Objective Classification of Atlantic Hurricanes

Abstract

Previous groupings of Atlantic tropical cyclone activity into baroclinically influenced and tropical-only hurricanes have required subjective evaluations. In this paper, a set of statistically significant and valid rules are introduced that objectify this previously subjective evaluation. This is done with the aid of classification trees. The tree classifications are better than 90% accurate with respect to an earlier subjective discrimination. Objective classification rules are the basis for a climatology of Atlantic hurricanes. The average latitude of origin for tropical-only hurricanes is 18.8°N, compared to 29.1°N for baroclinically influenced storms. The baroclinically influenced hurricane season extends from-mid May to December, while the tropical-only season is largely confined to the months of August through October. There is a fairly abrupt shift to fewer numbers of tropical-only hurricanes around 1960.