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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586. xcool
a
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Quoting wunderkidcayman:
ok guys I need links the Ob. data from these Islands:
antigua & Barbuda
guadaloupe
montserrat
saint kitts & nevis
saint martin

likely the places that gaston will pass over thanks in advance



http://weather.rabirubia.com/
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Quoting breald:
Was it 2005 when they ran out of names? What do they do if that happens again I forget?


Greek Letters.
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Quoting beell:
EZ Poll.

Hermine Landfall:

A. North of the Rio Grande?
B. South of the Rio Grande?
B.
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Quoting FLdewey:
Maybe this will be the year of repeating storms. Outer banks should secure their liquor stores now.


LOL!!
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Is Gaston doom?
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Quoting breald:
Was it 2005 when they ran out of names? What do they do if that happens again I forget?
Go to Greek!
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Quoting beell:
EZ Poll.

Hermine Landfall:

A. North of the Rio Grande?
B. South of the Rio Grande?


Um B, but, it would be funny if she crossed the Rio Grande and then made a second landfall north of near Corpus Cristi lol. That is unlikely, but you never know.
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Quoting F4PHANTOM:
which year?
1999
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576. IKE
Quoting docrod:


Agreed but I will continue to watch this one. Something from nothing seems to be possible in the past few years.


Always best to keep an eye on it.
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575. beell
EZ Poll.

Hermine Landfall:

A. North of the Rio Grande?
B. South of the Rio Grande?
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Here Orca, our substitute vortex in the form of radar lol. You can see it has turned back about due north since the last vortex fix.

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Quoting Levi32:
If we want to microanalyze the radar, a turn back to the NNW may be occurring as Hermine nears the northeast tip of Mexico, which would make sense.

When you look at this radar, remember that the Northern coast of Mexico looks nothing like what is pictured. It is much, much smoother, and there is no huge island.
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Was it 2005 when they ran out of names? What do they do if that happens again I forget?
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Quoting Levi32:


Eh, we have an eye on radar, who needs the bird lol.


Bird Is The Word.
Member Since: September 10, 2007 Posts: 0 Comments: 11155
Hermine almost as big as Texas.
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Member Since: September 10, 2007 Posts: 0 Comments: 11155
Quoting Orcasystems:
Ok, now its going to get nutty in here... the Bird appears to be on its way home....






Eh, we have an eye on radar, who needs the bird lol.
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Is exGaston on his last leg? IF so good riddance, we don't need him in the Western or Eastern Caribbean for that matter!
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Ok, now its going to get nutty in here... the Bird appears to be on its way home....




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Quoting wunderkidcayman:
ok guys I need links the Ob. data from these Islands:
antigua & Barbuda
guadaloupe
montserrat
saint kitts & nevis
saint martin

likely the places that gaston will pass over thanks in advance


http://stormcarib.com/
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Quoting IKE:
Not much left....



Agreed but I will continue to watch this one. Something from nothing seems to be possible in the past few years.
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You guys in the gom are so lucky.. its coming ashore quickly? Godspeed
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Who would have thunk it? Back in Brownsville - same hotel I was at when I came down to "chase" Alex... even though Hermine is a lot less strong than Alex, B-ville looks to get more bad wx, as it will be moving much closer... I'll keep you posted on conditions!
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If we want to microanalyze the radar, a turn back to the NNW may be occurring as Hermine nears the northeast tip of Mexico, which would make sense.

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"I'm gonna dawdle 'til you guys admit that I'm the her in hurricane."

TropicalStormHermine's heading had turned northward to (5.7degrees north of) NorthNorthWest
from its previous heading of (3.8degrees west of) NorthWest
TS.Hermine's average speed moving between its last 2 reported positions was ~7.3mph(~11.8km/h)

Invest90L
06Sep . 12amGMT - - 20.4n9.54w - - 25knots - - 1003mb - - NHC-ATCF
TD.10 -- 3hour intervals between positions (including the previous one and the next)
06Sep . 03amGMT - - 20.7n95.2w - - 30mph - - 1003mb - - NHC.Adv.#1
06Sep . 06amGMT - - 20.9n95.0w - - 35mph - - 1003mb - - #1A
TS.Hermine
06Sep . 09amGMT - - 21.6n95.0w - - 40mph - - 1001mb - - #2
06Sep . 12pmGMT - - 22.4n95.3w - - 45mph - - - 995mb - - #2A
06Sep . 03pmGMT - - 23.4n95.8w - - 50mph - - - 998mb - - #3
06Sep . 06pmGMT - - 24.1n96.5w - - 60mph - - - 995mb - - #3A
06Sep . 09pmGMT - - 24.5n97.0w - - 60mph - - - 992mb - - #4
07Sep . 12amGMT - - 24.8n97.1w - - 65mph - - - 991mb - - #4A

25knots=~28.8mph __ ~26.1knots=30mph

Copy and paste 20.4n95.4w, 20.7n95.2w, 20.9n95.0w, 21.6n95.0w, 22.4n95.3w-23.4n95.8w, 23.4n95.8w-24.1n96.5w, 24.1n96.5w-24.5n97.0w, 24.5n97.0w-24.8n97.1w, mid, bro, mam, 24.8n97.1w-25.4n97.3w into the GreatCircleMapper for a look at the last*12hours.

Using straightline projection upon the speed&heading averaged
over the 3hours spanning the last two reported positions:
~5hours from now to beach southeast of Matamoros,Tamaulipas,Mexico
on its way to Brownsville,Texas

* The final line-segment is the straightline projection.
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It sure looks like Hermine has wobbled back to the north and even a little bit east. How long before landfall?
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If you look at the satellite loop of Hermine and observe the low pressure envelope, you can see how the storm is almost "pointing" towards where it wants to go. The clouds align nearly due north. But, because the ridge is building into the Gulf of Mexico and pushing in from the east, the track will probably be west of that line. However, these northward wobbles that we're seeing are only possible because that's where the storm "wants" to go, but probably can't for long.

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The eastward component we are seeing is from Hermine moving more northward, then northwestward as the NHC has forecasted her to be moving, therefore going from NW to N is an eastward component.
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Quoting btwntx08:

also about getting alot more rain over there than expected but for me its gonna be a long night


yeah, be safe....hopefully this isn't a trend for y'all the rest of the season...
Member Since: July 2, 2009 Posts: 0 Comments: 2811
ok guys I need links the Ob. data from these Islands:
antigua & Barbuda
guadaloupe
montserrat
saint kitts & nevis
saint martin

likely the places that gaston will pass over thanks in advance
Member Since: Posts: Comments:
545. xcool
btwntx08 you better going to store
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Quoting StormW:


What it looks like may be happening, is the flow, if you look right around Oklahoma, given the orientation of things, may be going a little more zonal (west to east)
What does that mean Storm?
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I don't see this eastward componet on Hermine at all.
Member Since: September 10, 2007 Posts: 0 Comments: 11155
Member Since: August 19, 2007 Posts: 0 Comments: 2973
Quoting F4PHANTOM:
which year?
1999
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539. xcool
dam jason2010xx got money he baller.
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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...
Member Since: July 2, 2009 Posts: 0 Comments: 2811

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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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