NEW DELHI: The numbers say it all. In one week (August 8-15), Kerala received more than 3.5 times its normal rainfall. Then, on August 16, the state was pounded with 137mm of rain, more than 10 times the normal for the day. There was hardly any let up on Friday either, with the state getting more than five times its normal rain.

While the Met department records show 2.7 times higher rainfall in Kerala in August so far, the severe weather really began on August 8. It has been unrelenting since then. The cumulative effect of the last nine days' rainfall has left the state battered, leading to floods that are being described as possibly the worst in a century.

What caused the deluge are weather conditions that developed far away from the state - on India's east coast. "Two low pressure systems formed on the Bay of Bengal, close to Odisha. The first one developed on August 7, and the second, which went on to become a depression, happened on August 13," said M Mohapatra, head of services at India Meteorological Department.

Low pressure systems over Bay of Bengal, a normal occurrence during this season, attract winds from the high pressure regions over south Indian Ocean.

From exactly where the winds are sucked in depends on the strength and position of low pressure systems. "The location of both systems was such that high-speed monsoon winds rushed into Kerala and hit the Western Ghats, causing heavy rains in the region," Mohapatra said. Just how much rain the systems brought in can be gauged from districtwise statistics.

The rainfall in six out of the state's 14 districts was more than 10 times the normal on Thursday. That day, Idukki, one of the worst-hit districts, was battered with 266mm of rain, more than 13 times the normal for the day.

To put that in perspective, if Thursday's rain over just 1sq km area was to be poured over a football field, it would create a pool nearly 10 storeys (38 metres) high. "The impact of the low-pressure systems is now wearing off. Rainfall over Kerala should decrease tomorrow, although some areas are still likely to get heavy showers. By Saturday, there is likely to be a further decrease in rain activity," Mohapatra said.

