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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HEY EVERYONE, HAVE YOU SEEN DA RECENT 12Z CMC MODEL RUN FARTHER WEST AND STALLS IT AT THE END WITH A RIDGE REBUILDING!!
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ooops; forgot to link it sorry



Link
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I think that former-NHC director, Dr. Franks, covered this general issue several years ago. He basically stated that the US need not worry too much about a potential US landfall until we get a TD or storm approaching Puerto Rico (he was referring to the long-track storms) which then gives us better model guidance and sufficient lead time for the US.
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There is a good chance that 91L could be a hurricane by the time it makes it to the Caribbean islands. If that is so, the Hebert box comes into play...Not trying to scare anyone, just sayin'.

It's totally possible that a trough could come and pick "Emily" up, but as we saw with Don, that did not happen. We need to watch this VERY closely.
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241. flsky
ha ha
Quoting 2COOL:
I think fear attracts hurricanes and faith repels them. Maybe we need a localized fear index?!!
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Ummm check this out Jasonweatherman2011 what do think is going on in the Carib?
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Quoting ncstorm:
well 12Z NOGAPS obliterates 91L..

Link


yeah...and it also predicts that there will be a storm that pops out of no where in SC and goes east off the coast...too early to say anything at this point
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To all bloggers: Only post DOOMCASTER type comments regarding 91L. Let's stay away from those pathetic and weak thoughts and forecasts about the system. Maybe we can "WILL" those models into the most BULLISH models ever seen for a storm!

Let's kick this thing into HIGH GEAR NOW!!!! 2011 ROCKS!!! YEAH. LOL.
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Quoting blsealevel:
This will have to be watched

huh?? perhaps you meant it will have had to have been watched... back in January?
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235. flsky
Why have you posted this??
Quoting blsealevel:
This will have to be watched

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The "Models" have done absolutely horrible with pre-storms this year, why would 91L be any different. Look at the satellites and observe, there will be a TD under your nose before you know it.
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Uh-Oh. All models go through..... Herbert box.

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Quoting jasonweatherman2011:
t.d coming soon!!



Surely need to shift focus as soon as Don lands.
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Quoting jasonweatherman2011:
t.d coming soon!!


Yep if its already on that page count on it.
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well 12Z NOGAPS obliterates 91L..

Link
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already is at 30%
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Quoting DookiePBC:


Ok...I predict a cat 5 making landfall in Miami. The storm surge will be full of sharks with frickin' laser beams attached to their heads.

In all seriousness...probably best right now to just keep an eye on things and let's see what the models do with 91L if (or when depending on your perspective) it becomes a depression.
YEAH! That's the spirit!
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Quoting Jax82:
I dont think we need to worry about 91L, its 94L i'm worried about. ;-)


94L? It woulda been easier if you'd have just said "pre-Harvey".
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My thinking on 91L(if it becomes a TD) is a track similar to Hugo. Every time there is a new model run, it's a little more to the right. However, I don't think it will be a fish because I don't believe it will avoid the eastern Carib islands.
Member Since: May 22, 2008 Posts: 0 Comments: 182
Quoting weatherspawn:
Getting some nice thunderstorms from Tropical Storm Don here in SE Texas. Not much different than what we've been getting most afternoons though.
I think your rain is coming from the disturbance off La. Don is small and 500 miles from you. Don will give Extreme south Texas rain and that is about it but that disturbance has been there for days, the high pressure should knock all rain out of Texas by Sunday. 95 here mostly sunny with higher humidity and No wind. Pretty miserable here in south central Texas and I work out in this.
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Don on a more westerly track now, Recon seems to find (last center fix).
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This will have to be watched

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216. 2COOL
I think fear attracts hurricanes and faith repels them. Maybe we need a localized fear index?!!
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215. JRRP

mmmm looks like GFS
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Getting some nice thunderstorms from Tropical Storm Don here in SE Texas. Not much different than what we've been getting most afternoons though.
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The National Hurricane Center should raise this to 40-50%. There is at least a medium chance of this becoming a tropical cyclone by Sunday afternoon.
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A
Quoting stormpetrol:
91L imo will take a path very close to Don , maybe even a tad further south, jmo.
i agree
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Don still running a little right of the track.


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Quoting Waltanater:
I just love the DOOMCASTING. Keep it up.


Ok...I predict a cat 5 making landfall in Miami. The storm surge will be full of sharks with frickin' laser beams attached to their heads.

In all seriousness...probably best right now to just keep an eye on things and let's see what the models do with 91L if (or when depending on your perspective) it becomes a depression.
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Rain comes in:
http://www.spadre.com/southpadrebaycam.jpg
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91L imo will take a path very close to Don , maybe even a tad further south, jmo.
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205. Gorty
Quoting jasonweatherman2011:
new update at 2pm!! invest 91L WILL BE AT 30%


So it will remain the same?
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Quoting ncstorm:


850 mb Vorticity run was what I was posting..the navy is so funny with links and all..you cant post the images, at least I cant and sometimes the links dont work when I do post them....here is the link below

https://www.fnmoc.navy.mil/wxmap_cgi/cgi-bin/wxma p_loop.cgi?&area=ngp_troplant&prod=z85& ;dtg=2011072 912&set=Tropical


same thing...idk...maybe i should show it my DD214 from being in the Navy, maybe that would work lol
....................


I believe the https in the URL, (s for secure) is causing your problem, as you are trying to access an internal page and the server doesn't recognize you.
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Brownsville radar has a shear marker near where I think the COC is.
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Quoting ldhall05:


Thanks for the advice... however, we are flying down and staying in a condo. So we are either all in or all out. No ship taking a different course here.
If Grand Cayman is threatened with a hurricane,especially a major one they do mandatory evacuations for tourists first before any locals evacuate. I don't know about refunds but we do have excellent shelters as Hurricane Ivan can attest to.
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Quoting metwombly:
Sometimes it will give you a message that the certificate is not valid...If its a Navy site, its ok to go into. Had this issue come up a few times.


clicked the go ahead and go to this site option...still a no go...could be the puter...im at work not home...old thing i am on here...
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Quoting tiggeriffic:


same thing...idk...maybe i should show it my DD214 from being in the Navy, maybe that would work lol
Sometimes it will give you a message that the certificate is not valid...If its a Navy site, its ok to go into. Had this issue come up a few times.
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Bloggers...please remember the unoficial blog rules regarding models....if they're bullish and pointing to the US then we believe them. If they're bearish or pointing away from the US, then they must be missing something.
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196. Gorty
Quoting jasonweatherman2011:
New England is save from a hurricane!! the jetstream its there!!


but it can change down the road.
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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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