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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Man, Dr. Masters takes more vacations than anybody I have ever known! LOL!

Enjoy your Vacation Doc...... and how many times have we had tropical development in your absence? But seems unlikely we will see a Major though!

Howdy to all my Wunderground friends! :) Don't post often, but always lurking! :)
Member Since: Posts: Comments:
Quoting FrankZapper:
2 weeks. They are not weather savy at all. I told them to not go at this time of the year but their aniversity is Aug 5th so they had to do it now.


Ouch...ummmm....It would not be wise to go right now with all models pointing that direction. But..Who am I to tell you to tell them not to go?

Member Since: July 6, 2010 Posts: 113 Comments: 32257
Opinions
We will finish the season with___named storms.
A.10-12
B.13-15
C.16-18
D.19-21
E.More
F.Less
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Will guess 91L goes to 40% at 8PM.
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Quoting TropicalAnalystwx13:


How long are they staying? Just tomorrow?
2 weeks. They are not weather savy at all. I told them to not go at this time of the year but their aniversity is Aug 5th so they had to do it now.
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...CENTER OF DON ABOUT TO MAKE LANDFALL ON THE TEXAS COAST NEAR BAFFIN BAY...STRENGTHENING NO LONGER ANTICIPATED...

7:00 PM CDT Fri Jul 29
Location: 27.1N 97.1W
Max sustained: 50 mph
Moving: WNW at 16 mph
Min pressure: 1004 mb
Member Since: July 6, 2010 Posts: 113 Comments: 32257
987. JLPR2
Quoting hunkerdown:
first, be real, like the people making these comparisons know what the appearance of Bill, Felix, Dean, etc. were at the same stage of development; second, from the people who are saying this and posting images of the tracks, they are comparing just that, the tracks if not tracks and intensity.


That's why I said right now. Not talking for the ones that posted before.
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Quoting TheWeatherMan504:


His point is that Bill and Earl developed further East than where 91L is and that allowed those systems to gain more latitude while in the MDR and recurve before impacting the US. This system may not develop for a few more days and this could allow it to have a greater threat to land and potentially the United States down the road. That is his point.
those storms recurved because of the persistent deep troughs that were in place, not because they developed further East.
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Quoting JNCali:

Has anyone of you tecknologiculy inclined come up with a chart with conformational data reflecting the Dr. Masters Vacation TS Effect??


It's kinda like the Madden cover jinx - you just know it's real. You ain't need no data to confirm.

Like Xcool would say: Doc gone Emily come.
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Good Evening...
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I will go with about 40-50% on the NHC TWO.
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Quoting PcolaDan:


Just stand out there and yell "hey OZ", he will answer if he is there. :)

at home now in Rockport, think I'll stay put!
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Quoting JLPR2:


The thing is that right now we are comparing in terms of appearance, not track.
first, be real, like the people making these comparisons know what the appearance of Bill, Felix, Dean, etc. were at the same stage of development; second, from the people who are saying this and posting images of the tracks, they are comparing just that, the tracks if not tracks and intensity.
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18z Early Cycle NHC model tracks
Invest91
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)



Dynamic Models (More sophisticated models)



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Cantore tweet

@JimCantore
Jim Cantore
Business as usual in North Padre tonight as TS # Don nears shore http://twitpic.com/5xwl89 http://twitpic.com/5xwl8y
Member Since: August 22, 2008 Posts: 12 Comments: 6010
Link

the link to the surf cam at Bob Hall Pier in CC TX.
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Quoting stormwatcherCI:
A VIGOROUS TROPICAL
WAVE ALONG 44W WITH LOW PRES 1007 MB NEAR 10N 42W IS BECOMING
BETTER ORGANIZED

From NHC less than two hours ago.
That's the weird thing.

I wouldn't put too much stock into WindSAT though, pretty unreliable.

Quoting JLPR2:


The thing is that right now we are comparing in terms of appearance, not track.
Exactly.

I'm comparing 91L to Bill when it was in its formative stages.
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Quoting TomTaylor:
right here!

not yet it's not.

But it will certainly become an issue

18z GFS 72 hr




18z GFS 96 hr




Feel free to watch the whole loop. I don't think shear will be too high, but it certainly will not be low or extremely favorable. It will be moderate


As long as it doesn't go above 20 knots, 91L should be fine. But according to that, it does go above 20 knots?
Member Since: July 6, 2010 Posts: 113 Comments: 32257
Quoting cctxshirl:

none of the guys I saw were heavyset, but I think that's where he was taping unless he moved. Lots of people there taping though, including news.


Just stand out there and yell "hey OZ", he will answer if he is there. :)
Member Since: August 22, 2008 Posts: 12 Comments: 6010
Though void of heavy convection 91L imo is more organized , I'll go with 50% at 7pm cst.
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Sorry i thought you guys meant track wise. looks a little better. don has just made landfall or in about 10 minutes will make landfall..
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Quoting MiamiHurricanes09:
Your point?


His point is that Bill and Earl developed further East than where 91L is and that allowed those systems to gain more latitude while in the MDR and recurve before impacting the US. This system may not develop for a few more days and this could allow it to have a greater threat to land and potentially the United States down the road. That is his point.
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Quoting stormwatcherCI:
A VIGOROUS TROPICAL
WAVE ALONG 44W WITH LOW PRES 1007 MB NEAR 10N 42W IS BECOMING
BETTER ORGANIZED

From NHC less than two hours ago.


Definitely not less organized. In fact, probably BETTER organized.
Member Since: July 6, 2010 Posts: 113 Comments: 32257
Quoting Hurricanejer95:

:| any Californian bloggers here
right here!

Quoting TropicalAnalystwx13:


Gaston's problem was wind shear...91L doesn't have to deal with that. Fiona's problem was Earl, 91L won't have to deal with that.

It has dry air to deal with...that's it.
not yet it's not.

But it will certainly become an issue

18z GFS 72 hr




18z GFS 96 hr




Feel free to watch the whole loop. I don't think shear will be too high, but it certainly will not be low or extremely favorable. It will be moderate
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Quoting FrankZapper:
Does anyone have a fix on where 91L is going? My parents are going to St Thomas tomorrow for their 50th anniversary.Will they be OK. Should they cancel?
ask Mother...Nature
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Quoting FrankZapper:
Does anyone have a fix on where 91L is going? My parents are going to St Thomas tomorrow for their 50th anniversary.Will they be OK. Should they cancel?


How long are they staying? Just tomorrow?
Member Since: July 6, 2010 Posts: 113 Comments: 32257
966. JLPR2
Quoting hunkerdown:
I think a better point to be made is stop comparing storms/invests to a prior years storm just by the invests location and where you WANT it to track. It is too far out to know what the conditions will be to know if it will match this storm or that storm. There are soooo many variables that determine a storms track to say what 91L, or any other invest/storm, will encounter the exact same conditions and patterns and say, Dean, Bill or Felix, etc., is ludicrous.


The thing is that right now we are comparing in terms of appearance, not track.
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Quoting MiamiHurricanes09:
Looks more disorganized than yesterday. Just a trough of low pressure it appears.
A VIGOROUS TROPICAL
WAVE ALONG 44W WITH LOW PRES 1007 MB NEAR 10N 42W IS BECOMING
BETTER ORGANIZED

From NHC less than two hours ago.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
Does anyone have a fix on where 91L is going? My parents are going to St Thomas tomorrow for their 50th anniversary.Will they be OK. Should they cancel?
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962. JLPR2
Quoting JRRP:


I prefer ASCAT to Windsat but if that is true then it's time to party for me. xD
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Quoting MiamiHurricanes09:
Your point?
I think a better point to be made is stop comparing storms/invests to a prior years storm just by the invests location and where you WANT it to track. It is too far out to know what the conditions will be to know if it will match this storm or that storm. There are soooo many variables that determine a storms track to say what 91L, or any other invest/storm, will encounter the exact same conditions and patterns and say, Dean, Bill or Felix, etc., is ludicrous.
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Quoting stormwatcherCI:
He does not have a profile on WU but he is on FB. He is a heavyset guy.

none of the guys I saw were heavyset, but I think that's where he was taping unless he moved. Lots of people there taping though, including news.
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Quoting MiamiHurricanes09:
Looks more disorganized than yesterday. Just a trough of low pressure it appears.


Quoting JRRP:

yeap...


I highly doubt that. Visible satellite imagery clearly supports a closed, LLC. Go check...
Member Since: July 6, 2010 Posts: 113 Comments: 32257
958. JRRP
Quoting MiamiHurricanes09:
Looks more disorganized than yesterday. Just a trough of low pressure it appears.

yeap...
Member Since: August 16, 2007 Posts: 0 Comments: 5965
Quoting JRRP:
Looks more disorganized than yesterday. Just a trough of low pressure it appears.

Quoting floridaboy14:

my point is everyone is comparing 91L to strong hurricane that formed by cape verde. Thats my point....
91L still has the potential to develop into something as strong as a Cape Verde hurricane.

The reason that 91L reminds me of Bill is because when Bill was in its formative stages, it was a very large system that spanned hundreds of miles. Didn't really mean to compare it to Bill's track or intensity.
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Quoting MiamiHurricanes09:
Your point?

my point is everyone is comparing 91L to strong hurricane that formed by cape verde. Thats my point....
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Quoting yonzabam:
If it causes some damage as a tropical storm in the Antilles, but recurves before it hits a continental land mass as a hurricane, it's understandable that people living in the US would call that a 'fish storm'. Personally, I don't have a problem with that, but some folk seem to have a need to appear as more caring human beings and be seen to be more sympathetic towards those islanders. I wonder why that is.

because people in the US seem to write off storms as "fishes" the minute they realize it won't be affecting them. Once they write it off as a fish storm, suddenly they lose interest and it's not even an issue. It's selfish thinking to say the least.

By all means continue your selfish thinking, I won't stop you. But I certainly won't respect you either lol

Quoting Stormchaser2007:
For now this is a threat to PR and the islands. Anyone who says that this is a "fish" is simply uneducated.

agreed.
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Quoting cctxshirl:

Does he have a pic on his profile? I drove down to the bayfront where people were video taping and was going to stop and talk, but they didn't look like they wanted any interruption because the conditions were just starting to change a little.
He does not have a profile on WU but he is on FB. He is a heavyset guy.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
952. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 5965
Quoting floridaboy14:
People stop comparing 91L to storms like EARL, BILL ETC. All those are CAPE VERDE storms. 91L wont develop until maybe just 50 to 100 miles east of the islands or west of the islands :) any one have a camera showing conditions in texas?
Your point?
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Total number of named storms in August since 2000:

2000: 4

2001: 3

2002: 3

2003: 4

2004: 7

2005: 5

2006: 2

2007: 3

2008: 4

2009: 4

2010: 4

2011: My Prediction - 4-7

Member Since: July 6, 2010 Posts: 113 Comments: 32257
People stop comparing 91L to storms like EARL, BILL ETC. All those are CAPE VERDE storms. 91L wont develop until maybe just 50 to 100 miles east of the islands or west of the islands :) any one have a camera showing conditions in texas?
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Quoting doabarrelroll:

link

Does he have a pic on his profile? I drove down to the bayfront where people were video taping and was going to stop and talk, but they didn't look like they wanted any interruption because the conditions were just starting to change a little.
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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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