Influence of Different ENSO Types on Tropical Cyclone Rapid Intensification Over the Western North Pacific

Abstract

AbstractThis study investigates the influence of different types of El Niño‐Southern Oscillation (ENSO) on the properties of tropical cyclone (TC) rapid intensification (RI) over the western North Pacific (WNP). The RI numbers during all types of ENSO events have no significant difference from that of neutral years, except that eastern Pacific (EP) El Niño corresponds to fewer RI cases. The most robust response of RI properties is occurrence position. The mean RI occurrence position in La Niña events shifts northwards by about 2° in latitude during the peak TC season (July–September), which may be related to the northwestward shift of TC genesis positions. On the other hand, the mean RI occurrence positions during EP El Niño and La Niña events in the late TC season (October–December) shift westwards by about 10° and 14° in longitude, respectively. This westward shift in RI occurrence positions is mainly caused by the favorable conditions over the western part of the WNP in the late TC season. During October–December, EP El Niño shifts to a La Niña phase and warms the upper ocean of the western part of the WNP. La Niña events result in similar upper ocean conditions because they maintain negative phases during October–December. The warmed upper ocean is also accompanied by a moistened mid‐troposphere and weakened vertical wind shear, which are favorable for RI occurrence.