A study on the potential vorticity (PV) distribution of tropical cyclones (TCs) on different isentropic surfaces is performed to understand the dynamics of TCs. The Final Analyses dataset from the Tropical Cyclone Motion (TCM-90) Experiment is used in this study. Cyclones in the dataset are categorised by the direction of motion. For TCs in each category, PV maps on different isentropic surfaces are constructed. These maps are then examined to identify the features related to the movement of the TCs.
Composite analyses of westward-moving TCs show an area of maximum PV located at about 10° latitude ahead of the TCs in both the upper (350K) and middle (330K) layers. This shows that westward-moving TCs are generally moving towards an area of maximum PV. However, for those recurving TCs, no such pattern can be observed after recurvature. These results indicate that the PV distribution in the upper level would have an effect on TC motion. In addition to the above investigation, the PV distribution from northward-moving TCs will also be studied. The PV distribution pattern from all these categories will then be compared and a hypothesis on the effect of PV distribution to TC motion will be presented in the conference.