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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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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495. JLPR2
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)


2007 had two cat 5 hurricanes.

Still haven't reached 4years since Felix.
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Jefferson and Hardin Counties in Texas are receiving a lot of much needed rain, 2+ inches in most places. Thanks TS Don.
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Quoting nigel20:
The track of 91l will move towards the south with each model run, that's just my opinion.

with you on that 91L is going to be a Carib/Gulf Hurricane/maybe major(maybe the first cat 5 in 5 years)
Member Since: June 13, 2009 Posts: 2 Comments: 12419
I'm still seeing a pretty potent looking rainband on the local on the 8's and from my previous knowledge, there radars are pretty accurate for me at least.
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting nigel20:
The track of 91l will move towards the south with each model run, that's just my opinion.


Just as Don did but unluckily Don got thrown into land masses.
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting TheDawnAwakening:
Low-Level Convergence is increasing with 91L as cumulus clouds and thunderstorm activity are increasing and a southern outflow band appears to be developing in association with the monsoonal trough. if it can continue to gain some latitude and moisture, this will become a tropical cyclone in less than 48 hours, depending upon how quickly the low level circulation can consolidate and close off, but the low level convergence needed is certaintly there. As well as upper level divergence associated with the upper level anticyclone.


Closing off the center won't be a problem since it's already closed. It's just elongated at the present time.
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The track of 91l will move towards the south with each model run, that's just my opinion.
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Been in the ER all day with mom.

Will Dons rains reach central TX?

Is 91 an invest?

Will we ever get some rain here in NE Fl.

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moving west!!
Member Since: July 12, 2011 Posts: 0 Comments: 1532
TS Don Update with Video
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whats up nigel? I agree with your statement
Member Since: July 25, 2011 Posts: 0 Comments: 453
I think 91l will continue westward for the next couple of days.
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By this time next week week we might not be able to afford a Hurricane in the US...
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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.
Member Since: July 25, 2011 Posts: 0 Comments: 453
Low-Level Convergence is increasing with 91L as cumulus clouds and thunderstorm activity are increasing and a southern outflow band appears to be developing in association with the monsoonal trough. if it can continue to gain some latitude and moisture, this will become a tropical cyclone in less than 48 hours, depending upon how quickly the low level circulation can consolidate and close off, but the low level convergence needed is certaintly there. As well as upper level divergence associated with the upper level anticyclone.
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Quoting jpsb:
now why am I not getting any rain here on Galveston Bay? What's up with that?


Sometimes what shows on radar doesn't always reach the ground and evaporates as it falls.
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Quoting GHOSTY1:
Look at the LBAR model?


Just realized it made a wrong turn, so hit the brakes and turned left.
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Quoting druseljic:


Link?


I was mentioning the LBAR model shown on Jasonweathermans post its kinda of a strange movement imo.
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting jpsb:
now why am I not getting any rain here on Galveston Bay? What's up with that?


I have no clue i was just watching the local on the 8's and someone elses posted radar loop and i saw it coming? They didn't look like false echoes.
Member Since: July 25, 2011 Posts: 0 Comments: 453
Don reminds me of the late Andy Farley.

Loud, Rambunctious, Interesting but never really could pull it together.
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Quoting GHOSTY1:
Look at the LBAR model?


Link?
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Quoting ackee:
I think the models will contiue to shift further south with 91L NE CARRB BHAHAMS AND SE US in my view might need to watch this one very close
Crownweather:After passing the Leeward Islands, it’s tough to say where it will go given that it is up to 5 to 7 days away.

Dr. Masters: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.
Member Since: October 9, 2008 Posts: 0 Comments: 8424
473. jpsb
Quoting GHOSTY1:
We got an incoming moderate squall heading in off the coast toward the Houston area with the potential for some well needed rain.
now why am I not getting any rain here on Galveston Bay? What's up with that?
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Look at the LBAR model?
Member Since: July 25, 2011 Posts: 0 Comments: 453
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
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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


Thank you so much!! This was the exact one I was looking for. Thank you to the other posters who led me to the canefever link too though, it will be a blast to get lost in those links for a few days as well. :D
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hey guys I am back home in grand cayman and back to work
Member Since: June 13, 2009 Posts: 2 Comments: 12419
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new modeles are out!!
Member Since: July 12, 2011 Posts: 0 Comments: 1532
We got an incoming moderate squall heading in off the coast toward the Houston area with the potential for some well needed rain.
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465. ackee
I think the models will contiue to shift further south with 91L NE CARRB BHAHAMS AND SE US in my view might need to watch this one very close
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jasonweatherman, from the picture you had posted earlier, didn't your shower curtain have fishes but your picture next your name has flowers, or am i just seeing things?
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Quoting overwash12:
@432 , It was called Canefever I don't have a link though.
Link Google is your friend :)
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Quoting GHOSTY1:
are the model tracks moving farther south or north for 91L i havent been paying attention to 91L very much.
moving south!!
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Quoting jasonweatherman2011:
very bad news!!


Pretty remarkable model consensus over the next three days.
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460. jpsb
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
I think TampaSpin has a bunch of links in his blog, could be he's looking for that.
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are the model tracks moving farther south or north for 91L i havent been paying attention to 91L very much.
Member Since: July 25, 2011 Posts: 0 Comments: 453
18z SHIPS text below on 91L. It foresees a spike in upper-level winds in about 84 hours (around the time the system is approaching the northern Lesser Antilles). Nevertheless, the model still keeps it at hurricane intensity.

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Quoting NOLALawyer:


He looks like Katrina compared to Bonnie. Bonnie would not even knock over a paper plate. She was little more than a wisp.


I'm talking about radar presentation with both storms. Both Bonnie and Don only had one strong thunderstorm band on one side of the circulation center.
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very bad news!!
Member Since: July 12, 2011 Posts: 0 Comments: 1532
Please tell me Cyclone OZ is doing a live chat from S Texas.
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Quoting MiamiHurricanes09:
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:

more south i see!!
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453. jpsb
Quoting P451:
Well, Don, you've been an odd system to watch but an educational one.

12hr IR Loop ending 145pm et

Bye Don.
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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.


He looks like Katrina compared to Bonnie. Bonnie would not even knock over a paper plate. She was little more than a wisp.
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Quoting MiamiHurricanes09:
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:




Short track seems pretty good.
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Quoting HTownJitters:


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!


True that, he also had a small bandwagon of followers pulling him along.
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting FirstCoastMan:
Jim cantore is in south padre island,tx.


North Padre actually unless he mived in the last couple of hours.

He's at Corpus Christi

South Padre is Brownsville/Port Isabel area

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448. xcool
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JamesSA it looks as if has a little NW movement maybe it can move itself north
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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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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.