[AAS01-08] 100-member ensemble forecast by NICAM to examine forecast bust case Typhoon Krosa (2019)
キーワード：アンサンブル予報、NICAM、NEXRA、台風
Typhoon Krosa formed near the Mariana Islands at 0600 UTC on 6 August 2019 then translated northwest-north northwestward and made landfall western part of Mainland of Japan on 15 August. At the early stage of Krosa’s lifetime, multicenter operational models predicted huge diversity of track: JMA (ECMWF) model predicted Krosa would translate north-northeastward (northwest-north northwestward), thus it would not (would) hit Japan.
To examine why such diversity in predicted tracks occurred, 100-member ensemble forecast experiments were performed using 28-km mesh nonhydrostatic icosahedral atmospheric model (NICAM). The model was initialized with NICAM-LETKF JAXA Research Analysis (NEXRA).
In the experiments initialized at 1200 UTC on 6 August showed large uncertainty of Krosa’s track as predicted in multicenter operational models and the west most simulated tracks captured Krosa’s analyzed track by RSMC Tokyo. An ensemble-based sensitivity analysis revealed that westward extension of subtropical Pacific high led to northwest/north-northwest trajectory. Dependency of initial data and mechanism which caused westward extension of the subtropical high will be discussed at the presentation.
To examine why such diversity in predicted tracks occurred, 100-member ensemble forecast experiments were performed using 28-km mesh nonhydrostatic icosahedral atmospheric model (NICAM). The model was initialized with NICAM-LETKF JAXA Research Analysis (NEXRA).
In the experiments initialized at 1200 UTC on 6 August showed large uncertainty of Krosa’s track as predicted in multicenter operational models and the west most simulated tracks captured Krosa’s analyzed track by RSMC Tokyo. An ensemble-based sensitivity analysis revealed that westward extension of subtropical Pacific high led to northwest/north-northwest trajectory. Dependency of initial data and mechanism which caused westward extension of the subtropical high will be discussed at the presentation.