Numerical Study of the Response of Typhoon Hato (2017) to Grouped Mesoscale Eddies in the Northern South China Sea.

The influences of grouped anticyclonic eddies (AEs) in the ocean on the intensity of tropical cyclone (TC) in the atmosphere are investigated in the present study. The research was carried out using numerical methods taking the development of TC Hato (2017) in the northern South China Sea (SCS) as an example. Three AEs were observed, one at the TC track (defined as the inner area) and the other two in the south of the TC center (defined as the outer area), at about three times the radius of maximum wind speed. The results show that the outer AEs suppress TC development, but the inner AEs greatly favor TC development. This opposite influence primarily results from the different responses of TC secondary circulation to the AE‐induced local sea surface warm anomaly in the inner and outer areas. The outer AE triggers a low sea level pressure anomaly and convergent wind toward the AE, which weakens TC inflow at the lower layers and further weakens TC secondary circulation. Consequently, the energy conversion from ocean heat energy to TC kinetic energy is decreased by the weakened TC secondary circulation. The AE in the outer area also extends the TC eyewall, weakens the TC warm core, and increases the outer precipitation. As a result, the TC intensity is weakened. The inner AE causes opposite changes in TC secondary circulation, eyewall, warm core, and outer precipitation, so that favors TC development. These results provide evidence for the suppression effect of the outer AEs on TC development, providing a new perspective toward improving TC intensity forecasts. Plain Language Summary: The intensity of tropic atmospheric cyclone, that is, hurricane or typhoon is influenced by oceanic warm eddies on its track. The presence of warm eddies on the tropical cyclone track suppresses tropical cyclone‐induced ocean surface cooling and provides extra heat flux, which intensifies the tropical cyclone. However, it remains uncertain how tropical cyclone intensity change when a warm eddy occurs outside of the tropical cyclone track. This study investigates the changes in tropical cyclone intensity when a warm eddy is located near the cyclone center and finds that the tropical cyclone is intensified if the warm eddy is close to the tropical cyclonic center but weakened if it is distant. These results can help understand how eddies affect tropical cyclonic intensity when the eddy is positioned in different areas of the cyclone and accurately forecast cyclonic track and intensity. Key Points: Oceanic anticyclonic eddy located in inner and outer areas of tropic cyclone has favor and inhibiting opposite effect on cyclone developmentWeather Research and Forecasting model and Price‐Weller‐Pinkel ocean model are combined to simulate typhoon Hato (2017) in South China SeaModel results reveal that cyclone intensity change is due to changes in secondary circulation and accompanying kinetic energy conversion [ABSTRACT FROM AUTHOR]