What Caused the Unprecedented Absence of Western North Pacific Tropical Cyclones in July 2020?

Abstract

Abstract While the Atlantic basin experienced the busiest hurricane season in 2020, the typhoon activity over the western North Pacific (WNP) was also record‐setting with no tropical cyclone (TC) formation in July 2020, which is the first time in available historical records. The unprecedented absence of TC formation is consistent with the extremely unfavorable large‐scale conditions that are linked to an anomalous anticyclonic circulation over the WNP, which results mainly from sea surface temperature (SST) anomalies across the tropical oceans. Numerical experiments suggest that the tropical Indian Ocean SST anomalies, which were warmest in July 2020 since 1965, play a dominant role in the anomalous WNP anticyclonic circulation, while the increased zonal SST gradient across the tropical Pacific and the Atlantic SST warming also have important contributions. This study suggests that the configuration of SST anomalies across the tropical basins is quite important to the WNP TC activity.