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 , 5. elokuuta 2009 klo 14:45 (GMT)
As is often the case in an El Niño year, there's nothing to talk about today in the Atlantic, but the Eastern Pacific is very active. It has been 17 years since we went this long without a tropical cyclone in the Atlantic--the hurricane season of 1992 didn't start until August 16--but in the Eastern Pacific, we've already had six named storms this year. Hurricane Felicia is the latest addition, and Felicia has put on an impressive burst of intensification this morning by powering up to Category 3 status with 115 mph winds. Recent satellite loops show that Felicia has continued to intensify, with the cloud tops surrounding the eye cooling as they push higher into the troposphere.
Figure 1. Current satellite image of Hurricane Felicia.
While Felicia is an impressive hurricane now, its days of glory will be short-lived. Felicia is currently passing over a region of warm sea surface temperatures (SSTs) of 28.5°C, a full 2.5°C above the 26°C threshold needed to sustain a hurricane. These warm waters also extend to great depth, as seen on the Ocean Heat Content image (Figure 2). Felicia's west-northwest track will take the storm into a region of cooler waters with lower Oceanic Heat Content beginning tonight, which should induce a steady weakening trend beginning Thursday night. By Friday morning, SSTs should fall to 26°C, and decline to 25°C by Saturday. While wind shear is expected to remain in the low to moderate range over the next five days, 5 - 15 knots, the cooler SSTs should be able to significantly weaken the hurricane. By Monday, when most of the computer models indicate that Felicia will be nearing the Hawaiian Islands, the storm will be at tropical depression strength with top winds of about 35 mph, according to the latest runs of the HWRF and GFDL models. Exactly how close Felicia will get to the Hawaiian Islands is a bit tricky to call right now, since the hurricane is interacting with nearby Tropical Storm Enrique. Whenever two storms get within 900 miles of each other, they tend to rotate around a common center in a dance called the Fujiwhara Effect. This sort of storm-storm interaction is a complicated affair not well-handled by the computer forecast models.
Figure 2. Total oceanic heat content (also called the Tropical Cyclone Heat Potential, TCHP) along the forecast path of Hurricane Felicia. The initial time of the forecast is 06 UTC (1 am EDT) on August 5, 2009. Oceanic heat content of 90 kJ per square cm is often associated with rapid intensification of hurricanes. Felicia is currently over waters with high heat content, but the heat content will steadily decrease over the next two days. Image credit: NOAA/RAMMB.
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 Thursday.
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