Detection of Possible Thunderstorm Formation Inferred from Weather Element Changes at Ground Level on a Mountain Slope

ABSTRACT

In India, Kerala state is known to have relatively high lightning incidence. The nature of spatial and temporal distribution of past incidents, type of thunderclouds which cause lightning, the topography, proximity to a mountain range and sea point to the possibility of the mountain weather aiding in Cb formation. For investigating the role of mountain weather in convective Cb formation a field station consisting of an automatic weather station and a lightning detector was established on the slope of the nearby Western Ghats mountain range. On thunderstorm days the mountain weather data show specific reduction in air temperature with synchronized increase in relative humidity along with a reduction in pressure of the order of 0.5 hPa between 10:00 h and 18:00 h. The variations in data are indicative of a strong updraft. The lightning detector showed thunderstorm activity, aligned with the direction of the mountain range, about an hour after detecting the changes in weather elements. Water vapour for thunderstorm formation seems to come from the nearby sea as indicated by the wind data. Data collected for three years show that existence of strong updrafts seem to be a characteristic of the mountain weather during thunderstorm months. Data from a coastal station located 40 km south west of the mountain station do not indicate updrafts either on the thunderstorm days or otherwise. As updrafts can lead to Cb formation monitoring weather elements as discussed here is useful for detecting thunderstorms at the developing stage itself.