Role of Sensible and Latent Heat Fluxes from the Ocean in the Genesis of Tropical Cyclone Nargis (2008)

On May 2, 2008, Tropical Cyclone Nargis killed over 130,000 people in southern Myanmar making it the 8th deadliest cyclone of all time. A better understanding of the mechanisms in the early stages of development of tropical cyclones, such as the role of latent and sensible heat fluxes from the ocean, could help forecast modelers better understand the physics of the cyclogenesis, improve the model forecasts and ultimately gain a greater lead time in detecting and predicting cyclones. We conducted two experiments using the Weather Research and Forecast (WRF) model version 3.3.1 to determine the impact of surface fluxes on the genesis of Cyclone Nargis during a 60-hour forecast. The two experiments included: a control run (CNTRL), where the model forecast had full physics, including sensible and latent heat fluxes from the surface, and a no flux run (NOFLX), which turned off both surface sensible heat and latent heat fluxes. The CNTRL produced a strong cyclone, with a maximum wind of 65 knots (33.4 m/s) and a minimum pressure of 955 hPa. The NOFLX produced a weak cyclone with a maximum wind of 25 knots (12.9 m/s) and a minimum pressure of 1002 hPa. Thus major factors in the genesis of Cyclone Nargis were the surface latent and sensible heat fluxes over the ocean, where the sea-surface temperature was above normal.