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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#88. The seasoned ones will watch, analyze, and form opinions over time based on a scientific approach, and those are the posts and users I look forward to reading.

That's too much work....lets just make up stuff and argue about it.....:/
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POSS T.C.F.A.
XX/INV/91L
MARK
9.45N/43.75W
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91L will continue on a w/wnw path until it is developed IMO
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lets just hope this Emily doesn't follow the last one (2005)!!
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04L/TS/D/Cx
NEARING LANDFALL


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89. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 5964
Quoting IKE:
My rainfall total for July here in the Florida panhandle is at 8.08.


My weeds are celebrating. :>|
Member Since: August 22, 2008 Posts: 12 Comments: 6010
Quoting islander101010:

don is beginning to unleash his fury on brownville i predict 15 total tornados with him the next few days. good soaking as for 91 change of mind. lots of rotation on that vis. loop looks well on its way to td status

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Quoting Dr. Jeff Masters:
Omidieh, Iran and Shoshtar, Iran hit a scorching 52.6C on July 27, the hottest temperatures ever recorded in the country. 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 39.2C at M'Pouya...Also this July, a 50.2C temperature was measured at Aydyngkol Lake, China--the highest temperature on record at any official Chinese weather station.

So with the year barely half over, that's three all-time national high temperatures already. Adding that to the 19 from last year brings the total to 22 all-time national high temps in the past 19 months, and 0 all time national low temperatures.

Pretty amazing.
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Quoting stormwatcherCI:

The reason Emily took that path was because Dennis had just hit the central gulf coast and a High pressure built in behind it shoving Emily that way. I don't see that happening with this wave. Although I could be wrong.
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Quoting IKE:
My rainfall total for July here in the Florida panhandle is at 8.08.


For me in the foggy SF: Zero
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Quoting stormwatcherCI:
I think a track like this is quite possible.
Quoting Matt1989:
Looking at the computer models for 91L. The high isn't going to be strong enough to keep a stronger system south. So if this developes into a hurricane it's going to be a bermuda storm IMO.
I don't think 91l will develope as quickly as the models are suggesting.
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Quoting islander101010:
91 might not even develop as a td remain a wave move into the carib. towards the gulf as for don he is beginning to unleash his fury on brownville


There is a very high chance of 91L developing into TD #5/Emily.
Member Since: July 6, 2010 Posts: 113 Comments: 32256
don is beginning to unleash his fury on brownville i predict 15 total tornados with him the next few days. as for 91 change of mind. lots of rotation on that vis. loop looks well on its way to td status
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Looking at the computer models for 91L. The high isn't going to be strong enough to keep a stronger system south. So if this developes into a hurricane it's going to be a bermuda storm IMO.
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Quoting angiest:
Did recon miss the center?

Nope

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 29th day of the month at 15:57Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Storm Number & Year: 04L in 2011
Storm Name: Don (flight in the North Atlantic basin)
Mission Number: 5
Observation Number: 12
A. Time of Center Fix: 29th day of the month at 15:27:30Z
B. Center Fix Coordinates: 26°19'N 94°59'W (26.3167N 94.9833W)
B. Center Fix Location: 158 miles (254 km) to the E (80°) from Brownsville, TX, USA.
C. Minimum Height at Standard Level: 1,466m (4,810ft) at 850mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 34kts (~ 39.1mph)
E. Location of the Estimated Maximum Surface Wind: 63 nautical miles (72 statute miles) to the SW (229°) of center fix
F. Maximum Flight Level Wind Inbound: From 232° at 25kts (From the SW at ~ 28.8mph)
G. Location of Maximum Flight Level Wind Inbound: 80 nautical miles (92 statute miles) to the SW (228°) of center fix
H. Minimum Sea Level Pressure: 1003mb (29.62 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 14°C (57°F) at a pressure alt. of 1,534m (5,033ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 25°C (77°F) at a pressure alt. of 1,516m (4,974ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 8°C (46°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind, Pressure and Temperature
N. Fix Level: 850mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 1 nautical mile
Remarks Section:
Maximum Flight Level Wind: 52kts (~ 59.8mph) in the east quadrant at 11:43:20Z
Maximum Flight Level Wind Outbound: 51kts (~ 58.7mph) in the northeast quadrant at 15:38:00Z
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Quoting IKE:
My rainfall total for July here in the Florida panhandle is at 8.08.


That may be the total I have had all year (not a big exaggeration).
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75. jpsb
Quoting IKE:
My rainfall total for July here in the Florida panhandle is at 8.08.

Drought easing a little here in Galveston Bay area, got a good rain yesterday and might get some more today :) dark skies all around me, nice breeze too.
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Quoting weatherh98:
Mimic tpw shows strong circulation and very moist air a couple sustained storms over the center and 91l will go through a stage of ri


We are a long way away from any possible RI with 91L. Way to early to tell if that will happen. I do not see any sustained storms over the possible LLC.
Look at this 1km visible loop.
Link
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Did recon miss the center?
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So is Don heading closer to Corpus than what was forecast earlier this morning? Just curious since there has been a little more of a Northward pull on him.
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71. IKE
My rainfall total for July here in the Florida panhandle is at 8.08.
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Mimic tpw shows strong circulation and very moist air a couple sustained storms over the center and 91l will go through a stage of ri
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Quoting SuperYooper:


Dude, we live in Michigan. Have to experience summer while we can. LOL

Fall is only a month away.........


In da U.P. fall is only a month away. I'd say the trolls still have a good 1 1/2 - 2 months of great summer weather before fall inches in.
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Recon will be in Sunday, along with upper data flight.

2. OUTLOOK FOR SUCCEEDING DAY:
A. INVEST SUSPECT AREA AT 31/1800Z NEAR 14.0N 54.0W.
B. ADDED....A G-IV MISSION FOR 01/0000Z.
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Quoting twincomanche:
And not a word about the recent research by Roy Spencer?


Are you really surprised? That kind of material is a bannable offense around these parts.
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65. jpsb
Quoting islander101010:
all this model worshiping might go to pot if 91 remains a tropical wave and moves into the carib.
Right now model are running on satellite data not direct observations with I might add very low resolution. I would for sure take these early runs as mere suggestions at best.
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Not to mention those in the islands are going to be here looking for input, that's as early as Monday. Game on once Don goes ashore.
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Quoting stormwatcherCI:
I think a track like this is quite possible.
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1001.8mb according to latest recon pass on Don.
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Quoting NotCircumventing:
9,

Pig Latin comes after Greek.

Check the Rules of the Road


and then Klingon....and then Elvish.
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Quoting IceCoast:

I don't know anything about the FIM, but i've checked it pretty frequently this season.

108 hrs hits the northern islands.


Then PR


Then Bermuda



not typical for a storm to hit PR then swing a 90 and hit Bermuda like that...would have to go further wnw, nw before it would do that...
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Member Since: October 9, 2008 Posts: 0 Comments: 8392
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all this model worshiping might go to pot if 91 remains a tropical wave and moves into the carib.
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Quoting JRRP:

I don't know anything about the FIM, but i've checked it pretty frequently this season.

108 hrs hits the northern islands.


Then PR


Then Bermuda

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Quoting TropicalAnalystwx13:


It's far too early to say at this time. We will have a better understanding on where 91L will track by the middle/latter part of this upcoming week.


Supposed to be approaching 75W by the latter part of next week, hopefully we have a pretty good idea before then, lol.
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1Km Visible Imagery of 91L.
A good one to watch today.
Link
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Thank you Dr. Masters. Have a great vacation!
Angela, thank you for keeping us posted in his absence. It is much appreciated!
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Quoting ClearwaterRain:
anyone think 91L will make its way to florida? i am dying for a nice storm. for some reason i love nasty storms!! back when ivan ,i think it was, hit close to here. i drove directly into the eye, it was scary but so awesome at the same time.. as long as there are no deaths or major damage bring on the storm!!!


Be careful what you wish for!
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Hey Doc, you know every time you go vacation storms develop, now we are all in trouble from 91L!
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Link

check this emily is here
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Quoting aspectre:
Iceberg in GooseCove,Newfoundland harbor


bet they don't wanna go swimming lol...BBBRRRRRR
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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.