NUMERICAL ANALYSIS ON THE ROLE OF TROPICAL STORM NAMTHEUN IN THE UNUSUAL TRACKS OF THREE TROPICAL CYCLONES IN 2010

Tropical cyclones(TCs) Lionrock,Kompasu,and Namtheun were formed successively within 40 hours in 2010.Over the next several days afterwards,these TCs exhibited unusual movements which made operational prediction difficult.Verifications are performed on the forecasts of the tracks of these TCs with six operational models,including three global and three regional models.Results showed that the trends of TC tracks could be reproduced by these models,whereas trajectory turning points and landfall locations were not simulated effectively.The special track of Lionrock should be associated with its direct interaction with Namtheun,according to a conceptual model of binary TC interaction.By contrast,the relation between Kompasu and Namtheun satisfied the criteria for a semi-direct interaction.Numerical experiments based on the Global and Regional Assimilation and Prediction System-Tropical Cyclone forecast Model(GRAPES-TCM) further confirmed the effect of Namtheun on the unusual tracks of Lionrock and Kompasu.Finally,the physical mechanism of binary TC interaction was preliminarily proposed.