Studies on forecasting local rainfall in India with the help of precipitation index.

Abstract

Following schell’s single radio-sonde analysis in local 8 hr forecasting of precipitation, radiosonde data of three Indian stations namely Madras, New Delhi and Nagpur was analysed. Precipitation index , I where w is the mixing ratio and L the pressure fall during ascent to the saturation level for layers upto 600 mb) for the periods considered and compared with the subsequent precipitation in twelve hours at each stations. Studies suggest that
the precipitation index itself can be used for forecasting local weather without reference to the synoptic situation over an area with a fair measure of success. Critical values of I varied between station for the occurrence of rainfall. However, it was concluded that low precipitation index leads to low probability of occurrence of rain while with high index higher probability with more correct forecasts of precipitation occurs. Precipitation index during dry months mostly falls under low index group (0.1 – 3.0).