Intensifying Hermine closes in on the Texas/Mexico coast
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
Reader Comments
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Lurking here, under clear, starry skies....
That island is a deep feature. You have been using the wrong layer.
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.
Serriously - I predict about 35 miles south of Brownsville.
But there still isn't and island (in Mexico) close to that part of Texas (Brownsville). :)
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.
Yea well be thankful they aren't falling on your head! Hey Pottery!
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.
She's gonna hit very soon.
Indeed.
Clearly.
Gone through....
Peace!
What happened to her western side? Good evening.
Facepalm
That was a joke. I was comparing to steering layer maps....
I see that. Going to be worse in a hour or 2 too!
Hope the rainfall is not too bad...
:):)
LMAO!!!
Peace Levi!
hmm the COC seems to be at 17.2N 58.9W so no not to the sw the convection is
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
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...
LOL.
But 'less' pathetic is still pretty dismal...
You shouldn't ask that question. He gets upset when you reference where he lives.
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