Hanna's Threat

Forecasting Hanna’s path is difficult – a high pressure system over the eastern U.S. that develops this weekend complicates the situation. First, Hanna heads for Florida, approaching the Bahamas, then it bobbles south and does the loop-da-loop, then it goes - where exactly?

NOGAPS suggests that Hanna veers south, following the tracks indicated on the Weather Underground site you mention. Then, instead of trying to slip around Florida, like a spirograph loop, it retraces its movement back more-or-less to where it was a few days earlier, and continues moving towards Florida’s eastern coast, arriving somewhere around Daytona Beach about Sat. Sept. 6th.

That’s a reasonable solution. Right now, the entire eastern coast of Florida is vulnerable to Hanna. That loop-da-loop movement depends on how rapidly the eastern U.S. high pressure system develops, and how rapidly it fades. Interestingly, Hurricane Gustav helps weaken the high pressure system and opens the door for Hanna to approach Florida.

Meanwhile, the models are pushing Gustav farther west. GFS now suggests a Louisiana landfall, but NOGAPS suggests Port Arthur, Texas is the landfall site. It’s going to be a mess wherever Gustav goes.