"Primarily the reason that we forecast a very active September was due to the fact that the low level winds are spinning up waves off the coast of Africa and pressure readings at near record low levels in August. That implies more instability, basically an atmosphere that's more conducive for tropical cyclone formation and intensification."
Four Atlantic hurricanes have been recorded so far this season: Bertha and Dolly in July; Gustav in August and Hanna in September. The most recent seasonal prediction, issued August 5, called for a total of nine Atlantic hurricanes during the season, which runs from June 1 to November 30.
Phil Klotzbach says that's nearly twice as busy as an average September.