The East China Sea Kuroshio Current Intensifies Deep Convective Precipitation: A Case Study.

Deep atmospheric convection is often observed over the Kuroshio in the East China Sea (ECSK). However, the mechanisms by which warm oceanic currents fuel transient deep convection are not fully understood. This study investigates an atmospheric cold front that brought heavy precipitation as it traversed the ECSK in April 2004. The southwesterlies ahead of the cold front advected moist and warm air, creating a zone with high convective available potential energy (CAPE) values. As the cold front approached the ECSK, the pre‐frontal high CAPE values coalesced with those over the warm current that substantially strengthened the deep convection, with precipitation rate increasing from 3 mm hr−1 to 10 mm hr−1. A numerical model well simulated the marked increase in precipitation over the ECSK, permitting the isolation of the ECSK's influence by contrasting the control (CTRL) run with an experiment with smoothed sea surface temperatures (SMTH run). Results show the ECSK contributed to 46% of the precipitation over the warm current. The ECSK was found to amplify ascending motion and elevate neutral buoyancy levels, extending its effect up to the tropopause. Furthermore, the strengthened deep convection significantly lowered the sea level pressure (SLP) over the ECSK and impressed upon the time‐mean SLP field. An additional experiment with lowered SST underscored the high SST's critical role in deep convection. This case study suggests a novel pathway by which the effects of warm oceanic currents influence the upper troposphere under extreme conditions with strong baroclinic instability. Plain Language Summary: Warm ocean currents like the Kuroshio in the East China Sea can shape the weather above, often causing towering clouds and heavy rainfalls. Understanding how this happens is key to better weather forecasts. Our research focused on an event in April 2004, when a cold front passing over the Kuroshio led to intense rain. We used satellite data and computer simulations to see how the warm current influenced the storm. We found that the Kuroshio, by warming and adding moisture to the surface air, strengthened the storm and increased its height, resulting in more rainfall. This effect also left a noticeable imprint on the sea‐level pressure field. These results are important because they help us understand and better predict the impact of warm ocean currents on severe weather events. Key Points: An atmospheric cold front swept over the East China Sea Kuroshio (ECSK) and produced heavy precipitation over the warm currentThe ECSK increased surface moist entropy, which intensified the precipitation from deep convectionThe cold‐frontal deep convection projected the ECSK's effect up to the tropopause [ABSTRACT FROM AUTHOR]