ATMOSPHERIC STABILITY INDICES AND SOME THERMO-DYNAMICAL PARAMETERS FOR FORECASTING THUNDERSTORMS OCCURRENCES OVER KANO, NIGERIA

Abstract

The study investigated the roles of some atmospheric Stability Indices and Thermo-dynamical Parameters (SITPs) on thunderstorms occurrences and hence determined the threshold values of these SITPs necessary for thunderstorm and squal line occurrences so as to be used for short-range forecasting of the occurrence of thunderstorm and squal line. This study was conducted to assess the roles of Convective Instability (CI) and Convective Available Potential energy (CAPE) in short-range forecast of thunderstorms and squall line occurrences over Kano, Nigeria. Daily upper air data and hourly significant weather for August and September in years 2012 and 2013 obtained from the achieve of Nigerian meteorology agency were used. This study uses the concept of “a 2x2 contingency Table” for evaluating and analysing thunderstorm occurrence. This table helps to obtain some simple skill scores such as accuracy (AC), bias (B), probability of detection (POD), false alarm ratio (FAR), probability of false detection (POFD) and success ratio (SR). The study established that if CI between 925 and 850mb pressure levels is greater than or equal to100hpa-1 and CAPE is greater than equal to 2500J/kg simultaneously, the probability of thunderstorm occurrence is 70%. It means that success ratio of a 2x2 contingency table is 68% and the accuracy is about 74% and the FAR is 29%. The result has finally shown that short range-range forecast of the occurrence of thunderstorm and squall line is possible with the availability of upper air data