Seasonal predictions of summer humid heat extremes in the southeastern United States driven by sea surface temperatures

Humid heat extreme (HHE) is a type of compound extreme weather event that poses severe risks to human health. Skillful forecasts of humid heat extremes months in advance are essential for developing strategies to help communities build more resilience to the risks associated with extreme events. This study demonstrates that the frequency of summertime HHE in the southeastern United States (SEUS) can be skillfully predicted 0-1 months in advance in the SPEAR (Seamless system for Prediction and EArth system Research) seasonal forecast system. The sea surface temperature (SST) at the tropical North Atlantic (TNA) basin is found as the primary driver of the prediction skill. The responses of large-scale atmospheric circulation and winds to anomalous warm SSTs in TNA favor the heat and moisture flux transported from the gulf of Mexico to the SEUS. This research demonstrates the role of slowly-varying sea surface conditions in modifying large-scale environments that contribute to the predictions of HHE in SEUS. The results are potentially applicable for developing early warning systems of HHE.