEAN. THE FRONT WILL
GRADUALLY DISSIPATE AS IT MOVES S TO A POSITION FROM THE STRAITS
OF FLORIDA TO NEAR BROWNSVILLE TEXAS BY TUE. THE REMNANT TROUGH
WILL THEN PERSIST IN THIS GENERAL LOCATION THROUGH WED.

[srainhoutx]

The 12Z Euro suggests a mid/upper level low with perhaps a bit of surface wave nearing the Lower Texas Coast Thursday into Friday. That bodes well for increased rain chances...

[Rip76]

Just curious.
Most of these early speculative models are showing mostly Southern Texas.

Is there an area of high pressure that just won't allow these clouds/disturbance to move due west?

[srainhoutx]

Afternoon Update from Jeff:

Today will be the last in the strong of very warm days before changes arrive starting tonight.

Upper level low pressure trough extending from the SE US across the Gulf of Mexico toward NE MX is moving westward. Convection has increased today in relation with this feature along and offshore of the Louisiana coast. At this time there is no indication of any low level surface low pressure and convection is poorly organized. This feature will move westward and onshore of the TX coast late tonight into early Tuesday. Forecast models have been suggesting thunderstorms may approach the area later this evening from the east (possibly the activity along the C LA coast now). Additionally these models have been showing development of convection over the NW Gulf tonight into early Tuesday in association with favorable large scale ascent working with a tropical air mass. This tropical air mass will spread inland early Tuesday with PWS increasing from near 1.25 in to over 2.0 in Tuesday morning. I am a little concerned that offshore thunderstorms could “rob” inland moving moisture and focus the heavy rainfall offshore…this tends to happen with these kinds of setups.

The trough axis will then lay across the TX coast Wed-Fri with onshore flow and copious moisture influx into the region. The area seems at least primed for good thunderstorm chances especially south of I-10 during this period with coastal morning development spreading inland during the day.

Tropical Development:
A couple of the forecast models…most notably the NAM and the CMC attempt to try and close off a surface reflection on the east side of the trough axis at varying periods this week. There is also some recent support from the UKMET model which shows a 1007mb closed low east of Brownsville late this week. There has been very little support on tropical development from the most reliable models the GFS and ECMWF. Convection thus far has been unorganized and as mentioned earlier there is no indication that surface pressures are falling at offshore platforms off the Louisiana coast or across the central Gulf where some of the models show surface low pressure development. Something to keep an eye on this time of year as things can change fairly quickly over the warm Gulf waters.

Coastal Tides:
Long fetch ESE winds will be building a SE swell against the TX coast this week. ET surge guidance suggest some total water level rise of .50 to 1.0 ft by mid to late week as swells begins to pile more water onto the coast at both Galveston and Sabine Pass which are a favorable run-up locations with ESE wind flow due to Ekman transport of water to the right of the mean wind. Currently not looking at any concerns at times of high tides…but something to keep an eye on as the week progresses.

Extended:
Pattern remains unsettled both over the Gulf and TX through next weekend into next week with an approaching and slow moving upper level trough from the western US interacting with deep tropical moisture in place….so rain chances will stay elevated through much of the short and long term period.   

[djmike]

It does look like rotation in this system south of LA. Looks like a mini hurricane. I know it's mid-upper level L but we know all too well how quick these home brew storms can spin up. With or without model support. Something to keep an eye on. If anything, I could use this rain.

[BlueJay]

We could use the rain also!

I have a question: KHOU reports that the current temperature in Houston is 100F. Is this an official temperature? And, if so, is this the first 100F of the year?

[Texaspirate11]

We could use the rain also!

I have a question: KHOU reports that the current temperature in Houston is 100F. Is this an official temperature? And, if so, is this the first 100F of the year?

Bluejay - I don't believe we have achieved the 100 degree mark today although indices were 104-107

Here is something from our Hou/Gx NWS

Back in 2011, August 25th was the only day of the month with temperatures failing to reach 100 degrees at both Houston and College Station.

During the brutal summer of 2011, College Station endured 26 consecutive days with 100 degree heat and 36 out of 37 days with 100 degree heat. All told, College Station recorded 69 days with temperatures at or exceeding 100 degrees. The official forecast is calling for a high of 100 degrees today. If the temperature does not reach 100 degrees today, it probably won't reach it this year. The last time College Station went a year without 100 degree heat was in 2004.

Houston has also failed to reach 100 degrees this year. The last time Houston went a year without 100 degree temperatures was back in 1997. Back in 2011, Houston recorded 46 days with 100 degree heat including 24 consecutive days in August.

[BlueJay]

That is amazing! Great info! Thanks so much Texaspirate11!

[djmike]

Wow, 51mph wind gust with these storms rolling into the Golden Triangle area. Many areas already approaching 2". Looks to be weakening though. Hope you guys in Houston will be able to cash in on some of this action. Hopefully the 51mph winds here wasn't a pre-curser of things to come with this developing L in the gulf. We shall see. (By the way, we should see about adding on some weather related emoji's. THAT would be fun. Just a thought. lol)

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LAKE CHARLES LA
646 PM CDT MON AUG 25 2014

LAZ073-TXZ201-215-216-261-260100-
HARDIN TX-JEFFERSON TX-ORANGE TX-SOUTHERN JASPER TX-WEST CAMERON LA-
646 PM CDT MON AUG 25 2014

...SIGNIFICANT WEATHER ADVISORY FOR CAMERON PARISH...SIGNIFICANT
WEATHER ADVISORY FOR HARDIN...JEFFERSON...ORANGE AND JASPER COUNTIES
UNTIL 800 PM CDT...

AT 644 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
LINE OF STRONG THUNDERSTORMS FROM 5 MILES NORTHEAST OF EVADALE TO 9
MILES SOUTHEAST OF SABINE PASS...MOVING SOUTHWEST AT 20 MPH.

* THE LINE OF STRONG THUNDERSTORMS WILL BE NEAR...
PINE FOREST BY 655 PM...
ROSE CITY BY 700 PM...
NEDERLAND BY 705 PM...
WEISS BLUFF...SOUTHEAST TEXAS REGIONAL AIRPORT...PORT ACRES AND
CENTRAL GARDENS BY 710 PM...
LAKEVIEW BY 715 PM...
BEAUMONT BY 720 PM...

THE PRIMARY THREATS FROM THESE STORMS ARE FREQUENT LIGHTNING AND WIND
GUSTS TO NEAR 40 MPH...WHICH COULD DOWN TREE LIMBS AND BLOW AROUND
UNSECURED SMALL OBJECTS. SEEK SHELTER IN A SAFE HOME OR BUILDING
UNTIL THESE STORMS HAVE PASSED.

THESE STORMS COULD PRODUCE RAINFALL AMOUNTS OF ONE TO TWO INCHES IN A
SHORT PERIOD OF TIME...RESULTING IN PONDING OF WATER AROUND LOW LYING
ROADWAYS. REMEMBER...DO NOT DRIVE YOUR VEHICLE INTO WATER COVERED
ROADWAYS. THE DEPTH MAY BE TOO GREAT TO ALLOW A SAFE CROSSING.