STATISTICAL-ANALYSIS OF THE CHARACTERISTICS OF SEVERE TYPHOONS HITTING THE JAPANESE MAIN ISLANDS

Characteristics of 51 severe typhoons hitting the Japanese main island s with central pressure equal to or less than 980 hPa during the perio d 1955-94 were analyzed by an objective method using hourly station ob servation during typhoon passages. Position of a typhoon center, centr al pressure depth Delta p, and radius of the maximum wind r(m), were o btained at hourly intervals after landfall on the main islands of Japa n. The pressure profile of severe typhoons used in this analysis was c hosen from formulas presented in previous papers, namely the same as o ne used by the U.S. Army Corps of Engineers for hurricanes hitting Flo rida. Coastlines of the main islands were divided into three sections: areas A, B, and C extending from west to east. Statistical analyses o f parameters were made for each area. At time of landfall, the maximum value of Delta p was 83.2 hPa for area A, 85.2 hPa for area B, and 47 .8 hPa for area C. The differences in return period of Delta p among a reas are considered to be caused by the SST distribution off the Pacif ic coast. On average, typhoons making landfall in area C have larger r (m) and speed, and display a more eastward component of translation th an those in the other two areas. The differences of speed and directio n among areas and months can be explained to be caused by variation of the synoptic-scale air current at the 500-hPa level.