Assessing Warm Season Drought Episodes in the Central United States

Recurrent drought episodes are a signature feature of the climate of the central United States. Using a particular set of definitions, this study examines some of the basic statistical features of previous drought episodes. It shows that there are distinct intraseasonal preferences for the onset of long periods of dry weather and that these preferences vary regionally in ways that are consistent with seasonal climate controls. Evaluation of past drought occurrences indicates that there is no simple or strong teleconnection between drought and the El Nino-Southern Oscillation (ENSO) phenomenon. Individual drought episodes certainly evolve with unique character. However, based on analysis of large-scale variations in sea level pressure patterns, evidence is presented for systematic links between drought and the interdecadal climate mode often referred to as the Pacific decadal oscillation (PDO).