India Meteorological Department (IMD) said cyclone ‘Sitrang’ over the North Bay of Bengal moved rapidly on Monday night and crossed the Bangladesh coast between Tinkona and Sandwip, close to Barisal, during 9.30 pm to 11.30 pm earlier than forecast. It had also failed to intensify as a severe cyclone apparently due proximity to land features and high wind shear.
By Tuesday evening, the remnant of the cyclone had weakened three times over into a low-pressure area as it performed an elaborate stroll over Bangladesh before entering Indian territory over South Assam and adjoining areas of North-East Bangladesh and East Meghalaya, where it was located last, the IMD said.
Heavy rain over North-East
The cyclone dumped very heavy to isolated extremely heavy rainfall over Meghalaya, Arunachal Pradesh, Assam and Manipur during the 24 hours ending Tuesday morning. Tamil Nadu was another region to report heavy rainfall during this period as a cyclonic circulation lay not far away from the coast. Numerical model projections from the IMD suggest that the circulation will hover over the region for next few days to be joined by an easterly wave in a week’s time. The North-East monsoon could likely use this window to make a delayed onset over the Tamil Nadu coast.
Circulation, easterly wave
Easterly waves in the South Bay of Bengal mimic the activity of weather-altering western disturbances that move over North-West India, but in the opposite direction. These waves are potential rain generators during the North-East monsoon and have been variously known to pack low-pressures areas depressions or the odd cyclone. These waves move straight along a line to the West and impact Tamil Nadu and Kerala the most. An extended La Nina in the West Pacific should fuel easterly wave movements
Watch for North-East monsoon
Cyclone ‘Sitrang’ having blown over, weathermen will shift their focus back to the Bay for signs of the North-East monsoon, which has been delayed by a few days. In an extended forecast for three days from October 30 to November 1, the IMD has predicted isolated to scattered light to moderate rainfall over Kerala, Tamil Nadu and Coastal Andhra Pradesh, as the winds get reorganised and the cyclone-churned Bay waters return to calm.
US agency forecast
The US Climate Prediction Centre indicates the possibility of south coastal Tamil Nadu and Kerala receiving moderate to heavy rainfall during the week ending November 1. The rains will get heavier during the next week (November 2 to 9) along the coasts of south coastal Andhra Pradesh, Tamil Nadu and Kerala as well as the ghats of Karnataka and Tamil Nadu and with slightly lesser intensity over interior Tamil Nadu and Karnataka. A productive western disturbance will ambush into North-West India bringing rain and thundershowers, and importantly helpful winds to clear the air and lessen pollution.