San José State University

Transient behavior of the North American monsoon allows for episodic northward pulses of atmospheric moisture into the southwestern US. These surge events pose a difficult forecasting issue due to an accepted means to qualify their occurrence and the ill-defined influence of tropical and extratropical features that enable and drive them. Surge events have often been misidentified by ground observation sites due to bias related to localized influences not associated with surges. This study proposes a novel method for the classification of surges based on their regional, rather than local, signature. This method is shown to be more accurate in capturing widespread summertime precipitation events across the Desert Southwest of the US than previously established methods. To further the understanding of mechanisms responsible for surge initiation, this study explores the influence that midlatitude troughs have on surges. Midlatitude troughs are shown to initiate surges that result in widespread precipitation across th