The Hindu : Tamil Nadu / Chennai News : They won't say it, but it's a heat wave alright

Online edition of India's National Newspaper
Saturday, Aug 28, 2004

Tamil Nadu

Tamil Nadu - Chennai

They won't say it, but it's a heat wave alright

By T. Ramakrishnan

CHENNAI, AUG. 27. Three months ago, Chennaiites were relieved that they did not experience `Katri' or `Agni Nakshatram,' which is synonymous with sweltering heat. But, now, they are finding that August has given them the ``feel of summer'', which May did not.

This August, the mercury touched 40 degrees Celsius both at Nungambakkam and Meenambakkam, which is unheard of, as Meteorological Department records for the last 25 years show.

The maximum temperature of 40 degrees C was recorded at Meenambakkam on August 17 and at Nungambakkam five days later. ``This is first time this year that the maximum temperature touched the 40 degrees Celsius mark,'' says a meteorologist.

Ironically, the maximum temperature did not cross 100 degrees F in May this year.

Although another meteorologist says the department cannot declare that Chennai is under a ``heat wave'' when the southwest monsoon was in progress, he does admit that the conditions are that of a heat wave.

Uninterrupted trend

It is not just that the mercury crossed the 40 degrees C mark this month. It is also that the number of days on which the maximum temperature crossed 38 degrees C is unusually more this August -- 11 days in Nungambakkam and 16 days in Meenambakkam. To be precise, the trend, which started on August 6, is virtually having an uninterrupted run.

Meteorologists point out that the mean maximum temperature for Chennai is 34 degrees C. If the deviation is four to five degrees C from this figure, it is called ``appreciably above normal.'' This is why 38 degrees C is taken as the base.

The ``unprecedented heat conditions'' are attributed to the presence of a dry northwesterly wind in the lower layers of atmosphere, preventing the early onset of sea breeze.

Normally, the onset of sea breeze happens about noon in August. But, this year it happened as late as 7 p.m. on a couple of days.

``On August 22, there was no onset of the sea breeze at all in the city,'' a meteorologist points out.

Also, the variation in the degree of solar radiation is not very huge between May and August. But, cloud covers normally develop over the city in August, lessening the degree of radiation. This time, it has not happened.

Lull in monsoon

Another aspect is that Chennai and other parts of the State usually experience rain in August when there is a lull in the southwest monsoon in the rest of the country. But, this year, the rainfall began in most parts of the country only from late July.

Since June 1, Nungambakkam has recorded 94 mm rain, a shortfall of 141 mm, and Meenambakkam received 148 mm, a deficit of 134 mm.

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