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 , 2:10 PM GMT on August 07, 2009
Hurricane Felicia is steadily weakening as it heads west-northwest over cooler waters. Recent satellite imagery shows that the eye is less distinct, and the tops of thunderstorms surrounding the eye are warming, indicating that the updrafts sustaining the eyewall are weakening. The storm appears rather ragged and lopsided, and probably is not as strong as the advertised Category 3 status.
Figure 1. Current satellite image of Hurricane Felicia.
Sea surface temperatures (SSTs) under Felicia have now fallen below the 26°C threshold needed to sustain a hurricane, and will continue to decline as the storm tracks west-northwest over cooler waters. By Saturday morning, SSTs should fall to 24.5°C. While wind shear is expected to remain in the low to moderate range over the next three days, 5 - 15 knots, the cooler SSTs should be able to significantly weaken the hurricane. On Sunday, Felicia will be encountering strong westerly winds aloft, which should create 15 - 20 knots of wind shear. This should be enough shear to tear the storm apart, thanks to its weakened condition due to the cool SSTs underneath it. By Monday night, when Felicia will be nearing the Hawaiian Islands, most of the computer models predict Felicia will have dissipated. One exception is the GFDL model, which predicts Felicia could be a tropical depression with 35 mph winds when it passes just south of the Big Island on Monday night. In general, the models have been trending more south with their recent runs, so it currently appears that the Big Island is most likely to feel the most impact from Felicia's rain and winds. While the current forecast calls for Felicia to have a minor impact on Hawaii, the Hurricane Hunters are scheduled to be out in full force over the next two days to monitor the storm. The NOAA jet flies into Felicia today, and will drop a series of dropsondes that will gather data to be fed into tonight's 00Z computer model runs. Regular low-level flights by the Hurricane Hunters are scheduled to begin Saturday afternoon.
Typhoon Morakot hits Taiwan
Typhoon Morakot has moved ashore over northern Taiwan this morning, and is battering the island as a strong Category 1 storm with 95 mph winds. At 9:30 pm local time today, the Taipei airport recorded sustained winds of 56 mph, gusting to 76 mph, and a pressure of 972 mb. Morakot is expected to weaken today as it interacts with the mountainous terrain of the island. Storm chaser James Reynolds is intercepting the storm and will be posting live updates on his typhoonfury.com web site and twitter for those who want to follow the storm. Morakot is also visible on Taiwan radar.
Figure 2. Radar image of Typhoon Morakot as it made landfall over northern Taiwan at 21:30 local time on 8/7/09. At the time, Taipei was experiencing sustained winds of 56 mph, gusting to 76 mph. Image credit: Taiwan Central Weather Bureau.
The Atlantic is quiet
There are no areas of disturbed weather in the Atlantic worth mentioning today, and no computer models forecast tropical storm development over the next seven days.
I'll have an update on Saturday.
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