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 , 2:23 PM GMT on September 26, 2012
Super Typhoon Jelawat completed an eyewall replacement cycle over the past 24 hours, resulting in a slight weakening of the storm below Category 5 strength. Jelawat is now a Category 4 super typhoon with 155 mph winds. Fortunately, Jelawat is located well east of the Philippine Islands, and the storm is not expected to hit land while it is at major typhoon strength. Wind shear remains a light 5 - 10 knots over Jelawat, and the typhoon is over very warm ocean waters of 29°C that extend to great depth, so it is possible that Jelawat could regain Category 5 status later today. Satellite loops show an impressive, well-organized typhoon with a 25 mile-wide eye, and a large, symmetric area of heavy thunderstorms with cold cloud tops.
The models are fairly unified on the track of Jelawat. The typhoon is expected to move northwest, roughly parallel to the Philippines, then turn to the north and north-northeast a few hundred miles east of Taiwan. Jelawat will likely pass close to Okinawa, Japan as a Category 2 typhoon on Friday near 20 UTC, and could hit the main island of Honshu in Japan as a tropical storm over the weekend. Wind shear will begin increasing over Jelawat beginning on Thursday, which should cause a steady weakening of the storm.
Figure 1. Microwave satellite image of Jelawat taken at 7:12 am EDT Tuesday September 26, 2012. A solid ring of echoes surrounds the calm eye. Image credit: Navy Research Lab, Monterey.
Tropical Storm Miriam steadily weakening
In the Eastern Pacific, Tropical Storm Miriam is being attacked by high wind shear of 20 - 25 knots, and satellite imagery shows the storm is falling apart. High wind shear in excess of 30 knots will attack Miriam by Thursday, and Miriam should dissipate off the coast of Baja by Friday. Miriam's moisture is expected to stay out to sea.
Figure 2. MODIS satellite image of Tropical Storm Nadine taken at 11:15 am EDT Monday September 25, 2012. At the time, Nadine had top winds of 45 mph. Image credit: NASA.
Except for Nadine, the Atlantic is quiet
Never-say-die Tropical Storm Nadine continues to wander in the middle of the Atlantic Ocean, far from any land areas. Nadine may circle back to bother the Azores Islands on Monday, according to the latest run of the GFS model--though the model shows Nadine stopping short of a direct hit on the islands. Nadine has already been around as a named storm for thirteen days, and will still probably be around a week from now. According to the Tropical Cyclone FAQ, the average Atlantic named storm lasts about six days, and the all-time longest-lived Atlantic tropical cyclone lasted 27.75 days.
A small area of heavy thunderstorms has developed about 700 miles east-northeast of the northern Lesser Antilles Islands. This disturbance is under a high 20 - 30 knots of wind shear, is struggling with dry air, and none of the reliable computer models are predicting development. In their 8 am Tropical Weather Outlook, NHC gave the disturbance a 10% chance of developing into a tropical cyclone by Wednesday.
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