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 GHOSTY1:
Poor Don, never got any respect.


Well, Don soldiered ahead through difficulties. A lesser system would have just give up and retired near Jamaica, but not Don...he showed he is a true figher. Hats off to you Don...and thanks for the showers!
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Quoting LoveThemCanes:



is this the link you are referring to?? Sorry not sure how to do links on here

http://www.wunderground.com/blog/TomTaylor/commen t.html?entrynum=0


re dundant

#414...:^)
Member Since: August 29, 2010 Posts: 0 Comments: 5236
444. BVI
We have a 3 day holiday here next week in the British Virgin Islands, at least the media are getting info out early in case of a potential storm.

Tropical Disturbance 23 Strengthening; Tropical Storm Or Hurricane Conditions Could Impact VI

http://bviplatinum.com/news.php?page=Article&arti cleID=1311963723

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2.80" of Rain Houston, Texas -Houston Heights from Tropical Showers today so far.....well appreciated.
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Quoting KEEPEROFTHEGATE:
XX/AOI/XXL


That area looks very frisky! I don't see that it has anywhere to go though, unless it can move north.
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18z model plots are just about the same as the 12z plots (on 91L) with the exception of a very slight southerly shift on the BAM suite.

Edit:

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Quoting KEEPEROFTHEGATE:
XX/AOI/XXL


What do you think will happen with that wave?
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting P451:


Wasn't hinting that at all. But he had two good explanations for Don's antics both his erratic motion and the up and down vortex readings of his pressure. So rather than write my reply to your question I just quoted his answers which happened to be spot on.






It really wasn't a question, just a statement on the jump to 1006. I did read his blog this morning, usually do. I purposely put a question mark there to leave comments open.
Member Since: August 19, 2005 Posts: 5 Comments: 5458
@432 , It was called Canefever I don't have a link though.
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Quoting cchsweatherman:
Tropical Storm Don, unfortunately, not looking impressive at all on radar this afternoon. Thunderstorms seem to be struggling to maintain and hold and the bands also seem to be dissipating as they try to come ashore into Texas. Not anticipating more than an inch or two rainfall across Texas with Tropical Storm Don. Very much reminds me of Tropical Storm Bonnie last year that came into South Florida.


I don't recall Bonnie ever looking this healthy. ;)

I'm guessing he is drawing some dry air in from Texas. Storms here seem to have had a tendancy to do that for the last several years.
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It looks like we have two different model solutions. The ones that strengthen 91L into a tropical cyclone want it to turn north because she's feeling the weakness from the trof. The ones like the Euro want to keep 91L weak and on a more southerly route because it doesn't feel the weakness.
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XX/AOI/XXL
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Actually, I think Texas may get at least some rain from this. There is quite a bit of moisture in the area NE of Tropical Dust Devil Don that is beginning to stream into Texas, as seen on this floater... Link

I'm in San Antonio and I am starting to see moisture coming in from the SE already accompanied by a refreshingly moist feeling breeze. Maybe we will at least get a cooling shower out of this.
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Quoting KittyTwister:
I know this is a shot in the dark, but a few weeks ago someone here on this blog posted a link to what I think was his blog. Once clicked it led to a page that seemed to have hundreds of other weather related links, basically just a link page. Does anyone here have any idea what I am speaking of? If so please can you please help me find it again?
TIA



is this the link you are referring to?? Sorry not sure how to do links on here

http://www.wunderground.com/blog/TomTaylor/commen t.html?entrynum=0
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Quoting NotCircumventing:
Not sure what happened to Emily here on the 12Z ECMWF



Was in Caribbean on previous image:


But look at the high built in, GOM open for business with 1014 draped across central gulf:


Same for the east coast as well.
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So i guess that means S. Padre Island won't get hit, thanks Jim... Just Kidding
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting jasonweatherman2011:
wow!! two yellow marks!



MJO is coming around the mountain.
Member Since: August 19, 2005 Posts: 5 Comments: 5458
POSS T.C.F.A.
XX/INV/91L
MARK
9.45N/43.75W
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Does 91L bear watching or can I set sail to the Ivory Coast in a 16ft. hobi cat!LOL
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425. xcool
353
WHXX01 KWBC 291836
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
1836 UTC FRI JUL 29 2011

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL912011) 20110729 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
110729 1800 110730 0600 110730 1800 110731 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 9.5N 41.6W 10.4N 43.9W 11.4N 46.6W 12.3N 49.3W
BAMD 9.5N 41.6W 10.3N 43.8W 11.3N 46.1W 12.1N 48.4W
BAMM 9.5N 41.6W 10.4N 43.7W 11.3N 45.9W 12.1N 48.1W
LBAR 9.5N 41.6W 10.4N 43.7W 11.7N 46.4W 12.9N 48.9W
SHIP 25KTS 29KTS 35KTS 42KTS
DSHP 25KTS 29KTS 35KTS 42KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
110731 1800 110801 1800 110802 1800 110803 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 13.0N 51.8W 14.1N 56.6W 15.6N 61.5W 17.2N 66.4W
BAMD 12.9N 50.7W 14.0N 55.0W 15.4N 58.8W 17.8N 62.7W
BAMM 12.7N 50.2W 13.6N 54.5W 15.3N 59.2W 17.6N 63.8W
LBAR 14.2N 51.6W 15.9N 56.2W 18.4N 59.7W 17.1N 64.3W
SHIP 50KTS 64KTS 73KTS 71KTS
DSHP 50KTS 64KTS 73KTS 71KTS

...INITIAL CONDITIONS...
LATCUR = 9.5N LONCUR = 41.6W DIRCUR = 285DEG SPDCUR = 11KT
LATM12 = 8.8N LONM12 = 39.6W DIRM12 = 292DEG SPDM12 = 11KT
LATM24 = 8.2N LONM24 = 37.6W
WNDCUR = 25KT RMAXWD = 80NM WNDM12 = 25KT
CENPRS = 1007MB OUTPRS = 1010MB OUTRAD = 250NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
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04L/TS/D/Cx
NEARING LANDFALL
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Jim cantore is in south padre island,tx.
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Tropical Storm Don, unfortunately, not looking impressive at all on radar this afternoon. Thunderstorms seem to be struggling to maintain and hold and the bands also seem to be dissipating as they try to come ashore into Texas. Not anticipating more than an inch or two rainfall across Texas with Tropical Storm Don. Very much reminds me of Tropical Storm Bonnie last year that came into South Florida.
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Where is Jim Cantore? Does he not even like Don?
Member Since: July 25, 2011 Posts: 0 Comments: 453
Poor Don, never got any respect.
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting ProgressivePulse:


While I do value Levi's opinion, he is not the gospel sorry to say, lol.


Hallelujah!!!! Can I get an AAAAAAmen!


(disclaimer: not meant as an attack on Levi)
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Who was looking for the links a while back?

This is on TomTaylor's blog

Hundreds of links
Member Since: August 29, 2010 Posts: 0 Comments: 5236
HCW is there quite a bit of lightning associated with, i didn't think of looking at that aspect of the storm.
Member Since: July 25, 2011 Posts: 0 Comments: 453
When 91L becomes Emily:

* It should be larger than most of the systems over the past year or two (Besides Alex).

* It should be stronger than Don ever was.

* It should draw a lot more attention than Don did.
Member Since: July 6, 2010 Posts: 113 Comments: 32870
411. HCW
64 image level 3 radar of Tropical Storm Don. I turned off lightning and SPC stuff cause it was getting cluttered

Link
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Pressure 1mb lower:

AL, 91, 2011072918, , BEST, 0, 95N, 416W, 25, 1007, LO,
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Quoting P451:


YES.

lol.


While I do value Levi's opinion, he is not the gospel sorry to say, lol.
Member Since: August 19, 2005 Posts: 5 Comments: 5458
Quoting P451:
Well, Don, you've been an odd system to watch but an educational one.

12hr IR Loop ending 145pm et



From the loop you posted it looks as if some of the northern most bands or convection should give Houston some rain which is a great thing.
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting ProgressivePulse:



So i guess we should all just hang it up and follow Levi's orders for fear of being redundant?

Quoting ProgressivePulse:



So i guess we should all just hang it up and follow Levi's orders for fear of being redundant?
Member Since: August 29, 2010 Posts: 0 Comments: 5236
Quoting MississippiWx:


Not necessarily, but the conditions seem ripe for a strong tropical cyclone. The size of it will decrease as the low pressure tightens, but it will be much larger than Don ever was most likely.


Kind of like Charley in 04.
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Quoting P451:
Well, Don, you've been an odd system to watch but an educational one.

12hr IR Loop ending 145pm et

been thinking the same since the TD classification!
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Quoting OracleDeAtlantis:
Are you saying this is potentially a monster in the making?


Not necessarily, but the conditions seem ripe for a strong tropical cyclone. The size of it will decrease as the low pressure tightens, but it will be much larger than Don ever was most likely.
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Quoting MississippiWx:
91L resembles a developing Western Pacific typhoon:

Are you saying this is potentially a monster in the making?
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397. xcool
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Mexico is having a drought too, but not quite as severe as texas is going through and they got some slight relief from TS Arlene.
Member Since: July 25, 2011 Posts: 0 Comments: 453

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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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