Felix's aftermath; 99L less organized

By: Dr. Jeff Masters , 1:22 PM GMT on September 06, 2007

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Hurricane Felix was not the catastrophe feared when it slammed ashore in Nicaragua as a Category 5 hurricane two days ago. While rains have been heavy over Nicaragua, Honduras, and surrounding countries, they have not been heavy enough to trigger widespread flooding and mudslides like Hurricane Mitch of 1998 and Hurricane Fifi of 1974 did. Rainfall estimates for the 24 hours ending at 8am EDT yesterday (Figure 1) show that rains of up to 125 mm (5 inches) fell in only a few isolated areas, and additional rains of 125 mm (5 inches) were the most expected from Felix.

While this is great news, particularly for Honduras, Nicaragua has suffered a severe blow in the Puerto Cabezas region where the eye of Felix came ashore. Nearly every structure in Puerto Cabezas sustained at least roof damage, and many buildings were destroyed. Along the Miskito Coast of northeast Nicaragua, flooding and mudslides were reported, destroying many homes and blocking highways. The Government of Nicaragua declared the northern Caribbean coast a disaster area. At least 48 people have been reported dead--47 of them in Nicaragua, and one in Honduras (in a motor vehicle accident caused by heavy rain and landslides). However, dozens are missing (mostly at sea), and communications are difficult to impossible in many areas. At least 40,000 people have been affected and 9,000 houses destroyed, most of them in the Nicaraguan city of Puerto Cabezas, where a "State of Disaster" has been declared by the government.


Figure 1. Satellite estimated rain amounts for the 24 hours ending at 8am EDT Wednesday September 5 (12 GMT). Maximum rain amounts of about 125 mm ( 5 inches) were estimated over a few spots due to Felix. Image credit: Navy Research Lab.

U.S. East coast watches tropical disturbance 99L
An area of disturbed weather (99L) that formed along an old frontal boundary has grown less organized over the past 24 hours, thanks to an increase in wind shear. Strong upper level winds from the west are creating about 20-25 knots of wind shear over 99L, and satellite loops of 99L show a much less organized circulation, with only a few thunderstorms far removed from the center. The disturbance is interacting with an upper-level trough of low pressure, and this trough is creating a long line of thunderstorms from southwest to northeast that passes just east of the center of 99L's circulation.

Wind shear is forecast to drop below 15 knots on Friday, which may allow some slow development. I wouldn't be surprised to see 99L become a tropical storm on Saturday. Most of the computer models bring 99L to the coast of North Carolina on Sunday. This does not give it much time to develop, and it is unlikely 99L would be able to intensify into a hurricane. The storm may not develop into a tropical cyclone at all, but even as a non-tropical storm, residents of the Carolinas can expect heavy rain and high winds on Sunday from this system. The storm is then expected to track northward and then northeastward along the coast, bringing heavy rains to the mid-Atlantic and New England areas on Monday and Tuesday. The Hurricane Hunters are scheduled to investigate 99L at 2pm EDT today, but NHC may cancel this flight unless 99L shows some significant improvement in organization.

African development?
The models are less gung-ho today about developing a tropical depression near the Cape Verdes Islands off the coast of Africa 2-4 days from now. As always, this region will need to be watched.

Riders of the storm
NOAA P-3 Orion Hurricane Hunter airplane N42RF (AKA "The Princess") had a wild ride in Hurricane Felix on September 2 as it intensified into a Category 5 storm. The airplane hit what the Hurricane Hunters fear most--a powerful updraft followed a few seconds later by an equally powerful downdraft. The resulting extreme turbulence and wind shear likely made the aircraft impossible to control. Four G's of acceleration in both the up and down directions battered the airplane, pushing it close to its design limit of 6 G's. Although no one was injured and no obvious damage to the airplane occurred, the aircraft commander wisely aborted the mission and N42RF returned safely to St. Croix. The airplane was out of commission for the next day, which unfortunately meant that wunderblogger Mike Theiss was unable to get on his scheduled flight into Felix (he's written a blog today about this disappointment). However, the aircraft has now passed a detailed six-hour inspection to look for turbulence damage, and has been cleared to fly again. Welcome back, Princess!


Figure 2. Still shot from the 7-minute video of the Air Force Hurricane Hunters' penetration of Hurricane Felix at 06 GMT (2am EDT) September 3, 2007. Felix had just intensified into a Category 5 hurricane with 165 mph winds. Lightning in the eye is lighting up the eyewall clouds here.

Wunderblogger Randy Bynon, a meteorologist with the Air Force Hurricane Hunters, flew through Hurricane Felix on the mission that followed N42RF's. He and Lt Colonel Scott Dufreche have posted a 7-minute video of their flight through Felix. The camera looks forward through the cockpit windows, and one can see the cockpit instruments and the view out the front window. The video starts about 20 miles outside the eye, and during the 4-minute penetration of the eyewall, steadily increasing turbulence shakes the C-130 aircraft and frequent flashes of lightning light up the eyewall clouds. After four minutes, the turbulence suddenly slackens as the airplane breaks into the eye, and you can see spectacular glimpses of the eyewall clouds lit up by lightning flashes. The video finishes with some radar screen shots and fish-eye views of the top of the eye showing the full moon. Amazing stuff!


I'll have an update Friday morning.

Jeff Masters

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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