Forecasting of onset of southwest monsoon over Kerala coast using satellite data

The Global Precipitation Climatology Project and in situ gauge data have been used in the present study of the Indian monsoon for the region bounded by 8° to 13°N; 70° to 95°E, from March 1 to May 31 for the years 1979 to 2001. The monsoon onset dates over Kerala, as declared by India Meteorological Department has been used in the present study as an indicator of the onset of this event. For each year, the midday of the pentad with the rainfall peak was located in the period from 1st April to 10th May and identified as the pre-monsoon rainfall peak (PMRP). The analysis showed that the PMRP exists about six pentads prior to the onset of the monsoon over the Kerala coast. A regression equation developed using the first 20 years of data (1979-1998) with a standard error estimate of four days was used for predicting the onset dates for the years 1999, 2000 and 2001, with encouraging results. Thus, we feel that the pre-monsoon rainfall estimate from the satellite data can be used for predicting the monsoon onset over Kerala coast.