LAUSR

ABSTRACT The authors previous study reported the important role of extratropical intraseasonal oscillation (ISO) on the occurrence of a typical heatwave event over the Yangtze River Valley. Based on the ECMWF subseasonal reforecast database, this follow-up study evaluates the extended-range prediction skill of the heatwave event and further unravels the close link between the ISO and extended-range prediction of the event. With a two-week lead time, this heatwave event fails to occur in the reforecast because the predicted surface temperature is significantly underestimated. More detailed analysis demonstrates that the biases for both the intensity and the location of the warming region are primarily attributable to the inaccurate extratropical intraseasonal traveling signals. This work strongly indicates that accurately capturing the extratropical intraseasonal signal from the Eurasian continent is indispensable for extended-range prediction of East Asian extreme heatwave events.