Intensity changes in Typhoon Sinlaku and Typhoon Jangmi in response to varying ocean and atmospheric conditions

Abstract

Impacts of ocean heat content (OHC) and vertical wind shear on intensity changes of Typhoon Sinlaku and Typhoon Jangmi during the Tropical Cyclone Structure-2008 and THORPEX Pacific Asian Regional Campaign are investigated. Observations of ocean structure variables were obtained in the environment of each typhoon via aircraft-deployed expendable bathythermographs (AXBTs). Strong correspondence among storm intensity changes, ocean features, and vertical wind shear is identified as each tropical cyclone passed over regions of warm and cold ocean features with varying vertical wind shears. Typhoon Sinlaku passed over a cold ocean and with a consistently low vertical wind shear, the storm did not intensify for 12 hours. Sinlaku then reached maximum intensity as it passed over a warm ocean feature while vertical wind shear remained low. Sinlaku also weakened as it passed over an intense cold eddy at a time when vertical wind shear was increasing. Similar impacts are defined for TY Jangmi. Comparison of the AXBT profiles with the East Asian Sea Nowcast/Forecast System (EASNFS) analyses consistently indicated the EASNFS mixed layer depths (MLD) were too shallow, had steeper slopes in the thermocline, and a warm sea-surface temperature (SST) bias. The MLD and SST biases compensated causing OHC differences to be reduced.