Tropical cyclone genesis potential parameter (GPP) and it's application over the north indian sea

Abstract

An analysis of tropical cyclone genesis potential parameter (GPP) for the North Indian Sea is carried out. The genesis potential parameter developed by Kotal et al. (2009) is computed based on the product of four variables, namely: vorticity at 850 hPa, middle tropospheric relative humidity, middle tropospheric instability and the inverse of vertical wind shear at all grid points over the area. The GPP at a grid point is considered under the conditions that all the variables vorticity, middle tropospheric relative humidity, middle tropospheric instability and the vertical wind shear are greater than zero and it is taken as zero when any one of these variables is less or equal to zero. The variables are computed using the European Centre for Medium Range Weather Forecast (ECMWF) model data. Forecast of the genesis parameter up to seven days is also generated on real time using the ECMWF model output (available at http://www.imd.gov.in/section/nhac/dynamic/Analysis.htm). Higher value of the GPP over a region indicates higher potential of genesis over the region. Region with GPP value equal or greater than 30 is found to be high potential zone for cyclogenesis. The analysis of the parameter and its effectiveness during cyclonic disturbances in 2010 affirm its usefulness as a predictive signal (4-5 days in advance) for cyclogenesis over the North Indian Sea and for determining potential for intensification of developing and non-developing systems at the early stages of development.