Factors for an Abrupt Increase in Track Forecast Error of Typhoon Hagibis (2019)

令和元年東日本台風の進路予報誤差の要因を検証 --上陸3日前の誤差急増の要因を特定--. 京都大学プレスリリース. 2021-04-20.The predictability of Typhoon Hagibis in October 2019 is examined with ensemble forecasts from four major operational numerical weather prediction centers. From six to four days before the landfall, the forecast from the Japan Meteorological Agency was the best among the four centers. However, the error increased sharply three days before the landfall. Consistent with the westward track error, a northwestward bias is found in the environmental winds. The ensemble sensitivity analysis for the landing region indicates a large sensitivity to a ridge located to the southeast of the typhoon. The member with the largest track error has perturbations that act to weaken the ridge. A low-pressure disturbance to the southeast of the ridge is found to migrate westward faster than the member with the smallest track error. Therefore, the typhoon is advected westward by the easterlies associated with the low. These results indicate a significant influence of the tropical disturbance on the predictability of Hagibis