Intensifying Hermine closes in on the Texas/Mexico coast

By: Dr. Jeff Masters , 9:47 PM GMT on September 06, 2010

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Steadily intensifying Tropical Storm Hermine is closing in on the coast near the Texas/Mexico border, and should move ashore late tonight. Hermine became a tropical depression at 11pm last night, and could become a minimal hurricane by 11 pm tonight. Hermine's rate of intensification from nothing to a strong tropical storm is one of the fastest on record. It turns out that the extreme southwestern Gulf of Mexico's Bay of Campeche, where Hermine formed, is prone to these sort of rapidly intensifying tropical storms. The curvature and topography of the land help induce a counter-clockwise spin to the air over the region, which helps get tropical storms spinning up unusually quickly. Helping the spin-up process are the very warm 30°C waters, low 5 - 10 knots of wind shear, and moist atmosphere. Hermine promises to be a very wet storm, and latest long range radar out of Brownsville, Texas shows a large area of heavy rain has been drenching southern Texas and northern Mexico all afternoon, with radar estimated rainfall amounts exceeding two inches in a few areas along the coast. Radar loops show that an eyewall is attempting to form, but a region of dry air from over land spiraled into Hermine's core between 4 - 5pm EDT, disrupting eyewall formation. However, it now appears that Hermine has closed off its eye from this dry air, which should aid in intensification. Satellite imagery shows Hermine has vigorous thunderstorms with very cold tops, and improving low-level spiral banding.

Forecast for Hermine
Hermine doesn't have much time over water before it comes ashore, which is a good thing. The storm is steadily organizing, and has a shot at reaching hurricane strength before the center moves ashore late tonight, near midnight. Heavy rain will be the main threat from Hermine, though isolated tornadoes may also cause damage, particularly over South Texas. Hermine is expected to accelerate through Central Texas Tuesday and Wednesday, and the storm's rains will help alleviate moderate to severe drought conditions affecting Central Texas.


Figure 1. Late afternoon radar image of Tropical Storm Hermine. Note the band of dry air spiraling into the core of the storm from the north.

Gaston continues to suffer from dry air
An Air Force Hurricane Hunter aircraft spent the afternoon in Gaston's remains, and found a weak 1012 mb center of low pressure with only a limited region of westerly winds on the south side of the center of circulation. Top surface winds uncontaminated by heavy rain seen by their SFMR instrument were in the 30 - 35 mph range. The airplane found plenty of dry air in the storm's environment, and there are not enough heavy thunderstorms in ex-Gaston's circulation for it to qualify as a tropical depression. The remains of Gaston are now approaching the northern Lesser Antilles, and residents can expect a few heavy rain showers and wind gusts up to 40 mph beginning early this evening and continuing into the night. Latest radar out of Martinique doesn't show much in the way of heavy rain, and satellite imagery confirms that the thunderstorm activity associated with Gaston's remains is quite sparse. A large amount of dry air surrounds Gaston's remains on all sides, as seen on water vapor satellite loops.


Figure 2. Afternoon satellite image of the remains of Gaston, approaching the Lesser Antilles Islands.

Forecast for Gaston
There is little change to the forecast for Gaston's remains. Dry air will continue to be the major impediment to development, and the system is unlikely to become a tropical depression today. However, wind shear, which is currently a moderate 10 knots, is forecast by the latest SHIPS model run to fall very low, 0 - 5 knots, tonight through Wednesday. With almost no wind shear affecting it, Gaston will a better chance of keeping the moisture from its heavy thunderstorms near its core on Tuesday. This will insulate the storm from the dry air surrounding it. The atmosphere is also moister in the eastern Caribbean, further increasing the chances of development. I believe it is probable Gaston will become a tropical depression again on Tuesday. NHC is currently giving Gaston a 70% chance of developing into a tropical depression by Wednesday, which is a reasonable forecast.

Heavy rain showers and gusty winds from the storm will affect Puerto Rico Tuesday morning through Wednesday afternoon. This activity will spread to the Dominican Republic Tuesday afternoon through Thursday morning. Assuming dry air and an encounter with Hispaniola's high mountains do not destroy Gaston, heavy rain from the storm should move over Haiti, eastern Cuba, and Jamaica Wednesday night and Thursday morning. The models don't give much support for Gaston surviving past Wednesday. The ECMWF, GFS, NOGAPS, Canadian, and HWRF models all dissipate Gaston. However, two models--the GFDL and UKMET--predict that Gaston will survive the dry air and an encounter with Hispaniola, and pass far enough south of the island to find a favorable environment in the Central Caribbean for development on Wednesday. Wind shear will be low, water temperatures will be hot, and the atmosphere will be plenty moist. Gaston could intensify into a hurricane in the Western Caribbean by the end of the week, as predicted by the latest run of the GFDL model.

Elsewhere in the tropics
The models are fairly unanimous in predicting development late this week of a tropical wave expected to emerge from the coast of Africa on Tuesday or Wednesday. The next storm will be called Igor.

Next post
I'll have an update in the morning.

Jeff Masters

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Quoting doorman79:


Yea well be thankful they aren't falling on your head! Hey Pottery!

:):)
Member Since: October 24, 2005 Posts: 0 Comments: 24399
Quoting pottery:

I see that. Going to be worse in a hour or 2 too!
Hope the rainfall is not too bad...
I dunno, looks a little on the juicy side.
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Quoting StormW:
Good night all!

Have a good evening.
Later Storm.
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Quoting hydrus:
Wuzup Pott...Some people on here gettin whacked with a strong storm...

I see that. Going to be worse in a hour or 2 too!
Hope the rainfall is not too bad...
Member Since: October 24, 2005 Posts: 0 Comments: 24399
Quoting scott39:
NHC drops Gaston to 50%, yet pressure has dropped to 1008mb with 30knts.
Not surprised.
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Quoting Levi32:


No there are no layers to pick from, it's a WU mistake. The full zoom-out shows the island but if you zoom in even a tiny bit it shows the correct coastline.


Facepalm

That was a joke. I was comparing to steering layer maps....
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Personally I think ex Gaston has a large circulation. If you look at LLC signature, regardless of what the Recon found I think it has a very pronounced circulation, jmo.
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Out to dinner, later all.
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Quoting jpritch:


Why?
How do I respond without getting political?
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Quoting StormW:
Good night all!

Have a good evening.
Good night Storm!
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The northwestern eyewall is now starting to scrape the coast; landfall is immanent.

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Quoting CybrTeddy:
Landfall should be around 9:30 or so.
Look at your post# Ted.....Are you possessed yet?:0
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Huge squall line just hit N. PI at Corpus.
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Quoting MiamiHurricanes09:
Yeah, I noticed that. If you zoom out, the coastline is shaped incorrectly and there is an imagery island just off of the northern Mexican coastline.

Actually, no, it isn't happening to me anymore. Before, every time I would zoom out, the aforementioned imaginary island and improper coastline would show up.


What happened to her western side? Good evening.
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Quoting StormW:
Good night all!

Have a good evening.


Peace!
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Quoting RecordSeason:
651:

Ex-Gaston is looking extremely pathetic.

Indeed.
Clearly.
Gone through....
Member Since: October 24, 2005 Posts: 0 Comments: 24399
NHC drops Gaston to 50%, yet pressure has dropped to 1008mb with 30knts.
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Quoting MiamiHurricanes09:
Hermine seems to have picked up in speed (slightly) as it heads generally towards the N/NNW.



She's gonna hit very soon.
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Landfall should be around 9:30 or so.
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Quoting angiest:


That island is a deep feature. You have been using the wrong layer.


No there are no layers to pick from, it's a WU mistake. The full zoom-out shows the island but if you zoom in even a tiny bit it shows the correct coastline.
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Quoting pottery:
'evening all.
Lurking here, under clear, starry skies....


Yea well be thankful they aren't falling on your head! Hey Pottery!
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Quoting IKE:


O-kay.
Don't call him out on anything Levi. You know how that goes. And it looks like a little blob of convection is firing sw on Gaston, again.
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Quoting Levi32:


Um B, but, it would be funny if she crossed the Rio Grande and then made a second landfall north of near Corpus Cristi lol. That is unlikely, but you never know.


That's what I'm thinking she could do, Levi. Maybe or maybe not a true landfall S of River. With W turn coming N of river, but over Ranch land, south of Corpus.
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Quoting Leafgreen:

Pff, anytime it rains hard for more than an hour it floods.
Whoa, that avatar is hypnotizing. LOL, anyways, yeah, the streets flood quite easily here. Funny that they didn't flood when Bonnie came through. :)
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Quoting skkippboo:
Good question. I dn't know. And there is a big difference in MX and TX.


But there still isn't and island (in Mexico) close to that part of Texas (Brownsville). :)
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Quoting pottery:
'evening all.
Lurking here, under clear, starry skies....
Wuzup Pott...Some people on here gettin whacked with a strong storm...
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Hello all. Longtime lurker and rare poster. Located here in Harlingen, TX. Looks like we're getting ready to get pounded. Ugly looking clouds to my southeast. I'll post some tonight if I get a chance.
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I vote South Florida...LOL!!!
Serriously - I predict about 35 miles south of Brownsville.
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Quoting Levi32:


Now see, you zoom in on WU radar and the coastline is absolutely perfect.
Yeah, I noticed that. If you zoom out, the coastline is shaped incorrectly and there is an imaginary island just off of the northern Mexican coastline.

Actually, no, it isn't happening to me anymore. Before, every time I would zoom out, the aforementioned imaginary island and improper coastline would show up.

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Port Isabel getting pounded right now.
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Quoting Levi32:
Here guys, do this, zoom in the least that you possibly can and you can summon the correct coastline. Use this loop link:



That island is a deep feature. You have been using the wrong layer.
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'evening all.
Lurking here, under clear, starry skies....
Member Since: October 24, 2005 Posts: 0 Comments: 24399
Quoting btwntx08:
raining pretty hard now here wind is PICKING up
Where exactly are you at btwntx08?
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Quoting btwntx08:
raining pretty hard now here wind is PICKING up
You are about to get POUNDED there. Take care.
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Quoting MiamiHurricanes09:
Tell me about it. I'm not in Miami Beach but the streets are beginning to flood here.

Pff, anytime it rains hard for more than an hour it floods.
Member Since: July 8, 2008 Posts: 0 Comments: 26
647. IKE
Quoting Levi32:


Highlights do wonders though :P I knew exactly what you were thinking.


O-kay.
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622: ya'll putting a show on tonight.
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Quoting IKE:


I didn't say or think a word. Just posting their observation.


Highlights do wonders though :P I knew exactly what you were thinking.
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Quoting ginajo:


You and me both!! lol


Why?
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Here guys, do this, zoom in the least that you possibly can and you can summon the correct coastline. Use this loop link:

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639. IKE
Quoting Levi32:



Give it time. The core is small and the storm is immature.


I didn't say or think a word. Just posting their observation.
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Quoting wunderkidcayman:
live Ob data Eugeniopr I really don't find them there much unless you can show me


sorry stormpetrol not yet let us see what happens by morning if in any case are you ready for when it comes (if it comes)


Try this one
http://weather.rabirubia.com/
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85 knts at 4000 ft according to radar
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FLdewey what!?!?!?!?

I think you watch too much Greenzone
Member Since: June 13, 2009 Posts: 2 Comments: 12164

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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.