Study on pre-monsoon thunderstorm frequency and its relation with rainfall in Bangladesh during 1990-2017

Abstract

Thunderstorm is a short-lived and violent weather phenomenon which synchronizes with rain, lightning, hail or gusty wind. In this study, pre-monsoon (March-May) thunderstorm frequency and its relation with rainfall are carried out for 28 years (1990-2017) using Bangladesh Meteorological Department (BMD) 34 stations data. BMD archived the thunderstorm as gusty, squall and hail types. The thunderstorms are also further classified into severe (> 64 km/h) and non-severe (≤64 km/h) based on their wind speed. In the present study the highest thunderstorm frequency is found at 12 UTC (18 LST) in May. The maximum occurrence of thunderstorm is found 12-18 UTC (18-24 LST) during 1990-2017. The occurrence of squall type thunderstorm is found maximum (54%). The occurrence of severe and non-severe thunderstorms is found maximum in the month of May in 1993 and March in 2004, respectively. Strong yearly variation of different types of thunderstorms is found during pre-monsoon season in Bangladesh. Spatial distribution showed the maximum occurrence of thunderstorm is found central and northeastern part of Bangladesh and minimum in Teknaf, Maijdee Court and Feni. During pre-monsoon wind speed of thunderstorm is found maximum in May. The highest average wind speed of thunderstorm is found in Teknaf in May is 98 km/h and lowest in Hatiya in March is 38 km/h. On average, about 26% thunderstorm is found to propagate southeastward during pre-monsoon season. The highest number of thunderstorm day is found in the month of May. During pre-monsoon season maximum average rainfall occurs in May and minimum in March. The highest amount of rain is found at Srimangal in the month of May. Daily rainfall is showed increasing trends as the monthly progress during pre-monsoon season. Generally, the thunderstorm frequency as well as average rainfall is highest in May. The correlation coefficient of thunderstorm occurrence and rainfall is found 0.45, 0.57 and 0.61 for the month of March, April and May, respectively. This study reveals that rainfall increases with increase of thunderstorms in Bangladesh during pre-monsoon season.