Tropical Storm Don forms in the Gulf of Mexico

By: Dr. Jeff Masters , 9:29 PM GMT on July 27, 2011

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Tropical Storm Don, the fourth tropical cyclone of the 2011 season, has formed in the Gulf of Mexico just north of the Yucatan Peninsula. Hurricane Hunters began investigating the system earlier this afternoon and quickly found a closed surface circulation. As the mission continued to gather data from what was thought to be a tropical depression at the time, winds of around 39 mph were found, as well as a 1001 mb central pressure, bringing the system up to tropical storm strength.


Figure 1. Satellite loop of Tropical Storm Don. This loop will stay current.

The official forecast for Don agrees with what most of the models have been suggesting over the past 24 hours. Don will make its way toward the northwest over the next 48 hours before making landfall somewhere between Brownsville and Galveston. The statistical models tend to suggest a more southerly track toward Brownsville, and the dynamical models are forecasting anything from Corpus Christi to Galveston. They all tend to agree landfall will occur late on the 29th (Friday night). Whether or not Don will reach hurricane status is still in question. The Hurricane Center's initial forecast is that Don will remain a tropical storm until landfall. Today some models were intensifying Don to a strong tropical storm, but none crossed the hurricane threshold. Now that we have data from aircraft reconnaissance, the models will be able to get a better handle on potential intensity. The runs that occur later tonight and early tomorrow will have much less uncertainty than those from today.


Figure 2. Model forecast tracks for Tropical Storm Don as of Wednesday afternoon.

I believe Jeff will be back tomorrow for an update.

Angela

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Quoting MrstormX:


Sorry :P

No problem.
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Quoting superweatherman:
it about to blow...they are finding 55mph winds... at 11am advisory it going to be 60mph..


Maybe 50mph is my guess.
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Just curious, why is the storm south of Don heading south and into the Yukatan?
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Quoting NICycloneChaser:


The SE certainly needs some rain, but be careful before wishing a long-track storm across the Atlantic towards the coast, could be more than a rain maker. A few models have suggested some development a few times, be interesting to see how it organises.

trust me a cat 1 out of it wouldnt be bad although its a week and more away the ecmwf and cmc try to recurve it but funny how when don was in that EXACT same spot instead of recurving how most of the models showed, it made its way into the gulf towards texas.. interesting :)
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Quoting WeatherNerdPR:

You beat me to it!


Sorry :P
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it about to blow...they are finding 55mph winds... at 11am advisory it going to be 60mph..
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Quoting JrWeathermanFL:
At 11:00 Don will be______
A.40 mph
B.45 mph
C.50 mph
D.55 mph
E.Higher
F.Lower


B.
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Quoting P451:


It's what we can't see that the NHC is looking at thanks to observations. The inner core structure, winds at different levels. We can't see these things from satellite imagery which can be very misleading at times.



Yeah, plus it is out of radar range. It must be really tight in there.
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Quoting MrstormX:
Fist Visible image of the day:


You beat me to it!
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Quoting floridaboy14:

bad thing is there is a trough trying to recurve it. i wish the CMC bought it into the SE coast because they are in some need of rain


The SE certainly needs some rain, but be careful before wishing a long-track storm across the Atlantic towards the coast, could be more than a rain maker. A few models have suggested some development a few times, be interesting to see how it organises.
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1514. WxLogic
Also check the TEMP/TD profile:

Significant Temperature And Relative Humidity Levels...
Level Air Temperature Dew Point
1003mb (Surface) 26.8°C (80.2°F) 26.4°C (79.5°F)
970mb 25.8°C (78.4°F) 22.7°C (72.9°F)
909mb 24.0°C (75.2°F) 21.2°C (70.2°F)
887mb 24.2°C (75.6°F) Approximately 17°C (63°F)
861mb 23.0°C (73.4°F) Approximately 17°C (63°F)
850mb 22.2°C (72.0°F) Approximately 11°C (52°F)
843mb 21.8°C (71.2°F) Approximately 6°C (43°F)

It is pretty dry above 850MB... once they get another drop out then it could further validate the extend of the dry air in the environment Don is in.
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At 11:00 Don will be______
A.40 mph
B.45 mph
C.50 mph
D.55 mph
E.Higher
F.Lower
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if DON be comes stronger then forcast a hurricane watch will be needed some time this PM for parts of TX
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
Fist Visible image of the day:

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Product: Air Force Temp Drop (Dropsonde) Message (UZNT13 KNHC)
Transmitted: 28th day of the month at 12:10Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Storm Number: 04
Storm Name: Don (flight in the North Atlantic basin)
Mission Number: 2
Observation Number: 04

Part A...

Date: Near the closest hour of 12Z on the 28th day of the month
Highest Mandatory Level For Which Wind Was Reported: 850mb
Coordinates: 23.7N 89.4W
Location: 436 miles (701 km) to the S (175°) from New Orleans, LA, USA.
Marsden Square: 081 (About)

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1003mb (29.62 inHg) Sea Level (Surface) 26.8°C (80.2°F) 26.4°C (79.5°F) 155° (from the SSE) 32 knots (37 mph)
1000mb 27m (89 ft) 26.4°C (79.5°F) 25.9°C (78.6°F) 155° (from the SSE) 38 knots (44 mph)
925mb 716m (2,349 ft) 24.4°C (75.9°F) 21.8°C (71.2°F) 165° (from the SSE) 47 knots (54 mph)
850mb 1,458m (4,783 ft) 22.2°C (72.0°F) Approximately 11°C (52°F) 155° (from the SSE) 52 knots (60 mph)

Information About Radiosonde:
- Launch Time: 11:56Z
- About Sonde: A descending radiosonde tracked automatically by satellite navigation with no solar or infrared correction.

Remarks Section...

Splash Location: 23.72N 89.41W
Splash Time: 11:59Z

Release Location: 23.7N 89.4W
Release Time: 11:56:58Z

Splash Location: 23.72N 89.41W
Splash Time: 11:58:58Z

Mean Boundary Level Wind (mean wind in the lowest 500 geopotential meters of the sounding):
- Wind Direction: 165° (from the SSE)
- Wind Speed: 50 knots (58 mph)
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Quoting hydrus:
The CMC still wants to develop that wave in the Atlantic...Even with all the dry air present..

bad thing is there is a trough trying to recurve it. i wish the CMC bought it into the SE coast because they are in some need of rain
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I suppose compact storms are difficult to forecast. Nothing about this system screams that it is strengthening to me (but apparently it is).
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Time: 12:01:00Z
Coordinates: 23.8167N 89.2W
Acft. Static Air Press: 843.3 mb (~ 24.90 inHg)
Acft. Geopotential Hgt: 1,545 meters (~ 5,069 feet)
Extrap. Sfc. Press: 1007.8 mb (~ 29.76 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 160° at 44 knots (From the SSE at ~ 50.6 mph)
Air Temp: 17.1°C (~ 62.8°F)
Dew Pt: 4.7°C (~ 40.5°F)
Peak (10s) Flt. Lvl. Wind: 47 knots (~ 54.0 mph)
SFMR Peak (10s) Sfc. Wind: 38 knots (~ 43.7 mph)
SFMR Rain Rate: 4 mm/hr (~ 0.16 in/hr)
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Quoting NICycloneChaser:
HH just found several very high surface winds, including one at 73knots (83.9mph). They have of course been marked as suspect, but I doubt Don is still a 40mph storm. I'd expect to go up to perhaps 50mph at the next advisory.

The high winds could have been from an embedded severe thunderstorm. Either that or Don is whack.
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Dropsonde


Level Wind Direction Wind Speed
1003mb (Surface) 155° (from the SSE) 32 knots (37 mph)
995mb 160° (from the SSE) 50 knots (58 mph)
991mb 160° (from the SSE) 53 knots (61 mph)
953mb 170° (from the S) 51 knots (59 mph)
941mb 165° (from the SSE) 45 knots (52 mph)
882mb 160° (from the SSE) 49 knots (56 mph)
843mb 155° (from the SSE) 53 knots (61 mph)
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I think with 53-54mph winds at flight level, I think Don is at 45mph winds now.
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Quoting NICycloneChaser:
HH just found several very high surface winds, including one at 73knots (83.9mph). They have of course been marked as suspect, but I doubt Don is still a 40mph storm. I'd expect to go up to perhaps 50mph at the next advisory.



we need more dated from the HH whats see whats else they find
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
Product: Air Force Temp Drop (Dropsonde) Message (UZNT13 KNHC)
Transmitted: 28th day of the month at 12:10Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Storm Number: 04
Storm Name: Don (flight in the North Atlantic basin)
Mission Number: 2
Observation Number: 04

Part A...

Date: Near the closest hour of 12Z on the 28th day of the month
Highest Mandatory Level For Which Wind Was Reported: 850mb
Coordinates: 23.7N 89.4W
Location: 436 miles (701 km) to the S (175°) from New Orleans, LA, USA.
Marsden Square: 081 (About)

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1003mb (29.62 inHg) Sea Level (Surface) 26.8°C (80.2°F) 26.4°C (79.5°F) 155° (from the SSE) 32 knots (37 mph)
1000mb 27m (89 ft) 26.4°C (79.5°F) 25.9°C (78.6°F) 155° (from the SSE) 38 knots (44 mph)
925mb 716m (2,349 ft) 24.4°C (75.9°F) 21.8°C (71.2°F) 165° (from the SSE) 47 knots (54 mph)
850mb 1,458m (4,783 ft) 22.2°C (72.0°F) Approximately 11°C (52°F) 155° (from the SSE) 52 knots (60 mph)

Information About Radiosonde:
- Launch Time: 11:56Z
- About Sonde: A descending radiosonde tracked automatically by satellite navigation with no solar or infrared correction.
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just curious you guys think the hurricane hunters will find don stronger and is it true there are some ugly lookin hurricanes but can attain hurricane status i mean shear is low dry air is there but waters are warm possible it could become a hurricane?
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this thing has sure got it stronger it looks
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
HH just found several very high surface winds, including one at 73knots (83.9mph). They have of course been marked as suspect, but I doubt Don is still a 40mph storm. I'd expect to go up to perhaps 50mph at the next advisory.
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SFMR this found 50kt winds al so fight level is 48kt
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
Quoting Tazmanian:
1001.7 mb
(~ 29.58 inHg) - From 159° at 49 knots
(From the SSE at ~ 56.3 mph) 20.2°C
(~ 68.4°F) 5.8°C
(~ 42.4°F) 52 knots
(~ 59.8 mph) 66 knots*
(~ 75.9 mph*)



SFM found 66kt winds all so a 1001mb

SFMR(75mph) higher than Flight Level(60mph) = Invalid
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1493. Gearsts
Quoting Tazmanian:
1001.7 mb
(~ 29.58 inHg) - From 159 at 49 knots
(From the SSE at ~ 56.3 mph) 20.2C
(~ 68.4F) 5.8C
(~ 42.4F) 52 knots
(~ 59.8 mph) 66 knots*
(~ 75.9 mph*)



SFM found 66kt winds all so a 1001mb
NVM
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Quoting floridaboy14:

that makes no sense. yeah don is organizing but a hurricane with a pressure of 1001mb is weird


Please note the "*" in the report
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Quoting floridaboy14:
Will we get an earlier advisory than the 11pm one if the HH find stronger winds in don?


Since there is a T.S. Watch out, there will be an 11:00 a.m. EST update.
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Quoting Tazmanian:
1001.7 mb
(~ 29.58 inHg) - From 159° at 49 knots
(From the SSE at ~ 56.3 mph) 20.2°C
(~ 68.4°F) 5.8°C
(~ 42.4°F) 52 knots
(~ 59.8 mph) 66 knots*
(~ 75.9 mph*)



SFM found 66kt winds all so a 1001mb


Flagged though.
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1489. hydrus
Quoting stormpetrol:
The CMC still wants to develop that wave in the Atlantic...Even with all the dry air present..
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1488. WxLogic
Quoting Tazmanian:
1001.7 mb
(~ 29.58 inHg) - From 159° at 49 knots
(From the SSE at ~ 56.3 mph) 20.2°C
(~ 68.4°F) 5.8°C
(~ 42.4°F) 52 knots
(~ 59.8 mph) 66 knots*
(~ 75.9 mph*)



SFM found 66kt winds all so a 1001mb


One thing learned from Nrt... comments yesterday. If SFMR is higher than the Flight Level winds then SFMR is dropped. So that 66kts is not valid.

We'll see what else the HH comes up with.
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Quoting Tazmanian:
1001.7 mb
(~ 29.58 inHg) - From 159° at 49 knots
(From the SSE at ~ 56.3 mph) 20.2°C
(~ 68.4°F) 5.8°C
(~ 42.4°F) 52 knots
(~ 59.8 mph) 66 knots*
(~ 75.9 mph*)



SFM found 66kt winds all so a 1001mb

that makes no sense. yeah don is organizing but a hurricane with a pressure of 1001mb is weird
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1001.7 mb
(~ 29.58 inHg) - From 159° at 49 knots
(From the SSE at ~ 56.3 mph) 20.2°C
(~ 68.4°F) 5.8°C
(~ 42.4°F) 52 knots
(~ 59.8 mph) 66 knots*
(~ 75.9 mph*)



SFM found 66kt winds all so a 1001mb
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
Impact's latest is Corpus landfall at 80 mph with gusts to 100 mph. Corpus 6 refinieries will have to make the call today on shutting down and most use ImpactWeather to make that decision. There goes gas prices at the pump. Also a direct hit would effect future windstorm insurances rates. Those of us along the Gulf will all pay the cost. Corpus hasn't had a direct hit in so many years since Celia nobody knows how the old refineries will hold up.

Don lost that interaction with the Yucatan. He shouldn't disappoint today.
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Quoting Neapolitan:

Agreed. A Cat 5 can rip through the Caribbean, tear north along the Bahamas, and smack Bermuda head-on--but to too many here, it wouldn't bear watching as it would be "just a fish storm". :-\


GASP.. we agree on something 100%
BRB, have to go and check the news... there has to be some kind of tear in the time warp somewhere.
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1483. WxLogic
Definition of CDO (so the term won't get used loosely):

"CDO" is an acronym that stands for "central dense overcast". This is the cirrus cloud shield that results from the thunderstorms in the eyewall of a tropical cyclone and its rainbands. Before the tropical cyclone reaches hurricane strength (33 m/s, 64 kts, 74mph), typically the CDO is uniformly showing the cold cloud tops of the cirrus with no eye apparent. Once the storm reaches the hurricane strength threshold, usually an eye can be seen in either the infrared or visible channels of the satellites. Tropical cyclones that have nearly circular CDO's are indicative of favorable, low vertical shear environments.

Source

This is seen on stronger TS before they attain HURR status.
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Don has barely been moving, and needs to get it's act together.


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Sheer has done a number on Don. I think the latest blowup shows he may be getting away from it. No convection north of the center, and dry air northwest of center will keep Don in check.
Member Since: October 5, 2005 Posts: 0 Comments: 700
115530 2340N 08929W 8434 01504 0022 187 079 057007 010 026 003 00
115600 2341N 08927W 8429 01506 0025 178 076 142017 027 040 017 03
115630 2341N 08926W 8447 01490 0032 174 069 155040 043 073 047 03
115700 2342N 08924W 8429 01511 0017 202 058 159049 052 066 024 03
115730 2342N 08922W 8424 01537 0034 204 048 153043 044 055 012 03


1002.2 1001.7 mb, looks like ~40 kt (flight level to surface) SFMR has flag set.
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Not sure...but wierd...Don is 400 miles from the coast and going 10 mph.....that's 40 hours over very hot water....
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Quoting Orcasystems:


The term "Fish Storm" is used on here fairly often by people who think that any system that does not endanger the CONUS is irrelevant. Lose of life or vessels to them doesn't really count, if its not from the CONUS.

P.S. You have no idea how peeved I get when I see that term used.

Agreed. A Cat 5 can rip through the Caribbean, tear north along the Bahamas, and smack Bermuda head-on--but to too many here, it wouldn't bear watching as it would be "just a fish storm". :-\
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Don is developing convection over the center, or I guess the beginning signs of a CDO forming. Tropical wave by 40w is getting interesting. Also Don was effected by several factors, wind shear, cooler waters and dry air, these should begin getting more favorable as he develops convection over the center of circulation.
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1476. jpsb
Quoting dan77539:
Our local (Houston) NWS office shows us with a 50% chance of rain on Friday. I think the Texas drought map was on the blog a couple days ago--it showed that central areas of the state need the rain more than the Corpus-Brownsville area, so the southward shift is not very welcome news on that front.
Yeah, I am thinking we in South East Texas are not going to get much rain out of Don. Very bad news for us, hope they need it in South Texas would be a real shame to waste this rain on folks that don't need it.
Member Since: June 30, 2009 Posts: 0 Comments: 1276

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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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