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 PensacolaDoug:



You mean there's people on those islands?


So, you wanna be a comedian. LOL
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91L-TD5-Emily will be a big time issue for any land betwen Lesser Antillas to Florida ,USA
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Although I have been A member for a while. I rarely post these days. Having said that. ANYONE, who thinks an Island busting storm is a "fish", needs therapy. Or..if.., you are basing your entire forecast on one model ,a bit of advice. Keep your ears and eyes open, and your big mouth shut! Ignorance is curable, stupidity is permanent.
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Quoting SLU:


Well almost 5 million lives are in the path of this "fish storm" in case you didn't know ....



You mean there's people on those islands?


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The fury of Don....

Brownsville / South Padre Island Intl Airport
Lat: 25.9 Lon: -97.43 Elev: 19
Last Update on Jul 29, 3:53 pm CDT


Light Rain

81 °F
(27 °C) Humidity: 85 %
Wind Speed: W 5 MPH
Barometer: 29.88" (1011.6 mb)
Dewpoint: 76 °F (24 °C)
Heat Index: 87 °F (31 °C)
Visibility: 7.00 mi.
More Local Wx: 3 Day History:


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Quoting Seawall:


Yep, I can truthfully say, since September, 2005, we don't have hardly any shade around my house. Rita made a stark change in the landscape!


That she did.
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Quoting AtHomeInTX:


We had our last giant pine standing brought down in 2010, much to our neighbors delight. Then everyone had there's brought down too. Sad thing it is to do. But they become killers in hurricanes. Haven't seen any towering oaks around since 2005.


Yep, I can truthfully say, since September, 2005, we don't have hardly any shade around my house. Rita made a stark change in the landscape!
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If you are looking at the RGB sat loop from NHC website you can see the two swirls people where talking about, but if you look at the end it looks like the circulation in front of it has eaten the second circulation and have become one. There is also convection starting to form there with banding patterns taking shape. Just my uneducated observation. I have no Idea of the track but it does look to be just below 10 lat. I would put it at 9.9N and 43.9W. I think it is also probable it will be a TD with in 48 hr. and possibly a TS with in that time. Just my uneducated opinion.
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787. tj175
i'm going to take the low road and go with 40%.
Quoting ackee:
what will the NHC do at 8pm with 91L

A 30
B 40
C 50
D 60
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Don sure looks sorry on Brownsville radar.
Don Gone!


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Quoting nrtiwlnvragn:
Not liking were HPC has that low in the Bahamas day 7



That pacific high is still out there? More Above average temps here, we are having a warm July (Not as bad as TX) -.-



The Bay area is the only place in the West Coast with Above average july temps
Member Since: August 30, 2008 Posts: 1 Comments: 259
Quoting civilbull:
I guess it is time to stress about the tropics. I'm having my oak trees trimmed today and tomorrow.


We had our last giant pine standing brought down in 2010, much to our neighbors delight. Then everyone had there's brought down too. Sad thing it is to do. But they become killers in hurricanes. Haven't seen any towering oaks around since 2005.
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783. tj175
Wow thats not good at all. How reliable is that model run?
Quoting nrtiwlnvragn:
Not liking were HPC has that low in the Bahamas day 7


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accuweather:

Beyond Tropical Storm Don, Bullies Await
Alex Sosnowski
By Alex Sosnowski, Expert Senior Meteorologist
Jul 29, 2011; 3:25 PM ET
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In recent weeks, tropical waves emerging off the coast of Africa have progressively been more vigorous.

Don't look now, but a new system in the Atlantic is likely to be the next tropical system of concern and it could cause big problems over the Antilles next week.

A strong tropical wave is cruising westward past the Cape Verde Islands this weekend, and the early indications are that this system will bring heavy rainfall and gusty squalls to the Windward and Leeward islands next week.

The system, even if it is not yet a tropical depression or tropical storm at the time of passage could bring risk to lives and property from flash flooding, mudslides and washouts.

The same system is being shone by some of our forecast tools to grow stronger while crossing into the Caribbean or over the Antilles that border the Caribbean and the Atlantic.

According to Tropical Weather and Hurricane Expert Dan Kottlowski, "Interests in the Windward Islands, Virgin Islands and even Puerto Rico should monitor the progression of this new system."

This system is worth keeping a close eye on as we are entering the point in the Atlantic Hurricane Season, when Cape Verde systems take center stage. Storms that originate in this area of the Atlantic produce hurricanes among the strongest we ever see beginning in August.

Because there's a chance the blocking area of high pressure that has protected much of the northern Gulf of Mexico and the Atlantic Seaboard thus far this season may weaken starting next week, there is room for any tropical system that comes along to eventually get very close to the mainland U.S.

A modest and different tropical wave brought torrential rainfall on the island of Dominica this past week. The same tropical wave brought record rainfall to San Juan, Puerto Rico, Thursday.

The interaction of tropical waves with weak frontal zones from the north have led to excessive rainfall over parts of the Lesser Antilles since the second half of May. Even parts of Cuba, stricken by drought the past couple of years has been getting substantial rainfall over the past couple of months.

It was a tropical wave that passed through the Caribbean islands about a week ago that gave birth to Don.
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780. tj175
I agree totally I know that everyone here in Florida just knew IKE was coming here and and he went underneath the state and hit Texas.
Quoting AtHomeInTX:
This one here had a strange track. It was supposed to go out to sea a couple times. You never know what they will do. Don't see nothing wrong with discussing the what ifs. That's what we do around here. :)

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Tornado Watch back home...

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Not liking were HPC has that low in the Bahamas day 7


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Quoting ackee:
what will the NHC do at 8pm with 91L

A 30
B 40
C 50
D 60


C
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Quoting jasonweatherman2011:
wow!! we have a new low with 1008 MB i did not see that before!!


Looked pretty interesting on satellite earlier. Levi explained the area in his blog comments. :)
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Quoting CosmicEvents:there's a wind, blowing east! and a Strong tropical wave moving WEST!!
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Quoting ackee:
what will the NHC do at 8pm with 91L

A 30
B 40
C 50
D 60


Member Since: August 30, 2008 Posts: 1 Comments: 259
Quoting CosmicEvents:
He usually goes to London this time of year for a couple of weeks. Then it takes him a week back in the CI to clear out his digestive tract from all the mung that he ate over there.
.
.
.
there's a wind, blowing east!


LMAO!!
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Quoting ackee:
what will the NHC do at 8pm with 91L

A 30
B 40
C 50
D 60


50
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what will the NHC do at 8pm with 91L

A 30
B 40
C 50
D 60


mmmmmmm C C C C C or B B B B
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Quoting Tygor:
Loving how all the rain coming off Houston is dying before it gets near us in SA. Just another hot sunny day, only more humid than usual.


Actually most of the rain is evaporating before it hits Houston. There have been a couple of pop up storms but most of what you see on the radar is not making it to the surface. I have not seen a drop of rain.
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5:30 OFFSHORE WATERS FORECAST


A VIGOROUS TROPICAL
WAVE ALONG 44W WITH LOW PRES 1007 MB NEAR 10N 42W IS BECOMING
BETTER ORGANIZED AND HAS THE POTENTIAL TO BECOME A TROPICAL
CYCLONE WITHIN THE NEXT 48 HOURS AS IT MOVES WESTWARD AT 15 TO
20 MPH. THIS WAVE IS EXPECTED TO REACH 55W EARLY MON AND MOVE
ACROSS THE LESSER ANTILLES MON NIGHT AND TUE.
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Quoting SLU:


Well almost 5 million lives are in the path of this "fish storm" in case you didn't know ....


Exactly.

PR and the Bahamas are at a real threat from at least a hurricane.
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Quoting stormpetrol:


Kman lives just under 1 mile from me and come to think of it I haven't seen him on the road in about 2 weeks, though I know Kman is a very busy man!Probably off Island!
He usually goes to London this time of year for a couple of weeks. Then it takes him a week back in the CI to clear out his digestive tract from all the mung that he ate over there.
.
.
.
there's a wind, blowing east!
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I guess it is time to stress about the tropics. I'm having my oak trees trimmed today and tomorrow.
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763. ackee
what will the NHC do at 8pm with 91L

A 30
B 40
C 50
D 60
Member Since: Posts: Comments:
762. SLU
Quoting thewindman:
91L is already a FISH STORM per GFS model. I woudn't be surprised


Well almost 5 million lives are in the path of this "fish storm" in case you didn't know ....
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760. xcool
40% AT 8PM jmo
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759. xcool


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The 12z GFS brings Emily dangerously close to the US at 180 hours. The steering currents really break down as the trof lifts out. This is day 8 on the GFS and very unreliable. A lot can and probably will change. It remains to be seen if a ridge builds in over the top or another trof digs in to sweep it out to sea. Of course, it could always take the EURO path. Anyway, the consensus, at the moment, is north of the islands. The question is what will it do from this point on if this were to actually happen:


Member Since: July 15, 2006 Posts: 17 Comments: 10284
the 18Z map are out looks bad
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Quoting CanesfanatUT:


You ready for the Golden Era of UM football?!?!?!
You have no idea...LOL.

Be back in a while.
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Quoting floridaboy14:
Don about to make landfall in less than 3 hours? anyone have any live cams from texas?


Go to www.kiiitv.com, there are three webcams from Padre Island national seashore.
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Quoting wunderkidcayman:

With you on that orange/red alert 50-60% at 8pm
why not 80%...the visible is showing the low covering with thunderstorms...
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753. ackee
I think 91L will still be at 30% at 8pm nothing has change in my veiw
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THe Models will change they always do.
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Quoting MiamiHurricanes09:
He's one of the first 5 people I've put on my ignore list...ignorance at its finest. LOL.


You ready for the Golden Era of UM football?!?!?!
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If 91L remains large, it will be easier for it to be pulled northward by a passing trof. Still a lot of questions to be answered and they really won't be answered until 91L actually becomes a tropical cyclone.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting stormpetrol:


Welcome home WKC.Looks like a busy season from here on!

yep I think we are going to have a very bad ride form now on I'm telling ya even 91L reminds me of Ivan may even pull off Ivans track and just maybe catagory
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Well just our luck here in ole CC, finally get a rain event to come close enough to us and all the "normal" aspects don't exist. Like the NE quadrant having the majority of the moisture..... Oh well i guess we can enjoy the minimal breeze and the cloud cover, but for crying out loud will someone please send us some rain!
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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.

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