Tropical Storm Don unimpressive so far

By: Dr. Jeff Masters , 2:08 PM GMT on July 28, 2011

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Tropical Storm Don formed yesterday from an African tropical wave that crossed into the Gulf of Mexico, and the thus-far unimpressive storm appears poised to bring tropical storm conditions to the lower Texas coast by Friday night. An Air Force Hurricane Hunter plane arrived in the center of Don around 8am EDT this morning, and has found Don to be a small tropical storm with top winds near 40 mph. The 7:57am EDT center fix found a central pressure of 1002 mb, which is 2 mb higher than NHC was estimating in its 8am EDT advisory. However, a pass through the center at 9:49am EDT found the pressure had dropped 2mb, to 1000 mb. Top reliable surface winds seen by the Air Force plane with its SFMR instrument as of 9:45am EDT were 41 mph, at 8:10 am EDT. Water vapor satellite images show a region of dry air to the northwest of Don, over the western Gulf of Mexico. Wind shear as diagnosed by the University of Wisconsin CIMSS group and the SHIPS model show a moderate 10 - 15 knots of wind shear. The shear is from strong upper level winds out of the north. Since the atmosphere to the north of Don is relatively moist, the moderate shear will not be as damaging to the storm as if these winds had been blowing from the northwest, where the driest air lies. Thus the shear direction is often just as important as the strength of the shear, and in Don's case, the shear direction should not force significant amounts of storm-disrupting dry air into the core. Water temperatures in the Gulf of Mexico are near 29°C, which is 2.5°C above the 26.5°C threshold typically needed to maintain a tropical storm.


Figure 1. Morning satellite image of Don.

Satellite imagery shows that Don is a very small storm. Thus, the storm is vulnerable to pockets of dry air and modest-sized jets of wind shear that we can't see from the relatively coarse-resolution data collected by surface stations, hurricane hunter flights, and satellites. The moderate wind shear over Don is keeping Don's circulation tilted so that the surface center is displaced from the center at higher levels. This tilt is keeping the storm from intensifying. Latest visible satellite loops show a modest increase in the intensity of the thunderstorm's near Don's center began at 9am EDT, but this could be a transient burst and not a sign the storm is undergoing intensification.


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 big question for Don is, will it be a boon or bane for Texas? The state is currently suffering through its worst drought in recorded history, and Don has the potential to bring some decent drought-busting rains to the state. If Don can expand in size and intensify to a 50 - 55 mph tropical storm, it has the capability to bring hundreds of millions of dollars worth of beneficial rains to the state. However, we have a Goldilocks problem. We can't have Don intensifying into a hurricane, or its winds and flooding might bring hundreds of millions in damage. Neither do we want Don to stay in its current state, which is too small and weak to bring significant rains to Texas. If Don follows the current NHC forecast, which brings the storm up to a moderate-strength tropical storm, that would be just right. This forecast is low-confidence, though, since Don's small size makes it prone to sudden changes in strength, either upward or downward. NHC is giving Don just a 14% chance of intensifying into a hurricane in its 5am advisory, but this could easily change upward if Don manages to overcome its vertical tilt and start consolidating an eyewall. I put the odds of Don reaching hurricane strength at 30%. None of the computer models is predicting Don will become a hurricane.

A small system like Don is relatively difficult to resolve in some of the computer models we use to forecast tropical storm track, and the forecast tracks of Don from these models have a higher spread than usual. For those of you wondering about your odds of experiencing tropical storm force winds, I recommend NHC's wind probability forecast, which is showing that Corpus Christi and Port O'Connor, Texas have the highest chance of 39+ mph winds: 40%.

I'll have a new post this afternoon.

Jeff Masters

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895. Chicklit
12:04 AM GMT on July 29, 2011
Don is lookin pretty good right now imo


LinkIRLoop

Unfortunately looks like it jogged WNW tho. Shear map info is down.

LinkWVLoop
Member Since: July 11, 2006 Posts: 14 Comments: 11423
894. IceCoast
10:13 PM GMT on July 28, 2011

Member Since: October 17, 2010 Posts: 0 Comments: 1267
893. IceCoast
10:12 PM GMT on July 28, 2011
Surface circulation is getting pulled back under the deep convection. Don is looking better and should gradually intensify tonight.
Member Since: October 17, 2010 Posts: 0 Comments: 1267
892. stillwaiting
9:53 PM GMT on July 28, 2011
donnies about to blaze the comebackk trail,still dont think he'll be our firat cane, but a strong ts yes
Member Since: October 5, 2007 Posts: 20 Comments: 4970
891. smartinwx
9:24 PM GMT on July 28, 2011
Quoting stoormfury:
DON will be gone by sat/sun, but EMILY looms on the horizon and could be a big player next week.


Where is Emily, I don't see it on the NHC site.
Member Since: September 22, 2010 Posts: 0 Comments: 88
890. weathermanwannabe
9:17 PM GMT on July 28, 2011
While I am a regular here, and particularly during "down" time in the pre-season or during the season between storms (blob and model watcher), I tend to step-back a bit once we have an actual storm and let NHC take over and I watch how their forecasts pan out. So many folks on here always try to second guess NHC but generally speaking their forecasting is very good, as it should be as the Official source for information with the best computer resources and tropical forecasters in the world, when it counts the most which is with the general area of landfall (watches/warnings) and they are getting better with intensity forecasting vis-a-vis the models. Rapid intensification, or lack thereof in the current case of Don, is one of the trickiest areas to forecasts and one of the holy grails but it is hard for a human, or computers which they rely on, to nail down every exact detail because of shifting variables controlled by Mother Nature. My point is that while Don is in a very "dangerous" area in terms of hurricanes, I don't see any glaring errors that jump out to question the current NHC forecasts for Don based upon current conditions.
Member Since: August 8, 2006 Posts: 0 Comments: 9402
889. sunlinepr
8:56 PM GMT on July 28, 2011
Member Since: August 2, 2010 Posts: 21 Comments: 9882
888. sunlinepr
8:53 PM GMT on July 28, 2011
Serious watch Mid Atl
Member Since: August 2, 2010 Posts: 21 Comments: 9882
887. hurricanehunter27
8:51 PM GMT on July 28, 2011
Ima gona go on a long shot here, i bet i wak up to a monster in the morning friday, just got that feeling.
Member Since: July 22, 2010 Posts: 1 Comments: 3852
886. jonelu
8:41 PM GMT on July 28, 2011
Quoting GHOSTY1:
So if strengthens what direction do they predict it to head toward?


A stronger storm would head more to the north while a weaker storm would sag towards the south. Either way its most likely going to hit Texas.
Member Since: October 31, 2007 Posts: 2 Comments: 884
885. metwombly
8:25 PM GMT on July 28, 2011
It seems to me that Don has been tracking more nnw, than wnw, given the exposed surface circulation and recent convection.
Member Since: June 11, 2008 Posts: 0 Comments: 47
884. GHOSTY1
8:24 PM GMT on July 28, 2011
From the NOAA floater on Don the Low level center of circulation has quite a spin going i wouldn't be surprised to see the wind speeds have increased, just an observation
Member Since: July 25, 2011 Posts: 0 Comments: 453
883. Daveg
8:19 PM GMT on July 28, 2011
Question... the models seem to be bouncing back and forth from more northward to more southward.

What would be causing them to do that, and it is likely that the NHC track will tend to stay more where it is unless the tracks stop that back and forth?
Member Since: September 23, 2005 Posts: 0 Comments: 426
882. GHOSTY1
8:19 PM GMT on July 28, 2011
So if strengthens what direction do they predict it to head toward?
Member Since: July 25, 2011 Posts: 0 Comments: 453
880. GHOSTY1
8:16 PM GMT on July 28, 2011
its really looking like Don is starting to fire up his convection and hopefully get things goin' because he's got not to much time left but if he starts now he may be able to start something for himself
Member Since: July 25, 2011 Posts: 0 Comments: 453
879. GHOSTY1
8:14 PM GMT on July 28, 2011
whens the next modified projected path going to be shown and when are the blogs gonna start picking up, is it because alot of them are working?
Member Since: July 25, 2011 Posts: 0 Comments: 453
878. GHOSTY1
8:11 PM GMT on July 28, 2011
Quoting VAbeachhurricanes:
HH wheels up outta tampa


the HH are out again to survey Don? i hope they give a good report on Don for intensification.
Member Since: July 25, 2011 Posts: 0 Comments: 453
877. KEEPEROFTHEGATE (Mod)
8:11 PM GMT on July 28, 2011
Quoting Levi32:
Don looks a lot like Bret, which says quite a bit about the environmental conditions around the system. They are and have been much more unfavorable than the NHC and many others believed.
hostile is the word more than expected but thats a good thing don't want a monster in the gulf anyway
Member Since: July 15, 2006 Posts: 178 Comments: 55984
876. VAbeachhurricanes
8:09 PM GMT on July 28, 2011
HH wheels up outta tampa
Member Since: September 6, 2007 Posts: 0 Comments: 6704
875. GHOSTY1
8:09 PM GMT on July 28, 2011
Quoting KEEPEROFTHEGATE:
i like you ghost you are all right


thank you, your alright too because your one of the few bloggers who can see different points of view other than be stubborn
Member Since: July 25, 2011 Posts: 0 Comments: 453
874. nigel20
8:08 PM GMT on July 28, 2011
A
Quoting GHOSTY1:
whats up Nigel? what do you think will happen with Don?
I'm good, don is a fighter it's been fighting from it was an invest, so given the chance i think don will strengten
Member Since: November 6, 2010 Posts: 12 Comments: 8468
873. GHOSTY1
8:06 PM GMT on July 28, 2011
Quoting Levi32:
Don looks a lot like Bret, which says quite a bit about the environmental conditions around the system. They are and have been much more unfavorable than the NHC and many others believed.


but did Bret have favorable conditions forecasted? or did he have doom set in stone for his future becaue don doesn't
Member Since: July 25, 2011 Posts: 0 Comments: 453
872. KEEPEROFTHEGATE (Mod)
8:04 PM GMT on July 28, 2011
i like you ghost you are all right
Member Since: July 15, 2006 Posts: 178 Comments: 55984
871. Levi32
8:04 PM GMT on July 28, 2011
Don looks a lot like Bret, which says quite a bit about the environmental conditions around the system. They are and have been much more unfavorable than the NHC and many others believed.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
870. GHOSTY1
8:03 PM GMT on July 28, 2011
Quoting KEEPEROFTHEGATE:
ya but out of 6 cycliners he is only firing 3 and they are missing as well


true but its better than just having nothing goin at all, its like when your trying to get your car started and it sputters a few times but then you get it going.
Member Since: July 25, 2011 Posts: 0 Comments: 453
869. AniStarr
8:02 PM GMT on July 28, 2011
Thanks KaNa its normally not the brightest thing in the world to vary to much from the models but it may be all right to still fudge it to the south. And just wondering if NWS may use a path of least regret when predicting landfall position. In other words chose the most populated area just in case.
Member Since: July 22, 2011 Posts: 0 Comments: 8
868. KEEPEROFTHEGATE (Mod)
8:01 PM GMT on July 28, 2011
Quoting GHOSTY1:
Anything Don does to continue his life is good if there was no new storms he will just totally be destroyed so he's trying and he'll eventually get his engines going.
ya but out of 6 cycliners he is only firing 3 and they are missing as well
Member Since: July 15, 2006 Posts: 178 Comments: 55984
867. GHOSTY1
8:01 PM GMT on July 28, 2011
When will the next forecasted path be given out by the NHC?
Member Since: July 25, 2011 Posts: 0 Comments: 453
866. KEEPEROFTHEGATE (Mod)
7:59 PM GMT on July 28, 2011
04L/TD/D



Member Since: July 15, 2006 Posts: 178 Comments: 55984
865. GHOSTY1
7:59 PM GMT on July 28, 2011
whats up Nigel? what do you think will happen with Don?
Member Since: July 25, 2011 Posts: 0 Comments: 453
864. GHOSTY1
7:57 PM GMT on July 28, 2011
Anything Don does to continue his life is good if there was no new storms he will just totally be destroyed so he's trying and he'll eventually get his engines going.
Member Since: July 25, 2011 Posts: 0 Comments: 453
863. metwombly
7:57 PM GMT on July 28, 2011
Quoting HurricaneHunterJoe:
They parole prisoners in Texas?
Some of them ;-)
Member Since: June 11, 2008 Posts: 0 Comments: 47
861. caneswatch
7:56 PM GMT on July 28, 2011
I made my first blog, FWIW.

Link
Member Since: October 8, 2008 Posts: 14 Comments: 4553
860. GHOSTY1
7:56 PM GMT on July 28, 2011
Quoting HurricaneHunterJoe:
They parole prisoners in Texas?


Thats what we want you to think. Ooops... probably shouldn't have said that...
Member Since: July 25, 2011 Posts: 0 Comments: 453
858. HurricaneHunterJoe
7:54 PM GMT on July 28, 2011
Quoting NotCircumventing:
Parole board meets in a little over 3 days.

Location: Matagorda Bay, TX.
They parole prisoners in Texas?
Member Since: September 18, 2010 Posts: 0 Comments: 5248
857. GHOSTY1
7:54 PM GMT on July 28, 2011
The more thunderstorm activity that builds around will become like a protective barrier allowing for more strengthening so dont downplay his progress he's fighting the forces of DOOM
Member Since: July 25, 2011 Posts: 0 Comments: 453
855. GHOSTY1
7:51 PM GMT on July 28, 2011
Is the the thunderstorm activity to the NE of Don combining with him or is just flaring up with him and it looks as the new convection is heading in a generally NW direction because earlier it looked west
Member Since: July 25, 2011 Posts: 0 Comments: 453
853. HurricaneHunterJoe
7:49 PM GMT on July 28, 2011
Quoting BA:
some hi-res sat. should allow you to see Don leaving harsh conditions and entering into more favorable conditions

http://srf.to/gomsat1
those clouds south of Don seem to wanna get drawn up in the circ after they get off Yucatan and over BOC
Member Since: September 18, 2010 Posts: 0 Comments: 5248
852. nigel20
7:49 PM GMT on July 28, 2011
I think the tropical wave in the CATL wilk traverse the carib. If the wave can moisten it's environment and avoid land for the most part, then we may see our first hurricane, unless don have something in store.
Member Since: November 6, 2010 Posts: 12 Comments: 8468
851. floridaboy14
7:48 PM GMT on July 28, 2011
Quoting TropicalAnalystwx13:
Q: Will we surpass 2010 in terms of total tropical cyclone numbers?

A. Yes
B. Maybe
C. Probably
D. Unlikely
E. No

haha dont forget that was a la nina year and conditions were nearly perfect just the tracks were bad because everything recurved lol well i see us getting anywehre from 15 to 18 storms so ill go with maybe
Member Since: July 25, 2011 Posts: 0 Comments: 1102
850. xcool
7:46 PM GMT on July 28, 2011
new blogggggggggggg
Member Since: September 26, 2009 Posts: 2 Comments: 15684
849. GHOSTY1
7:46 PM GMT on July 28, 2011
i gotta say it, Don is "DON of the Dead" he never dies and wont die till' landfall of course.
Member Since: July 25, 2011 Posts: 0 Comments: 453
848. MississippiWx
7:43 PM GMT on July 28, 2011
Quoting TropicalAnalystwx13:
Q: Will we surpass 2010 in terms of total tropical cyclone numbers?

A. Yes
B. Maybe
C. Probably
D. Unlikely
E. No


Eh, we might tie it. If you'll remember back to last year, the conditions during August/September/October were nearly perfect for development, especially in the Eastern and Central Atlantic. A lot will depend on how many strong tropical waves we see emerging from Africa this year. Last year, we had a ton. This year has been lacking in the number/frequency of strong waves. The reason that we might tie last year's numbers is because of the 4 early storms we have had already. The MSLP forecast from the ECMWF for ASO looked remarkably similar to last season in the deep tropics, except a little more focused to the west with the negative anomalies. We'll see, but it's hard for the Atlantic to have back to back seasons of 19+ named systems.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
847. j2008
7:43 PM GMT on July 28, 2011
Quoting tristanh72:
I'm sure you'll correct me if I'm wrong, but I recall hearing that if the pacific was very active, it tended to show a less active atlantic season, and vice versa.

Is that the pacific as a whole, or just the eastern pacific?

Just the EPAC.
Member Since: December 19, 2008 Posts: 1 Comments: 224
845. GHOSTY1
7:43 PM GMT on July 28, 2011
Jasonweatherman2011, im sticking to my guns and im gonna say that Don will become a hurricane just wait and see!
Member Since: July 25, 2011 Posts: 0 Comments: 453

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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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