Rain alert with eye on path

May 20: Cyclone Laila struck the Andhra Pradesh coast this afternoon and weakened but air currents could nudge it back over the Bay of Bengal where it may intensify again, scientists said.
Heavy rain is forecast for south Bengal, including Calcutta, on Saturday. Weather officials stressed that there was no reason to panic yet, though they advised caution in states such as Andhra Pradesh and Orissa. The advisories may change depending on the cyclone’s advance.

Numerical weather predictions have thrown up two scenarios — in one, Laila moves over the land and decays; in the second, the cyclone moves along the coastline and re-emerges over the northern Bay of Bengal, regaining energy over the seawater.

If the cyclone moves over land, heavy rainfall is expected in Gangetic Bengal on Saturday. Squalls with speeds ranging from 40-60kmph — higher than the typical 30kmph moderate breeze but lower than the 110kmph witnessed during Aila a year ago — are likely in south Bengal.

Director of weather section at Regional Meteorological Centre in Alipore, G.C. Debnath, said tonight that there was no need to panic as the cyclone was losing strength.
However, Debnath said that as the cyclone was moving along the coast, there are chances of the system slipping into the sea and gathering strength.

.P. Sharma, chief meteorologist of private met agency Skymet, said there was no reason for Bengal to apprehend an Aila-like devastation (May 25 last year) from Laila. “Aila had made landfall in Bengal, whereas Laila made landfall in Andhra Pradesh,” he added.

However, Ajit Tyagi, director general of the India Meteorological Department, said: “The cyclone is moving along a northeasterly track parallel to the coast. It may re-emerge and intensify -- we must not lose our caution.”

Laila crossed the Andhra Pradesh coast about 50km southwest of Machlipatnam around 4.30pm today. Gale force 110kmph winds gusting to 120kmph will batter the Andhra coast over the next 12 hours, the IMD said.

Nearly 20 people have died in Andhra in heavy rain.
If the cyclone does not move back over the sea, the forecasts suggest, it will steadily weaken.
Laila’s fate could influence the flow of the monsoon in the coming days although, meteorologists say, it is too early predict its likely impact on the monsoon's surge toward the mainland, or whether it will affect the expected onset date of May 30.

A Laila rejuvenated by moisture from the sea could drift towards Bangladesh or Myanmar, the forecasts also suggest. As the cyclone builds up energy, picking up evaporated seawater, less moisture will be available for the monsoon currents.


“After a cyclone, it could take a few days to about a week for moisture to build up and drive the monsoon flow again,” said a scientist at IMD, Pune. It is still 10 days before the monsoon is expected to strike Kerala.

Some meteorologists are predicting an early demise of the cyclone. Laila’s landfall will cause a dramatic cut-off of moisture supply to the lower level of the western side of the cyclone circulation.
When a cyclone is over the sea, the evaporating seawater is soaked by winds and moisture laden winds flow into the cyclone’s centre. But on landfall, as half of the cyclonic circulation moves over land, there is no moisture supply from the land side of the cyclone. This process has led to a significant weakening of the cyclone between May 19 and May 20, a scientist said.