North-East monsoon rains commenced over coastal Tamil Nadu, Puducherry, South Tamil Nadu, and the adjoining areas of South Coastal Andhra Pradesh and South Kerala today.
India Met Department (IMD) has said that the conditions are favourable for seasonal rains over the rest of Tamil Nadu, Kerala, South Interior Karnataka and Rayalaseema by tomorrow.
Helpful features
A facilitating trough of low (not amounting to a conventional low-pressure area) lies over South-West Bay of Bengal and adjoining Sri Lanka. Another trough runs from here to South Interior Karnataka across Interior Tamil Nadu. A cyclonic circulation lies over South Tamil Nadu.
Earlier, global weather models said that the 10-to-15-delay in the onset of monsoon (from the usual October 15-20 window) would be adequately make up for the lost time. They cited the forecasts of passage of a friendly Madden-Julian Oscillation (MJO) wave after it sets off for its voyage across Indian Ocean during the ongoing week.
Boosts rain prospects
The MJO wave travels periodically from the African coast across the Indian Ocean into the Maritime Continent and the West Pacific, and boosts the formation of cloudiness and rainfall on the way.
This 'wet phase' of the MJO has presided over monsoon onsets, setting up low-pressure areas and depression, which have gone on to become even cyclones under ideal conditions.
The global models are of the view that the incoming wave would get amplified (strengthened) when it enters the Indian Ocean during November 7 to 13. Based on good model agreement and relatively low spread among ensemble members, forecast confidence is high in a robust MJO propagating across the Indian Ocean during early to mid-November.
And, these models observe that this journey would not be without its attendant benefits for rain-starved parts of the South Peninsula in Tamil Nadu, Kerala and Karnataka.
The Global Forecast System model of the US Climate Prediction Centre sees an elevated chance of a 'low'/depression develop in the eastern half of the Indian Ocean during the first week.
Depression hinted at
The confidence is relatively higher that a system develops to the South-East of Sri Lanka. According to a weather tracker of the US National Weather Services, this would move towards the Tamil Nadu coast.
It could bring under its rainy spell the entire Tamil Nadu coast and adjoining South Andhra Pradesh, cross the South Peninsular into Kerala, and step out into the South-East Arabian Sea. Here, it is forecast to gain further traction and redevelop using the warmth of the sea waters, though models do not agree on a single track for its onward movement.
Scarcely would the system have faded out over the Arabian Sea than a fresh system develops over the South-East Bay of Bengal and travels towards the Sri Lanka and South Tamil Nadu coast. This time too, Chennai and neighbourhood could be the likely area of landfall, before setting up a ripple in the Arabian Sea just as its predecessor, and get a move to the East away from the Kerala coast.
Meanwhile, Thiruvananthapuram woke up to a cloudy morning today after light overnight showers ahead of a the fifth one-day cricket match between India and the West Indies.
Cricketing weather
The day-night match is scheduled to begin at 1.30 pm in the afternoon, with one model predicting an afternoon shower or a thunderstorm that should not prove too much of a problem. Another model predicted scattered thunderstorm with 50 per cent of rain during the day, growing to 60 per cent at night.
But the Sports Hub, the venue here, has excellent draining facilities. Although India Met Department (IMD) has hinted at the possibility of heavy rainfall (7-11 cm during 24 hours) today for Kerala, Thiruvananthapuram does not fall under the category of the warned areas.
The 'nowcast' issued by the Thiruvananthapuram Met Office issued at 10 am also did not indicate the chance of thunderstorm activity for subsequent three hours (until 1 pm). But the Kerala Cricket Association said that it would wait before giving the clearance in view of a massive fire that gutted a sprawling plastic goods unit not too far away.
The billowing noxious smoke is hanging in the air over a two-km stretch around the fire site that prompted the administration to announce holidays for schools in the neighbourhood. But the Sports Hub is situated at least six km away, and should be relatively from the reach of the smoke and ash/dust, official sources said.