Hurricane watches for Mexico and Texas as Hermine suddenly develops

By: Dr. Jeff Masters , 4:15 PM GMT on September 06, 2010

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Hurricane watches are up for the Texas/Mexico border region as fast developing Tropical Storm Hermine steams towards the coast at 13 mph. Hermine was a tropical depression twelve hours ago, got its name just six hours ago, but already is a threat to intensify into a hurricane by tonight. It's remarkable how fast Gulf of Mexico disturbances can blow up into strong tropical storms, when the right mix of warm waters and low wind shear develops. Indeed, water temperatures are a very warm 30°C, wind shear is a low 5 - 10 knots, and the atmosphere is very moist in the Gulf--ideal conditions for a tropical storm. 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 moved ashore over southern Texas and northern Mexico, with radar estimated rainfall amounts already exceeding two inches in a few areas along the coast. Radar loops show that an eyewall may be beginning to form, and I expect this process will continue through the afternoon and early evening. Satellite imagery shows that Hermine is getting more organized, with vigorous thunderstorms with very cold tops building, low-level spiral bands developing, and improving upper-level outflow occurring on all sides except the west. There is some dry air to the west of Hermine over land that is restricting the storm's development there.

Forecast for Hermine
Hermine doesn't have much time over water before it comes ashore, which is a good thing. Hermine is organizing rapidly, and has a shot at reaching hurricane strength before the center moves ashore late tonight, near midnight. Neither the GFDL or HWRF models develop Hermine into a hurricane, but the HWRF model does predict that tropical storm force winds of 39+ mph will affect the coast as far north as Corpus Christi, Texas. 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. Early afternoon radar image of Tropical Storm Hermine.

Gaston continues to suffer from dry air
The remains of Tropical Storm 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 late this afternoon and continuing into the night. A pass from the ASCAT satellite this morning at 9:03 am EDT showed a large region of 25 mph winds on the north side of Gaston's circulation, and these winds will move into the northern Lesser Antilles late this afternoon. 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. Gaston does have developed a well-organized surface circulation, but not enough heavy thunderstorm activity to be considered a tropical depression. A large amount of dry air surrounds Gaston's remains on all sides, as seen on water vapor satellite loops.


Figure 2. Morning satellite image of the remains of Gaston, approaching the Lesser Antilles Islands.

Forecast for Gaston
Dry air will continue to be the major impediment to development for Gaston, 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 it 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. The models don't give much support for Gaston surviving past Wednesday, since many of them have the storm hitting the rugged island of Hispaniola, disrupting the storm.

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, the Turks and Caicos Islands, and Jamaica Wednesday night and Thursday morning. Though none of the global dynamical computer models are showing this, should Gaston survive the dry air and its coming encounter with Hispaniola, the storm will find itself in a very favorable environment for development in the Western Caribbean late in the week, and could intensify into a hurricane by next weekend.

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, and let's hope it doesn't live up to its fearsome-sounding name!

Next post
There will be an update by early this evening.

Jeff Masters

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Just noticed something. we are AHEAD of 2004.. We were still tracking Frances at this time.
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Quoting challengerpr:
Link

Cyclone alert for ex Gaston


UFF!!
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Hermine looks to be moving at a decent clip towards the northern coast of Mexico. It really doesn't have much time.
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Be back in a few hours. ;)
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Quoting ElConando:


If it did not know any better it looked like it was trying to build an eye up.


Excuse me an eye wall.
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Thanks Dr. D! :)
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Good morning all. I see we now have Tropical Storm Hermine and it is looking mighty impressive and going a little further north. It has been raining off and on here and getting breezy. I wonder if it will get worse here as time goes on. Stay safe everyone...
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Quoting ozzyman236:
yes weatherguy03 had this nailed this morning...congrats to bob he knows what hes talking about..im glad the blog has hime..
In all seriousness, my daily routine is to FIRST check out the NHC site and dicussions(if there are any), and then watch Weatherguy03's video blog. Then read what Dr. Masters has to say. That about covers it. This blog has a few nuggets of info hidden, particularly when we here from experienced watchers like KMan, but it's like panning throgh sluice to find any little gold flake in these parts.
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Did recon have problems? I see it is headed back to Biloxi without having made it to Hermine.
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Member Since: September 2, 2009 Posts: 130 Comments: 21193
damn 3/4 eyewall
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Quoting Levi32:
Radar continues to show a banding structure that is only beginning to develop, which means that Hermine is not close to a hurricane yet, but is likely near a 50kt TS right now.


She'll make a cool radar loop that's for sure.
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Quoting 1900hurricane:


If it did not know any better it looked like it was trying to build an eye up.
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Quoting Levi32:


Yeah but the NAM is now being ridiculous in the recent runs.


I know I know but just wanted to make the point it forecasted it last week. Right now we are real time - things unfolding as they happen.
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Link

Cyclone alert for ex Gaston
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South Texas getting slammed again with heavy rain, hope no tornadoes develop with the storm.
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Plenty of rainfall already starting to spread across portions of Mexico and southern Texas, particularly the area of Brownsville already receiving 2.5 inches of rain.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
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Quoting ticka1:
The NAM was forecasting Hermine last week. Don't be too quick to discount it on this systerm. Bring alot of rainy weather to Texas today.


Yeah but the NAM is now being ridiculous in the recent runs.
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:) Thanks Dr. Masters.
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The NAM was forecasting Hermine last week. Don't be too quick to discount it on this systerm. Bring alot of rainy weather to Texas today.
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Quoting Drakoen:
GFS did a good job in forecasting Hermine's development.


I agree, I didn't think it was going to happen, but it did. This may reach minimal Hurricane Status right before landfall, similar to when Alex reached category 2 status from 1 right before it's landfall.
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30. JRRP
and let's hope it doesn't live up to its fearsome-sounding name!

lol
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Hermine's going to run out of room.
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Quoting StormW:


Yeah. It appears to be hitting better on cyclogenesis than track.


Agreed....I believe it had the track coming up just North of Corpus, around Port Lavaca
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Radar continues to show a banding structure that is only beginning to develop, which means that Hermine is not close to a hurricane yet, but is likely near a 50kt TS right now.

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Quoting StormW:


Yeah. It appears to be hitting better on cyclogenesis than track.


Ain't that he truth!

Hermine ruined my morning, I had run out and mow. :P
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Thanks Dr.
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Thanks!
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Link

keep track of core on long range radar..you can see eyewall forming..going to lunch
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Quoting StormW:
Thanks Dr. Masters!

Hey Levi!


Hey Storm!
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Quoting CaribBoy:
The Navy/NRL has a TC formation alert for ex-Gaston.


Link?
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Thanks Dr.M
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Our new website...and other info...
Link
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Thanks Dr. Masters!

Quoting Neapolitan:
Think of this as the second trimester ultrasound for both Igor (left) and Julia. Yikes!

Click for larger image:

It's a complicated scenario depicted by the models when it comes to these two waves and which one becomes the tropical cyclone. The GFS and NOGAPS depict that PGI41L (the weaker pouch located just off the African coast) absorbs PGI42L (the stronger pouch still over land and east of PGI41L). The ECMWF on the other hand does the opposite when it has PGI42L absorbing PGI41L. The CMC also appears to be on the same bandwagon as the ECMWF.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Thanks, Dr. M

Thanks to you to Storm,
Some great reads there!
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GFS did a good job in forecasting Hermine's development.
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Here's another great shot of Things To Come:

Click for larger image:

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Thanks Dr. Master, great update!
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Thanks
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So could Hermine be a Humberto in the making?
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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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