Sudden Vertical Velocity Regime Shifts Initiate Flash Drought in Puerto Rico

Abstract This study focuses on flash drought events in Puerto Rico and the Caribbean. Because the rapid onset and intensity of flash drought can potentially cause more devastation without established prediction methods, this research seeks to understand the synoptic scale atmospheric drivers of flash drought events. The primary goal of this study is to understand how the vertical velocity environments over and upwind of the eastern Caribbean can potentially initiate flash drought. We use a flash drought definition that implements Evaporative Demand Drought Index (EDDI) on a pentad temporal scale to adequately resolve the rapidity of drought onset possible in tropical regimes. Results indicate that flash droughts typically initiate during rapid changes in the vertical velocity environment, initiating at the transition from upward vertical velocity regimes to highly subsident regimes. This suggests some longer‐term predictability may be possible and could have linkages to subseasonal atmospheric oscillations.