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 Relix:
50% lol. Gaston fail


Is dead
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Galveston waves right now. Some rain not much wind to speak of. Driving down from Austin I did run into some heavy bands.

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Quoting Wots:
Longer Brownsville radar loop, shows H turning NNE

Link
I see the little bit of possible jog NNE, but I am going to jump and put out my first ever prediction. Hermine makes landfall about 11 PM central about 30 miles SSE of Matamormos just north of where the barrier islands end. I see strong tropical storm, but not quite hurricane.
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Quoting Neapolitan:
Unless something very much out of the ordinary happens--a huge injection of dry air, a sea monster rearing its angry head, an impromptu HAARP experiment--Hermine will definitely be at least a Cat 1 by 11 PM.

IF she makes landfall before that, they'll probably issue an update statement/special advisory saying she has made landfall as a Cat1 in NE Mexico.
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Quoting Wots:
Longer Brownsville radar loop, shows H turning NNE

Link

Is dead.
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Quoting jeffs713:

Its probably feeling the coastline. It is not uncommon for storms coming into a coastline at a shallow angle to "bounce" off the coast a bit.


I'm guessing that's what we saw Saturday morning with Earl. It finally crossed the Nova Scotia coastline much closer to Halifax (i.e. farther NE) than expected. Good for me; bad for Halifax.
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yellow convection just about all the way around the eye...
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428. 7544
atlantic is in the sleep mode we have two red dots out there thats it for now it should wake up soon tho
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Quoting MoltenIce:
I corrected it. :)


35% Gaston on the South and 15% Gastonette to the north.
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Miami, send it west!
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Quoting StormW:


Agree.


Storm,

Did you see my ? on 232? tia
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Come tomorrow morning ex Gaston will be blooming again, what a tormenting little devil he has become!!!muy pelegroso hombre
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Hermine just updated to 65mph winds. She is trying to get to hurricane status!
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Was expecting 50%, was afraid of being pelted with little virtual stones for saying so though lol. Gaston is leaving dry air behind however, and as long as it can slip below Haiti, DR, and Cuba I don't really see a reason for it not to develop.
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Where does the GFDL predict that ex-Gaston will go if it survives all week? the GOM??
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Quoting sammywammybamy:


Sammywammybammy's Track:

Looks like you think the center will pass right over Harlingen and San Benito, and possibly Santa Rosa.
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We notice that the recon hasn't shown any strengthening of Hermine for several vortex messages now, and that is likely because the NW quad is still running into some dry air and although the core is gradually become more defined, that dry air is not allowing things to really take off just yet. The core is not all that impressive to look at on visible satellite imagery.

However, the longer it procrastinates and stays over water, the more it will strengthen.

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Quoting MiamiHurricanes09:
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.


Raining at a pretty good clip on this side of the state too Miami. No lightning so far.
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Hermine says: Land? I ain't going on no stinkin land! Not yet anyway lol. Switching subjects, I really wish people would give it a rest about ex- Gaston. Clearly there is still something there and until it dissipates, it is a a threat. Period.
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Quoting btwntx08:

50%
I corrected it. :)
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Quoting foggymyst:
Miami- what area ar you in? I am in Way west-beyond Kendall, cloudy no rain.
Brickell.
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Good luck Miami, i am just north of all that mess. Came through here with high winds, heavy lightning and rain. Some hail was reported out west as well, good luck.
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Unless something very much out of the ordinary happens--a huge injection of dry air, a sea monster rearing its angry head, an impromptu HAARP experiment--Hermine will definitely be at least a Cat 1 by 11 PM.
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Quoting Stormchaser2007:
If by tomorrow ex-Gaston doesn't pull off some sort of spontaneous bout of organization, I think that will be pretty much the end of it.



yea I have to agree with you there

we all had high hopes for a storm named Gaston, we were all so sure it would be a big deal

It has been big alright, a big dud

In the end its good, we do not need a system going through the Caribbean as a storm or hurricane

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Quoting futuremet:


Dry air is the only problem.


and some light easterly shear
Member Since: April 17, 2010 Posts: 0 Comments: 1753
If by tomorrow ex-Gaston doesn't pull off some sort of spontaneous bout of organization, I think that will be pretty much the end of it.

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It is never wise to turn your back on a tropical storm, no mater how pathetic it looks at present. These things have and will continue to spin up in extreme fashion in relatively short periods of time. It's not something to scoff at or take lightly. You could go to sleep expecting a stiff breeze off your porch and wake up with a full on Hurricane bearing down on you.
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Seems to me that IMO Hermine its about to end that NNE wobble and its about to return to the NW.
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Quoting StormW:


Have to be speaking of the dry air.


Dry air is the only problem.
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Quoting TcuFrogs:

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.


It appears to be Stormtop's Louisiana magnet, but there is a major metropolitan center in the way.
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I'm out for a bit. The lightning and thunder is very, very intense, plus nonstop rain. Be back when it clears up a bit.



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Miami- what area ar you in? I am in Way west-beyond Kendall, cloudy no rain.
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Quoting skkippboo:
Hmm, is this nature's way of taking care of itself and correcting the overly hot water we have out there?

Maybe so
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399. JLPR2
Gaston has been slapped in the face by D-min. LOL!
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398. beell
Aside from the effects of storms bouncing off land I might add that the location of the steering ridge might also play a part in where Hermine makes a landfall.

TROPICAL STORM HERMINE DISCUSSION NUMBER 4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL102010
400 PM CDT MON SEP 06 2010

...THE MID-LEVEL RIDGE TO THE NORTHEAST OF THE STORM...



RUC 500mb Steering @ 9AM local




and at 6PM local-not a big change. Eased south and to the west a bit.

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Quoting DDR:

Wow!
You know what to do!
Sounds like the stuff we had a few days ago.


here in miami I'm not getting much, the beach is getting slammed though
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Miami, you got at least one tornado nursery in your area, got one up here thats trending to the south as well.
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Quoting mcluvincane:
Any models predicting a conus hit in the near futere?


No. Why?
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Quoting Neapolitan:


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

True. But nearing depression status followed by waning convection over and over again is kind of annoying.
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390. Relix
50% lol. Gaston fail
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389. Wots
Longer Brownsville radar loop, shows H turning NNE

Link
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388. DDR
Quoting MiamiHurricanes09:
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.

Wow!
You know what to do!
Sounds like the stuff we had a few days ago.
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386. JLPR2
Quoting TropicalAnalystwx13:
Ouch! Down to 50%!


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

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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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