Sunday, April 24, 2011

Early Tropical Disturbance in Atlantic

From the Palm Beach Post and the Weather Underground:

Early tropical disturbance in Atlantic not a sign of active season, hurricane expert says



91L 42211.jpg The low pressure system north of Puerto Rico was still holding together Friday, but the National Hurricane Center cut its chances of tropical development. (Credit: NOAA)

It’s unusual for the National Hurricane Center to start tracking a tropical system this early in the year - hurricane season doesn’t officially begin until June 1.

But there’s no need to hit the panic button, a hurricane expert says. Early disturbances in that part of the Atlantic basin do not portend a busy season.

The NHC began discussing the system, designated 91L, on Thursday. It was still on their radar Friday morning, although forecasters had reduced the chances that the disturbance would grow into Tropical Storm Arlene, the first of the 2011 season.
Satellite images showed the swirl of clouds and storms was still holding together, though.

“It’s interesting that it’s done as well as it has, because there’s really high wind shear,” meteorologist Jeff Masters, co-founder of online weather portal Weather Underground, said in an interview Thursday. “We’re talking 70 or 80 knots when 20 is often enough to tear something apart.

“It is early to be having a tropical disturbance like this because you don’t often see that in April. But it’s definitely not a harbinger of an active season. Sings of an early season are systems that are coming off the coast of Africa, or in the Caribbean.
“You start to get a lot of early activity down there and that’s when you worry. But early activity between the Bahamas and Bermuda doesn’t really matter that much.”

On Friday, 91L was plotted at 25.3N 63W, or 496 miles south-southeast of Bermuda and 1,064 miles due east of Palm Beach. It had winds of 40 mph but had not developed into a true tropical system. It was moving to the north at about 10 mph.
But some computer models show the system - or at least moisture associated with the low - nearing the Florida coast early next week.