Tropical Storm Isaac spent very little time over Haiti and Cuba in recent times, but has not intensified dramatically yet. The storm is over very warm water and in a low-shear environment that is favorable for strengthening, but the circulation is large which inhibits the inner core from organizing too easily.
As of 11 a.m. EDT, the maximum sustained winds were increased to 65 mph and tropical storm force winds extended 205 miles from the center.
Isaac is forecast to pass directly over the southern Florida Keys later this afternoon as a high-end tropical storm. Rainbands have been affecting all of southern Florida during the night and into the day, bringing with them gusty winds, torrential rain, and the risk of tornadoes. The center was located 80 miles southeast of Key West and moving west-northwest at 18 mph. A very long radar loop from Key West shows the progression of the rainbands and the inner core.
Link: Hurricane Tracker
The official forecast track has shifted west along with the model guidance. While the eastern Florida panhandle looked most likely for a landfall site a couple days ago, the latest consensus is further west, clustered over Mississippi and eastern Louisiana.
A hurricane warning remains in effect for the Keys and the southwestern Florida peninsula, and a hurricane watch is in effect for the northern Gulf coast from Morgan City La. to Indian Pass Fl., and now includes New Orleans.
The corresponding model intensity forecasts range anywhere from a strong tropical storm to a borderline major Category 3 hurricane, but the official forecast calls for a landfall intensity of a strong Category 2 storm. It should certainly be taken very seriously, and preliminary preparations begun.
The National Hurricane Center should always be consulted for the latest official forecasts, watches, and warnings.
As with any tropical cyclone, the rainfall is a big concern. Southern Florida could receive up to 10” in localized areas, then up near the expected landfall point on the northern Gulf coast, up to 18” is currently predicted. The storm will rapidly decay over land, but that doesn’t stop the rain.
A significant rain swath will follow Isaac’s remnants once it heads northeast toward the East Coast. In a rainy scenario, the D.C. area could receive a few inches of rain toward week’s end, but little in the way of wind. Given the storm’s expected movement, it’s hard to say whether or not the area will see much rain yet.
We will monitor Isaac as it heads north toward the central Gulf coast. It could become a strong hurricane by then, and make landfall exactly on the 7th anniversary of Katrina’s infamous landfall.
Brian McNoldy is a senior researcher at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.