One-month forecasts of wet and dry spells of the monsoon

Abstract

By filtering out the high-frequency modes, we are able to delay the contamination of low frequency modes for periods of the order of one month in global forecasts. A multilevel global model forecast is carried out to predict a wet spell over central China. It is shown that an initial state consisting of time-mean state, a low-frequency mode, and a specification of the sea surface temperature anomaly provides useful forecasts for the occurrence of dry or wet spells. The main finding of this paper is that the prediction of monsoonal low-frequency modes and the related dry and wet spells can be extended beyond the usual numerical weather prediction (NWP) predictability limit of six or seven days. -from Authors