Statistical Characteristics of Tornado in Hainan Province

Land tornadoes and water tornadoes of Hainan Island and along the coast (excluding the South China Sea) from 2004 to 2019 were analyzed. According to the impact system, land tornadoes are divided into tornadoes associated with tropical cyclones (TCs) and non-TCs. The results show that: (1) tornadoes associated with TCs occur most frequently from night to next early morning in September. About 90% of the tornadoes are caused by typhoons or severe typhoons. When the tornado occurs, it is 200-400 km away from the center of the typhoon. Tornados caused by the westward typhoons through the southern part of Hainan Island appeared in the eastern coastal region, while those caused by the westward typhoons through the middle and northwestward through the east appeared in the northern coastal region. (2) Tornadoes associated with non-TCs mainly occur in spring, with the most frequent occurrence in May, and more than 90% occur in the afternoon. Tornadoes triggered by the sea breeze front are located in the northern area of Hainan Island, with the strongest reaching EF2 level. The meso-β scale sea breeze front convergence line in the boundary layer is a key factor for the development of this type of tornado. The dry cold air induced tornadoes are located in the northern and eastern areas of Hainan Island, and about 23% are of EF1 level, with others EF0 level.The boundary layer shear line is the trigger mechanism of this type of tornado.