The Impact of an Oceanic Mesoscale Anticyclonic Eddy in the East China Sea on the Tropical Cyclone Yagi (2018)

Abstract

In August 2018, tropical cyclone (TC) Yagi rapidly intensified as it passed over an oceanic mesoscale anticyclonic eddy (eddy) in the East China Sea, increasing in TC intensity from a tropical storm to a severe tropical storm. The maximum surface wind speed increase (minimum sea level pressure decrease) of Yagi over sea surface temperature (SST) warm anomalies caused by the eddy accounted for 66.7% (36.4%) of the whole case. Regional atmospheric model experiments are conducted to aid the interpretations of the case of Yagi intensifying over the eddy. Model results indicate that the SST warm anomalies caused by the eddy increase and concentrate the heat flux transported from the ocean to the atmosphere, and the upper air warms up, which is conducive to the development of convection. As a result, the contribution of the eddy to TC enhancement is over 20% in the period over the eddy and the precipitation is more concentrated at the TC center. The model further showed that the eddy affects the TC, resulting in more favorable dynamic and thermal conditions around the TC after landfall for the formations of TC tornadoes.