A Train-Like Extreme Multiple Tropical Cyclogenesis Event in the Northwest Pacific in 2004

Abstract

Using observed data sets, an unprecedented multiple tropical cyclogenesis event over the northwest Pacific is identified, with seven tropical cyclones forming in sequence from 6 August to 10 September 2004. In this event, the preexisting tropical cyclones (TCs) generated the alternating cyclonic and anticyclonic disturbances in their wake region by exciting Rossby waves. The cyclonic disturbances subsequently intensified into new TCs within the monsoon trough, which was likely enhanced by anomalous warming in the tropical central Pacific and cooling in the tropical Indian Ocean, so that it lasted long enough to allow seven TCs to develop consecutively. An analysis of the historical records during 1979–2014 substantiates such linkage of the occurrence of this extreme multiple tropical cyclogenesis event to the anomalous sea surface temperature pattern and the monsoon trough. This result has important implications regarding the prediction of the multiple cyclogenesis events.