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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386. JLPR2
Quoting TropicalAnalystwx13:
Ouch! Down to 50%!


Seems appropriate since it seems the last convection is almost gone.

Member Since: September 4, 2007 Posts: 7 Comments: 8641
Quoting TXnovice:
I guess the longer Hermine stays over water, the more she can take advantage of the really warm water in the gulf right around and north of the boarder. Does she have time to intensify now that she has slowed down?
Hmm, is this nature's way of taking care of itself and correcting the overly hot water we have out there?
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Gaston 50% from NHC.
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Stay safe Miami, looks like you're in for a ride.
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:)

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...HERMINE STRENGTHENING AS IT NEARS THE COAST...


SUMMARY OF 700 PM CDT...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...24.8N 97.1W
ABOUT 80 MI...130 KM NNE OF LA PESCA MEXICO
ABOUT 80 MI...130 KM SSE OF BROWNSVILLE TEXAS
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/HR
PRESENT MOVEMENT...NW OR 325 DEGREES AT 14 MPH...22 KM/HR
MINIMUM CENTRAL PRESSURE...991 MB...29.26 INCHES
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I knew it, I was going to bet 50%
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Any models predicting a conus hit in the near futere?
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Ouch! Down to 50%!

000
ABNT20 KNHC 062346
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT MON SEP 6 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM HERMINE...LOCATED ABOUT 80 MILES SOUTH-SOUTHEAST OF
BROWNSVILLE TEXAS.

MULTIPLE AIRCRAFT RECONNAISSANCE REPORTS INDICATE THAT THE SURFACE
CIRCULATION ASSOCIATED WITH THE REMNANTS OF GASTON REMAINS POORLY
DEFINED...AND THAT THE SURROUNDING ENVIRONMENT IS ONLY MARGINALLY
CONDUCIVE FOR DEVELOPMENT DURING THE NEXT COUPLE OF DAYS.
THEREFORE...THERE IS A MEDIUM CHANCE...50 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE AGAIN DURING THE NEXT 48 HOURS.
REGARDLESS OF DEVELOPMENT...THIS SYSTEM IS CAPABLE OF PRODUCING
HEAVY SHOWERS AND WIND GUSTS TO TROPICAL STORM FORCE IN SQUALLS AS
IT MOVES OVER THE LEEWARD ISLANDS TONIGHT AND TUESDAY.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

PUBLIC ADVISORIES ON HERMINE ARE ISSUED UNDER WMO HEADER WTNT35 KNHC
AND UNDER AWIPS HEADER MIATCPAT5. FORECAST/ADVISORIES ON HERMINE
ARE ISSUED UNDER WMO HEADER WTNT25 KNHC AND UNDER AWIPS HEADER
MIATCMAT5.

$$
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Out-of-Gaston

The little engine that couldn't?
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Quoting ozzyman236:
ticka if it shifts a little north houston could get some flooding rains later from hermine....pay attention..

Oz i just have to ask, what your fascination with Houston is? If hermine moves this far North, I'll invite you over for steaks and beer.
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Quoting WeatherNerdPR:

This system is annoying. Can't he just make up his mind?


Why's he annoying? If any human traits are going to be ascribed to Gaston, it should perseverant. Tenacious. Dogged. Determined.... ;-)
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372. JLPR2
Quoting Relix:


Jeanne became a storm around 60W, and she also faced bad conditions. Gaston could try something but he truly looks bad. Jeanne at least looked fine. This is a joke, it's more like an open wave at the moment.


Sort of reminds me of Felix, remember the poor little 94L that kept loosing convection and expelling outflow boundaries due to dry air...
I want to see the low level circulation completely dead before saying it's over.
Member Since: September 4, 2007 Posts: 7 Comments: 8641
000
ABNT20 KNHC 062346
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT MON SEP 6 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM HERMINE...LOCATED ABOUT 80 MILES SOUTH-SOUTHEAST OF
BROWNSVILLE TEXAS.

MULTIPLE AIRCRAFT RECONNAISSANCE REPORTS INDICATE THAT THE SURFACE
CIRCULATION ASSOCIATED WITH THE REMNANTS OF GASTON REMAINS POORLY
DEFINED...AND THAT THE SURROUNDING ENVIRONMENT IS ONLY MARGINALLY
CONDUCIVE FOR DEVELOPMENT DURING THE NEXT COUPLE OF DAYS.
THEREFORE...THERE IS A MEDIUM CHANCE...50 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE AGAIN DURING THE NEXT 48 HOURS.
REGARDLESS OF DEVELOPMENT...THIS SYSTEM IS CAPABLE OF PRODUCING
HEAVY SHOWERS AND WIND GUSTS TO TROPICAL STORM FORCE IN SQUALLS AS
IT MOVES OVER THE LEEWARD ISLANDS TONIGHT AND TUESDAY.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

PUBLIC ADVISORIES ON HERMINE ARE ISSUED UNDER WMO HEADER WTNT35 KNHC
AND UNDER AWIPS HEADER MIATCPAT5. FORECAST/ADVISORIES ON HERMINE
ARE ISSUED UNDER WMO HEADER WTNT25 KNHC AND UNDER AWIPS HEADER
MIATCMAT5.

$$
FORECASTER ROBERTS/BRENNAN
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yeah, we have multiple meso cyclones in the area. So yes Miami, you are about to get slammed, heavy rain and winds up here in Broward County.
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.
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Quoting DDR:
Buckle up Mh09
Serious looking precip
The rain here is crazy strong...but that's not the worse part...I'm getting one lighting strike after another just miles away from me. Crazy weather.
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367. Vero1
Quoting sammywammybamy:
Looks Like a Blob is Forming E of Florida...



Looks like sea breeze got out of hand.

http://www.srh.noaa.gov/mlb/wrf/arw3_cz.php
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Up to 65 mph.
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363. DDR
Buckle up Mh09
Serious looking precip
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Recon confirms NNE movement
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Quoting weatherman12345:

did you even look at the image posted??
Well, if you look at previous images.
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Quoting btwntx08:
that nne is wobble and no its not gonna change direction fl ppl sorry


If this keeps up, Brownsville may not get the east side of this storm. You might be spared btwntx08.
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356. Relix
Quoting WeatherNerdPR:

This system is annoying. Can't he just make up his mind?


Jeanne became a storm around 60W, and she also faced bad conditions. Gaston could try something but he truly looks bad. Jeanne at least looked fine. This is a joke, it's more like an open wave at the moment.
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The center of Hermine appears to be almost due south of the southern tip of South Padre Island.
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If the Recon data is accurate, it appears their may have been a NE jog/wobble.....

Either that or they took a wrong turn! LOL
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Quoting thunderblogger:
Donde Matamoros????
Mexican neighbor to Brownsville.
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Recon confirms NNE movement
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Getting rainbands here in Baytown area - of course they are coming in from the south. Wind picked up with storms moving through.

How much rain do ya'll think we will receive here in SE Texas - Houston area?
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Quoting weatherman12345:

looks like its poofing again. this sytem never can grasp on to any convection without it dying.
It's been maintaining convection for quiet a while now.
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I guess the longer Hermine stays over water, the more she can take advantage of the really warm water in the gulf right around and north of the boarder. Does she have time to intensify now that she has slowed down?
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Quoting weatherman12345:

looks like its poofing again. this sytem never can grasp on to any convection without it dying.

This system is annoying. Can't he just make up his mind?
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343. iahwx
Quoting thunderblogger:
Donde Matamoros????


City in Mexico just south of Brownsville, TX. Looks to possibly take a direct hit if Hermine strays much farther north before landfall.
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edit: Oh and I forgot two things:
1. weatherman12345's poll
I'd say

B. lowered to 60 %

2. TropicalAnalyst's poll
I'd say

B. 65 mph TS

To be sure I just check whether I still have some crow in the freezer from last season, I might have some later tonight. lol
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Time: 23:35:30Z
Coordinates: 24.8N 96.9833W
Acft. Static Air Press: 842.9 mb (~ 24.89 inHg)
Acft. Geopotential Hgt: 1,465 meters (~ 4,806 feet)
Extrap. Sfc. Press: -
D-value: -
Flt. Lvl. Wind (30s): From 185%uFFFD at 60 knots (From the S at ~ 69.0 mph)
Air Temp: 15.7%uFFFDC* (~ 60.3%uFFFDF*)
Dew Pt: -*
Peak (10s) Flt. Lvl. Wind: 61 knots (~ 70.1 mph)
SFMR Peak (10s) Sfc. Wind: 50 knots (~ 57.5 mph)

Highest so far.
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I still say look out Brownsville....she is kinda just weaving and bobbing her way down the coast...
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800 TWO. Will be a TD again or needs to be. 30-35 sustained and 40gusts
will be a mess and right now it looks lime no one is taking it seriously
here except the more cuatious people. And gaston is only going to get stronger
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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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