Simulation of Track and Intensity of Gonu and Sidr with WRF-NMM Modeling System

Abstract

Tropical cyclones are organized convective activities, developed over warm tropical oceans. The Indian region is unique in nature than any other region of the world, as far as the genesis and death toll due to tropical cyclone is concerned. The tropical cyclones affect this region in two seasons: Pre-monsoon (April-May) and Post-monsoon (October-December). The peak frequency is found to be in the months of May and November. Though considered to be much weaker in intensity and smaller in size as compared to the cyclones of other regions, the Bay of Bengal storms are exceptionally devastating, especially when they cross the land. This is mainly due to shallow bathymetry, nearly funnel shape of the coastline, and the long stretch of the low-lying delta region entrenched with large number of river systems leading to high storm surges and coastal inundations. The Bay of Bengal contributes about 5% of the global annual tropical storms. At the same time, Arabian Sea contributes 1-2% of the global annual tropical storms. Therefore, reasonably accurate prediction of these storms has great importance to reduce the loss of valuable lives.

In recent years meso-scale models are extensively used for the prediction of different weather events worldwide. In the present study, WRF-NMM is used to simulate the pre-monsoon cyclone Gonu and the post-monsoon cyclone Sidr generated over Arabian Sea and Bay of Bengal respectively. The performance of the model has been evaluated and compared with observations and verifying analysis. Again, the advancement of data assimilation techniques indeed improves the forecast skill of the meso-scale models in wide ranges. A brief description of the meso-scale model used for the present study is given in Section 2. The numerical experiments and the data used are presented in Section 3. The synoptic situation for the above-mentioned cyclones is described in Section 4. The results are presented in Section 5, and the conclusions are in Section 6.