Enhanced Predictability of Rapidly Intensifying Tropical Cyclones over the Western North Pacific Associated with Snow Depth Changes over the Tibetan Plateau

Abstract

Abstract This study finds an enhanced relationship in recent years between January–March eastern Tibetan Plateau snow depth (TPSD) and the frequency of rapidly intensifying tropical cyclones (RITCs) over the western North Pacific (WNP) during the following peak TC season (July–November). The correlation between TPSD and RITCs is significant during 2000–14 but was insignificant during 1979–99. During 2000–14, when TPSD increases, there is an enhanced low-level anomalous anticyclone over the subtropical eastern North Pacific mainly due to the combined effect of advection and dynamics of the climatological prevailing westerly jet. Northeasterly wind anomalies are observed on the flank of the anticyclonic circulation anomaly, favoring anomalously cool sea surface temperature (SST). These anomalies lead to an anomalous pattern similar to the Pacific meridional mode (PMM), via a wind–evaporation feedback and cold advection. A Gill-type Rossby response to the PMM-like negative phase results in an anticyclonic circulation anomaly over the WNP, suppressing RITCs during 2000–14. A nearly opposite circulation anomaly occurred when TPSD was lower during 2000–14. There is a weak relationship between TPSD and RITCs, due to the lack of a link between TPSD and the PMM-like pattern from 1979 to 1999. Decadal changes in the relationship between TPSD and RITCs are mainly due to the meridional displacement of the prevailing westerly jet, which may be in response to decadal-to-multidecadal variability of SST anomalies. These changes then result in changes in the relationship between January–March TPSD and the PMM-like pattern. Significance Statement Forecasts of tropical cyclone rapid intensification, typically defined to be when a tropical cyclone intensifies by at least 30 knots (∼15 m s−1) in 24 h, remain extremely challenging. This study finds an enhanced relationship since the start of the twenty-first century between winter–spring Tibetan Plateau snow depth and western North Pacific rapidly intensifying tropical cyclones, while the relationship between snow depth and rapidly intensifying tropical cyclones was weak from 1979 to 1999. Decadal changes in the relationship between Tibetan Plateau snow depth and western North Pacific rapidly intensifying tropical cyclones is mainly due to the north–south displacement of the prevailing westerly jet, which may be in response to a transition in a midlatitude North Pacific climate mode. This study highlights the importance of the synergetic impact of the land, air, and sea on tropical cyclone climate and provides a potential predictor for seasonal-to-decadal prediction of rapidly intensifying tropical cyclones.