Well, it finally happened. . .Isaac became a hurricane late this morning when aircraft observations showed believable 75 mph surface winds over the Central Gulf. As disorganized as Isaac has been, it’s impressive in that the pressure continues to drop and winds are rising even without a well-developed inner core. This means that the wind field will be more spread out, hence the high risk for a widespread storm surge.
The track guidance for Isaac in the next 12 hours hasn’t changed much at all. There was an indication by the 12z GFS model that the storm might ride the coast of LA all the way to Cameron, but based on the current position and movement, this doesn’t look likely. The current intensity is 70 kts or 80 mph with gusts over 95 mph. Isaac will make landfall as a hurricane tonight and areas from Lafayette to Pensacola will be affected with the worst conditions from Houma, LA east to New Orleans and Biloxi, MS.
I have included the new Hydrometeorological Prediction Center (HPC) rainfall graphic and the Storm Prediction Center (SPC) tornado probability graphic above to emphasize the rainfall and tornado threat with Isaac as we head into tonight. Areas from Houma to Pensacola have an increased tornado threat tonight into tomorrow, while many areas will see an abundance of rain. The HPC forecast shows a bulls-eye on the western shore of Lake Pontchartrain of about 15″ of rain, but this could be higher depending on the training of cells and forward movement of Isaac.
Bottom line: The worst conditions tonight will be from about a Houma-Baton Rouge line east to New Orleans and Biloxi where winds may exceed 65-80 mph with gusts over 95 mph. Tornadoes will only be a threat to the east-northeast of the landfall point. Areas from Lake Charles through Lafayette will see increasing winds and heavy rain spreading west where up to 6″-10″ of rain could be expected. I expect winds of 50-60 mph with gusts approaching 80 mph possible as Isaac moves west-northwest into tomorrow. Beyond this point, a heavy rain threat will develop up the Mississippi Valley. . .something they need!
Feel free to leave questions or comments and I will have an update late tonight. Thanks for reading!