Evaluation of the WRF and Quasi-Lagrangian Model (QLM) for Cyclone Track Prediction Over Bay of Bengal and Arabian Sea

Abstract

Quasi-Lagrangian model (QLM) for cyclone track prediction is the operational limited area model used in India Meteorological Department (IMD) for providing numerical guidance in cyclone forecasting operations (Mathur 1991, Prasad and Rama Rao 2003). QLM is specially tailored for providing cyclone track forecasts using the methodology of a synthetic vortex superimposed on gridded fields to correct the location and intensity of the vortex in the initial fields. QLM has a horizontal resolution of 40 km and 16 sigma levels in the vertical. It is integrated in a domain of about 4,400 × 4,400 km² area that is centered on the initial position of the cyclone. The special feature of the QLM is an idealized vortex, which is generated from the current storm parameters; and a Dipole, which is generated based on the estimated storm speed and direction.

Recently, IMD implemented the Weather Research and Forecasting (WRF) model in the research mode. The model has a horizontal resolution of 20 km and 31 sigma levels in vertical, with domain of 0°-30°N; 65°E-105°E. Using this model, some case studies were conducted to examine the usefulness of this high-resolution advanced mesoscale models for the Indian region. The track forecast experiment results up to 3 days were compared with the operational QLM forecast. In the present study, we have selected two severe cyclonic storms namely (i) Super Cyclone “GONU” over Arabian Sea during 01-07 June, 2007, and (ii) very severe cyclonic storm “SIDR” over Bay of Bengal during 11-16 November 2007. Also sensitivity experiments were conducted with the WRF model to test the impact of various microphysical and cumulus parameterization schemes in capturing the track and intensity of the systems.