On the record 2005 hurricane season

The record 2005 hurricane season in the North Atlantic arose largely from anomalous July and October conditions, which produced record numbers of five and six named tropical storms and hurricanes, respectively. We examine the reasons for this remarkable surge in cyclogenesis, which occurred largely from the development of easterly wave systems between 10-25oN. Whilst we find that the climatological requirements for cyclogenesis were all favorable, we conclude that the primary cause was a highly unusual zonal flow regime that supported accumulation of energy and downscale vorticity transfer in easterly waves propagating westward from Africa, which drove the development of the record number of storms.