Impacts of High-Resolution Atmospheric Motion Vectors on Forecasts of Typhoon Meranty (2016) in HWRF

Accurate estimations of tropical cyclone intensity and structure are essential to improving tropical cyclone forecasts and for detailed diagnoses of numerical model characteristics. HWRF is one of the more sophisticated tropical cyclone forecast systems, which covers all basins. However the initialization method differs among basins; self-cycled EnKF hybrid data assimilation (DA) is applied in North Atlantic and Eastern Pacific basins but not in other basins. A new geostationary meteorological satellite, Himawari-8 provides high spatiotemporal resolution atmospheric motion vectors and has potential to resolve both the TC inner structure as well as initial conditions of the surrounding environment, leading to more skillful forecasts.

To investigate impacts of initialization through DA with GSI in HWRF, three sets of cycle forecast experiments of Typhoon Meranti (2016) were conducted. Each set contains 15 five-day forecast experiments. The HWRF configuration is almost the same as the recent operational HWRF (H217). One set includes a HWRF cycle run which includes vortex initialization without GSI (CTL), second run is HWRF with hybrid-GSI (HGSI), and third is HWRF with hybrid-GSI and high-resolution AMV derived from Himawari-8 (HGSI-AMV).

Preliminary verification shows that HGSI-AMV produced the smallest track errors for forecast hours 108-120 among the experiments and HSGI-AMV was better than HGSI for all lead times, indicating that assimilation of AMV is a promising way to further improve track forecasts. Detailed differences in TC development and structure among the three experiments will be presented.