Simulation of heavy rainfall over Mumbai on 26 july 2005 using high resolution icosahedral gridpoint model GME

In this paper an attempt has been made to simulate the exceptionally heavy rainfall event over Mumbai (Bombay) on 26 July 2005. Santa Cruz observatory near the International Airport of Mumbai recorded 944.2 mm of rainfall between 0300 UTC of 26 July 2005 and 0300 UTC of 27 July 2005 breaking all previous records. Some nearby places also recorded very heavy rainfall. Consequently, a deluge flooded the city and life in Mumbai came to a standstill. Mesoscale models or regional models are normally used to simulate such a small scale phenomenon. The model used in this paper to simulate the rainfall is the operational global numerical weather prediction model (GME) developed by the Deutscher Wetterdienst, The German Weather Service. Using European Center for Medium range Weather Forecast-ECMWF at T511 L91 data as the initial condition for the GME model, 24 hours accumulated precipitation has been computed. The model has a horizontal resolution of 40 km with 40 vertical levels and time step of 133s. The computed rainfall agrees reasonably well with the actual precipitation. The localized heavy rainfall might have occurred over Mumbai possibly due to several factors such as: well-marked low pressure over Orissa and adjoining Jharkhand with associated cyclonic circulation extending up to mid-troposheric level; off-shore trough on the west coast of India; low level jet over the peninsular India; intense convection and orographic lifting and interactions among these meteorological phenomena of different scales.