Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 1:46 PM GMT on September 30, 2005
The tropical disturbance in the western Caribbean Sea remains disorganized, but has a large area of thunderstorms covering an area from Cuba to Honduras to Jamaica associated with it. Surface pressures are falling over this area. For example, a pressure/wind plot from buoy 42056 about 100 miles southeast of Cancun, Mexico shows a steady drop in pressure the past two days (with an oscillation due to the daily pressure wave triggered by solar heating of the atmosphere also seen). However, the surface circulation center is weak and displaced to the southwest of the main convection, and there is poor upper-level outflow and no sign of low-level spiral banding.
Wind shear over the system is unchanged at 5 - 10 knots, and is forecast to remain the same or decrease as the system moves northwest towards the Yucatan Peninsula or Western Cuba. I still expect this system to eventually develop into a tropical depression, but not today. The hurricane hunters are on call today in case some dramatic development starts to occur, though. A small upper-level anticyclone remains over the system, and this favorable upper-level wind pattern is forecast to persist for the next few days. The system has plenty of moist air surrounding it, and will continue to do so for at least one more day. As the system moves closer to the Gulf of Mexico, it will have some dry air to contend with, since the Gulf is filled with relatively dry air, and there is always dry air over the high plateaus of the Yucatan that might get sucked in.
If the system does manage to develop, the Mexican Gulf Coast or Texas look like the most likely targets. The only model that develops the system into a tropical storm is the GFDL, which forecasts a motion past the tip of the Yucatan Peninsula northwestward, then a turn to the west-southwest as a strong ridge of high pressure builds over the Gulf of Mexico. The GFDL forecasts intensification into a Category 1 hurricane and a strike on the Mexican coast south of Brownsville on Tuesday. The GFS model, on the other hand, does not strengthen the ridge as much, and takes the system into South Texas Tuesday. Both of these solutions may be too fast, as some of the other computer models indicate that the system may linger near the Yucatan Peninsula for five or more days.
Figure 1. BAMM and GFDL track forecasts.
Several of the global computer models continue to forecast that a tropical storm may form near the Bahama Islands on Monday or Tuesday. Any system forming in this region would be forced westward or west-southwestward into the Southeast Coast by a strong ridge of high pressure building in. There is as yet no sign of this development occurring, but this is the same area Katrina and Rita formed, so extra attention should be focused on this area.
A concentrated area of thunderstorms about 600 miles west-southwest of the Cape Verde Islands has developed a spin. There is some evidence of spiral banding and upper-level outflow channels beginning to form, and this disturbance could very well become Tropical Depression 19 and Tropical Storm Stan in the next day or two. The system is expected to move slowly northwest for the next five days and not threaten any land areas.
Hawaii is watching Tropical Depression Kenneth, which is dissipating as it approaches the Big Island. The remnants of Kenneth may bring heavy rains and the threat of flash flooding to the islands Saturday.
The Baja Peninsula is watching Hurricane Otis, which may strike the central Baja Peninsula on Sunday. Otis is taking a path very close to the Baja coast, where a narrow tongue of warm water will enable him to maintain hurricane intensity at a much further north point than most East Pacific hurricanes are able to. A hurricane watch has been issued for much of the Baja Peninsula.
Otis's remnants are a good bet to bring heavy rains and flooding to Arizona and northern Mexico early next week.
Super Typhoon Langwang, a small but intense typhoon with 150 mph sustained winds, is headed towards China and may hit northern Taiwan as a Category 4 storm on Sunday. Longwang is expected to gradually weaken but still hit mainland China on Monday as a Category 3 storm.
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