Reduction of Rainfall During Tropical Cyclone Passage by Kuroshio Large Meander: A Case Study of Tropical Cyclone Talas (2011)

Abstract Tropical cyclone (TC) intensity and associated rainfall depend on sea surface temperature (SST). SSTs in southern Japan, which are often hit by TCs, are likely influenced by the path of the Kuroshio. During the Kuroshio large meander (KLM), Kuroshio creates a coexistence of local warm and cold SST anomalies near the Japanese coast. Here, we show that these SST anomalies significantly reduce rainfall through numerical experiments for Tropical Cyclone Talas (2011, non‐large meander year), if Talas followed the same path during a KLM year. These SST anomalies, about 2°C higher and lower than the surrounding water, reduce rainfall by 17% (131 mm). Talas brought onshore winds to the Kii Peninsula (KP), which intensified the horizontal water vapor flux toward land, resulting in heavy rainfall. However, the onshore winds from Talas weaken for the next two reasons. First, as Talas passes through the cold SST anomaly, its wind weakens. Second, these SST anomalies cause a pair of cyclonic and anticyclonic wind anomalies, which we consider to be due to an air‐sea interaction known as the pressure adjustment mechanism. The KP is situated in the southern (northern) part of the warm (cold) SST anomaly. Therefore, these wind anomalies become offshore wind, causing a local weakening of the onshore wind. The weakened onshore wind is stronger than the increase in water vapor evaporating from the warm SST anomaly, resulting in reduced horizontal water vapor flux inflow and precipitation. Local‐scale SST anomalies must thus be considered in the prediction of local precipitation.