Simulation of tornado over Brahmanbaria on 22 March 2013 using Doppler weather radar and WRF model

Abstract

A tornado occurred at Brahmanbaria in Bangladesh in the afternoon of 22 March 2013. The tornado event has been studied based on tropical rainfall measuring mission (TRMM) data, radar observations and model simulations. The maximum reflectivity and the vertical extent of the system have been recorded to be about 54.7 dBZ and 15 km, respectively, by the Doppler weather radar (DWR) at Agartala, India. The event has been simulated by using the WRF model at 3- and 1-km horizontal resolution nested domains based on six hourly final (FNL) re-analysis data and boundary conditions of National Centers for Environmental Prediction (NCEP). Results show that, while there are differences of 40 minutes before the observed time of the storm, the distance between observed and simulated locations of the storms is 0.5°. The maximum amount of vorticity transferred by directional shear in the storm updraft (helicity) due to convective motion simulated by the model is found to be 1774 m2 s−2, and the highest value of bulk Richardson number shear that defines the region in which low-level mesocyclogenesis is more likely has been 457.3 m2 s−2, which is generally supposed to produce rotating storms according to the prescribed range. The highest vertical velocity simulated by the model is about −28 to 58 m s−1.

Keywords

• Tornado
• DWR
• WRF
• vertical velocity