Why Is Isaac Being Such A PITA

This one will be studied because it has so many quirks that it may help forecasters in the future make better judgements.

There is a phenomenon called the Fujiwhara Effect that occurs when two tropical cyclones move close to each other. They essentially begin to move in a counterclockwise motion around a central point between them. Something like that is happening with Isaac and a low pressure center around the Cayman Islands. It isn’t the full effect because the Cayman Island low doesn’t have the strength, but it is impacting on Isaac’s motion.

The other major problem are the steering factors for the storm. Currently it is being directed by a ridge, but that ridge ends in the Gulf. Some of the models think that the storm will be attracted by trough that is coming down and curve to the East, while others a second ridge building in and taking the storm to the West. Both are reasonable solutions to steering. The NHC is splitting the difference between the solutions. They can’t be sure which scenario is actually going to be in control, so we have to wait.

The current spread is from Apalachicola [the tip of the ‘elbow’ on the Panhandle] to New Orleans for landfall. If I had a vote it would be Apalachicola, because this is a big storm and New Orleans isn’t far enough away. The worse of the storm is the Northeast Quadrant, so I would just as soon not see it head West. The other problem with heading West is that the storm would have more time to intensify.

OTOH, the West track would dump water in the Mississippi Valley which needs all the help it can get with rain. It might reduce the effects of the current drought.