Cyclone Mahasen sped through the last mile in quick time and crossed the Bangladesh coast on Thursday afternoon much earlier than anticipated.

Regional Specialised Meteorological Centre, Delhi, said in an update that the storm moved laterally across Northeast Bay of Bengal at an estimated 50 km/hr.

SPEED OF MOVEMENT

This is considered ‘super fast’ for cyclones, whose speed for movement (as distinct from wind speeds) falls within the 15-20 km/hr, according to statistics.

Average speed for a tropical cyclone is 15-20 km/hr, and it covers 360-480 km a day.

Direction change

It may change direction of movement, as Mahasen did when it turned north-east and away from the Indian coast.

During this changeover, the speed of movement of the cyclone could reduce to 10 km/hr or even less.

When it is down to 10-14 km/hr, it is called a slow moving cyclone.

A cyclone with moderate speed moves at 20-25 km/hr. If the speed is more than 25 km/hr, it is called a fast moving cyclone.

FRESH SYSTEMS?

The Delhi monitoring centre said that Mahasen crossed coast at 1.30 p.m. IST on Thursday and lay centred south-west of Aizal (Mizoram) and 85 km south-east of Agartala (Tripura).

It has since weakened into a deep depression but associated clouds spread across not just over Bangladesh but also adjoining North-East India, the North Arakan coast and adjoining Myanmar.

Meanwhile, European Centre for Medium-Range Weather Forecasts sees the possibility of another low-pressure area materialising over north-west Bay of Bengal during next week.

US National Centres for Environmental Prediction said that a counterpart ‘low’ could pop up over Arabian Sea around the same time and intensify later.

Both the seas are being closely watched for likely impact on dynamics associated with the onset of South-West monsoon over mainland India.

WEATHER ALERT

On Thursday evening, erstwhile cyclone Mahasen had massed up convective (rain-bearing) clouds over North Bay, Gangetic West Bengal, Tripura, Mizoram, Manipur, Nagaland, Meghalaya, Assam and West Arunachal Pradesh.

A weather warning from India Met Department said that fishermen along and off coastal areas of Odisha and West Bengal coasts should exercise caution while venturing into the sea on Friday.

Thunder squall could break out at one or two places over Assam, Meghalaya, Nagaland, Manipur, Mizoram and Tripura during next two days.

Heavy rain is likely at one or two places over south Assam, Manipur, Mizoram and Tripura during this period.

vinson.kurian@thehindu.co.in