Observations and mesoscale forecasts of the life cycle of rapidly intensifying super cyclonic storm Amphan (2020)

Super cyclonic storm Amphan (2020), formed over the Bay of Bengal, has been forecasted using the mesoscale model WRF to examine the rapid intensification (RI) features in the model forecast. The special surface and upper air weather observational campaigns were arranged from ISRO’s Balasore observatory during the life cycle of Amphan. Along with these observations, forecasts have been validated with the available surface and upper air observations along the east coast of India, the GPM-IMERG rainfall observations, and the ECMWF Reanalysis-5 (ERA-5) reanalysis. The dynamical parameters, viz. low-level convergence, middle tropospheric humidity, and diabatic heating in the middle troposphere, have been compared with reanalysis. It is seen that up to 124-h forecasts of track and intensities have significantly improved And the surface and upper air parameters forecast is reliable for up to 48 h. The study showed that the high SST in the range 30–31 °C along the track of the TC, TCHP range of 60–70 kJ cm −2 , ~ 100% Mid-tropospheric relative humidity (MTRH), enhanced diabatic heating in the rainband region. Intense rainfall in the front left quadrant of the system favored the rapid intensification of Amphan. Because of the large size, high shear (10–25 ms −1 ) is ineffective in hindering the system’s intensification process. The wind variation during the system’s landfall is also well captured, and 24 h forecast agrees with the observed data. The appropriate representation of vertical wind shear required for realistic simulation of axisymmetric, asymmetric, and landfall dynamics, is also evident from campaign observations.