Storm outlook further upgraded to extremely severe cyclone

India Met Department (IMD) has on Sunday afternoon further upgraded the storm outlook in the South-East Bay of Bengal from 'very severe cyclone' to 'extremely severe cyclone.'

As per the revised timeline, cyclone Fani would become a severe cyclone later in the day, a very severe cyclone by Monday night and an extremely severe cyclone by Wednesday night.

MASSIVE STRENGTH

It would wind back in strength to become a very severe cyclone by Friday night, signalling the progressive weakening of a rare cyclone of such massive strength during April. Its peak strength on Thursday morning would feature remarkably strong winds of 180 km/hr gusting to 195 km/hr, but at a safe distance away from the North Tamil Nadu and Andhra Pradesh coasts.

This is much lower than the peak wind speeds of 213 km/hr and gusting to 259 km/hr projected by the US Joint Typhoon Warning Centre.

The IMD located 'Fani' at 11.30 am on Sunday lying 730 km East-South-East of Trincomalee (Sri Lanka), 1,040 km South-East of Chennai (Tamil Nadu) and 1,210 km South-South-East of Machilipatnam (Andhra Pradesh).

It was very likely to intensify into a severe cyclonic storm during the course of the day and into a very severe cyclonic storm by Monday, according to the IMD. 

This means 'Fani' would have reached the status of 'category three' storm on the five-step Saffir-Simpson scale of classifying storms internationally.

It would keep travelling towards the North Tamil Nadu-SOuth Coastal Andhra Pradesh coast till Wednesday evening, as per IMD outlook. It may later recurve (move away from India's coast) northeastwards.

LET-DOWN FOR TAMIL NADU

The powerful storm is expected to retain the status of a very severe cyclone for three days at a stretch until Wednesday morning and as an extremely severe cyclone for two days before weakening.

Light to moderate rainfall has been at many places over Kerala with heavy falls at isolated places while it would be light to moderate over North Coastal Tamil Nadu and South Coastal Andhra Pradesh on Monday and Tuesday.

Light to moderate rainfall has been forecast at few places North Coastal Andhra Pradesh and and South Coastal Odisha on Wednesday. It may increase in intensity with heavy rainfall over coastal Odisha the next day.

The turn of events would be clearly a let-down for weather watchers in Tamil Nadu and Coastal Andhra Pradesh who swore by the building cyclone to bring in badly needed rains to fill reservoirs in the region.

But pre-monsoon cyclones have flattered to deceive in most cases, given their tendency to recurve and move away from coast as is projected to happen in the case of 'Fani.' 

Cyclones normally sniff out the warmest waters to sustain themselves, since it is the ocean convection that facilitates supply of moisture, which in turn fuels their massive engine.

Sea-surface temperatures along the Andhra Pradesh coasts have warmed up on a par with the warmest pool of waters located in the Bay (31 deg Celsius) but in a corridor tapering off to North-East Bay.

ADVERSE 'SHEAR'

'Fani' would turn East-North-East to enter the North-East Bay rather than Coastal Andhra Pradesh from Friday 3 and start weakening after running into an unfavourable 'wind shear' environment. Unlike on Sunday morning, adverse wind shear (sudden change in wind speed and direction with height) are lording it over the Andhra Pradesh coast as well.

Unfavourable wind shear values, which affect the structure of the storm tower that stands 10- to 12 km into the atmosphere, could cause 'Fani' to forfeit speed and intensity as it enters North-East Bay. 

Even otherwise, a seasonal ridge (area of high pressure) reaching out to Central and adjoining North-West India from the Arabian deserts was seen as repelling the storm away from the coast.

'Fani' is being allowed a track along the periphery of the ridge standing like a wall over Andhra Pradesh-Odisha until tomorrow (Monday), following which the latter is forecast to crumble. 

Meanwhile, a high wind alert issued by the IMD said roaring winds at 170 km/hr gusting to 185 km/hr may prevail over South-West Bay from Wednesday night. They would reach up to 155 km/hour gusting to 170 km/hour off North Tamil Nadu, Puducherry and South Andhra Pradesh coasts from Tuesday night.