Dean pounds Martinique; Erin soaks Texas; Sepat zeroes in on Taiwan

Hurricane Dean plowed into Martinique this morning as a Category 2 hurricane with 100 mph winds. Radar imagery from Meteo France (Figure 1) shows that the eye of Dean grazed the southern tip of Martinique at about 5am EDT this morning. Winds at the Martinique airport gusted as high as 89 mph, but the airport was north of the eyewall, and missed seeing the calm at the center (Figure 2). An intermediate report, not sent out as part of the regular observations received by wunderground, showed sustained winds of 75 mph, gusting to 103 mph, at 4:42am EDT. The airport is still sending in observations, which is a good sign, and it is likely that only the southern 1/4 of the island suffered heavy wind damage. The northern part of St. Lucia also suffered heavy wind damage, and Dean's winds lifted the roof off the pediatric wing at Victoria Hospital in St. Lucia's capital, Castries. Dean underwent a brief period of weakening just before hitting Martinque, thanks to some dry air intruding into the circulation, so may have brought only Category 1 winds to Martinique. The rains continue on the island this morning, and current radar imagery shows that Dean has intensified since departing Martinique. This is backed up by the 9:12am EDT Hurricane Hunter data, which found the pressure had dropped to 965 mb and the surface winds had risen to 105 mph. Dean's rainbands are dumping torrential rains on Martinique and Dominica, and life-threatening flooding and mudslides will be a major hazard on those islands today.


Figure 1. Radar image of Dean as it passed over the southern tip of Martinique. Image credit: Meteo France.


Figure 2. Current conditions for Friday, August 17, 2007 at Le Lamentin, Martinique. This airport is on the sheltered west side of the island, by the capital city of Fort de France, and was far enough north that the eyewall missed.

Latest model runs
The NOAA jet flew last night, collecting a large amount of high-quality data around Dean's environment that was used to initialize the latest (06Z) model runs. These models continue to unanimously show a grave threat to Jamaica and the Cayman Islands two days from now. Even if Dean misses these islands, it won't be by much, and residents should expect hurricane conditions, as Dean should be an extremely dangerous Category 4 storm by then. Haiti and eastern Cuba also appear likely to suffer severe flooding problems from Dean's outer spiral bands, but a direct hit in these areas appears unlikely. Lesser flooding problems, but still potentially life-threatening, will occur in Puerto Rico and the Dominican Republic. Additionally, Dean may grow so large and powerful that its spiral bands will cause heavy rains and flash flooding in Venezuela, Nicaragua, and Honduras. Hurricane Gilbert of 1988, which traced out a similar path, was large enough to cause several flooding deaths in each of those nations.

The NOAA jet mission did not help at all with narrowing down the uncertainty in the computer forecasts for the 4-5 day period, which remain divergent. The 06Z run of the GFS model takes Dean over the center of the Yucatan, then into the Texas/Mexico border region on Thursday. The 06Z GFDL is much faster and further north, taking Dean through the Yucatan Channel and into northeastern Texas near Galveston on Wednesday. The 06Z HWRF is in between and much slower, taking Dean over the tip of the Yucatan Peninsula by Wednesday. The problem is that each model has a different solution for the behavior of an upper-level low pressure system expected to be over the Gulf of Mexico early next week, and there is no is currently no way to guess which model will be right. Which model should you trust? I'll present the statistics for how these models performed last year in my update this afternoon.

Erin leaves a Texas-sized mess
Tropical Depression Erin continues to dump heavy rain on Texas, with another 2-5 inches expected today in west Texas. Erin dropped over 10 inches of rain near San Antonio, and areas near Houston received nine inches (Figure 3). Over 70 high water rescues were performed in the Houston area from Erin, and four people died in Texas due to flooding. The region encompassing Corpus Christi, Austin and Houston has already surpassed its average yearly rainfall total, with 40-48 inches having fallen. Erin's rains could be setting the stage for a major flooding disaster next week in Texas, should Hurricane Dean hit the state and dump heavy rain of its own. With Erin's rains leaving the soil saturated, Dean's rains will have nowhere to go.


Figure 3. Radar estimated precipitation from Tropical Storm Erin.

Super Typhoon Sepat
In the Western Pacific, residents of Taiwan are preparing for the arrival of Typhoon Sepat, which is expected to hit the island Saturday morning local time. Sepat is no longer a Super Typhoon, thanks to an eyewall replacement cycle it underwent yesterday. Still, the storm has a huge eye about 70 miles in diameter that will bring Category 3 or 4 winds to a large area of Taiwan. An impressive microwave image of Sepat's eyewall replacement is available from the Monterey NRL web site.

I'll have an update around 4pm EDT this afternoon, when I'll discuss which long-range computers model forecasts of Dean we should believe.

Jeff Masters