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 Levi32:


Well as soon as she hits land intensification will halt, but if she stays on a more NNW heading that will keep her closer to the coast longer before moving inland, and that will mean that SE TX will get much more of a bashing than the original forecast track would have given. These things in a good environment aloft can keep going pretty well even long after they have moved onshore, so they are no picnic especially if they are only barely inland.

The extreme scenario here is if she continues nearly due north, crosses the Rio Grande, and then skirts the coast of Texas and ends up east of Corpus Cristi instead of west of Corpus Cristi. That wouldn't be fun, but is least likely. What will likely happen is she will turn back west of north once she hits the northeast tip of Mexico and moves towards Brownsville.


ok, thanks Levi...
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Quoting ozzyman236:
im saying houston should pay attention this thing could hug the coast n or nne in your direction..


see my black hole post
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534. IKE
Not much left....

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It looks like high pressure has built in on Hermine and she will soon move ashore according to the tropical points on NOAA satellite.
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Quoting Levi32:


This is true, but unlike most cases, wobbles do actually matter a lot when the storm is less than 30 miles from shore.


shhhhhh dont cloud the blog with logic

remember the dumb arguments when Earl was near the outer banks lol, wobbles very much matter when a storm is close to land
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Thanks Storm, Levi, and 101!
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Quoting btwntx08:

he meant south tx lol


oh ok. I was thinking that was a tad to north. :)
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Quoting aislinnpaps:


Yeah. I used to teach school down there. Actually packed out the day before Allen hit.
I kinda remember that one, I was 4 years old.
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Quoting TexasHurricane:


meaning where I am (SE TX)...What are you thinking it will do?


Well as soon as she hits land intensification will halt, but if she stays on a more NNW heading that will keep her closer to the coast longer before moving inland, and that will mean that SE TX will get much more of a bashing than the original forecast track would have given. These things in a good environment aloft can keep going pretty well even long after they have moved onshore, so they are no picnic especially if they are only barely inland.

The extreme scenario here is if she continues nearly due north, crosses the Rio Grande, and then skirts the coast of Texas and ends up east of Corpus Cristi instead of west of Corpus Cristi. That wouldn't be fun, but is least likely. What will likely happen is she will turn back west of north once she hits the northeast tip of Mexico and moves towards Brownsville.
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Quoting Levi32:


This is true, but unlike most cases, wobbles do actually matter a lot when the storm is less than 30 miles from shore.


Agreed... the next fix will tell a lot
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Finally clearing up some here, the lightning is still a little intense but is much better than previously. Very heavy rain with strong gusts over us right now, but at least the lightning isn't as bad as before. Anyways, Brownsville is also about to get pounded with some heavy rain.

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521. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15684
I say it more like 17.3N 58.7W gaston as I said not dead will look better when we all wake up in the morn I did say gaston is getting out of it bad illness and when they do but after a while they start to look really good
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Quoting BDADUDE:
That was puff!!
made my day. :D
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Quoting GeoffreyWPB:


I think he was a magic dragon.


Great!! LOL

Are you dating yourself??
(Please don't answer) ;>)


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Quoting Orcasystems:


Actually as much as I would like to watch the panic of some on the Blog.... I would assume she is almost on track, if these were the standard two hours fixes... she would be on Track.



This is true, but unlike most cases, wobbles do actually matter a lot when the storm is less than 30 miles from shore.
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Quoting Orcasystems:


Actually as much as I would like to watch the panic of some on the Blog.... I would assume she is almost on track, if these were the standard two hours fixes... she would be on Track.



If she makes it far enough north work may start activating emergency plans, which would not be fun...
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Quoting wunderkidcayman:
ok guys just because they bumped it % down doesn't mean gaston is dead as I say wait for the next 24 hours things can change between then and I expect it to and gaston will likely be come a TD by tomrrow


I will let you know tomorrow or next after this thing cross us from E to W.
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Quoting Levi32:
It's not like this couldn't allow NNW movement right here. Southeast Texas may still be in for a long night if the center takes longer to make its way inland and stays close enough to the water to be a bugger.



meaning where I am (SE TX)...What are you thinking it will do?
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Quoting StormW:


Hard to tell how far north. From what it looks like to me...it appears we are in for some "stair stepping" action, except back and forth W-E


so basically NNE, N, NNW, N, NNE?
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Quoting skkippboo:
Water tends to kinda collect there doesn't it?


Yeah. I used to teach school down there. Actually packed out the day before Allen hit.
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Quoting GeoffreyWPB:


I think he was a magic dragon.


I think you're referring to "Puff" the magic dragon.
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Quoting doorman79:
Levi or Storm,

Isn't possible she slowed cause of the low over Minnisota? Kinda felt some effect as it pulled the high northward, or am I just dumb!
I am not saying it will pull her north just that she felt it for a little bit.


It's several things. Yes the shortwave over the plains has something to do with it because the ridge hasn't yet built in strongly in that area. Also affecting Hermine's track though are frictional effects and the envelope of low pressure extending to her north which is what took her north of the model consensus in the first place, and what could still pull her NNW for a while and give Texas a bad night.
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Nothing much left of Gaston,dry air is winning the battle, maybe a few showers left to the northern Antilles.
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Looks like it may switch to N or NNW again soon.
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Quoting StormW:


He was asking about the low over Minnesota having an effect on the ridge, in terms of Hermine slowing down. I replied that the flow north of her, appears to be going zonal (west to east)...a reason for slowing.


Does that mean this NNE movement is still just a wobble of the center or a real change in direction?
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Is it possible Hermine's faster-than-forecast strengthening is what they didn't account for?
Wasn't she already supposed to make landfall by now?
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Quoting Levi32:
Basically, an average heading of 345 or greater is going to be nasty for south Texas tonight.
Oh crap, I saw this coming on friday when this dang thing crossed mexico, I really didn't think she would mount to much.
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Quoting TcuFrogs:
Orca: Wobble or a true change in direction


Check 488
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Quoting ozzyman236:
EDITH WAS ANOTHER ONE


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Quoting MoltenIce:
If I may ask, what is this D-max?


when there's a lot of moisture available for a cyclone to feed from, it happens when the sun goes down, the temperatures tend to also go down in the tropics, and the dew point tends to get closer to the temperature, when that happens the amount of humidity the air can hold drops, so that moisture has to go somewhere, hence the amount of moisture available to a storm increases causing it to develop further and faster.
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting sammywammybamy:
Florida has been quiet since 2005 with Wilma and 2008 with Fay.

Lets Keep it that way.

IMO, doesnt appear florida will get a Hurricane or Ts (other than bonnie)this year.


What? October and November storms are MOST LIKELY to strike Florida, rather than any other state. ESPECIALLY if they form in the Caribbean due to the troughs.

Way to premature to say that.
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Quoting StormW:


He was asking about the low over Minnesota having an effect on the ridge, in terms of Hermine slowing down. I replied that the flow north of her, appears to be going zonal (west to east)...a reason for slowing.


you think she could ride the coast for a bit and if so how far north?
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Quoting GeoffreyWPB:


I think he was a magic dragon.
That was puff!!
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Quoting Levi32:


Well it is, lol. These storms love to do that, and most always try at least once. Even Alex tried but failed. Dolly in 2008 was one that succeeded. The frictional effects always try to pull them north when they try to hit northern Mexico. This time, we'll see how it goes, but Hermine could still take a mean track if she heads an average of NNW over the next 12 hours.

Now if she's really naughty and keeps going due north, well, that's not going to be very fun, but she likely won't stay on this particular heading for too awful long. They are often wobbles due to the frictional effects.


Actually as much as I would like to watch the panic of some on the Blog.... I would assume she is almost on track, if these were the standard two hours fixes... she would be on Track.

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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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