2009年10月13～14日に発生したAtmospheric Riverの予測可能性

Abstract

Atmospheric River (AR) is long and narrow filaments extending from tropics to extratropics, which often cause extreme precipitation along the US western coast. The predictability of AR during 13–14 October 2009 is investigated by numerical experiments using the NCEP Global Forecast System (GFS). For a 7-days lead time, GFS was able to predict AR's shape and location, on the other hand, ECMWF and JMA operational forecasts fail to predict them and had northward bias. To distinguish between the forecast errors attributable to the initial condition and those to the model, GFS was run from the initial conditions created from ECMWF analysis data. The northward bias of AR location was reduced by using GFS. This indicates the forecast errors of AR in ECMWF operational forecast are mainly attributable to the model.