2019年台風第19号の予報進路に対する海面水温と初期擾乱の影響

Abstract

Influence of the sea surface temperature (SST) and initial perturbations on track forecasts of Typhoon Hagibis (2019) is investigated by forecast experiments with the JMA-GSM. Initial perturbations are obtained from the ensemble sensitivity analysis for the westward drift of Hagibis in our previous study. SST has little influence on tracks except for accelerated migration with higher SST. Hagibis develops deeper and yields heavier precipitation with higher SST. The development is enhanced by the stronger secondary circulation due to increased surface latent heat flux. The westward bias is consistently reduced by adding initial perturbations estimated by the ensemble sensitivity analysis. Opposite perturbations lead to asymmetric track change because of changes in convective activity, implying that the estimation of peripheral tropical disturbances is a key to accurate track forecasts.