NUMERICAL SIMULATION OF THE RELATIONSHIP BETWEEN THE MAINTENANCE AND INCREASE IN HEAVY RAINFALL OF THE LANDING TROPICAL STORM BILIS AND MOISTURE TRANSPORT FROM LOWER LATITUDES

Abstract:

The NCEP/NCAR reanalysis, Japan Meteorological Agency (JMA) tropical cyclone tracks and intensive surface observations are used to diagnose the features of moisture transport of tropical storm Bilis (No. 0604), which is simulated by the WRF (weather research and forecasting) mesoscale numerical model. It is shown that the Bilis was linked with the moisture channel in the lower latitudes after its landing. Meanwhile, the cross-equatorial flows over 80°–C100°E and Somali were active and brought abundant water vapor into the tropical storm, facilitating the maintenance of the landing storm with intensified heavy rainfall along its path. The simulation suggested that the decreased water vapor from lower latitudes prevents the maintenance of Bilis and the development of rainfall. While the cross-equatorial flows over 80°–C100°E and Somali were in favor of keeping the cyclonic circulation over land. If the moisture supply from the Somali jet stream was reduced, the strength and area of heavy rainfall in tropical cyclone would be remarkably weakened. Consequently, the decreased water vapor from lower latitudes can remarkably suppress the deep convection in tropical storm, then Bilis was damped without the persistent energy support and the rainfall was diminished accordingly.