How the Met department forecast missed it

Early predictions talked only of cloudy sky

Published - November 04, 2017 12:42 am IST - CHENNAI

For Kanthimathi Selvan, a resident of Madambakkam, the rainfall on Thursday evening was a rude surprise. “There was no alert, no warning,” she said. Like many residents of the city and surrounding areas, she wonders whether the Meteorological Department erred in not predicting the intensity of the rainfall.

A bulletin issued by the Meteorological Department on Thursday afternoon (1 p.m.) had only this much to say for Chennai in the next 24 hours. “The sky condition is likely to be generally cloudy. One or two spells of rain or thundershowers [are] likely to occur.” Up to 6 cm of rain was anticipated.

But, what the city experienced some hours later was different. S. Balachandran, Director, Area Cyclone Warning Centre of the Regional Meteorological Centre, says his department revised its forecast by 8:30 p.m. According to him, the first two spells — between 3 p.m. and 4 p.m. and 5 p.m. and 7 p.m. — were “not that heavy.” But, it was only around 7.45 p.m. that the intensity heightened.

Conceding that his department did not initially forecast the intensity of rainfall but corrected it later in the day, S.B. Thampi, Deputy Director General of Meteorology, said that on Wednesday, rainfall took place over the sea. A similar pattern was expected on Thursday. But, a part of the low pressure area touched the coastal areas. Still, all the rainfall that took place yesterday was all within 5 km of the sea. “It did not rain beyond 5 km,” he asserted, adding that normally, rain spells during the northeast monsoon are more intense during the night and early hours.

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