Roles of Tropical Waves in the Genesis of Super Typhoon Haiyan (2013)

Previous studiies suggest that tropical waves make important contributions to the genesis of super Typhoon Haiyan (2013). The precursor of Haiyan comes from a cyclonic vortex embedded in a packet of Mixed Rossby-Gravity (MRG) waves and develops rapidly in a favorable large scale environment associated with Asian monsoon and tropical MJO signal. Experiments are designed to examine the effects of waves with different scales on the formation of Haiyan. It is found that the MJO provides large-scale vorticity and triggers the burst of deep convection with strengthened westerlies and moist convection. The quasi-biweekly oscillation (QBWO) and high-frequency eddies make combined weak influences. The MRG provides a initial cyclonic vortex with certain intensity and develops later under the favorable environment of moist MJO, weak VWS and high SST. Results suggest that both MJO and MRG play necessary roles on the genesis of super Typhoon Haiyan.