The South-east Bay of Bengal is now housing tropical cyclone ‘Laila' that lay parked southwest and adjoining east-central Bay around 400 km east-southeast of Chennai on Tuesday afternoon.
An India Meteorological Department (IMD) update said that the current environmental conditions and numerical weather prediction models suggest further intensification of the system.
LANDFALL PROSPECTS
An intensified ‘Laila' would keep moving in a west-northwesterly direction for some more time and then straighten out to hit a more northwesterly to northerly direction and cross Andhra Pradesh coast between Ongole and Visakhapatnam early Thursday.
Analysing various possibilities based on predictions available for next three to four days, it is difficult to foresee whether this system would cause much damage to the prospects of monsoon onset over Kerala, according to Dr Akhilesh Gupta, leading operational forecaster and Adviser to the Department of Science and Technology. There are some important arguments that go to support this, he said.
For one, the monsoon flow over the Arabian Sea is still in the process of building and hence if the system crosses the coast by Thursday/Friday, there is still enough time available for it to evolve and cause onset over Kerala by May 30 as predicted.
Model predictions suggest that even after weakening of ‘Laila', the strength of the southwesterly flow over the Bay remains intact. This would help build the flow over the Arabian Sea subsequently.
ITCZ ACTIVE
Predictions also suggest that the Inter Tropical Convergence Zone (ITCZ, the global band of low pressure hosting low pressure systems) may remain active over the Arabian Sea as well as over the Bay even after ‘Laila' weakens.
This lends credence to hopes for possible formation of an onset vortex-like low-pressure system over the Arabian Sea subsequent to weakening of the cyclone.
However, this is not a strong argument yet as models give no indication of such formation as of now, Dr Gupta clarified.
But Paul Roundy, a leading US-based ocean forecaster, has been signalling the development of a ‘flare-up' in the region around this time.
Prof Roundy has not withdrawn his outlook as on Tuesday. Any positive development, as suggested, would have implications for onset of monsoon over the southwest coast and would be monitored closely.
SPURT OF RAINS
The US National Centres for Environmental Prediction (NCEP) maintained its outlook for build-up of rains along the southwest coast during the week ending May 25.
This would continue into the next week as well, with a fresh spurt of rains indicated for the southeast Arabian Sea around the Lakshadweep area.
Meanwhile, the IMD said on Tuesday that ‘Laila' is expected to pack wind speeds of 115 to 125 km/hr gusting to 135 km just before landfall, almost ramping up to ‘Category 1' status on the Saffir-Simpson scale of storm intensity.
The US Joint Typhoon Warning Centre (JTWC) agrees, saying that the system is forecast to intensify over the next 36 hours before making a landfall.
Subsequently, it would gradually weaken along the coastal areas of east India and cross into Bangladesh as a minimal tropical storm.
Other models seem to suggest that the system might re-curve close to the Andhra Pradesh coast and track north to northeastward ahead of an approaching westerly trough expected to deepen over Central India around Thursday.
WIDESPREAD RAIN
In its forecast for the next two days, the IMD said that coastal areas of north Tamil Nadu and Andhra Pradesh are likely to experience widespread rainfall with scattered heavy to very heavy falls and isolated extremely heavy falls from Tuesday night.
Gale force winds clocking 65 to 75 km/hr will prevail along and off Andhra Pradesh coast. It may scale up subsequently as the system moves closer to coast.
Squally winds speed reaching 50 to 60 km/hr have been warned of along and off north Tamil Nadu coast as well.
Sea condition will be high to very high along and off Andhra Pradesh coast and very rough along and off north Tamil Nadu coast. Fishermen are advised not venture into the sea.
