Environmental Influence On Typhoon Megi’s (2010) Path,Intensity And Precipitation

Typhoon is one of the most serious severe weather systems in the southeast coast of China. In present, the prediction of typhoon’s complex path, intensity and distribution of precipitation has always been difficult in forecasting. Based on the reanalysis data from the National Centers for Environmental Prediction and best track data from Japan Meteorological Agency, the development of super typhoon MEGI (2010) over the Northwest Pacific is analyzed in this work. The results show that the westerly trough and the subtropical high are the main impacts on MEGI’s change. Then the piecewise PV inversion is used to study different systems’impacts on MEGI’s path, intensity and precipitation. The main results are as following:MEGI’s movement is highly consistent with large-scale environmental steering flow. Subtropical high (SH) as a major factor, guides MEGI to move west-northwestward at early time. In the middle of MEGI’s life, the High in southern China causes the southwestward deflection of MEGI’s path. In the latter time, the circulation related to westerly trough (TR) leads MEGI’s turning northeastward.In the early time, SH and TR can provide water vapor to MEGI, while other systems’(RP’s) northeast wind is in favor of MEGI’s divergence at upper levels. But the vertical wind shear related to SH is large, which causes MEGI’s slow development. As MEGI moving westward, closing to Luzon, the wind shear of TC, TR, SH and RP are all very small. At the same time, SH and RP provide water vapor to MEGI. Then, MEGI develops quickly, and typhoon’s (TC’s) own circulation strengthened its divergence at upper levels. Adding weak cold air advection by TR, MEGI reaches its maximum intensity of its whole time. In the latter time, as a result of the increasing wind shear by RP, MEGI’s structure is destroyed, and then water convergence is weakened at low levels. At the same time, TR brings a lot of dry air at low level and holds back upper level outflow together with RP. All the adverse factors lead to MEGI’s decline.MEGI causes precipitation in northeastern Taiwan under the influence of TR, SH and TC. Besides supplying water vapor and creating the upward motion in northeastern Taiwan, TC can also bring weak cold air to Taiwan in the middle troposphere with TR. The upper cold air can enhance precipitation with lower warm moist air. All of these lead to the heavy rain in northeastern Taiwan.