Don closing in on Texas; 91L a potential threat to the Lesser Antilles

By: Dr. Jeff Masters , 3:22 PM GMT on July 29, 2011

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Tropical storm warnings are flying along the coast of Texas from Brownsville to Matagorda as Tropical Storm Don closes in on the Texas coast. Don remains a disorganized, moderate strength tropical storm, and appears unlikely to cause major damage or bring much-needed drought-busting rains to Texas. A hurricane hunter plane is in Don, and found highest surface winds of 55 mph at 11:06am EDT. Don continues to have trouble with moderate wind shear of 10 - 20 knots, which is injecting dry air to the northwest into the storm. Water vapor satellite images show this region of dry air to the northwest of Don. Visible satellite imagery from this morning shows little change to Don so far today, with most of the heavy thunderstorms on Don's south side, and the cloud pattern elongated, the sign of a storm struggling with wind shear. Radar out of Brownsville, Texas shows the main rain areas are on the south of Don's center, and bands of heavy rain are now very close to the Texas/Mexico border.


Figure 1. Morning image of Tropical Storm Don from the Brownsville, Texas radar.


Figure 2. The latest drought map for Texas shows that over 75% of the state is in exceptional drought--the highest category of drought. Image credit: U.S. Drought Monitor.

Forecast for Don
The wind shear and dry air affecting Don will continue until landfall, and it is unlikely Don will intensify to more than a 60 mph tropical storm. With most of the heavy thunderstorms displaced to the south side of the storm, Mexico will be the primary beneficiary of Don's expected rains of 3 - 5 inches. South Texas will see modest rains of 1 - 2 inches over a few isolated areas, but Don is going to do very little to bring drought relief to the state. Most of Don's rains in Texas will be concentrated in the extreme southern portion of the state near Brownsville. This portion of Texas is experiencing only moderate drought, and the extreme to exceptional drought areas of the state will miss the bulk of Don's rains.

For those of you wondering about your odds of experiencing tropical storm force winds, I recommend NHC's wind probability forecast. The 11 am version of this forecast shows that Corpus Christi Texas has the highest chance of tropical storm-force winds (39+ mph): 48%. The primary threat from Don will be heavy rain, which will caused localized flooding problems. An isolated tornado is also a possible concern.


Figure 3. Morning satellite image of 91L.

African wave 91L a potential threat to the Lesser Antilles
A well-organized African wave near 9°N 44°W (Invest 91L) is headed west-northwest at 15 - 20 mph, and could arrive in the vicinity of the Lesser Antilles Islands as early as Monday night. Residents of the Lesser Antilles should pay careful attention to this system, as it has the potential to organize into a tropical storm before reaching the islands. While visible satellite loops currently show only minimal heavy thunderstorm activity and no signs of a surface circulation, there is a pronounced large-scale rotation to the cloud pattern. Water vapor satellite loops show that a large area of dry air from Africa lies just to the north of 91L, and this dry air is inhibiting development. The SHIPS model is diagnosing low shear, 5 - 10 knots, over 91L, but the University of Wisconsin CIMSS analysis shows that moderate shear, 10 - 20 knots, is affecting 91L. Sea surface temperatures are 27.5° - 28°C, which is 1° above the 26.5°C threshold usually needed to support a tropical storm.

Forecast for 91L
Low to moderate wind shear of 5 - 15 knots is predicted along 91L's path over the coming three days, which should allow the storm to steadily organize, assuming it can shut out any incursions of dry air that might intrude. The latest 06Z run of the GFS model does show 91L developing into a tropical storm by Monday, but the other three most reliable models for forecasting formation of a tropical storm--the ECMWF, NOGAPS, and UKMET models--show little or no development of 91L in their latest runs. On Monday, when most of the models predict that squalls of rain from 91L will begin affecting the Lesser Antilles, wind shear is expected to rise to the moderate or high range, which should act to interfere with development. The latest runs of the GFDL and HWRF models show 91L developing into a hurricane by Monday, but these models are not to be trusted for systems that have not developed into a tropical depression yet. The long-range path of 91L could take it through the Caribbean or towards the U.S. East Coast; it is too early to know with path might be more probable. NHC is giving a 30% chance that 91L will develop into a tropical depression by Sunday morning.

Iran records its hottest temperature of all-time
Omidieh, Iran and Shoshtar, Iran hit a scorching 52.6°C (126.6°F) on July 27, the hottest temperatures ever recorded in the country. The previous record was 52.5°C (126.5°F) set in Hamidiyeh on August 4, 2001. If confirmed by the Iranian weather service, these readings would rank as the third hottest undisputed temperatures ever measured in Asia. There have been only two Asian readings matching or exceeding Wednesday's new Iranian record of 52.6°C that are undisputed that I am aware of. Both of these occurred last year, and were recognized by their respective country's meteorological services as new official records for their country:

53.5° (128.3°F) in Moenjodaro, Pakistan on May 26, 2010
52.6°C (126.7°F) in Abdaly, Kuwait on June 10, 2010

Iran is the third nation this year to set a new all-time heat record (no nations have set an all-time coldest temperature record this year, or did so in 2010.) The Democratic Republic of the Congo, the world's 12th largest country, set a new all-time extreme heat record on March 8, 2011, when the temperature hit 39.2°C (102.6°F) at M'Pouya. Congo's previous all-time hottest temperature was 39.0°C (102.2°F) at Impfondo on May 14, 2005.

Also this July, a 50.2°C temperature was measured at Aydyngkol Lake, China--the highest temperature on record at any official Chinese weather station. Next week, our weather historian, Christopher C. Burt, will report on this record. Credit for researching these records goes to weather records researcher Maximiliano Herrera, who maintains a comprehensive set of world extreme temperature records on his web site.

Vacation
I'm taking some time off today through August 9 for a family celebration and vacation, and don't plan on blogging again until August 10 unless a major hurricane develops. In my absence, Angela Fritz will be handling most of the blogging duties, and she will have a post on the latest for Don this afternoon. Angela is on Pacific time, so her posts will be later in the day than I make them.

Jeff Masters

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Quoting NotCircumventing:
12Z GFS +174



shows some consistency with 6Z



the pressure on the upper pic looks like 1002, cant make out pressure on the lower....
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Quoting tiggeriffic:
decided on sushi and sushimi for lunch...may not be able to have it in 10 days or so if 91L causes much havoc....


Wife and kids going to Atlanta for the weekend and I do not cook (except for blackend or broiled filets); Love sushimi and headed in the same direction this weekend if I don't catch any fish myself.....My real men fishing buds won't eat "bait"........... :)
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Quoting PcolaDan:


We cry and complain when a winter is here about how cold it is and we live in the south to get away from the cold. Then the day after our week of spring when temps and humidity soar, we can't wait for our week of fall and then winter to come along to cool things off. :)
It's our nature. :|


I am from Miami so when I was younger I'd complain when it would get under 50 degrees in the wintertime. My brother who went to Florida State would laugh and now also going to FSU I can understand why. And the funny thing is, when I complain about it getting to 30 degrees in Tallahassee my cousins in the North East, laugh too because they know its much worse for them.
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Quoting ldhall05:
Guys&Gals

Noobie here to the blog. I need your thoughts. I know it's really early on this Invest 91L But....... I'm taking the family to Grand Cayman leaving this Sunday 7/31/11. We are from Kentucky and praying for great weather. First half of next week looks good. We will be leaving the Caymans the following Sunday. Any thoughts on this developing Wave? Am i gambling here still going down?


ships are the first to be warned and get out of the area if there is eminant danger in weather...worst case is you see a different area or they refund your money...it is a gamble either way, it is about 5 days from PR as of today...sunday would be 3 days away...call the cruise company and ask their policy is your best bet at this point today
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Quoting P451:


That is awesome.

Should I post the image of the JFV weather center?

Perhaps not, I'm not in the mood for WU prison.



You're right...no point in both of us going there...LOL!
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and everyone should focus on the development of 91L first...it is still part of the ITCZ and not its own seperate entity so where excatly it will go is anyone's guess as of now...ive seen the models change so much with these systems in the early going especially out in the CATL
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Large and broad, but once it gets going, its gonna go:

Member Since: July 6, 2010 Posts: 113 Comments: 31462
Quoting tiggeriffic:


roflmbo...bwhahahahaha...insert emoticon cracking up here...lol


.
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Quoting PcolaDan:


We cry and complain when a winter is here about how cold it is and we live in the south to get away from the cold. Then the day after our week of spring when temps and humidity soar, we can't wait for our week of fall and then winter to come along to cool things off. :)
It's our nature. :|



True that!
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Guys&Gals

Noobie here to the blog. I need your thoughts. I know it's really early on this Invest 91L But....... I'm taking the family to Grand Cayman leaving this Sunday 7/31/11. We are from Kentucky and praying for great weather. First half of next week looks good. We will be leaving the Caymans the following Sunday. Any thoughts on this developing Wave? Am i gambling here still going down?
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Don is cool and all but i have a feeling we will soon have alot bigger problems to worry about
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129. 7544
perhaps we might see two systems form out of 91l
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Quoting floodzonenc:
Now for the third installment of The Ghosts of Emily Past.  This one brushed the OBX as a major...




Does anyone else think that this installment of the Emilys looks like a Fish storm? I mean, the track actually looks like a fish, not that it only affected the fish.
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Wow, it rained for literally 1 minute in downtown Corpus Christi.
Member Since: July 15, 2005 Posts: 25 Comments: 334
Did sustained winds drop to 40mph in Don?
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Quoting P451:


That is awesome.

Should I post the image of the JFV weather center?

Perhaps not, I'm not in the mood for WU prison.



roflmbo...bwhahahahaha...insert emoticon cracking up here...lol
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Quoting P451:


I think a lot of folks in the southern areas, despite always crowing about the warmth during the winter, would be more than happy to see fall come in four weeks.



We cry and complain when a winter is here about how cold it is and we live in the south to get away from the cold. Then the day after our week of spring when temps and humidity soar, we can't wait for our week of fall and then winter to come along to cool things off. :)
It's our nature. :|
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Blog got quiet from 9:27 to 9:30 ...
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Seriously, Don has REALLY balled up into a huge area of convection. Interestingly, it's not really getting stronger which seems odd for that area where historically storms have really blown up at the last minute.

91L is a way out proposition but it's interesting watching the model runs...
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decided on sushi and sushimi for lunch...may not be able to have it in 10 days or so if 91L causes much havoc....
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Report and move on.
Member Since: May 17, 2009 Posts: 2 Comments: 904
Quoting NotCircumventing:
Where can one find this seasoning? is it in stores?

are wrinkles considered seasoning?
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.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

AN ACTIVE TROPICAL WAVE IS EXPECTED TO APPROACH THE LOCAL AREA
LATE MONDAY OR TUESDAY...INCREASING THE CHANCES FOR ACTIVE WEATHER
ACROSS THE ISLANDS AND REGIONAL WATERS. NO OTHER HAZARDOUS
WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.
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Catching up on yesterdays blog, boy! There are a lot of folks chomping at the bit for a hurricane aren't there.
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in case people forgot about our friends in the Islands..



Member Since: August 19, 2006 Posts: 13 Comments: 14453
Quoting ElConando:


There is no set requirement for invests, however those are what they tend to look for.


That is what it needs to do to achieve TD/TS status.
Member Since: July 6, 2010 Posts: 113 Comments: 31462
Quoting NotCircumventing:
Where can one find this seasoning? is it in stores?


Ummm, what seasoning might that be?
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Quoting ProgressivePulse:
Recon will be in Sunday, along with upper data flight.

2. OUTLOOK FOR SUCCEEDING DAY:
A. INVEST SUSPECT AREA AT 31/1800Z NEAR 14.0N 54.0W.
B. ADDED....A G-IV MISSION FOR 01/0000Z.


NHC taking 91 seriously!
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Quoting islander101010:
9n 42w
I think it will continue to drift west for a while.
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Quoting TropicalAnalystwx13:
Until the three things below are settled, 91L will not become a tropical depression or storm:

1.) It needs to fully separate from the ITCZ, which seems to be occurring at this time.

2.) Winds are still at 30 mph. I know they classified Ivan at 30 mph, but they most likely won't with 91L.

3.) It needs more organized convection, but that should come soon.

It has a closed, low-level circulation which is one of the hardest things to get. Winds will go up as the system becomes more organized, and it should achieve convection after it separates from the ITCZ. All given, we should see our fifth TD/TS by Monday.


There is no set requirement for invests, however those are what they tend to look for.
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9n 42w
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Looking like Corpus wont get any rain from Don at this point. Major dissapointment
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Until the three things below are settled, 91L will not become a tropical depression or storm:

1.) It needs to fully separate from the ITCZ, which seems to be occurring at this time.

2.) Winds are still at 30 mph. I know they classified Ivan at 30 mph, but they most likely won't with 91L.

3.) It needs more organized convection, but that should come soon.

It has a closed, low-level circulation which is one of the hardest things to get. Winds will go up as the system becomes more organized, and it should achieve convection after it separates from the ITCZ. All given, we should see our fifth TD/TS by Monday.
Member Since: July 6, 2010 Posts: 113 Comments: 31462
Quoting aspectre:
Iceberg in GooseCove,Newfoundland, temporarily blocking the harbor before breaking apart

Photo by GenePatey

WTH, No way, COOOOOOL.

Anyone noticed the spin in the SW Carib. Also 91L has a nice spin to it also.

Goodnight all, Everyone here in SW Tx. Stay safe please.
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Quoting P451:


It's wayyyyy too early to trust model guidance, be in fear of the Atlantic high pressure system, declare 91L a major hurricane, and try to compare it to Emily's of past.

Certainly jumping the gun in a big way this morning. About all I would say about 91L is it is large and broad and those take time to spin up, it looks pretty good, and I would expect it to develop and threaten the islands as at least a tropical storm. Beyond that - too early - not enough data or time watching it.

But, well, remember last night's declarations on Don? There is no shear. An eye is forming. Don is well organized. Don is rapidly intensifying. Don will be a hurricane. All that without taking a detailed look at satellite imagery to see none of that was occurring.

So, well, already putting Emily into the record books before it even formed isn't a shock.

What can ya do it's an open public blog and the users are free to voice opinion.

The seasoned ones will watch, analyze, and form opinions over time based on a scientific approach, and those are the posts and users I look forward to reading.





Thank You !!
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90. KEEPEROFTHEGATE 12:14 PM EDT on July 29, 2011

Kudos to NHC for their call as to intensity with Don. Anything can happen theoretically with a storm in the Gulf but they made a great call on this one (aided by the models of course).
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#88. The seasoned ones will watch, analyze, and form opinions over time based on a scientific approach, and those are the posts and users I look forward to reading.

That's too much work....lets just make up stuff and argue about it.....:/
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.