Tropical cyclones are amongst the most powerful and destructive meteorological systems on earth. Globally, 80 to 100 develop over tropical oceans each year. Many of these make landfall and can cause considerable damage to property and loss of life.
Dynamical seasonal prediction models from the Met Office (GloSea) and ECMWF are used to forecast the number of tropical storms forming over the North Atlantic.
http://www.metoffice.gov.uk/weather/tropicalcyclone/northatlantic.html