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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546. stormwatcherCI
7:55 PM GMT on July 29, 2011
Quoting CaneHunter031472:
I can't recall a storm that big forming that far south in the CATL. 91L will be impressive if it put it's act together and I am convinced it is doing just that.

Member Since: October 9, 2008 Posts: 0 Comments: 8268
545. angiest
7:54 PM GMT on July 29, 2011
Quoting GHOSTY1:


Yeah i know the thing where NOAA dropped Silver iodide into storms and it didn't work, it was a good thought but failed but it did yield great results by helping meteorologist better forecast storms and hurricanes and intensities.


It also had (potentially) unintended consequences. The moisture has to go somewhere.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
544. kshipre1
7:54 PM GMT on July 29, 2011
you could be right. just curious, do you have the latest model runs which depict the trough about a week from now?
Member Since: July 12, 2010 Posts: 0 Comments: 1130
543. ProgressivePulse
7:53 PM GMT on July 29, 2011
Quoting JLPR2:


That was my general thinking, an entrance to the Caribbean through the central Lesser Antilles.


3/4 days out for you guys. Focus will turn to 91L..
Member Since: August 19, 2005 Posts: 5 Comments: 5043
542. jpsb
7:53 PM GMT on July 29, 2011
Quoting jasonweatherman2011:
its starting to look like this invest 91L IS GOING TO HIT LAND somewhere on the east coast or the GOM i think that high will backup and more the storm back to the west!!
I must be looking at the wrong blob, the one I am looking at is going to get sucked north. Well maybe it will show up on my tool in a day or two.
I use this

http://www.atmos.washington.edu/~ovens/loops/wxlo op.cgi?wv_east_enhanced+12

and this

http://my.sfwmd.gov/sfwmd/common/images/weather/s atfloat.html
Member Since: June 30, 2009 Posts: 0 Comments: 1175
541. wunderkidcayman
7:53 PM GMT on July 29, 2011
Quoting CaneHunter031472:
I can't recall a storm that big forming that far south in the CATL. 91L will be impressive if it put it's act together and I am convinced it is doing just that.

hurricane Ivan 2004 good example famous one for us here in Grand Cayman
Member Since: June 13, 2009 Posts: 2 Comments: 11052
540. GHOSTY1
7:52 PM GMT on July 29, 2011
Quoting angiest:


If you aren't familiar with Project Stormfury, go read up on it.


Yeah i know the thing where NOAA dropped Silver iodide into storms and it didn't work, it was a good thought but failed but it did yield great results by helping meteorologist better forecast storms and hurricanes and intensities.
Member Since: July 25, 2011 Posts: 0 Comments: 453
539. BDAwx
7:52 PM GMT on July 29, 2011
Good afternoon blog!
there are a couple of interesting convectionless swirls to the north and northeast of Bermuda :)

Tropical Storm Don kinda looks like a hook on radar. I can't see any reason why Don's intensity would change too much before landfall. I hope rain goes where its needed/wanted from this storm.

91L is quite impressive... ya know, for an invest. I hope everyone is prepared for any potential storm to come from it, and for the Western Pacific tropical storms/typhoons.
Member Since: August 3, 2009 Posts: 51 Comments: 526
538. Baybuddy
7:51 PM GMT on July 29, 2011
Quoting wunderkidcayman:

with you on that 91L is going to be a Carib/Gulf Hurricane/maybe major(maybe the first cat 5 in 5 years)


It does seem to have that "vibe" doesn't it?
Member Since: June 26, 2006 Posts: 0 Comments: 1115
537. Jedkins01
7:51 PM GMT on July 29, 2011
Quoting MississippiWx:
For what it's worth, this is the HWRF track. For it to go on the HWRF track, it would have to start moving to the NNW now.



Current steering argues that such a track isn't possible:



Yeah Computer models have probably brought 100+ hurricanes over the last couple years into Florida and what has been the result? Nada. Now obviously Florida has a very high hurricane impact history, but when you break it down. There are periods where there are few and periods where there are massive amounts of them. We seem to be in a period with less of them over the last few years. Eventually time will run out and they will start getting in line to take their vacations into Florida. Hopefully that won't be for a while again.
Member Since: August 21, 2008 Posts: 0 Comments: 7285
536. ncstorm
7:50 PM GMT on July 29, 2011
Quoting GHOSTY1:
ncstorm, those models are looking alot more south, possibly another gom storm or hurricane? hmmmmm.


a lot more south equals land interaction, convergence vs divergence discussions, 30 hurricane hunter flights and a mexican landfall..good times ahead.
Member Since: August 19, 2006 Posts: 13 Comments: 14466
534. Stormchaser2007
7:48 PM GMT on July 29, 2011
AMSU shows a very nice circulation.

Member Since: June 9, 2007 Posts: 4 Comments: 15777
533. angiest
7:47 PM GMT on July 29, 2011
Quoting GHOSTY1:
i just had a thought, i don't if some of yall seen nuclear bomb tests but when the nuke goes it blows all the clouds away, i wonder if they could figure out a way to remove the radiation and harmful shrapnel and destruction and use the shockwave to somehow disrupt a dangerous hurricanes progress. Just a crazy thought that may save lives in the future if its possible.


If you aren't familiar with Project Stormfury, go read up on it.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
532. muddertracker
7:47 PM GMT on July 29, 2011
Just checking on Don..great...looks like very little impact on central Texas. I can't believe we are going to get missed AGAIN. Drought buster? Hardly...
30% chance today...50% chance tomorrow...and that's IT? WTH????
Member Since: August 16, 2007 Posts: 1 Comments: 2337
531. nigel20
7:46 PM GMT on July 29, 2011
Quoting GHOSTY1:
ncstorm, those models are looking alot more south, possibly another gom storm or hurricane? hmmmmm.
I think so too.
Member Since: November 6, 2010 Posts: 11 Comments: 7853
530. GHOSTY1
7:46 PM GMT on July 29, 2011
did the windshear pick up a little or is just normal cloud tops, imo they look like they may be getting a little shear
Member Since: July 25, 2011 Posts: 0 Comments: 453
529. CaneHunter031472
7:46 PM GMT on July 29, 2011
I can't recall a storm that big forming that far south in the CATL. 91L will be impressive if it put it's act together and I am convinced it is doing just that.
Member Since: August 1, 2007 Posts: 0 Comments: 167
528. ackee
7:46 PM GMT on July 29, 2011
IF 91L enters the carrb what will condtion be like ?
Member Since: July 15, 2008 Posts: 0 Comments: 1347
527. Hurricanejer95
7:46 PM GMT on July 29, 2011


2 models support major hurricane within 4 days
Member Since: August 30, 2008 Posts: 1 Comments: 224
526. nigel20
7:46 PM GMT on July 29, 2011
Quoting GHOSTY1:
ncstorm, those models are looking alot more south, possibly another gom storm or hurricane? hmmmmm.
I think so too.
Member Since: November 6, 2010 Posts: 11 Comments: 7853
525. AtHomeInTX
7:46 PM GMT on July 29, 2011
Quoting Col15thTex:
Jefferson and Hardin Counties in Texas are receiving a lot of much needed rain, 2+ inches in most places. Thanks TS Don.


I'm glad for y'all. Orange Co. not so much. Location, location, location... :)

Member Since: August 24, 2010 Posts: 0 Comments: 677
524. yonzabam
7:46 PM GMT on July 29, 2011
Quoting kshipre1:
compared to this morning, what are the models saying about the strength of the trough?

Just asking because I read somewhere that the High is supposed to buid back in


The models I've seen have the trough picking it up and recurving it.
Member Since: July 20, 2008 Posts: 0 Comments: 2901
523. kshipre1
7:45 PM GMT on July 29, 2011
I wonder if as of now, the models are seeing a much weaker trough in this run. of course, things could change
Member Since: July 12, 2010 Posts: 0 Comments: 1130
522. GHOSTY1
7:44 PM GMT on July 29, 2011
It looks like 91L is getting a really good spin goin, and some convection starting to flare.
Member Since: July 25, 2011 Posts: 0 Comments: 453
521. FLWxChaser
7:44 PM GMT on July 29, 2011
It's that early stage of life for 91L - the models will wig and wag over the next week.
Member Since: July 28, 2011 Posts: 3 Comments: 61
520. PrivateIdaho
7:43 PM GMT on July 29, 2011
Quoting JLPR2:


Sorry to say the NE Caribbean isn't composed of only water.


yeah. there's lots of fish there!
Member Since: August 29, 2010 Posts: 0 Comments: 5236
519. GHOSTY1
7:41 PM GMT on July 29, 2011
ncstorm, those models are looking alot more south, possibly another gom storm or hurricane? hmmmmm.
Member Since: July 25, 2011 Posts: 0 Comments: 453
518. AllBoardedUp
7:41 PM GMT on July 29, 2011
Quoting jpsb:
Just started raining in San Leon, Yeah!
Great news! I'm glad I cut my grass yesterday, or it would have really taken off with this shower.
Member Since: July 25, 2008 Posts: 0 Comments: 626
517. JLPR2
7:40 PM GMT on July 29, 2011
Quoting ProgressivePulse:
TAFB's take on 91L. Forecasting a more southern route.



That was my general thinking, an entrance to the Caribbean through the central Lesser Antilles.
Member Since: September 4, 2007 Posts: 7 Comments: 8500
516. GHOSTY1
7:40 PM GMT on July 29, 2011
Did my approaching rain band reach any of yall or was it just false echoes?
Member Since: July 25, 2011 Posts: 0 Comments: 453
515. ncstorm
7:39 PM GMT on July 29, 2011
18Z 91L


Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)


Dynamic Models (More sophisticated models)
Member Since: August 19, 2006 Posts: 13 Comments: 14466
514. Jedkins01
7:39 PM GMT on July 29, 2011
Don has a tight area of 8 inch per hour rainfall rates headed for South Texas, that's a little bit too heavy, don't ya think? LOL
Member Since: August 21, 2008 Posts: 0 Comments: 7285
513. GHOSTY1
7:39 PM GMT on July 29, 2011
Quoting weatherman566:


Here's how I look at it: Don't mess with mother nature. We aren't God.

Period. Controlling the weather such as that would probably cause worse things down the road.


I know and even if we did figure out a way God would throw us a curveball and then we would have to start all over. What about an idea for using lightning as a source of energy, i don't here too many people looking for that with all this renewable energy. There is never gonna be no lightning and it contains so much power it would perfectly. JMO :P Just trying to think of ways to improve the future
Member Since: July 25, 2011 Posts: 0 Comments: 453
512. jpsb
7:38 PM GMT on July 29, 2011
Quoting AllBoardedUp:
It's raining over here in Hitchcock. Oops, it stopped already.
Just started raining in San Leon, Yeah!
Member Since: June 30, 2009 Posts: 0 Comments: 1175
511. ProgressivePulse
7:37 PM GMT on July 29, 2011
TAFB's take on 91L. Forecasting a more southern route.

Member Since: August 19, 2005 Posts: 5 Comments: 5043
510. CaneHunter031472
7:37 PM GMT on July 29, 2011
91L gaining some very decent spin and convection on visible. I would not rule out a TD by tomorrow. Definitely Red circle tonight or in the Morning.

Link
Member Since: August 1, 2007 Posts: 0 Comments: 167
509. JLPR2
7:36 PM GMT on July 29, 2011
Quoting oracle28:


Fish storm. Recurve already projected.


Sorry to say the NE Caribbean isn't composed of only water.
Member Since: September 4, 2007 Posts: 7 Comments: 8500
508. HimacaneBrees
7:35 PM GMT on July 29, 2011
I was glad to see Stephanie Abrams back on TWC this morning.

91L looks much better than what pre-Don did when he was in that area. I'm really thinking 91 will be a named storm by Sunday.
Member Since: August 23, 2010 Posts: 0 Comments: 975
507. AllBoardedUp
7:35 PM GMT on July 29, 2011
Quoting jpsb:
now why am I not getting any rain here on Galveston Bay? What's up with that?
It's raining over here in Hitchcock. Oops, it stopped already.
Member Since: July 25, 2008 Posts: 0 Comments: 626
506. GHOSTY1
7:35 PM GMT on July 29, 2011
were just gonna have to wait and see how possible Emily acts and then we can determine is she'll be fighter
Member Since: July 25, 2011 Posts: 0 Comments: 453
505. MississippiWx
7:35 PM GMT on July 29, 2011
For what it's worth, this is the HWRF track. For it to go on the HWRF track, it would have to start moving to the NNW now.



Current steering argues that such a track isn't possible:

Member Since: July 15, 2006 Posts: 17 Comments: 10159
504. weatherman566
7:35 PM GMT on July 29, 2011
Quoting GHOSTY1:
i just had a thought, i don't if some of yall seen nuclear bomb tests but when the nuke goes it blows all the clouds away, i wonder if they could figure out a way to remove the radiation and harmful shrapnel and destruction and use the shockwave to somehow disrupt a dangerous hurricanes progress. Just a crazy thought that may save lives in the future if its possible.


Here's how I look at it: Don't mess with mother nature. We aren't God.

Period. Controlling the weather such as that would probably cause worse things down the road.
Member Since: July 15, 2008 Posts: 0 Comments: 108
503. PrivateIdaho
7:35 PM GMT on July 29, 2011
Quoting ProgressivePulse:
Don reminds me of the late Andy Farley.

Loud, Rambunctious, Interesting but never really could pull it together.


Andy Farley was bigger than Don.
Member Since: August 29, 2010 Posts: 0 Comments: 5236
502. JLPR2
7:34 PM GMT on July 29, 2011
I'm not sure if I'm looking at a different 91L since for me it seems to be moving WNW.



in fact the main circulation seems to have reached 10N.
Member Since: September 4, 2007 Posts: 7 Comments: 8500
Quoting jasonweatherman2011:
new modeles are out!!


Fish storm. Recurve already projected.
Member Since: Posts: Comments:
Quoting GHOSTY1:
whats up nigel? I agree with your statement
I'm good, just watching 91l.
Member Since: November 6, 2010 Posts: 11 Comments: 7853
498. jpsb
Quoting GHOSTY1:


Just as Don did but unluckily Don got thrown into land masses.
Well if I have the right blob (91L) it appears to be growing (going?) NW, no way if get past that truff sitting in front of the islands. Plus it is surrounded on 3 sides by dry air. Well Don, make it so I guess 91L has a chance too, but is 91L the fighter Don was (is)?
Member Since: June 30, 2009 Posts: 0 Comments: 1175
Quoting wunderkidcayman:

with you on that 91L is going to be a Carib/Gulf Hurricane/maybe major(maybe the first cat 5 in 5 years)


I don't know if we can predict a cat.5 this early, maybe a Cat.3 at strongest right now but for a cat.5 you really need to know everything that's in her path will be favorable, no dry air, no wind shear, no land, and warm water.
Member Since: July 25, 2011 Posts: 0 Comments: 453
91L could be something to watch. Too far out to say at this time, and too many variables to accurately state where it may go. However, trough dragging it up a bit, and high building back in is a classic recipe for an East Coast strike. We will see. Earl didn't quite make it last year.
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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.