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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Probably looking at a 1002mb and 50mph wind storm right now. Probably around 55mph by 11am EDT advisory.
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Quoting WeatherNerdPR:

45mph, 1001mb now.


Ever so slight strengthening.
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Quoting gulfscout:


bust season?
It is not even in the peak months of the hurricane season so it is way to early to call it a bust.
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Quoting Neapolitan:
ATCF says winds up, pressure up (?):

AL, 04, 2011072812, , BEST, 0, 237N, 895W, 40, 1001, TS, 34, NEQ, 50, 40, 0, 0, 1010, 90, 15, 0, 0, L, 0, , 0, 0, DON, M,



the nhc could go a little higher
Member Since: May 21, 2006 Posts: 5089 Comments: 114050
Quoting Neapolitan:
AL, 04, 2011072812, , BEST, 0, 237N, 895W, 40, 1001, TS, 34, NEQ, 50, 40, 0, 0, 1010, 90, 15, 0, 0, L, 0, , 0, 0, DON, M,

45mph, 1001mb now.
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000
URNT12 KNHC 281220
VORTEX DATA MESSAGE AL042011
A. 28/11:55:40Z
B. 23 deg 40 min N
089 deg 29 min W
C. 850 mb 1437 m
D. 30 kt
E. 297 deg 34 nm
F. 358 deg 19 kt
G. 266 deg 3 nm
H. EXTRAP 1002 mb
I. 18 C / 1522 m
J. 21 C / 1534 m
K. 8 C / NA
L. NA
M. NA
N. 1345 / 8
O. 0.02 / 3 nm
P. AF303 0204A DON OB 03
MAX FL WIND 19 KT W QUAD 11:54:40Z
MAX OUTBOUND FL WIND 52 KT E QUAD 11:57:10Z
SLP EXTRAP FROM 850 MB
MAX FL TEMP 21 C 234 / 20 NM FROM FL CNTR
MAX OUTBOUND SFC WINDS VISUALLY 45 KTS SOME RAIN CONTAMINATION ON SFMR
FIX MADE INSIDE CONVECTIVE BAND SLIGHTLY NORTH OF ACTUAL CTR
;
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Quoting cat5hurricane:

Don is very small is size, but let's not forget the sheer size of the drought suffering regions in TX. It is enormous.

It would have to take 2 or 3 Don's three times the size to really alleviate things down there.
Going to take 20 to 30 inches to get over the drought in parts of Texas is what I am hearing? Unfortunately Texas is a huge state, alot of times I don't get much rain from the larger tropical systems here unless they move just right. Right now a scattered shower sounds nice to me.
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Quoting gulfscout:


bust season?

For who?
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ATCF says winds up, pressure up (?):

AL, 04, 2011072812, , BEST, 0, 237N, 895W, 40, 1001, TS, 34, NEQ, 50, 40, 0, 0, 1010, 90, 15, 0, 0, L, 0, , 0, 0, DON, M,
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Waters getting deeper and getting away from land. Don is getting ready to pop the cork.
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Is he supposed to gain speed, because I don't see him covering enough ground to make landfall tomorrow
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Quoting gulfscout:


bust season?



3 or 4 name storms be for AUG is not a bust season
Member Since: May 21, 2006 Posts: 5089 Comments: 114050
Quoting P451:


I had to turn my laptop upside down to figure where that was... lol
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Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 28th day of the month at 12:20Z
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: 2
Observation Number: 03
A. Time of Center Fix: 28th day of the month at 11:55:40Z
B. Center Fix Coordinates: 23°40'N 89°29'W (23.6667N 89.4833W)
B. Center Fix Location: 438 miles (704 km) to the S (175°) from New Orleans, LA, USA.
C. Minimum Height at Standard Level: 1,437m (4,715ft) at 850mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 30kts (~ 34.5mph)
E. Location of the Estimated Maximum Surface Wind: 34 nautical miles (39 statute miles) to the WNW (297°) of center fix
F. Maximum Flight Level Wind Inbound: From 358° at 19kts (From the N at ~ 21.9mph)
G. Location of Maximum Flight Level Wind Inbound: 3 nautical miles (3 statute miles) to the W (266°) of center fix
H. Minimum Sea Level Pressure: 1002mb (29.59 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 18°C (64°F) at a pressure alt. of 1,522m (4,993ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 21°C (70°F) at a pressure alt. of 1,534m (5,033ft)
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: 3 nautical miles
Remarks Section - Remarks That Were Decoded...
Maximum Flight Level Wind: 19kts (~ 21.9mph) in the west quadrant at 11:54:40Z
Maximum Flight Level Wind Outbound: 52kts (~ 59.8mph) in the east quadrant at 11:57:10Z
Sea Level Pressure Extrapolation From: 850mb
Maximum Flight Level Temp: 21°C (70°F) which was observed 20 nautical miles (23 statute miles) to the SW (234°) from the flight level center
Remarks Section - Additional Remarks...
MAX OUTBOUND SFC WINDS VISUALLY 45 KTS SOME RAIN CONTAMINATION ON SFMR
FIX MADE INSIDE CONVECTIVE BAND SLIGHTLY NORTH OF ACTUAL CTR
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At least from Levi's tidbits I know even if Don were to pull a Rita, he will not develop into something bigger if he goes north, so I am off to a fun weekend. I'll try to jump in and lurk from time to time to see what's going on. See everyone Sunday night or so.
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Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 28th day of the month at 12:20Z
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: 2
Observation Number: 03
A. Time of Center Fix: 28th day of the month at 11:55:40Z
B. Center Fix Coordinates: 23°40'N 89°29'W (23.6667N 89.4833W)
B. Center Fix Location: 438 miles (704 km) to the S (175°) from New Orleans, LA, USA.
C. Minimum Height at Standard Level: 1,437m (4,715ft) at 850mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 30kts (~ 34.5mph)
E. Location of the Estimated Maximum Surface Wind: 34 nautical miles (39 statute miles) to the WNW (297°) of center fix
F. Maximum Flight Level Wind Inbound: From 358° at 19kts (From the N at ~ 21.9mph)
G. Location of Maximum Flight Level Wind Inbound: 3 nautical miles (3 statute miles) to the W (266°) of center fix
H. Minimum Sea Level Pressure: 1002mb (29.59 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 18°C (64°F) at a pressure alt. of 1,522m (4,993ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 21°C (70°F) at a pressure alt. of 1,534m (5,033ft)
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: 3 nautical miles
Remarks Section - Remarks That Were Decoded...
Maximum Flight Level Wind: 19kts (~ 21.9mph) in the west quadrant at 11:54:40Z
Maximum Flight Level Wind Outbound: 52kts (~ 59.8mph) in the east quadrant at 11:57:10Z
Sea Level Pressure Extrapolation From: 850mb
Maximum Flight Level Temp: 21°C (70°F) which was observed 20 nautical miles (23 statute miles) to the SW (234°) from the flight level center
Remarks Section - Additional Remarks...
MAX OUTBOUND SFC WINDS VISUALLY 45 KTS SOME RAIN CONTAMINATION ON SFMR
FIX MADE INSIDE CONVECTIVE BAND SLIGHTLY NORTH OF ACTUAL CTR
Member Since: April 29, 2007 Posts: 0 Comments: 7506
Look at the recent blowup of convection around the center. don is starting to get away from the yucatan and streghnthen
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Quoting WeatherNerdPR:

I'm guessing you meant that its pressures are slightly higher, not that his winds are lower. We'll see what the next pass shows.


Hard to know with the winds, though HH have found some surface winds of around 45mph which weren't flagged, so I don't think he's weakened considerably.
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Convection is expanding over Don's LLC. Wind shear is slowly weakening now. This is in evident by the more circular formation of the convection.
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Quoting JrWeathermanFL:
4 hurricanes in the E-PAC. None here.
4 TS in the Atlantic. No storms peaking at TS in the E-PAC


bust season?
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1552. Jax82
T-storms starting to build over the center again.

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1551. WxLogic
Quoting MrstormX:
Windspeeds are probably higher due to that thunderstorm blowup.


Correct... if you mix dry air with a TSTM(s) you get high WND speeds.

You can also see that Don is not uniform in its WND field from what I would expect to be a TS. Currently its W periphery severely lacks of any decent WND speed readings.
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Hi Everyone,

Been lurking the past few days just no time to post.. will continue to check in and out as I can to see what is happenening.

Good Luck to Texas, hope they get the rain they really need.

Be good!

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Quoting NICycloneChaser:


He's not weakening now, looks like he's getting his act together, but I'd say he did weaken a little overnight. I'd expect them to find maybe 1001/1000mb at the next pass.

I'm guessing you meant that its pressures are slightly higher, not that his winds are lower. We'll see what the next pass shows.
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Quoting NICycloneChaser:


He's not weakening now, looks like he's getting his act together, but I'd say he did weaken a little overnight. I'd expect them to find maybe 1001/1000mb at the next pass.


I'd agree with that, he obviously had overnight troubles.
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1545. hydrus
CMC in 144 hours..
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Nice little anticyclone forming over the TWave in Catl. This should help it break out of monsoon trough.

LinkShearMap

LinkWVLoop
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Quoting Neapolitan:
Dubuque, Iowa, has received around 3.0" of rain since midnight, atop the nearly 7.5" it received yesterday. There's a whole lot of flooding going on there right now. The radar-based storm total precipitation estimate is very telling.
The flooded areas cannot catch a break and the drought areas cannot get one either. The size of Don is almost if he does not come right over you in Texas you most likely will not get much rain. That is why our chances are 20 percent here.
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Quoting Tazmanian:




DON is not weaking by any means they be doing other pass


He's not weakening now, looks like he's getting his act together, but I'd say he did weaken a little overnight. I'd expect them to find maybe 1001/1000mb at the next pass.
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Windspeeds are probably higher due to that thunderstorm blowup.
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Quoting NICycloneChaser:


Levi explained this pretty well in his tidbit yesterday. Basically the high pressure is pushing convection towards the west, but there's a weakness which is pulling the surface low in Don slightly north, so Don is getting a mix of those and drifting northwest, while the convection behind Don is moving west.


Thank you. I did watch Levi's tidbits, but no coffee for me this morning as I drive up to Arkansas. No coffee means my brain is working too hard to wake up to be able to work right. At least the Yukatan will only get a good storm and not a ts or worse. Hope it's not enough to cause more floods or slides for them.
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Quoting NICycloneChaser:
First pressure reading at the centre from the HH is 1002mb, suggesting Don has weakened somewhat.




DON is not weaking by any means they be doing other pass
Member Since: May 21, 2006 Posts: 5089 Comments: 114050
Quoting NICycloneChaser:


B.


C
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First pressure reading at the centre from the HH is 1002mb, suggesting Don has weakened somewhat.
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4 hurricanes in the E-PAC. None here.
4 TS in the Atlantic. No storms peaking at TS in the E-PAC
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today will be a fun day for DON
Member Since: May 21, 2006 Posts: 5089 Comments: 114050
Quoting aislinnpaps:
Just curious, why is the storm south of Don heading south and into the Yukatan?


Levi explained this pretty well in his tidbit yesterday. Basically the high pressure is pushing convection towards the west, but there's a weakness which is pulling the surface low in Don slightly north, so Don is getting a mix of those and drifting northwest, while the convection behind Don is moving west.
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1531. 10Speed
... and the price of crude will be disproportionately up before the day is done.
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1530. hydrus
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
All the models have the Bermuda high weakening also. If that does not happen, the South Eastern U.S. could still be impacted. The GFS still takes this wave far south into the Caribbean..Here is 850 vort loop...Link
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Quoting superweatherman:
it about to blow...they are finding 55mph winds... at 11am advisory it going to be 60mph..


Yeah, already a big pop of convection is occurring. It would seem the Yucatan is becoming less of a problem.
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Don Dawn
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Good Morning. Don does not look like much at the moment but that may change although it has not expanded it's moisture field since yesterday (it has actually shrunk a bit)and fighting the plume of dry air ahead of it. In the big picture scheme of things, we have another pending E-Pac system on the rise exiting the coast of South America and you can see most of the energy and convection in those longitudes more prevalent on the E-Pac side rather than in the vicinity of Don. Just curious to note that this has been a very interesting year with cyclogenisis issues in both basins at the same time on numerous ocassions.
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Quoting MrstormX:


Sorry :P

No problem.
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About JeffMasters

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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