Don battling dry air and wind shear

By: Dr. Jeff Masters , 7:37 PM GMT on July 28, 2011

Share this Blog
24
+

Tropical Storm Don continues to be an unimpressive low-end tropical storm as it continues northwest towards the Texas coast. Don formed yesterday afternoon from an African tropical wave that moved into the Gulf of Mexico under a region of low wind shear. Don's formation date of July 27 is nearly a month ahead of the usual August 23 date for the arrival of the season's fourth named storm of the year. There is currently no hurricane hunter airplane in Don, and a new airplane is not due in the storm until tonight. The last center fix at 1pm EDT found surface winds of 45 mph and a central pressure of 1005 mb, a 4 mb rise from earlier this morning. 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 5 - 15 knots of shear from strong upper level winds out of the north. This shear is creating problems for Don by injecting dry air into the system. Visible satellite imagery from early this afternoon showed the presence of surface arc-shaped clouds expanding outwards to the north from the center of Don. These type of clouds are a sign that the storm is struggling with dry air. When dry air at middle levels of the atmosphere gets injected into thunderstorms due to wind shear, the dry air tends to create strong downdrafts that rob the storm of moisture. These downdrafts spread out at the ocean surface and create arc-shaped surface cumulus clouds.


Figure 1. Visible satellite image of Don from pm EDT July 28, 2011, showing arc-shaped surface clouds--the tell-tale sign of dry air interfering with the storm's organization.


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 bring significant rains to Texas? According to the National Climatic Data Center, the six-month period ending in June 2011 was the driest on record. Average rain between January and June was more than eight inches (203 millimeters) below average in Texas, and the state experienced record heat between April and June. The heat and lack of rain have brought exceptional drought--the highest category of drought--to over 75% of the state. 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. We don't 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. Don's small size makes it prone to dry air and wind shear, though, and it is uncertain whether the storm can overcome these problems enough to become a significant rain maker. NHC gave Don a 12% chance of intensifying into a hurricane in the 11am advisory, which is a reasonable forecast, since Don is running out of time to get its act together in time to become a hurricane. None of the computer models is predicting Don will become a hurricane.

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 Port O'Connor, Texas has the highest chance of tropical storm-force winds (39+ mph): 45%.

New hurricane archive search feature
The autocomplete entities in the wunderground search box has been extended to include hurricanes, so you can now search for a storm by name, year, or basin. Here are some examples in case you feel like exploring your new options:

By name:

Hurricane David - Atlantic, 1979
David, Major Hurricane - Atlantic, 1979
Major Hurricane David - Atlantic, 1979

By year:

2005 Hurricanes Atlantic
2007 Hurricanes Eastern Pacific

By basin:

Hurricanes Western Pacific 2011
Hurricanes Atlantic 2008

By category:

Tropical Storms Atlantic 2005
Tropical Depressions Indian Ocean 2011
Subtropical Storms Eastern Pacific 2010
Extratropical Storms Western Pacific 1988

I'll have a new post Friday morning.

Jeff Masters

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 1271 - 1221

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52Blog Index

1271. GHOSTY1
Don is kinda big when you look at, Texas is big and got a pretty long coast and Don is pretty wide storm compared to the coastline
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting NoNamePub:


...Love it there....

Check out Lanikai Beach - Should be in the guide books.
Parking can be tough....but get the before 10Am and you're in great shape. Bring the snorkel with you!
Dinner at Buzz's Steakhouse on your way home.
Reservations RECOMENDED!


Thanks No Name Pub: Hiking up an extinct volcano, Diamond Head, tomorrow...that should be fun. Buzz's Steakhouse sounds good. I'll see if we can add it to the list. Got to get to Wiamea (sp?)...big wave surfing fan...so it's a must.
Member Since: Posts: Comments:
Welcome back Levi, Just got back from vacation, and ready to get back to work in the tropics...
Member Since: October 3, 2010 Posts: 40 Comments: 4129
1268. angiest
Quoting CosmicEvents:
Don Bastardi is no fool.
There's tons of passivante down there who'll pay to be part of his "pro" program.
It would figure that his forecast is going to be where the potential economic damage to oil rigs/refineries..and their workers, would be coincidentally where he points the storm.


You mean pezzonavante? (I assume I messed up the spelling some.)
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting floridaboy14:

is this by the center and does this indicate don weakining?


it looks to me like they missed the center as the winds did not have a clean shift from NE to SW
Member Since: Posts: Comments:
1266. Patrap
Half Hour ago


Member Since: July 3, 2005 Posts: 428 Comments: 129902
Showers building offshore well NW of Don, about all we can expect up here

Member Since: July 14, 2008 Posts: 2 Comments: 9686
Quoting HurricaneDean07:
TAWX, im gonna have to disagree with ya buddy, Don is one of those storms that once it fixes one problem, it has to deal with another, thinking 65 mph, Maybe...


like what?
Member Since: July 6, 2010 Posts: 113 Comments: 32859
91L in the AM
Member Since: Posts: Comments:
j2008, they did pass the center, dunno if they went through or missed it...
Member Since: October 3, 2010 Posts: 40 Comments: 4129
1261. Levi32
Don's convection is waning again. The environment cannot support anything more than periodic pulsing, not a full-on sustained rapid intensification. Recon winds only support a 40-45kt TS at maximum right now.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
1260. Patrap
Easy,,Don had a good burst of Convection for 3-5 hours,,now hes waning some from that round,and the Highest cloud tops are Warming..
Member Since: July 3, 2005 Posts: 428 Comments: 129902
Quoting Hhunter:
Joe Bastardi predicts 975-985 cat 1 hurricane at landfall around corpus
Don Bastardi is no fool.
There's tons of passivante down there who'll pay to be part of his "pro" program.
It would figure that his forecast is going to be where the potential economic damage to oil rigs/refineries..and their workers, would be coincidentally where he points the storm.
Member Since: Posts: Comments:
1258. angiest
Quoting j2008:

I got a feeling they didnt get the center, did they get to the center yet?? I'm never good at fallowing HH data.


Doesn't look, to me, that they hit the center. I'm watching on Google Earth and it is always possible I am not seeing something.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1257. DFWjc
Quoting Patrap:
Seems Don may have finished with this latest Convective round, for now..he's beginning a Exhale seems.




can you dumb that down for me please, i'm still a newbie, thanks Patrap!
Member Since: Posts: Comments:
TAWX, im gonna have to disagree with ya buddy, Don is one of those storms that once it fixes one problem, it has to deal with another, thinking 65 mph, Maybe...
Member Since: October 3, 2010 Posts: 40 Comments: 4129
1255. j2008
Quoting HurricaneDean07:
Well, This is weird...
Recon either missed Don's center, or Don has tooken a turn back....
lowest pressure found is 999 now...

I got a feeling they didnt get the center, did they get to the center yet?? I'm never good at fallowing HH data.
Member Since: December 19, 2008 Posts: 1 Comments: 224
Quoting floridaboy14:

thats bad..


Just seems to be in flux apparently.
Member Since: Posts: Comments:
Quoting stormpetrol:
Looking more like a N MX landfall or extreme S TX.


Negative it will be between Corpus and Rockport.
Member Since: Posts: Comments:


Member Since: July 6, 2010 Posts: 113 Comments: 32859
Quoting MrstormX:
015330 2433N 09206W 8428 01525 9995 256 152 155015 021 029 002 03
015400 2433N 09207W 8434 01519 9997 252 161 239005 008 037 001 03

is this by the center and does this indicate don weakining?
Member Since: Posts: Comments:
1250. Patrap
Seems Don may have finished with this latest Convective round, for now..he's beginning a Exhale seems.


Member Since: July 3, 2005 Posts: 428 Comments: 129902
Quoting MrstormX:


Rising

thats bad..
Member Since: Posts: Comments:
Quoting thedawnawakening3:
If the low level convergence was weak, then wouldn't the convection be weak as well. Seeing as the convection is quite intense best guess is that low level convergence is not the problem with Don, more likely is the fact that dry air is present, wind shear is decreasing and SSTs are deeper.



Actually the Lower Levels has been a problem as well as Shear. The system has had very poor Convergence since birth. Watch the Convergence pick up now since we have a nice Red ball.....REally for the first time.
Member Since: Posts: Comments:
Don is looking good! Wow, now I am mad for doubting him. He has really made a comeback. No, go North young man!!!
Member Since: Posts: Comments:
Quoting TXStormWatcher2011:


Thanks for your input. Where it ends up also (IMHO) has some relation to how it arrives in the Gulf. I feel there are definite patterns which show up year after year. With the high record temperatures in Texas lately, the Gulf waters must be pretty favorable for storm development.


Yeah, that is also possible.
Member Since: March 7, 2007 Posts: 602 Comments: 21330
1245. KEEPEROFTHEGATE (Mod)
04L/TS/D/CX



WEAKENING FLAG FLAG
Member Since: July 15, 2006 Posts: 178 Comments: 56141
Anticyclone over Don, this should be interesting, maybe I'm wrong on this not reaching Hurricane Status.
Member Since: Posts: Comments:
Well, This is weird...
Recon either missed Don's center, or Don has tooken a turn back....
lowest pressure found is 999 now...
Member Since: October 3, 2010 Posts: 40 Comments: 4129
1242. scott39
Quoting FrankZapper:
I realize how many of you have your tongues hanging out for Don to become a hurricane before landfall. If anything it is weakening or just maintaining its current strength. It is small and is not pulling in lots of moisture like a deepening storm should. It has acted strangely and will
limp to shore not much stronger than it is now. And it is not going to the Tex/La border.
My tounge doesnt hang out for a 45mph TC. Now give me a beer at hooters and a cell phone to track a Cat5....then you will see it hang out longer than Gene Simmons of KISS!
Member Since: Posts: Comments:
Quoting floridaboy14:

pressure rising falling or the same?


Rising
Member Since: May 27, 2009 Posts: 0 Comments: 4438
1240. xcool


Member Since: Posts: Comments:
Quoting HurricaneDean07:
My Forecast for Don:(since i havent yet)
Strength: 65 to 70 mph Tropical Storm
Landfall location: 50 miles south of Corpus Christi, TX(Baffin Bay area)
Time: 3:15 AM, Saturday....

I believe that you said this storm would hit FL twice as a Cat. 2. I thought it would turn to FL as a Cat. 1.
Member Since: Posts: Comments:
Quoting MrstormX:
015330 2433N 09206W 8428 01525 9995 256 152 155015 021 029 002 03
015400 2433N 09207W 8434 01519 9997 252 161 239005 008 037 001 03

pressure rising falling or the same?
Member Since: Posts: Comments:
Quoting wilsonmc3:

Interesting you say that because, anecdotally, here in Galveston Lots of us have that opinion. People always say, "well they always come further up the coast [east] than predicted.". I wonder if it is actually true, or if it happened a few significant times and we all think it will always happen.


Absolutely! I bet you weren't one of the surprised ones when it was finally revealed that Ike was hurtling towards the island. Call it a sixth sense, or just plain experience? My people were farmer's so I consider it living close to the land. :-) If you look back over recent years (I feel) there are definite trends to how storms arrive in the Gulf and ultimately make landfall. Even a storm slap bang in middle of the Gulf (after the crucial point where it might have turned to Mexico) seems to generally turn towards the TX/LA border. Just my opinion anyway. :)
Member Since: Posts: Comments:
There is a really good chance that Don becomes a hurricane before landfall.
Member Since: July 6, 2010 Posts: 113 Comments: 32859
1235. Patrap
2km Storm Relative IR Imagery with BD Enhancement Curve

The same infrared imagery shown in the earth relative framework is displayed in a storm relative framework, with a 2km resolution and enhanced with the "BD Curve" which is useful for directly inferring intensity via the Dvorak Enhanced IR (EIR) technique. Scaling is provided by two lightly hatched circles around the center. The two circles have radii of 1 and 2 degrees latitude, respectively

Member Since: July 3, 2005 Posts: 428 Comments: 129902
Quoting TropicalAnalystwx13:
Now that it doesn't have any problems, tomorrow should be a very good DMAX for Don. I know I said that yesterday night for this morning also, but this time, it doesn't have land interaction, wind shear, and little dry air to deal with.


Tonite should be its time to grow if it does......Canes love the cooling of the nite.
Member Since: Posts: Comments:
1233. Hhunter
Joe Bastardi predicts 975-985 cat 1 hurricane at landfall around corpus
Member Since: Posts: Comments:
015330 2433N 09206W 8428 01525 9995 256 152 155015 021 029 002 03
015400 2433N 09207W 8434 01519 9997 252 161 239005 008 037 001 03
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Quoting Patrap:

Patrap, can you explain why Don won't wash the bugs off our windshields here in Centex while Hermine washed people into the lake?



Same relative strenth, windspeed, footprint, trajectory, available precipitable water, but we only have a 30% chance of rain with Don?
Member Since: Posts: Comments:
Good Night. Don, behave, little one.
Member Since: Posts: Comments:
If the low level convergence was weak, then wouldn't the convection be weak as well. Seeing as the convection is quite intense best guess is that low level convergence is not the problem with Don, more likely is the fact that dry air is present, wind shear is decreasing and SSTs are deeper.
Member Since: Posts: Comments:
My Forecast for Don:(since i havent yet)
Strength: 65 to 70 mph Tropical Storm
Landfall location: 50 miles south of Corpus Christi, TX(Baffin Bay area)
Time: 3:15 AM, Saturday....
Member Since: October 3, 2010 Posts: 40 Comments: 4129
Quoting muddertracker:

Just went snorkeling with the family at Hanauma Bay? (Nature Preserve Place) That might be the most beautiful place I have ever seen in my life.


...Love it there....

Check out Lanikai Beach - Should be in the guide books.
Parking can be tough....but get the before 10Am and you're in great shape. Bring the snorkel with you!
Dinner at Buzz's Steakhouse on your way home.
Reservations RECOMENDED!
Member Since: Posts: Comments:
I'm thinking that CATL wave will track a tad south of Don.
Member Since: April 29, 2007 Posts: 0 Comments: 8134
Now that it doesn't have any problems, tomorrow should be a very good DMAX for Don. I know I said that yesterday night for this morning also, but this time, it doesn't have land interaction, wind shear, and little dry air to deal with.
Member Since: July 6, 2010 Posts: 113 Comments: 32859
I realize how many of you have your tongues hanging out for Don to become a hurricane before landfall. If anything it is just maintaining its current strength. It is small and is not pulling in lots of moisture like a deepening storm should. It has acted strangely and will
limp to shore not much stronger than it is now. And it is not going to the Tex/La border.
Member Since: Posts: Comments:
Quoting NoNamePub:


Yeah...moved here from Florida about a year ago....
We did have some waterspouts a few months ago....VERY rare in these parts!
Enjoy Ko'Olina....BUT you have to explore. Get up to Haleiwa Neat little town with shops and restaurants!

Check out Windward...my home....Kailua - Great Beaches.

Just went snorkeling with the family at Hanauma Bay? (Nature Preserve Place) That might be the most beautiful place I have ever seen in my life.
Member Since: Posts: Comments:
Quoting KoritheMan:


It's because many Gulf storms have to contend with approaching cold fronts, which steers them poleward (easterly).


Thanks for your input. Where it ends up also (IMHO) has some relation to how it arrives in the Gulf. I feel there are definite patterns which show up year after year. With the high record temperatures in Texas lately, the Gulf waters must be pretty favorable for storm development.
Member Since: Posts: Comments:
Quoting Patrap:



Looking a lot better tonite......Pressure will be falling and for once we might get some convergence going in the lower levels so it can streghten some. The larger ball means a larger distance of rain for Texas....NICE
Member Since: Posts: Comments:

Viewing: 1271 - 1221

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron