Don battling dry air and wind shear

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

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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

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Quoting SouthDadeFish:
Well it did have an 8mb drop in an hour and a half. I would almost consider that rapid intensification. The process came to a quick halt through ingestion of dry air that collapsed the convective complex. However, he is bursting nicely as we speak.

Link


Had conditions been favorable, it could have been rapid intensification. Point is, they are not.
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Quoting duajones78413:


Uniformed was what was going on there for awhile


He experienced a decent pressure drop, but nothing suggestive of rapid intensification. The synoptic environment also does not support that, as the vortex is tilted southward with height due to northerly shear.
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1568. j2008
Quoting cat5hurricane:
Don looks awful. Poor guy. I'm still thinking that Mexican landfall is in store.

I see we have a near yellow blog out there. 20%. We'll monitor.

Did you mean near orange, because it is already yellow?
Member Since: December 19, 2008 Posts: 1 Comments: 224
Quoting SouthDadeFish:
If this recent convective burst can stay away from eating dry air like the last one, Don can make a run at becoming a hurricane. I don't think it will get there, but we all saw how fast the pressure dropped last time. Over very warm waters and wind shear isn't much of an issue anymore.


Eh, I don't think Don is ever going to be able to sustain these bursts of convection. He hasn't his whole lifetime.
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Quoting cat5hurricane:
Don looks awful. Poor guy. I'm still thinking that Mexican landfall is in store.

I see we have a near yellow blog out there. 20%. We'll monitor.


Don looked awful yesterday, tonight he looks pretty good, nice outflow in parts of the storm

Way better than yesterday
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Quoting KoritheMan:


Don was never rapidly intensifying. Those who stated he was were uniformed.
Well it did have an 8mb drop in an hour and a half. I would almost consider that rapid intensification. The process came to a quick halt through ingestion of dry air that collapsed the convective complex. However, he is bursting nicely as we speak.

Link
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1563. GHOSTY1
Quoting want2lrn:


If i may ghosty, that is HWY 35
thats it, you got it i wanted to say that but i was unsure, thank you. We travel that route because at night if you go down 35 to rockport there is a reststop about 10 miles from rockport where you can see the stars and the milky way perfectly, sometimes lightning bugs and coyotes get close.
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If this recent convective burst can stay away from eating dry air like the last one, Don can make a run at becoming a hurricane. I don't think it will get there, but we all saw how fast the pressure dropped last time. Over very warm waters and wind shear isn't much of an issue anymore.
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1560. j2008
Quoting duajones78413:


Uniformed was what was going on there for awhile

Got pretty confusing to fallow there for a while.
Member Since: December 19, 2008 Posts: 1 Comments: 224
1559. JLPR2
Quoting Floridian2011:


Pues, eso era lo que me habian dicho a mi, que habia ocurido hoy alla, pero si fue falso, lo lamento entoonces.


Checked a local newspaper online page and yeah, there was a 4.62 earthquake but it was felt by the northwest side of the island, I'm at the northeast.
If you hadn't told me I would have never know it had happened.

But thank you for worrying.
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Quoting MississippiWx:
Don is really ticking me off...Nice new convective burst:

all these small systems have been giving a lot of forecasters and even the models trouble lol

Good for Texas though, should give them exactly what they need, rain. Storm surge and wind shouldn't be too much of an issue, although this could make it to hurricane status
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1557. angiest
Quoting jpsb:
Here in San Leon we are still recovering from Ike. Ike was HORRIBLE, I think I speak for everyone in this little fishing village when I say no more Ikes! At this very moment I have a family living in my house because they lost thiers to Ike. They will be moving in a week or two, I can't wait, lol.


Glad to hear they are getting out of your hair. ;) Note I did say that we needed something with the rain shield (and forward speed!) of Ike, and not the wind and surge.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting KoritheMan:


Don was never rapidly intensifying. Those who stated he was were uniformed.


Uniformed was what was going on there for awhile
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Quoting GHOSTY1:
angiest, we usually take 59 till just past victoria where we exit and go to a small town called tivoli and then follow an old highway that goes from SW Houston to Rockport but i cant remember the name


If i may ghosty, that is HWY 35
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1554. JLPR2
Quoting KoritheMan:


But there are no sea breezes for at least a day after the hurricane, since it disrupts the ordinary wind flow.


Nor before, everytime a storm passes close by it sucks up all my fresh air. But eventually it returns, helps big time while the power is restored.
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Quoting duajones78413:
what changed? Don RI to almost no mention.
Not sure what to expect here, wish someone with more knowledge would speak up


Don was never rapidly intensifying. Those who stated he was were uniformed.
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1552. angiest
Quoting GHOSTY1:
angiest, we usually take 59 till just past victoria where we exit and go to a small town called tivoli and then follow an old highway that goes from SW Houston to Rockport but i cant remember the name


That's 35 you pick up in Tivoli. They way I go skirts Tres Palacios Bay, crosses Carancahua Bay, then Lavaca Bay, and then Copano Bay. A nice scenic route, not as busy as 59, and pretty speedy. One day I will make the sidetrip to Indianola.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1551. GHOSTY1
another problem with the drought in texas and around houston is that the city is sink because underground aquafers or whatever there called are becoming so empty that the ground weight and additional weight from buildings is causing the area to sink causing major foundation damage especially in my area of NW Houston.
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1550. jpsb
Quoting angiest:


Ike covered a large area, and therefore dropped rain over a large area. I don't remember the amounts, but since Ike came in and left it probably wasn't too bad.

Tropical systems are the only reasonable chance of making a dent in the drought in the near to medium term. It's just kinda dicey. Need the rain, not the wind and surge. And we don't need too much rain falling on the very dry ground too quickly or it all runs off.
Here in San Leon we are still recovering from Ike. Ike was HORRIBLE, I think I speak for everyone in this little fishing village when I say no more Ikes! At this very moment I have a family living in my house because they lost thiers to Ike. They will be moving in a week or two, I can't wait, lol.
Member Since: June 30, 2009 Posts: 0 Comments: 1197
1547. JLPR2
Quoting angiest:


You only recently discovered you live two miles from the coast? Glad you don't sleep walk...


Yeah, need to do some twists and turns to reach the beach so I never figured it was close. Google Earth clarified that.
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what changed? Don RI to almost no mention.
Not sure what to expect here, wish someone with more knowledge would speak up
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Knowing the NHC, they will leave the wave in the C ATL at 20%. However, with very little obstacles to overcome before becoming a TD, I think it should be closer to 30% or 40%.

JMO. Night all.
Member Since: July 6, 2010 Posts: 113 Comments: 32553
Don is really ticking me off...Nice new convective burst:

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The models have been horrible with storms this year.

If I took a bet on a track, I'd say the 40W wave would head to the NE Caribbean/PR, in the general direction of the Bahamas, and it should easily become Emily.
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Sad thing is, it's looking less and less likely that Texas will get any meaningful rain out of Don. The state is about ready to blow away.
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Quoting JLPR2:


True. It wasn't until recently that I discovered I actually lived so close to the shore.
I'm a strange one. XD

If a hurricane comes by I will ride it out with my family here. One of the best things of living in an island is that the sea breeze keeps the temps below dangerous levels so no extreme misery after a storm.


But there are no sea breezes for at least a day after the hurricane, since it disrupts the ordinary wind flow.
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1540. GHOSTY1
angiest, we usually take 59 till just past victoria where we exit and go to a small town called tivoli and then follow an old highway that goes from SW Houston to Rockport but i cant remember the name
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1539. JLPR2
Quoting Floridian2011:
JP, sigues ahi? I heard about el terremoto, estas bien?


What earthquake? Was out all day... There was an earthquake here? O.o
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1538. angiest
Quoting JLPR2:


True. It wasn't until recently that I discovered I actually lived so close to the shore.
I'm a strange one. XD

If a hurricane comes by I will ride it out with my family here. One of the best things of living in an island is that the sea breeze keeps the temps below dangerous levels so no extreme misery after a storm.


You only recently discovered you live two miles from the coast? Glad you don't sleep walk...
Member Since: August 26, 2006 Posts: 16 Comments: 4766
You all have thought the Models have performed bad. I don't think they have been that bad. Has Don been much of a force........NO......did the models show Don..........NO not really. But, they should have at least shown at least a small system one would have thought.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting MississippiWx:


Also have to worry about landslides in the mountainous regions.


Yeah... I think I'd rather take the (generally) weak tornadoes, myself.
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1533. JLPR2
Quoting KoritheMan:


Oh geez, I always assumed you were farther inland for some reason. Then again, in your case, perhaps it's better that you are close to the coast, because Puerto Rico has inland mountains, which would enhance the wind effect of a landfalling hurricane.


True. It wasn't until recently that I discovered I actually lived so close to the shore.
I'm a strange one. XD

If a hurricane comes by I will ride it out with my family here. One of the best things of living in an island is that the sea breeze keeps the temps below dangerous levels so no extreme misery after a storm.
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Well looks like SE Texas will continue to suffer as Don decided to go visit south. Very disappointing..this drought is becoming depressing. We have actually had a thunderstorm or two, but my house has started to fall into the earth and the Grand Canyon has nothing on some of the cracks in the ground. I think my suburb has had about 4-5 inches of rain(maybe) since September/October of last year. Sigh.
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Quoting Hurricanes101:


you forgot one - persistence

If it lacks that, the rest of it does not mean much


Oh crap at nearly 47 I'm allowed to forget something :)
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Quoting angiest:


We take TX 60 from Wallis to Bay City to pick up 35. All the corn was dead, the cotton didn't look great. The Sorghum was. But that was a month ago.


I'm not a cotton farmer, just a rancher. The cotton doesn't look as robust as usual but let's at least let them get what they do have in before the bottom falls out.

Or as my daddy always says "Bovine urinatin' of smooth stone" lol

Us agriculturalists have to look out for one another. After the cotton farmers have their crops in (for what they are) then bring on the rain n lots of it! (notice everyone, I did not say winds, hurricanes or otherwise...I've lived on the Texas Coast all my life, been there - done that...don't wish it on anybody!)
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Quoting KoritheMan:


A hurricane? If I'm not mistaken, he became a major hurricane.

Thank you!! I forgot, I still feel his wrath!!!
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1528. GHOSTY1
Quoting doabarrelroll:

didnt you just apologize? Didnt i just accept?
Btw an immature joke is not the equivalent of what you saidl


I apologized for the comment about the multiple tx impacts of tropical systems, but it makes me a little angry when you tell i'm immature for asking for something that would provide a good when your talking about immature jokes. I'm willing to put this in the past and restart things because im only looking for the best for my state
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1526. angiest
Quoting doabarrelroll:


You can see why people would be sensitive. Imagine if Ike was a Cat 3 4 or 5


I still think Ike will eventually be upgraded to at least a 3 retrospectively. Like Alex, he had the pressure of a major. It took a decade to upgrade Andrew to a 5, and it took a couple of years, I think, to upgrade Cindy to a hurricane.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1525. MTWX
Quoting stormpetrol:
I think Ivan 04(cold Chills) became a hurricane below 10N , a closed low ,warm core, reasonable convection, and 30mph = a TD

Ivan was my first "hands on" experience with a hurricane. (cold chills)
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THis Season when I hear the words model support , I feel like screaming:), they been good with track though!Goodnight all.
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Quoting KoritheMan:


Oh geez, I always assumed you were farther inland for some reason. Then again, in your case, perhaps it's better that you are close to the coast, because Puerto Rico has inland mountains, which would enhance the wind effect of a landfalling hurricane.


Also have to worry about landslides in the mountainous regions.
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Quoting TropicalAnalystwx13:


Screw the models, they've performed horrible this season.
eh, I'm not too upset with them.

Out last three systems have all been tiny, which is obviously going to be harder for low resolution global models to pick up on. Also note the NAM did better than all the other models with the last three systems...most likely because of its higher resolution.

This wave may develop slightly before it enters the Caribbean, but the large disorganized nature will make anything slow. Got a lot of dry air ahead and shear should also increase so I don't expect much of anything to come out of it in the short term.
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Quoting Floridian2011:


Hi there, NONE of those criterias are needed in order for it to be designated as an invest, now, a TD designation on the other hand, that's an entirely different other story.

Courtesy: The NHC website, =).


The KID really just repeated what has been said about pre 91L and yes there really is NO criteria for an Invest other than someone at NHC yelling we have an INvest. What he said in the 3 bullets are comments that have been said about the current condition of pre 91L and he was correct about those conditions.
Member Since: September 2, 2007 Posts: 179 Comments: 20448

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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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