September has been the calmest month for tropical storms since 1997, largely because of the weather pattern known as El Nino, Florida meteorologists said.
Just two systems in September were strong enough to be named — Tropical Storm Erika and Hurricane Fred.
September, historically, is the most active storm month, averaging four named storms, including two hurricanes, the South Florida Sun-Sentinel reported Tuesday.
El Nino’s storm-suppressing wind shear held down the number of storms originating in the Pacific, the Sun-Sentinel reported.
El Nino, which occurs every three to eight years, is defined in the atmosphere by the pressure difference between Tahiti and Darwin, Australia, and in the ocean by the warming of surface waters in the central and eastern Pacific Ocean.