When it comes to making these types of seasonal predictions, I more or less go look to the expert researchers on the topic. Dr. Gray has been making these predictions for a while now, however i dont think he's exactly nailed it every year.
When it comes to hurricanes, there are 2 main factors to look at.
1) Sea Surface Temperatures - warmer is more conducive for development
2) Wind flow (in the tropics) - less upper level shear is good for development
What the tropical researchers do, is correlate winter/spring time patterns with what they expect to occur on average during the summer/tropical season. These include, El Nino/ La Nina influences and other large scale weather patterns (or what is referred to as teleconnections).
What good does is this sort of prediction? Well, I"m not sure there's a whole lot. The govt may be able to allocate more money for after-math clean up and such, but really the number of storms doesn't at all tell us, how many are going to hit land and where, and what the damage will be.
It does however, give us surfers something to get stoked about, while were fantasizing of good surf with no wet suits!
just to let you guys know I gained some insight from the chesapeake bay epic conditions show on the weather channel the other day. It is about sailing but it was really interesting and informative about the weather on the east coast. Definately worth checking out, I think they're showing it frequently. and about hurricane season, well summers not even here yet but I already can't wait.
I hate to even hear the word Ernesto because I was bent over sick for the best days of it. There were some great waves in the winter that made up for it though.