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

Share this Blog
10
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 46 - 1

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 — Blog Index

Quoting aspectre:
Iceberg in GooseCove,Newfoundland harbor


bet they don't wanna go swimming lol...BBBRRRRRR
Member Since: Posts: Comments:
Quoting Vincent4989:
How did that iceber get in there?


The Inuits harpooned it and hauled it ashore.
Member Since: Posts: Comments:
44. JRRP
Member Since: Posts: Comments:

A long night
Member Since: Posts: Comments:
sorry for lots of misspellings. maybe my brain is toying me around
Member Since: Posts: Comments:
Brian Osbourn (CycloneOz) is currently LIVE!
Member Since: Posts: Comments:
Quoting aspectre:
Iceberg in GooseCove,Newfoundland harbor
How did that iceber get in there?
Member Since: Posts: Comments:
Quoting Vincent4989:
one word: WHY MEXICO?!
Also, 91L not looking too impressive.

I think 91L looks like that because it's separating from the ITCZ. Not to sure though.
Member Since: Posts: Comments:
STeering for Don:

Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:


What makes you say that?

i mean two words
Member Since: Posts: Comments:
Quoting WeatherNerdPR:
Thanks.
Jeff is going to vacation again? Aww man.


Dude, we live in Michigan. Have to experience summer while we can. LOL

Fall is only a month away.........
Member Since: Posts: Comments:
Thank You Dr.; as we are starting to approach what seems to be start of the Cape Verde season in earnest, have you formulated any thoughts yet on the general "set-up" of steering patterns and general position of the A-B high towards the peak of the season? You usually do a general post on this issue every year but I don't recall if you do it in early August or late August......Thank You.
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:


It's far too early to say at this time. We will have a better understanding on where 91L will track by the middle/latter part of this upcoming week.




thx for the fast reply
Member Since: Posts: Comments:
Iceberg in GooseCove,Newfoundland, temporarily blocking the harbor before breaking apart

Photo by GenePatey
Member Since: Posts: Comments:
Quoting Vincent4989:
one word: WHY MEXICO?!
Also, 91L not looking too impressive.


What makes you say that?
Member Since: July 6, 2010 Posts: 113 Comments: 31424
Quoting ClearwaterRain:
anyone think 91L will make its way to florida? i am dying for a nice storm. for some reason i love nasty storms!! back when ivan ,i think it was, hit close to here. i drove directly into the eye, it was scary but so awesome at the same time.. as long as there are no deaths or major damage bring on the storm!!!


It's far too early to say at this time. We will have a better understanding on where 91L will track by the middle/latter part of this upcoming week.
Member Since: July 6, 2010 Posts: 113 Comments: 31424
Thanks for the update Dr. Masters... bummer that TX just won't get the relief most of the region needs.
Member Since: Posts: Comments:
Thanks.
Jeff is going to vacation again? Aww man.
Member Since: Posts: Comments:
one word: WHY MEXICO?!
Also, 91L not looking too impressive.
Member Since: Posts: Comments:
anyone think 91L will make its way to florida? i am dying for a nice storm. for some reason i love nasty storms!! back when ivan ,i think it was, hit close to here. i drove directly into the eye, it was scary but so awesome at the same time.. as long as there are no deaths or major damage bring on the storm!!!
Member Since: Posts: Comments:
Quoting divdog:
did i miss something


Doc is going on vacation.
Member Since: Posts: Comments:
thanks doc
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:
Well, we all know Emily will be a major hurricane.
did i miss something
Member Since: Posts: Comments:
No Dr. Masters stay home, lol. EVERY TIME you go on vacation a storm forms.

Thanks for the update BTW.
Member Since: Posts: Comments:
Thanks for the update.
Have a good vacation, although it may be short lived! :)
Member Since: Posts: Comments:
13. IKE

Member Since: Posts: Comments:
Angela look forward to your posts you do a nice job when the Doctor is out of the office. Thank you!
Member Since: Posts: Comments:
Uh oh. Dr. Masters is going on vacation....that means one thing:

Bad things are going to happen in the tropics!

Member Since: Posts: Comments:
Well, we all know Emily will be a major hurricane.
Member Since: July 6, 2010 Posts: 113 Comments: 31424
Ah, Matagorda......or so
Member Since: Posts: Comments:
Thanks, Dr. Masters!
Member Since: Posts: Comments:
Doc on vacation. We will get Emily and she will be a big one.
Member Since: Posts: Comments:
Thanks for the update. Was hoping for more rain in the San Antonio area. :(
Member Since: Posts: Comments:
Thanks for the update. We shall see what happens with 91L down the road
Member Since: July 25, 2011 Posts: 0 Comments: 1102
thanks for the update
Member Since: Posts: Comments:
Will we get to Greek this year?
Member Since: Posts: Comments:
Interesting times these are; lots more to watch. Thanks!
Member Since: Posts: Comments:

Viewing: 46 - 1

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 — Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.