Sudden rise in mercury level

CHENNAI May. 9. The city has witnessed a sudden rise in its mercury level in the last two days.

Till Tuesday, the maximum temperature at Nungambakkam did not cross even 37 degree Celsius. But, yesterday, it went up to 40.1 degree Celsius and on Thursday, the figure was 41.4 degree Celsius.

``The present condition is due to the presence of strong westerlies-northwesterlies'', according to S.K. Subramanian, Director of the Area Cyclone Warning Centre.

This has also delayed the onset of sea breeze. On Wednesday, the time of onset was 11-45 a.m., whereas it was 12-45 p.m. on Thursday.

Mentioning that there is ``nothing unusual'' about the summer heat of the city, the Director says two years ago, the maximum temperature crossed 40 degree Celsius even during April (on April 26, 2000) while this year, it touched the figure only this week.

The figures of maximum temperature registered by Nungambakkam and Meenambakkam reveal that it is during the second half of May that the two observatories record the peak. The highest of 45 degree Celsius was registered by Nungambakkam on May 21, 1910 and in the case of Meenambakkam, it was on May 22, 1980 that the observatory recorded the highest of 44.3 degree Celsius.

In the 1990s, the highest was 44 degree Celsius at Nungambakkam and 44.2 degree Celsius at Meenambakkam. This was recorded on the same day - May 30, 1998.

The trend of Chennai recording less than 40 degree Celsius in May has been occuring every fourth year since 1995. In that year, Nungambakkam registered the month's maximum temperature of 39.1 degree Celsius. One reason for this feature was that during the first week of May 1995, a deep depression lashed the city. On May 8, Nungambakkam received 12 cm rain.

In 1999, the month's maximum temperature was 39.8 degree Celsius.

However, in that year, the rainfall was not much.

During May, the normal rainfall is five cm. The record highest of 24 cm happened on May 22, 1952, followed by 15 cm on May 8, 1990.

Apart from October-December, this month is the ``second peak'' for the Bay to experience cyclonic systems.

Even this year, the city might experience a brisk shower in the early hours of Friday. ``A cloud patch is lingering over the south Andhra coast.

There are favourable conditions for it to drift towards north Tamil Nadu coast. In that eventuality, Chennai may receive rain'', the Director says.

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