Vanakkam! The American Farmers’ Almanac contains this bit of folk wisdom: “Rain foretold, long last. Short notice, soon will pass.”  Meaning, if the horizon is gray and overcast it means a large area is affected, and the rain when it comes down, will stick around for a while. Conversely, if you get caught in a surprise shower, its likely to be short-lived.

Easterly waves, rain-bearing systems travelling across the Bay of Bengal towards Tamil Nadu and Sri Lanka, are now dictating weather in parts of South India though with a bias against the northern parts of Tamil Nadu. So, Chennai will be lucky to see much rain.

No surprises in the forecast for the city this Monday. The sky will generally be cloudy over Chennai city, an outlook by the Chennai Met Office said. Light rain is likely to occur in some areas. International models say it will be partly cloudy but see a 60 per cent chance of rain and thunderstorms for the city.

Cloudy to partly cloudy conditions with the maximum temperature at around 30 degrees Celsius have been forecast by the IMD. Winds north-easterly at 15-30 km/h. Towards evening and night, a few passing clouds but otherwise generally clear with a minimum of 25 degrees Celsius and winds north-easterly at 10-15 km/h.

Monday morning has already seen towering clouds over the horizon and thunderstorms roar past areas some distance to the South of Chennai, including Sewa Nagar, Periyar Nagar, Marai Malai Nagar, Chengalpattu, and Mahabalipuram and further South-West to Kanchipuram, Thenambakkam, Uthiramerur, and East of Vandavasi.

The Chennai Met Office of India Meteorological Department said moderate to heavy rain was recorded mostly to the South of Tamil Nadu during the 24 hours ending on Sunday morning. The main centres recording rain (in cm) during this period were Karaikal-9; Anna University-5; Trangambadi-4; Arimalam-3; Nannilam-3; Vedaranyam, DGP Office (Chennai), and Peravurani-2 each.

Potent force

Back to the easterly waves. These waves move real fast (unlike cyclones or low-pressure areas with their laggardly pace) and create heavy weather on impact along the coast. It is quite another thing that some of these waves can be potent enough to set up low-pressure areas, depression or even cyclones on their own! In which case, the weather being generated would be of a totally different proportion.

So, easterly waves are one of the most keenly awaited rain-bearing systems during the North-East monsoon, producing massive rainfall. Trust them to stand in for cyclones, and trigger severe weather, including floods, over parts of their command areas in South India.

Some of the rain heads packing the waves have gone on in the past to become low-pressure areas and depressions, even cyclones. But no such intensified form of weather is being forecast this time round, though a weather tracker of the Climate Prediction Centre of the US National Weather Service sees extended easterly wave action towards the central and southern parts of Tamil Nadu and some burning embers shooting past the South Peninsula into the Arabian Sea.

Chennai International Airport (MAA/VOMM) saw overcast/rain with winds northerly to north-westerly at 7 km/hr and temperature 25 degrees Celsius at 8 am this morning. There was an average delay of five minutes in arrivals (reducing tendency); 10 minutes in departures (increasing tendency). A Chennai-London Heathrow had taken off (scheduled 7.30 am; actual 8.04 am) while an Etihad Airways flight from Abu Dhabi was descending for landing at 8.16 am (scheduled 8.25 am); an IndiGo from Kolkata (scheduled 8.45 am; estimated 8.22 am); and a Corendon from Ahmedabad (scheduled 8.25 am; estimated 8.17 am). A lone thunderstorm stood just over the sea waters just to the South of Kelambakkam with no flights operating within the immediate vicinity.

The outlook for Chennai

The IMD forecast for today (Monday) pointed to the possibility of scattered rain for South Tamil Nadu and isolated rain for the North. As for tomorrow (Tuesday), it should be isolated over the whole of Tamil Nadu. It is forecast to be fairly widespread over Central Tamil Nadu and Puducherry on Wednesday and isolated over the interior on Thursday and fairly widespread over Tamil Nadu and Puducherry on Friday.

The national weather forecast issued by the India Meteorological Department, New Delhi, said that active easterly wave conditions over the south peninsula would cause scattered to fairly widespread rainfall with isolated heavy falls over Tamil Nadu and Puducherry.

Thunderstorms accompanied by lightning are forecast at isolated places over Tamil Nadu and Puducherry until tomorrow (Tuesday) morning. An extended outlook from Friday (November 29) to Sunday said fairly widespread to widespread rainfall with isolated heavy falls is forecast over Tamil Nadu and Puducherry. Isolated to scattered rainfall is likely over Kerala, Rayalaseema, South Coastal Andhra Pradesh and Lakshadweep.

Puducherry: 20% chance of rain

Low chance of rain, Puducherry, with a mix of clouds and sun being forecast and a mostly clear day forecast for this Monday. The day temperature may see a peak of around 30 degrees Celsius. Winds will be north-easterly and pacy at 15-30 km/h. The evening may give way to clouds and a few showers after midnight. Temperature may dip to a low of 24 degrees Celsius, while winds would be north-north-easterly at a comparably less pacy 15-25 km/h. But the chance of rain is slightly elevated at 30 per cent.

Salem: 20% chance of rain

Low chance of rain happening today with sunshine and clouds mixed being forecast for the day. The high may creep up to 31 degrees Celsius and winds east-north-easterly at at a moderate clip of 10- 15 km/h. Otherwise a mostly clear day. Not much happening into the evening and night with temperature likely dipping to around 20 degrees Celsius with east-north-easterly holding steady from the day.

Coimbatore: 10% chance of rain

Low chance of rain during the day might improve to 40 per cent into the night. The day would mostly see sun and clouds mixed with a high temperature near 30 degrees Celsius and sedate east-north-easterlies at 10 to 15 km/h. Showers early into the evening, turning partly cloudy into the night with winds light and variable and temperature dipping to 21 degrees Celsius.

Tiruchirappalli: 30% chance of rain

A foggy morning to be followed by 30 per cent of isolated thunderstorms rolling out in the afternoon. Winds to be pacy at 15-30 km/hr from the North-East with the day temperature peaking to 31 degrees Celsius. The evening could likely see a few passing clouds across an otherwise generally clear sky with the night temperature at a low of 23 degrees Celsius with north-easterly winds slowing down to 10- to 15 km/hr

Madurai: 30% chance of rain

An estimated 30 per cent chance of rain in the afternoon with scattered clouds as an isolated thunderstorm develops late in the morning. Day temperatures may peak to 31 degrees Celsius and north-easterly winds at 15-25 km/hr. Only 20 per cent chance of rain in the night with winds being north-easterly at 10- to 15 km/hr.

Thoothukudi: 60% chance of rain

Looks like a wet day out there, as the easterly wave maintains a prominent bias to South Tamil Nadu, with an elevated 60 per cent chance of rain (quantified at around 2 mm). The evening/night would have even elevated chance of 80 per cent rain. Basically cloudy skies in the morning would give in to scattered showers and thunderstorms in the afternoon. Still, the city may witness temperatures peaking to 30 degrees Celsius with north-easterly winds working up a speed of 15- to 30 km/hr. Winds turn north-north-easterly while holding steady and temperature dipping to a low of 25 degrees Celsius.

Reading the tea leaves, Chennai’s bloggers, their followers and Twitterati see the weather for today as follows:

 

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