WunderBlog Archive » Category 6™

Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.

Hermine drenching Texas; Gaston's remains less organized

By: Dr. Jeff Masters, 1:21 PM GMT on September 07, 2010

Tropical Storm Hermine hit the Mexican coast 40 miles south of the Texas border at 9:30 pm EDT last night, with 60 mph sustained winds. Top winds observed in Texas from the storm were 50 mph with gusts to 59 mph at Port Isabel near the Mexican border, and winds at Brownsville hit 45 mph, gusting to 69 mph. Harlingen had the highest gust observed from Hermine, 72 mph, and local storm reports indicate that half of the city lost power and a roof caved in on an apartment complex, with no injuries. Heavy rains have fallen along a 30-mile wide stretch of the Mexican and Texas coast, with 1.41" reported thus far in Harlingen, 3.71" at Brownsville, and 2.00" at Corpus Christi. Radar estimated rainfall amounts (Figure 3) exceed four inches along most of the Lower Texas coast, with maximum amounts near eleven inches twenty miles north of Brownsville.

Figure 1. Radar image of Hermine at landfall.

Figure 2. MODIS satellite image of Hermine at 12:45pm EDT Monday September 6, 2010. Image credit: NASA.

Hermine became a tropical depression at 11pm Sunday night, and intensified into a 65 mph tropical storm in just 21 hours, an extremely fast intensification rate. It turns out that the southwestern Gulf of Mexico's Bay of Campeche, where Hermine formed, is prone to these sort of rapidly intensifying tropical storms. This region produced two similar rapidly intensifying storms in 2007, Humberto and Lorenzo. Since 6-hourly position records of Atlantic hurricanes began in 1970, Hurricane Humberto holds the record for fastest intensification from first advisory issued to hurricane strength--18 hours. (Actually, Humberto did the feat in 14 1/4 hours, but this was rounded off to 18 hours in the final data base, which stores points every six hours). The curvature and topography of the land surrounding the Bay of Campeche 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 yesterday for Hermine were the very warm 30°C waters, low 5 - 10 knots of wind shear, and moist atmosphere.

Figure 3. Morning radar-estimated rainfall for Hermine.

Forecast for Hermine
Heavy rain and isolated tornadoes will continue across southern and central Texas today and tomorrow. Hermine is expected to accelerate northward today, limiting the potential for damaging floods along its future path. The storm's rains will help alleviate moderate to severe drought conditions affecting Central Texas.

Gaston's remains less organized
Dry air has significantly disrupted the remains of Tropical Storm Gaston, which are now over the northern Lesser Antilles Islands and Puerto Rico. Morning visible satellite imagery shows that Gaston's remains no longer have a well-defined surface circulation, though there is still some spin. Latest radar out of Martinique and Puerto Rico show a few heavy rain showers moving through the islands, but no organization to the showers. A large amount of dry air surrounds Gaston's remains on all sides, as seen on water vapor satellite loops. None of the computer models show Gaston redeveloping, and NHC has downgraded the odds of development to 10%. I think the odds should be higher than this, perhaps 30%. Gaston's remains will be disrupted some on Wednesday, when they will encounter the high terrain of Hispaniola.

Elsewhere in the tropics
There are two tropical waves off the coast of Africa that NHC is giving a 10% chances of developing into tropical depressions by Thursday. The models are fairly unanimous in predicting development of one or more tropical waves off the coast of Africa 3 - 7 days from now. The next storm will be called Igor.

Eastern Pacific Tropical Depression 11E kills 44 in Guatemala
In the Eastern Pacific, heavy rains from Tropical Depression 11E killed at least 44 people in Guatemala over the weekend. At least 56 are injured, and 16 missing. The heavy rains triggered fifteen landslides that hit portions of the Inter-American Highway, burying a number of vehicles and a bus. Guatemala is still recovering from the impacts of Tropical Storm Agatha, which killed 287 people in the country and did over $1 billion in damage.

Figure 4. Satellite image from Friday, September 3, 2010, showing Tropical Depression 11E over Guatemala. Image credit: NASA.

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question to broadcast@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line.

Today's show will be about 30 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Next post
I'll have an update Wednesday morning.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Quoting StormW:

Current run of the forecast wind shear map, out to 108 hours. NO shear in the Caribbean, and two upper level anticyclones on the map...one at 40W, and the other just developing off the African coast. And, you can pretty much pick out the jetstream across North America

Looks like another anticyclone due south of Puerto Rico, too.
Gaston.... still there :(
91L seems to be playing follow the leader....






Quoting reedzone:

Like I said, the EURO does NOT recurve 91L, takes it north of the islands, but doesn't curve it north, heads WNW, WSW near the islands, then heads NW to WNW, north of the islands.. Pretty much heading towards the CONUS. The high is too strong and elongated for 91L to get picked up on this run. The GFS has switched to this idea on the 06Z run as well, gotta see if this trend continues with the GFS. The EURO has been showing this ever since it started forming 91L.

Thanks Reed. What does the CMC and ECMWF show?
Gaston could do anything from fizzle in the very next frame, to blow up and become a cat 5 within 48 hours, or anything between.
Quoting MZT:
I get up in the morning and Hermine is still squatting over Texas dumping rain. We spent a week hyping and gushing over Earl, which turned out to be a non-event. But that sneaky tropical storm Hermine could be the real story with all the flooding it creates.
Yep. Funny how Mother Nature operates.
What is spinning at 18N 34W? This is not 91L is it?
3008. IKE
I know, I know, it's the NAM, but I am using it to illustrate the point that quite a few models are trying to develop that piece of energy that is entering the southeast carrib., which you can see on the satellite in post 3005.

Something to keep an eye on, wonder if that is the remains of 99l...

Nam @ 84 hrs...

Just a quick question...Looking at the visible sattelite of the Carribean, there appears to be a huge swirl just South of Western Cuba...anything to be concerned about?
3011. Jax82
Rise and Shine
Quoting StormW:
Not good: