日本に近づいてから発達する台風の特徴

Abstract

The dissipation/development trend of tropical cyclones (TCs) approaching to the south coast of Japan Islands was investigated. Among 203 cases from 1979 to 2013, 23 cases (11%) developed more than 7.5 hPa and 66 cases (33%) dissipated more than 7.5hPa during their migration after crossing a southern reference latitude (27°N). For the developed case Typhoon Roke (T1115) and the dissipated case Typhoon Jelawat (T1217) atmospheric and oceanic environment along their tracks were closely analyzed. Roke passed over the Kuroshio region, when it began to develop, where the warm current (≥ 26℃) was thick and the tropical cyclone heat potential (TCHP) was high. Decrease of sea surface temperature (SST) caused by passage of Roke was low over the Kuroshio Current. It was considered that the thick warm layer suppressed the typhoon’s self-induced ocean cooling over the Kuroshio Current, which in turn brought about a favorable condition for intensification of typhoon. Jelawat rapidly dissipated though the oceanic condition was not unfavorable for development. According to the cyclone phase space (CPS) analysis, it was shown that Jelawat had already started its extratropical transition when it passed over the reference latitude, 27°N, as the upper westerly shifted southward.