The effect of interaction between meso-scale system and typhoon on Its motion and structure change

Tropical cyclone sudden structure change and irregular motion (meandering track (Holland and Lander,1991), looping, sharp turning etc.) are always resulted in big forecasting error. They are also the critical issues in operational numerical prediction. Most of the numerical models are invalid to forecast such sudden change of the tropical cyclone behavior. Case analyses (Chen, 1991) show that those sudden change of tracks usually arise from the variation of large scale environmental steering flow field or the interaction with surrounding synoptic scale/meso scale weather systems. Some times it also can be arisen from the asymmetric structure of the cyclone circulation in a weak flow field such as col environment. This paper is going to show that the interaction between different motion scale is able to trigger the evolution of the asymmetric structure of typhoons in the weak environmental flow field which would lead to the meandering or oscillations of typhoon tracks. In experiment 1, the track is quite smooth showing no oscillation in its motion. The experiment 2-5 with small vortex in four different quadrants of the typhoon circulation, the distinct oscillation of typhoon motion can be found. Especially typhoon would turn left wards with prominent oscillation when a small vortex appears in its first (North East) quadrant. Typhoon motion would have a little influence from a smaller scale system in the third (North West) quadrant of the typhoon circulation.