PREDICTABILITY OF THE HEAVY RAINFALL DISASTER AT KANI CITY IN JULY 2010 BASED ON MODEL ENSEMBLE FORECASTS

Abstract

The predictability of the heavy rainfall disaster at Kani City, Japan in July 2010 is investigated using a model ensemble approach which relies on the combination of 32 member ensembles obtained from multiple parameterizations in the mesoscale meteorological model PSU/NCAR MM5. The model is initialized using the 20-km resolution global analyses JMA GSM-GPV with and without the radar-data assimilation system developed by Yoshino et al. (2009). It is found that the multi-parameterization ensemble forecasts averaged by 32 members during 24 hours are very skillful in indicating the area of severe local storm activity, while each member deviates largely from the ensemble mean. Furthermore, the radar-assimilated ensemble forecasts enable us to more precisely predict the area of greatest rainfall potential, because the initial conditions used here realistically represent 3-dimensional distributions of cloud microphysical properties in the atmosphere.