Interaction Between Typhoon Megi (2010) and a Low Frequency Monsoon Gyre

Abstract:

The WRF model is used to investigate the sharp northward turn of super typhoon Megi (2010) after it moved westward and crossed the Philippines. Analysis of observational data shows that during this period a low-frequency (10-60-day) monsoon gyre interacted with Megi. To investigate the effect of the low-frequency flow on Megi, numerical experiments were designed. The flow field is divided into a slowly varying background state, a 10-60-day low frequency component representing the monsoon gyre, and a 10-day high-pass filtered component representing Megi. In the control experiment, all three components are included, and the model is able to simulate Megi’s sharp northward turning track. In the second experiment, the 10-60-day mode is removed from the initial and lateral boundary fields. In the absence of the low-frequency mode, Megi moves westward and slightly northwestward without turning north. Tracks of the relative positions between the Megi and the monsoon gyre centers indicate that a Fujiwhara effect existed between them and was responsible for the northward turn of both Megi and the monsoon gyre.