Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 8:15 PM GMT on October 01, 2005
Tropical Depression 20
Tropical Depression 20 is intensifying as it moves slowly towards the Yucatan Peninsula. More spiral banding is evident on satellite imagery this afternoon, and the storm now has two good outflow channels, to the north and the south. The wind shear has fallen significantly, and is now just 5 knots out of the east. The center of the depression is about 70 miles south of buoy 42056, which itself is about 100 miles southeast of Cancun, Mexico. The buoy recently measured sustained winds of 34 mph gusting to 40 mph. A hurricane hunter aircraft measured peak winds of 30 mph in the southeast quadrant of the storm at 3 pm EDT today.
The system is expected to cross the Yucatan Peninsula Sunday, and will have to re-organize once it pops out into the Gulf of Mexico Monday. It will then have at least 36 hours or so to intensify over the warm 29 - 30C waters of the Gulf. Wind shear is expected to remain very low, under 5 knots, and TD 20 may be a strong tropical storm or Category 1 hurricane as it approaches the Mexican coast south of Brownsville on Tuesday. The forecast track is problematic, as none of the forecast models did a good job initializing this small and weak system this morning. Several models get confused about the identity of this system, and try to develop another tropical storm near the Florida Keys on Tuesday, and still keep this storm in the southwest Gulf of Mexico. The Canadian model suggests that TD 20 will threaten the northeast Mexican coast, but move northward and threaten Texas as well. The coast of northeast Mexico well south of Texas is the most likely target suggested by the rest of the models, but we won't have a good idea of where TD 20 will go until Sunday morning, after the 00Z (8pm EDT) model runs are available.
Hurricane Otis threatening Baja and Arizona
Hurricane Otis reached its peak intensity early this morning--a Category 2 hurricane with winds of 105 mph. Otis is now a Category 1 hurricane with 85 mph winds, and is expected to slowly creep northwestward over cooler waters and gradually weaken. By the time it takes a more northerly track and crosses the Baja Peninsula on Monday, Otis will probably be a strong tropical storm or weak Category 1 hurricane. Hurricane force winds extend outwards only 15 miles from Otis's center, so only a small portion of the coast will receive wind damage. Heavy rains of 5 - 10 inches will be the main problems with Otis, potentially triggering serious flash flooding in the desert mountains of Mexico. By Tuesday, portions of southern Arizona may receive 3 - 5 inches of rain, creating flash flooding problems there.
Figure 2. Hurricane Otis.
Tropical Depression 19 is far out over the Atlantic Ocean, about 600 miles west-southwest of the Cape Verdes Islands. The environment for strengthening is fair, and we will probably see this system become a tropical storm tonight. A hurricane seems unlikely, as this system is expected to move northwest or northward for the next five days into a region of increasing wind shear. It will be interesting to see if this storm or TD 20 wins the race to become Stan--loser gets the name Tammy. If they both get upgraded on the same advisory, how does NHC decide which storm gets which name? I'm not sure the problem has ever arisen, and I hope they do something scientific like play a game of Rock, Paper, Scissors to decide.
Disturbance 500 miles east of Trinidad
A disturbed area of weather has developed 500 miles east of Trinidad and the southern Lesser Antilles Islands this afternoon. This disturbance is currently under an area of 10 - 15 knots of wind shear, but this shear is forecast to diminish the next several days. This may allow some slow development to occur as the disturbance tracks westward at 15 mph.
Flood watches are posted for all of the Hawaiian Islands as the moisture from Tropical Depression Kenneth moves over today. As yet, no heavy rains have impacted the islands.
Taiwan and China
Typhoon Langwang, a small but intense typhoon with 130 mph sustained winds, is headed towards a landfall on Taiwan Sunday. The upper-level outflow from the typhoon has degraded today, but there is no apparent wind shear affecting it, so landfall as a Category 3 storm is likely. Longwang is expected to weaken to a Category 1 storm after passage over the 10000 foot high mountains of Taiwan and continue on to strike mainland China on Monday.
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Light Freezing Rain