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 , 12:49 PM GMT on August 27, 2006
Ernesto is now a hurricane, the first hurricane of the 2006 season. This first hurricane of season appears likely to do something the Hurricane Season of 2005 can't boast of--get its name retired. Ernesto is delivering a deadly blow to Haiti, and Cuba and Florida are next in line. The 6am Hurricane Hunter eye report found surface winds of 75 mph, good enough for upgrading the storm to a hurricane. The pressure fall has only been an unspectacular 2 mb in the past 12 hours, but the improvement in satellite appearance has been spectacular. An eye is now clearly visible on infrared satellite imagery, and upper-level outflow channels have opened to the north and south. Wind shear has fallen to 5-10 knots, and an upper-level anticyclone (clockwise-rotating region of winds) has developed over Ernesto, a highly favorable situation for strengthening.
The eye of Ernesto will pass just south of or over the southwestern tip of Haiti today, pounding that impoverished nation with hurricane force winds and rains of up to 20 inches. I expect the death toll will be in the hundreds.
Figure 1. Tropical Cyclone Heat Potential for the Caribbean. Value of over 90 kJ/m^2 are commonly associated with rapid deepening phases of hurricanes.
The intensity forecast
The upper level winds have calmed down significantly in the past 12 hours, and the low-shear environment with an upper-level anticyclone is expected to remain for the duration of Ernesto's life. Furthermore, Ernesto is over waters of 30-31 C (86-88 F), and these waters warm up to nearly 90F in the narrow channel between Jamaica and Cuba. These warm waters extend to great depth, and the total heat content available to fuel rapid intensification is high. In fact, the highest heat content waters anywhere in the Atlantic, 120 kJ/cm^2, are found here. Anything over 90 kJ/cm^2 are considered high enough to fuel rapid intensification, and I expect Ernesto will be a Category 2 hurricane when it hits Cuba.
Once Ernesto encounters Cuba, it should go down at least one Category in strength. The eastern end of Cuba is very rugged and will interfere with the storm's circulation. Exactly how long Ernesto spends over Cuba will be critical in determining what kind of blow the Florida Keys will receive. Ernesto will most likely emerge from Cuba into the Florida Straights as a tropical storm. The extremely warm waters with high heat content in the Florida Straights should fuel rapid intensification once more, after a 12-hour reorganization period. I expect the order for visitors to evacuate the Lower Keys will be given this afternoon, the 7th evacuation order for the Keys in the past 3 years. I think it is unlikely Ernesto could affect the Keys as anything stronger than a Category 2 hurricane with 105 mph winds. A hit as a tropical storm or Category 1 hurricane is more likely. If Ernesto spends another day or two traversing the warm waters along the west cost of Florida, then it could grow to a major Category 3 or 4 hurricane. Probably the best scenario would be to have Ernesto pop off Cuba and proceed straight north to the Everglades, spending very little time over water. This might allow Ernesto to affect Florida only as a tropical storm.
The track forecast
The models have come into better alignment now. They unanimously predict a stronger trough of low pressure than originally forecast will act to pull Ernesto northwards across Florida, and then northeastwards out to sea. The exact highest risk Florida landfall is difficult to pin down so far in advance, and everywhere from Miami to Pensacola is at risk. It appears now that New Orleans can breathe easy, as Ernesto should miss that city by a wide margin. Residents of North Carolina should be alert, as Ernesto may brush the Outer Banks after traversing Florida.
The storm surge forecast
The waters along the west coast of Florida are very shallow, and extend out far into the Gulf of Mexico. This creates an ideal environment for a large storm surge to build, and storm surge heights over 10 feet are likely if Ernesto comes ashore as a Category 2 or stronger hurricane along the west coast of Florida. If Ernesto takes a track parallel to the coast and just offshore, a large storm surge could affect a very long portion of the Florida coast, causing immense damage.
The hurricane hunters have left Ernesto, and the next Hurricane Hunter mission into Ernesto is at 2pm EDT this afternoon. The NOAA jet is scheduled to fly tonight, so we'll have our first set of higher-reliability model runs Monday morning. The NOAA P-3 gets its first action Monday morning, and will fly their SFMR instrument that measures surface winds over the entire area. I'll have an update this afternoon when new model runs and Hurricane Hunter information becomes available.
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