Gangetic West Bengal is a very sensitive weather pocket during the pre-monsoon season. Even in this sub-division, the areas having proximity to the Bay of Bengal and Sunderban Delta are more susceptible to intense weather activity. These hazardous conditions peak in the month of May and last till the arrival of the monsoon by 10th June. Locations like Midnapore, Panagarh, Purulia, Hugli, Howrah, 24 Parghana, Digha and Kolkata are infamous for violent thunderstorms threatening life and property.
The city of Kolkata and its suburbs have already witnessed the lead thunderstorm activity yesterday as a precursor to the main event. Though the rainfall amount was limited to 2mm at Alipore and 3.6mm at Dumdum, Meteorological conditions are building up and becoming favorable for severe thunderstorms over the next 3-4 days over Kolkata and the neighborhood. Predominantly the weather activity will take place during the late hours of the day and the main threat is wielded by gale speed winds accompanied with heavy rain and lightning.
Synoptically a cyclonic circulation is persisting over parts of Jharkhand and Bihar with a trough extending eastward across south Gangetic West Bengal. Contiguous positioning of the Bay of Bengal is sufficiently pumping the important ingredient of moisture. A fair amount of clear weather during the morning and afternoon is providing the trigger of heat and the combination of this trio will cast this long spell of 'Kalbaisakhis' over and around the capital city. Rainfall amounting to about 100mm or more is quite likely during the next one week or so.