2019年台風第19号の進路予報精度低下の要因

Abstract

We have investigated the quality of track forecast for Typhoon Hagibis 2019 using ensemble forecast data from four major operational numerical weather forecast centers, ECMWF, NCEP, UKMO, and JMA. From six to four days before the landfall, the JMA forecast was the best among other centers, but the error increased sharply three days before the landfall. Compared to the forecast from 0000 UTC 9 October, the typhoon drifted westward about two days before the landfall in the forecast from 1200 UTC 9 October. Consistent with the westward track error, there was a northwestward bias of the environmental winds. The sensitivity analysis at the verification time close to the landfall indicates a large sensitivity to a low pressure disturbance located to the south of the typhoon.