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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1086. pottery
Quoting ShenValleyFlyFish:
If you want a bunch of choices on how to approach viewing a weather event just open a second tab to nws.gov and follow your nose. I tend to bounce back and forth between there and WU when something is going on.

Good Advice there...
Member Since: October 24, 2005 Posts: 0 Comments: 24226
Quoting pottery:

That could happen...


If it moves directly North from where it is, I don't see how it could go back over water. It would have to at the very least move NNE.
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1084. pottery
Quoting Halyn:


Pottery .. could the eye follow/relocate with the convection ?

Not sure if that can happen, with such pronounced rotation.
I wish a couple of the more knowlegable people were on to answer that...
Member Since: October 24, 2005 Posts: 0 Comments: 24226
Where is all this east nonsense coming in from:

Member Since: September 10, 2007 Posts: 0 Comments: 11102
Quoting txsweetpea:

I dont know, that is what I am waiting to see.


hmmmmm.....
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Quoting pottery:
Want2lrn,
From the radar at post 1042, I see the center just inland, just south of the border (down Mexico way LOL).
I see the main convection northeast of that, so you may be looking at the convection moving north, but the center seems to be staying inland.


Thank you, not enough experience to decipher that kind of thing yet, but i see what you are talking about. I am up the coast in Corpus and am not interested in any surprises when i get up in the morning, that is if i sleep. LOL
Member Since: Posts: Comments:
If you want a bunch of choices on how to approach viewing a weather event just open a second tab to nws.gov and follow your nose. I tend to bounce back and forth between there and WU when something is going on.
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Quoting TexasHurricane:
Is it moving NE? If so, will this continue?

I dont know, that is what I am waiting to see.
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1078. Halyn
oops .. meant 'center'
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Hermine is definitely moving N with a wobble to the east(lets hope its a wobble).
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1076. Halyn
Quoting pottery:

That could happen...


Pottery .. could the eye follow/relocate with the convection ?
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1075. pottery
Quoting btwntx08:
omg just recorded a 54 mph gust a minute ago

Let us know if you get a wind-shift.
Member Since: October 24, 2005 Posts: 0 Comments: 24226
Is it moving NE? If so, will this continue?
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Gaston is finally leaving the paths of Danielle and Earl. Now it has to go through the area of the Caribbean called the "graveyard of hurricanes". Still, that area is more conducive to development the later the season goes. Also, there should be less subsidence from former storms there.
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1071. pottery
Quoting houstongator:
I agree, but if it keeps moving N, it will be back over water by 2 AM and bring a shock to the entire SE part of Texas in the morning.

That could happen...
Member Since: October 24, 2005 Posts: 0 Comments: 24226
Quoting leo305:
how unexpected would it be if Hermine moves NNE and moves off shore, and rides up the texas coast and doesn't really weaken

Yea very unexpected...and would not be good
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Quoting pottery:
Want2lrn,
From the radar at post 1042, I see the center just inland, just south of the border (down Mexico way LOL).
I see the main convection northeast of that, so you may be looking at the convection moving north, but the center seems to be staying inland.
I agree, but if it keeps moving N, it will be back over water by 2 AM and bring a shock to the entire SE part of Texas in the morning.
Member Since: August 28, 2005 Posts: 0 Comments: 112
Quoting traumaboyy:


I apologize personally to my WU family and take full responsibility for getting off track from solely discussing the tropics....I will try to be good in the future!!
lol...but seriously, you have to admit it was getting out of hand.....and we DO have the fact that we have a CONUS affecting tropical storm right now. I would think if Dr. Masters checked his blog an hour ago, he'd be upset. Let's just move on.
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btwntx08

I'm glad your getting it all, hasn't rained here in a couple of hours. And I'm just outside of galveston. You Keeep It!
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1065. xcool
btwntx08 how about cell phone.
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1064. xcool
hey fatlady99
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1063. pottery
Want2lrn,
From the radar at post 1042, I see the center just inland, just south of the border (down Mexico way LOL).
I see the main convection northeast of that, so you may be looking at the convection moving north, but the center seems to be staying inland.
Member Since: October 24, 2005 Posts: 0 Comments: 24226
1062. leo305
how unexpected would it be if Hermine moves NNE and moves off shore, and rides up the texas coast and doesn't really weaken
Member Since: April 17, 2010 Posts: 0 Comments: 1753
hey xcool
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1059. Skylink
do you have a WU station
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1058. leo305
Quoting houstongator:
Definately moving North and east the past 30 minutes. I hope its just a jog and this doesn't get back over water. Was the quick run to the coast just a jog?


I think so, it jogged to the WNW then returned to its NNW movement
Member Since: April 17, 2010 Posts: 0 Comments: 1753
1057. Hhunter
Quoting btwntx08:
omg just recorded a 54 mph gust a minute ago
hmm
Member Since: August 19, 2007 Posts: 0 Comments: 2973
btwntx08

Where in texas do you live? You must be appalled by all these sneak attacks from the bay of campeche.
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1055. leo305
Quoting btwntx08:
omg just recorded a 54 mph gust a minute ago


record it! So we can see!

must be exciting..

you know kinda sucks that TWC has Mike Sidel on south padre and they aren't showing live coverage of Hermine moving through.. I guess to them a landfall means it's dead..
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting xcool:



Looks to be going NE
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Definately moving North and east the past 30 minutes. I hope its just a jog and this doesn't get back over water. Was the quick run to the coast just a jog?
Member Since: August 28, 2005 Posts: 0 Comments: 112
1051. xcool
byebye rob & power
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sorry I meant hate

anyway that UUL is getting weaker and becoming elongated NNE-SSW

plus the shear over gaston is 5-20 kt and falling so shear won't be much of a problem much longer

and soon expected to start moving WSW soon maybe in the next 3-6 hours time so DR'[s Mt. won't be a problem anymore
Member Since: June 13, 2009 Posts: 2 Comments: 11695
1049. leo305
Quoting btwntx08:
geez wind just got stronger gusting to about 50 mph now raining very hard


the center is headed right for you, it's likely you will lose power
Member Since: April 17, 2010 Posts: 0 Comments: 1753
1048. xcool
F4PHANTOM .no lies really boring imo haha
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1047. xcool
traumaboyy heyy ;)
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1045. xcool
. btwntx08 bye bye
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Quoting xcool:
boring hurricane season haha


What Up Xcool!!
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Quoting btwntx08:
appears thats shes hugging up the coast


I see that too....is this another jog/wobble or will this me an actual motion?
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1042. xcool


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Quoting pottery:

Can you link that radar?


I am sorry i dont know how...i am just typing in Brownsville on the WU home page and pulling it up :(
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1040. pottery
Quoting traumaboyy:


I apologize personally to my WU family and take full responsibility for getting off track from solely discussing the tropics....I will try to be good in the future!!

No Prob.
But Admin takes a dim view of 'off topic' stuff when there is a storm-threat. People have been banned for less around here LOL.
Member Since: October 24, 2005 Posts: 0 Comments: 24226
1038. lparky
Quoting lparky:
get out there and get video! :)


that was for btwn. it wouldn't quote you!
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1037. leo305
Quoting btwntx08:
big wind and very heavy rain hitting me now gusting easily over 40-45 mph


record it on camera!
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting Tazmanian:

round 1


90L bust


91L bust


92L bust

93L be comes Alex

94L bust

95L bust

96L be come TD 2

97L be comes BONNIE

98L bust

99L bust


round 2



90L bust

91L be comes .COLIN

92L bust

93L bust

94L be comes TD 5

95L be comes Danielle

96L be comes Earl

97L be comes FIONA

98L be comes Gaston

99L bust


round 3


90L be comes hermine


Interesting. Glad to see somebody is keeping that scorecard.
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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.