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 Walshy:


why look out to Africa then to far out...
there is a huge difference in monitoring waves and development in and off of Africa than trying to predict a track 7-10+ days out on a system that has not even formed yet.
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Post 904:
I basicaly said thet yesterday.
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942. HCW
Don since 8AM this morning on Radar

Link
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Quoting JLPR2:
91L is a biggie. :\

Reminds me of Bill from 2009.
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Quoting atl134:
Strange to me to have the name Emily coming around again. 6 years ago Emily was the first hurricane I really tracked/followed beyond just turning on the weather channel :50 after the hour once a day mostly because my best friends' sister was a missionary serving in Belize at the time. Darn good thing that storm hit primarily very sparsely populated areas (why it wasn't retired in the end).


Well I think they had "Retired So Many" that year they had to leave something on that list LOL

Taco :o)
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Quoting TropicalAnalystwx13:


I really do not understand it, but it ends up verifying every single time.
Has anyone of you tecknologiculy inclined come up with a chart with conformational data reflecting the Dr. Masters Vacation TS Effect??
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937. JLPR2
91L is a biggie. :\

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Strange to me to have the name Emily coming around again. 6 years ago Emily was the first hurricane I really tracked/followed beyond just turning on the weather channel :50 after the hour once a day mostly because my best friends' sister was a missionary serving in Belize at the time. Darn good thing that storm hit primarily very sparsely populated areas (why it wasn't retired in the end).
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Quoting floridaboy14:
anyone have acess to a live camera in texas so see how conditions are?


www.kiiitv.com Corpus Christi station. Two live feeds from the beach and one for the bay.
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Quoting bamagirl1964:
Hello Again! I am so excited to have received so many responses to my first post!! I am truly impressed that several of you were actually able to provide the actual track of Frederic for me! That was very kind! I was fifteen years old at the time, but I remember it clearly. I am surprised that many of you do remember that terrible hurricane, as well. You all have made me feel very welcome and I thank you again and look forward to hearing more from you all!


Welcome Bamagirl we are glad you came by.... I too was in that storm called Fredric and remember like it was yesterday.... I too wanted to let you know there are a lot of ppl in here that can give you Great Info and then there are some well just want to "Stur Up The Pot" if you know what I'm saying....
Anyway "Welcome" and sit back and enjoy the ride cause this year will be Busy thats for sure....

Taco :o)
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Quoting bamagirl1964:
Hello Again! I am so excited to have received so many responses to my first post!! I am truly impressed that several of you were actually able to provide the actual track of Frederic for me! That was very kind! I was fifteen years old at the time, but I remember it clearly. I am surprised that many of you do remember that terrible hurricane, as well. You all have made me feel very welcome and I thank you again and look forward to hearing more from you all!


Hi Bama ! I remember Frederic very well too. It was quite the night. I was in 9th grade at the time but remember it like it was yesterday. This site is a great place for informatation. Sorry about the previous post, my dog hopped in my lap and posted it for me.
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Got a bad feeling bout Emily...my neighbors lil girl's name...told her bout the storm...she said NO STORM would ever compare to her Emily...i scared now
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Google any Hurricane Name and one should get a few good wiki images and info.


Hurricane Elena





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Quoting bamagirl1964:
Hello Again! I am so excited to have received so many responses to my first post!! I am truly impressed that several of you were actually able to provide the actual track of Frederic for me! That was very kind! I was fifteen years old at the time, but I remember it clearly. I am surprised that many of you do remember that terrible hurricane, as well. You all have made me feel very welcome and I thank you again and look forward to hearing more from you all!

Quoting bamagirl1964:
Hello Again! I am so excited to have received so many responses to my first post!! I am truly impressed that several of you were actually able to provide the actual track of Frederic for me! That was very kind! I was fifteen years old at the time, but I remember it clearly. I am surprised that many of you do remember that terrible hurricane, as well. You all have made me feel very welcome and I thank you again and look forward to hearing more from you all!
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Quoting taco2me61:


No you are "Not" hehehehe

Taco :o)


roflmbo Taco :0)...my hubby would beg to differ snicker snicker snort snort
Member Since: September 16, 2007 Posts: 0 Comments: 3650
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926. xcool
CosmicEvents lmaooo
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Quoting jasonweatherman2011:
to far out!!
Stop screaming.
You sound like the guy at the chinese restaurant I just called to ask if they delivered to me.
.
.
.
.
too windy.
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Quoting Stormchaser2007:
August should be exceptionally active.

I might actually do a forecast for the rest of the season on August 1st.

Could easily see 5 storms.
maybe 6 i think

iam going to update season numbers on monday by two it looks like if 91l forms if not they stay the same
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Quoting Patrap:
18z Early Cycle NHC model tracks
Invest91
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)



Dynamic Models (More sophisticated models)



Further south with every update.
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Quoting tiggeriffic:


first of all, anything that is potential is not a waste of time or space...second of all...you are the silly one since i am definately NOT A BOY!


No you are "Not" hehehehe

Taco :o)
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Quoting Stormchaser2007:
August should be exceptionally active.

I might actually do a forecast for the rest of the season on August 1st.

Could easily see 5 storms.

I agree. This could be one of the most active August's that the Atlantic has seen.

The 2005 AHS only had 6 named storms ("Only" used as a relative term).
Member Since: July 6, 2010 Posts: 113 Comments: 31554
Quoting MiamiHurricanes09:
At first, yeah. It was supposed to affect the Bahamas, the "F" state, and surrounding areas and look how that turned out.

Sounds like a plan. Hopefully 91L remains weak in between now and the time it affects Puerto Rico, but it's always good to be prepared ahead of time.
That's why I asked. Forecast tracks for Don kept shifting further and further south and I think there is a good chance the same will happen with 91L/Emily.
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Hello Again! I am so excited to have received so many responses to my first post!! I am truly impressed that several of you were actually able to provide the actual track of Frederic for me! That was very kind! I was fifteen years old at the time, but I remember it clearly. I am surprised that many of you do remember that terrible hurricane, as well. You all have made me feel very welcome and I thank you again and look forward to hearing more from you all!
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918. JLPR2
Quoting MiamiHurricanes09:
Earl was pretty bad though.



Ehh... Not really that bad.

Jeanne was worse, but that one crossed the island as a TS.
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Quoting MiamiHurricanes09:
Earl was pretty bad though.



Yeah...Earl was a Category 4 hurricane. "Emily" will probably come closer, but it will be weaker. Kind of levels each other out.
Member Since: July 6, 2010 Posts: 113 Comments: 31554
August should be exceptionally active.

I might actually do a forecast for the rest of the season on August 1st.

Could easily see 5 storms.
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Complete Update

TS BUSTED FORECAST ALIBI






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Quoting jasonweatherman2011:
its a wait of time modeles are never right at 210 hours silly boy!!
does someone need a break
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18z NOGAPS keeps it south and takes it to the northern GOM as nothing..

Link
Member Since: August 19, 2006 Posts: 13 Comments: 14612
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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909. JLPR2
Dry air seems to be 91L's lone problem and it has been dealing with it nicely.

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Quoting angelafritz:
Waiting for recon to make a pass or two before I post an update.... stay tuned. :)
Quoting TropicalAnalystwx13:


Do we get your analysis on 91L? :)

oh yes please angelafritz give your update on 91L
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Quoting TropicalAnalystwx13:


This one will be a higher threat to you, directly.
Earl was pretty bad though.

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Quoting jasonweatherman2011:
its a wait of time modeles are never right at 210 hours silly boy!!


first of all, anything that is potential is not a waste of time or space...second of all...you are the silly one since i am definately NOT A BOY!
Member Since: September 16, 2007 Posts: 0 Comments: 3650
All four tropical systems in the Atlantic have been tropical storms.

All four tropical systems in the Eastern Pacific have been hurricanes.

Looks like both streaks will end with Emily/Eugene.

Invest 91L:




Invest 95E:

Member Since: July 6, 2010 Posts: 113 Comments: 31554
Latest local forecast from one of our local Mets (and I'm not sure how reliable that is!) is saying that Don is going in just north of Baffin Bay but most of the rain is south of Baffin and that Brownsville had been getting rain most of the afternoon. We are seeing clouds here in Rockport and CC was starting to get a little breezy, but nothing out of the ordinary.
It does look like we might see a little rain, but nothing significant-still, we'll take it.
Member Since: July 15, 2005 Posts: 25 Comments: 334
Quoting jasonweatherman2011:
why are peolpe looking at computer modeles are 216 hours out!! to far out!!


yet you have posted pics all day long of the same stuff...ironic isn't it?
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Quoting jasonweatherman2011:
why are peolpe looking at computer modeles are 216 hours out!! to far out!!


why look out to Africa then to far out...
Member Since: May 17, 2009 Posts: 2 Comments: 904
Quoting WeatherNerdPR:

Funny. Last year, the 'E' storm affected PR too.


This one will be a higher threat to you, directly.
Member Since: July 6, 2010 Posts: 113 Comments: 31554
Quoting stormwatcherCI:
Isn't this basically the same track Don was supposed to take ?
At first, yeah. It was supposed to affect the Bahamas, the "F" state, and surrounding areas and look how that turned out.

Quoting JLPR2:


Well I guess that I should get batteries and all the necessary things just in case; I hate making long lines.
If it passes over me I will be ready, if it doesn't I'll save everything for September.
Sounds like a plan. Hopefully 91L remains weak in between now and the time it affects Puerto Rico, but it's always good to be prepared ahead of time.
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Quoting jasonweatherman2011:
why are peolpe looking at computer modeles are 216 hours out!! to far out!!


Curiosity
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With 91l, steering patterns suggest a westward to west northwestward track for at least the next 24-36 hours, it won't be until the trough approaches it that a real northwesterly track is possible, but that's a while out. This invest is certainly interesting, and potentially dangerous.
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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.