CLIMATOLOGICAL FEATURES OF RAPIDLY INTENSIFYING (RI) TROPICAL CYCLONES IN NW PACIFIC WEST OF 135°E1

Tropical cyclones which rapidly intensify (ΔV≥ 20 m/s in 24 h)in the Northwest Pacific Ocean west of 135°E could have adverse influence on oceanic and coastal economic activities in China, 71% of which land in China. Rapid intensification is mostly seen east and northeast of the Luzon Island. It is much correlated with sea surface temperature(≥28℃)and upper air conditions, such as enhanced subtropical high, onset of Southwest monsoon surge, invasion of modest cold air, and Tropical Upper Tropospheric Trough(TUTT) etc. Abovementioned processes enhance inflows in the low level and deep convection in the area of inner core. Statistics of satellite pixels have confirmed that rapidly intensifying tropical cyclones are marked by a sharp increase in the inner core convection and stable or slowly-increasing deep convection in outer region. Non-rapidly intensifying tropical cyclones have only constant or decreased deep convection in inner core and outer region. The sharp increasing of deep convection in the inner core and the rapid warming in its upper level is a forewarning of rapid intensification of tropical cyclones.