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Katrina falters, does not intensify overnight

By: Dr. Jeff Masters, 12:04 PM GMT on August 25, 2005

The chances for Katrina undergoing a major rapid intensification and reaching Category 2 or Category 3 status now appear very dim. Katrina faltered overnight, and increased only slightly in intensity. Dry air on the west side continued to prevent convection from wrapping all the way around the storm, and some shearing also appeared to be occurring on the storm's west side.

However, Katrina is still expected to intensify today and reach Category 1 hurricane status by tonight or early Friday morning, when it makes landfall over South Florida. The storm slowed in forward speed some, giving it more time today over the very warm (31C) waters of the Gulf Stream. Other than the small amount of shear noted on her west side overnight, Katrina is in a low-shear environment, and the shear may decrease today. The combination of low shear and warm water may allow Katrina to strenthen rapidly into a Category 1 hurricane just before landfall. The Miami radar loop shows an increase in low-level banding during the past two hours, and an eye-like feature trying to form. Katrina is getting more organized. Upper level outflow looks pretty ragged on satellite imagery, but appears to be improving and slowing expanding.

The major threat to South Florida from Katrina is freshwater flooding from her rains. Rainfall amounts of 6 - 10 inches are expected from this slow-moving storm. For comparison, Hurricane Irene of 1999, which hit South Florida as a Category 1 hurricane, dumped 10 - 20 inches of rain. Damage from Irene was over $800 million in Florida. Damage from Katrina will probably be much lower, in the $30 - $100 million range, since Katrina's rainfall will be half of what Irene's was.

Once Katrina makes landfall early Friday morning, the storm will cross over the Florida Peninsula and re-emerge into the Gulf of Mexico. If her path in the Gulf allows her to remain over water for at least a day, Katrina could easily strengthen to a Category 1 or 2 hurricane before making her second landfall.

I'll make several updates today as new Hurricane Hunter data becomes available; I was unable to make many updates yesterday, as I was travelling.

For observations of what's happening now in South Florida, we have several bloggers writing today. If you're in South Florida and are blogging today, let me know where you are at so I can add you to this list:

turtlehurricane (Weston, Broward County)

sngalla (Fort Lauderdale)

MrJ76 (Okeechobee)

Zeenster (Cape Coral, SW Florida)

evolution (Charlotte Harbor, SW Florida)

Dr. Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.