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 Hurricanes101:


you sure about that?

Pressure was 1015mb with Andrew and the LLC completely disintergrated
lol.. I said LOOKED better.
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Quoting doorman79:
Night All,

Stay safe to those that are being affected!

Night.
Dont forget to close the Door, Man.
Member Since: October 24, 2005 Posts: 0 Comments: 24314
Ahh,, finally,, some differnt f5 ads. And no, I'm not gonna pay to get rid of ads.
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Quoting MiamiHurricanes09:
Where do you find that information?


I'm wondering the same thing - I see a couple blips of 64kt using the storm relative mean radial velocity... but mostly just a large area of 36kt and 50kt...

So far here in Bville (about 2.5 miles north of downtown along the freeway)... just some rain and puny winds...

I haven't gone out to measure yet but maybe 10-15KT with some gusts around 20 *maybe* 25...
Member Since: September 12, 2008 Posts: 0 Comments: 74
Quoting whipster:


Btown consists of a bad part of town and a worse part of town.


LOL!
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Quoting hydrus:
Even Andrew looked better than Gaston..lol


you sure about that?

Pressure was 1015mb with Andrew and the LLC completely disintergrated
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very true Potter...but i'm just saying it don't take much this time of year for anything to form...
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Quoting hydrus:
No problem...I wondered because of the storm. How much of it he will get, etc..


Btown consists of a bad part of town and a worse part of town.
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Night All,

Stay safe to those that are being affected!
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Quoting Hurricanes101:
Andrew looked extremely pathetic on August 20th, 1992

What happened 4 days later?

Also Fay, Dolly and Jeanne all struggled to develop for days before they finally did, anyone remember them too?
Even Andrew looked better than Gaston..lol
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Quoting btwntx08:

get mad asking where i live lol i dont get mad at that..that didnt make sense

OK. So where do you live?
Is Hermine going to affect you?
Member Since: October 24, 2005 Posts: 0 Comments: 24314
Quoting MiamiHurricanes09:
Where do you find that information?


I am using GRlevel3
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Quoting Chicklit:
Gaston's potential for development has gone from 70 to 50%. This is good news.


It is. Not only for the reason you stated, but because I'm tired of forecasting him. lol
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Quoting Greyelf:

You shouldn't ask that question. He gets upset when you reference where he lives.
No problem...I wondered because of the storm. How much of it he will get, etc..
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Quoting Thundercloud01221991:
93 knt on current scan... that would be 80 knt surface
Where do you find that information?
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Quoting MiamiHurricanes09:
TORNADO WATCH 645 IS IN EFFECT UNTIL 500 AM CDT FOR THE
FOLLOWING LOCATIONS


TX

. TEXAS COUNTIES INCLUDED ARE
ARANSAS BEE BROOKS
CALHOUN CAMERON GOLIAD
HIDALGO JIM WELLS KENEDY
KLEBERG LIVE OAK NUECES
REFUGIO SAN PATRICIO VICTORIA
WILLACY
Dangit, Hidalgo is my county!!
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Gaston's potential for development has gone from 70 to 50%. This is good news.
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93 knt on current scan... that would be 80 knt surface
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Quoting Hurricanes101:
Andrew looked extremely pathetic on August 20th, 1992

What happened 4 days later?

Also Fay, Dolly and Jeanne all struggled to develop for days before they finally did, anyone remember them too?
Tomorrow it should finally be in a more favorable environment, let's see if it takes advantage of it.
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Quoting angiest:



The highest on my current scan is apparent 75kt, but I can't locate it. 65kt seems the safer one.

What angle are you using?


I was talking about older images about 2-3 images ago at 0.5 angle
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713. xcool
look out rob Tornado Watch
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Quoting angiest:



The highest on my current scan is apparent 75kt, but I can't locate it. 65kt seems the safer one.

What angle are you using?


Strike that, just had a 93kt reading on the current scan.
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Quoting Nolehead:
Ex-Gaston is looking extremely pathetic.

this is true, but you know it don't take much of anything to get started....um...just like o'l Hermine just popped up like that "snap"...if it can keep anything together and get in the carribean it could just explode...

But Hermine had a VAST area of moist atmosphere to draw on.
Gaston has suffered from lack of moist (poor Fellow) for his whole life....
Member Since: October 24, 2005 Posts: 0 Comments: 24314
you guys on North Padre Island are getting ready to get some heavy rain. There are two cells moving in at 35-39kts.
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Quoting Thundercloud01221991:


there has been some as high as 85 knts at 4300ft



The highest on my current scan is apparent 75kt, but I can't locate it. 65kt seems the safer one.

What angle are you using?
Member Since: Posts: Comments:
TORNADO WATCH 645 IS IN EFFECT UNTIL 500 AM CDT FOR THE
FOLLOWING LOCATIONS


TX

. TEXAS COUNTIES INCLUDED ARE
ARANSAS BEE BROOKS
CALHOUN CAMERON GOLIAD
HIDALGO JIM WELLS KENEDY
KLEBERG LIVE OAK NUECES
REFUGIO SAN PATRICIO VICTORIA
WILLACY
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707. IKE
Quoting pottery:

LOL.
But 'less' pathetic is still pretty dismal...


It looks pathetic.
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It will be very interesting to know the wind gusts and waves the Islands experience as ex Gaston is passing , probably more than some bargain for , I suspect!
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Andrew looked extremely pathetic on August 20th, 1992

What happened 4 days later?

Also Fay, Dolly and Jeanne all struggled to develop for days before they finally did, anyone remember them too?
Member Since: Posts: Comments:
704. IKE
Brownsville, Texas (Airport)
Updated: 9 min 12 sec ago
Rain
79 °F
Rain Mist
Humidity: 89%
Dew Point: 75 °F
Wind: 16 mph from the ENE
Wind Gust: 25 mph
Pressure: 29.69 in (Steady)
Visibility: 2.0 miles
UV: 0 out of 16
Pollen: 6.80 out of 12
Pollen Forecast new!
Clouds:
Mostly Cloudy 1000 ft
Mostly Cloudy 1600 ft
Overcast 3800 ft
(Above Ground Level)
Elevation: 20 ft
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Quoting scott39:
NHC drops Gaston to 50%, yet pressure has dropped to 1008mb with 30knts.


Where'd you see the 1008? I'm curious, as ATCF says 1011/30 as of 25 minutes ago...
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Quoting angiest:
Hmmm, radar may support hurricane strenght. May. the 0.5 degree base velocity scan has some ~65kt winds east of the eye.


there has been some as high as 85 knts at 4300ft
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Quoting hydrus:
Where exactly are you at btwntx08?

You shouldn't ask that question. He gets upset when you reference where he lives.
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Quoting wunderkidcayman:
maybe so RecordSeason but atleast less pathetic then it was about an hour or 2 ago

hmm the COC seems to be at 17.2N 58.9W so no not to the sw the convection is

LOL.
But 'less' pathetic is still pretty dismal...
Member Since: October 24, 2005 Posts: 0 Comments: 24314
Hmmm, radar may support hurricane strenght. May. the 0.5 degree base velocity scan has some ~65kt winds east of the eye.
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698. IKE
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Tornado Watch
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Ex-Gaston is looking extremely pathetic.

this is true, but you know it don't take much of anything to get started....um...just like o'l Hermine just popped up like that "snap"...if it can keep anything together and get in the carribean it could just explode...
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TORNADO WATCH NUMBER 645
NWS STORM PREDICTION CENTER NORMAN OK
800 PM CDT MON SEP 6 2010

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

SOUTH TEXAS
COASTAL WATERS

EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 800 PM UNTIL
500 AM CDT.


DISCUSSION...PER LATEST NHC FCST...TS HERMINE SHOULD MAKE LANDFALL
SOON AFTER WW ISSUANCE AND MOVE NNWWD ACROSS LOWER RIO GRANDE VALLEY
REGION OVER DEEP S TX. ASSOCIATED RISK FOR MINI-SUPERCELLS AND A
FEW BRIEF TORNADOES SHOULD BE WITHIN SMALL SECTOR NNW-NE-SE OF
CENTER OF THIS RELATIVELY COMPACT SYSTEM...WHERE AT LEAST MRGL
BUOYANCY AND ENLARGED LOW-LEVEL HODOGRAPHS WILL BE PRESENT AS
EVIDENT IN 00Z BRO RAOB AND VWP. THIS REGIME SHOULD SHIFT NNWWD AND
NWD UP COASTLINE IN STEP WITH TRANSLATION OF CENTER OF HERMINE.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH EXTREME
TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI
WITH MAXIMUM TOPS TO 550. MEAN STORM MOTION VECTOR 13035.


...EDWARDS/HART
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maybe so RecordSeason but atleast less pathetic then it was about an hour or 2 ago

hmm the COC seems to be at 17.2N 58.9W so no not to the sw the convection is
Member Since: June 13, 2009 Posts: 2 Comments: 12038
Are the dry spots I see in the radar real dry air or is it just the radar not being able to see through the rain? I keep hearing strengthening, but I see lots of things that would keep her from getting any stronger.
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Quoting angiest:


But there still isn't and island (in Mexico) close to that part of Texas (Brownsville). :)
You are correct. I am just partial to Texas.
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Quoting Levi32:
Out to dinner, later all.


Peace Levi!
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689. xcool
KanKunKid lolol
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Quoting KanKunKid:


Ooops! I think I got the wrong layer again!

LMAO!!!
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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: 24314

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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.