‘Recurving’ cyclones dried August rains


IMD had forecast bountiful rain

A strange pattern of tropical cyclones (TC) in the Western Pacific appear to be the reason for the drying up of monsoon rains in August across India.

The India Meteorological Department (IMD) had predicted normal monsoon rains in August, typically the second most bountiful monsoon month after July.

During the monsoon months, cyclones in the Western Pacific move westwards towards India and aid rain-bearing systems over the sub-continent. But during some years they ‘recurve’, or start to swing north-east, and do not give as much of a push to the rains as they do in the good monsoon years.

This re-curving frequently happens during the El Nino years but this time it inexplicably occurred when an El Nino hasn’t yet taken shape. El Nino years are those when sea surface temperatures in the east equatorial Pacific rise, and often dampen the monsoon. While several international meteorological agencies had raised concerns about a likely El Nino forming in August or September this year, it didn’t happen.

“We will need a more thorough analysis. But it looks like re-curving Western Pacific tropical cyclones may have played a role in reducing the August rainfall,” said Madhavan Rajeevan, Secretary, Ministry of Earth Sciences and a former chief forecaster with the IMD.

In April, the IMD had said that India would get 96% of the normal rainfall during July-September. In August, it updated its forecast to 98%. Since August, however, rainfall across central India and north India was much lower than expected, and as of today, monsoon rains are 6% short of what they should have been for this time of the year.

Nearly 22% of the country faces drought-like conditions. IMD Director-General KJ Ramesh said that phenomena such as unfavourable cyclone activity in the Pacific were “transient” and couldn’t be captured in early forecasts. “These are apparent, at the most, 10 days ahead, and can’t be known, say, like the El Nino, months in advance. However, the monsoon hasn’t withdrawn yet, and we expect heavy rains after September 20th,” he added.

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Printable version | Jan 20, 2020 9:29:51 AM |

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