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.

来自四个主要业务数值天气预报中心的整体预报检查了2019年10月台风哈吉比斯的可预测性。在登陆前六到四天，日本气象厅的预报是四个中心中最好的。但是，登陆前三天的误差急剧增加。与向西走线误差一致，在环境风中发现向西北偏。对着陆区的整体敏感度分析表明，对位于台风东南方的山脊的敏感度较高。轨道误差最大的成员具有扰动，其作用是削弱山脊。发现对山脊东南部的低压扰动向西移动的速度比最小跟踪误差的移动速度快。所以，台风由于与低气压有关的东风而向西平移。这些结果表明热带干扰对哈吉比斯的可预测性具有重大影响。