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 KennyNebraska:
I checked out Oz's audio. It's actually good. Here is another of his FB updates.

"Okay...it's starting to get rough in CC. Don beginning to come ashore here. Switch over to FREE AUDIO and pay per view VIDEO is just 30 minutes away. I have my very nice audio system up and running right now on Channel 1 at http://crazymother.tv/ so take a moment to pop in and listen to Don's winds and my ramblings."

I drove down to the bayfront where I think he's "stationed", but I don't know what he looks like and there were news crews there. I did watch a little of his live broadcast-it is good, but that's not the best place for good footage unless it's a real storm. The best place is Port A, however I just heard the ferry service is shut down both ways because of a major brush fire.
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Quoting MiamiHurricanes09:
Emely over Puerto Rico in 120 hours/5 days:



In 180 hours it's north of the easternmost Bahamas with the trough starting to lift out. A model forecast this far out is unreliable, but it will be interesting to see what it does.


Funny. Last year, the 'E' storm affected PR too.
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finally home from working a 12...yesterday my sitter had to have emergency surgery so i had her 3 on top of mine and today my mom in law is at the er...waiting on news from the hubby...as far as the tropics go...we know Don is a minimal rainmaker so far...hope as it goes over land the back half gives them more of the much needed moisture...my interests are mainly on 91L as of now...which way will it go...guess it has to get closer to PR before we know
Member Since: September 16, 2007 Posts: 0 Comments: 3650
Quoting MiamiHurricanes09:
Trough picks it up, could make a close encounter with the central/northern eastern seaboard though. 216 hours:

Isn't this basically the same track Don was supposed to take ?
Member Since: October 9, 2008 Posts: 0 Comments: 8392
We had just moved in our brand new House in Semmes Al. when I was 9 years old in July of 1979. Frederic hit in September of 79 and I have been hooked ever since. It was and still is the most frightning night in my life. Being out of school for 2 weeks was cool though.
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Quoting jasonweatherman2011:
i see two tropical waves to watch here!!


And there's more behind these...the wave train has begun
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Edit: Never mind, actually brings it over Bermuda:

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888. JLPR2
Quoting MiamiHurricanes09:
Emely over Puerto Rico in 120 hours/5 days:



In 180 hours it's north of the easternmost Bahamas with the trough lifting out. A model forecast this far out is unreliable, but it will be interesting to see what it does.



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.
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Emely over Puerto Rico in 120 hours/5 days:



In 180 hours it's north of the easternmost Bahamas with the trough starting to lift out. A model forecast this far out is unreliable, but it will be interesting to see what it does.

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91L is HUMONGOUS!! Almost a 1000 miles wide!! I know it will shrink but.....WOW!!
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Quoting angelafritz:
Waiting for recon to make a pass or two before I post an update.... stay tuned. :)


Do we get your analysis on 91L? :)
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Thanks Angela
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880. angelafritz (Admin)
Waiting for recon to make a pass or two before I post an update.... stay tuned. :)
Quoting twincomanche:
Fish storms means it never makes landfall on the CONUS.


Where did you come up with that definition?
Member Since: August 22, 2008 Posts: 12 Comments: 6010
BamaGirl, BayBuddy - must be a few of us Frederic survivors here! Freddie was the worst hurricane I've ever been through -- 300 trees down on our five acres, all the outbuildings gone. Neighbor watched 2 tornadoes roll up through our place that night, then she passed out from fright.

Friend of mine in radio, years later showed me a website out of P'cola; some meteorologists had re-examined Frederic and found it was in rapid intensification mode when it hit and would almost certainly be about a 140-mph Cat 4 if it were closely re-examined on all points.

Ah well ... here's hoping none of us are facing THAT kind of storm this year! Nice to see ya ....
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Quoting twincomanche:
Not with me.


Thank you for your explanation of a fish storm. I did not mean to offend you. I was only being sarcastic with my first comment about fish storms. I did know at the time what a fish storm is and I was just making a joke. but like i said thanks for your explanation. Now I will move on from it.
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Some thunderstorms have fizzled on 91L at 1600 to 1700, is it because of D MIN
Member Since: August 30, 2008 Posts: 1 Comments: 259
anyone have acess to a live camera in texas so see how conditions are?
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Quoting kaiden:
BamaGirl, Yes I remember Freddie, the eye passed over us in Moss Point MS. It gave us about an hour to fight the house fire accross the street, but after the wind came back there was nothing to do but watch it burn down, and hope that other houses did not catch. The worst of it was the big stash of cold Barq's Root beer we had, got consumed by the Fire and Police Depts. They earned it though.


Its funny you mention Frederick. I found some old ch.5 video of the storms aftermath online the other day. And Mel Showers hair...wow! Btw...I just learned Mels Daughter passed away in Jan. I was saddened to hear that. She was sweet.
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04L/TS/D/Cx
landfall


Member Since: July 15, 2006 Posts: 173 Comments: 54338
POSS T.C.F.A.
XX/INV/91L
MARK
9.45N/43.75W
Member Since: July 15, 2006 Posts: 173 Comments: 54338
Quoting JrWeathermanFL:
Do I see an eye-like feature on DON?


No, definitely not.

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Quoting JrWeathermanFL:
Do I see an eye-like feature on DON?


Looks more like a belly-button
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looks like the majority of the precip is going into the southern tip of Texas and NE Mexico which in in drought condition but far less then the area to the North which is in Extreme Drought. That kinda sucks.
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Quoting Tropicsweatherpr:
Does anyone has the latest MJO forecast for the next few weeks? I want to see if the wet MJO arrives at the same time 91L is posibly developing.


I'll get the image in a second, but off the top of my head, the upward pulse is currently entering the Gulf of Mexico/Western Caribbean.

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Do I see an eye-like feature on DON?
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Does anyone has the latest MJO forecast for the next few weeks? I want to see if the wet MJO arrives at the same time 91L is posibly developing.
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Quoting twincomanche:
Fish storms means it never makes landfall on the CONUS.



Yes I know. Thank you MR. Obvious. just joking with ya!
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Quoting Stormchaser2007:
18z GFS has a very strong wave coming off of Africa in 72 hours...

Could be another thing to watch.


Went a little further, to 84 hours. Definitely something we need to keep our eyes on. We've started that time where we won't get much of a break between tropical cyclones.

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Quoting twincomanche:
Fish storms means it never makes landfall on the CONUS.
Shouldn't a fish storm be one that never effects land at all. Only open water?
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Quoting MiamiHurricanes09:
The fact that Dr. Masters is on vacation, LOL.

More often than not, when Jeff is on vacation, tropical cyclone activity always increases in the Atlantic. It's a running joke on the blog, but it always seems to verify...somehow LOL.


I really do not understand it, but it ends up verifying every single time.
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I keep reading all this discussion about "fish storms" I've not seen one person mention the poor little fishies that are affected by these storms. hahaha sarcasm now switched off.
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BamaGirl, Yes I remember Freddie, the eye passed over us in Moss Point MS. It gave us about an hour to fight the house fire accross the street, but after the wind came back there was nothing to do but watch it burn down, and hope that other houses did not catch. The worst of it was the big stash of cold Barq's Root beer we had, got consumed by the Fire and Police Depts. They earned it though.
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Jason, LOL Nice touch with the music on your video update!
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853. SLU
Lots of popcorn going off with pre-Emily. Looks like we will see an increase in convection tonight.

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18z GFS has a very strong wave coming off of Africa in 72 hours...

Could be another thing to watch.
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I,m from Mobile as well, I was 3 when Frederick hit however I remember it well. I had to take a bath with my cousins in Big Creek Lake until water was restored haha
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Quoting Gearsts:
based on what?i dont understand:/
The fact that Dr. Masters is on vacation, LOL.

More often than not, when Jeff is on vacation, tropical cyclone activity always increases in the Atlantic. It's a running joke on the blog, but it always seems to verify...somehow LOL.
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Quoting PensacolaDoug:





A little overboard don't ya think? Just 'cause somebody refers to a storm as a "fish" doesn't mean they don't have any empathy for the folks in the islands..And who knows..It may just miss.


Its a race to see who is the most sensitive around here.
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10-20% chance of rain this weekend than back to totally dry 104 next week. I can't even get a pool built because they need to go to hospital for fluids. Only a 100 today, no rain but some afternoon cloud buildup associated with Don. Boy was hoping for a little more than 4 degree drop in temp.
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Even Brian Norcross was surprised. He guessed the circulation near Brownsville is the mid level, and the one s of Corpus is the low level one. To me it looks like its reforming near Brownsville.
Quoting hurricanejunky:
How about that mesocyclone that's formed in Don just east of Brownsville? Looking at radar it's really pronounced! Is that common? I've not seen that before that I can remember.
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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.