Maverick monsoon? -- The MJO

A little-known weather phenomenon may hold the key to the sudden surge in showers this festive season and also the extended stay of the monsoon.

Experts blame the erratic behaviour of the monsoon on the Madden-Julian Oscillation (MJO), a fluctuation in the atmospheric pressure over the equatorial Indian Ocean and western Pacific Ocean.

MJO is named after the American atmospheric scientists Roland Madden and Paul Julian, who first documented the phenomenon in 1971.

"The mechanism and cause of MJO is still being studied. It's the most likely cause for the surge in September rainfall in the city and the rest of the state," said an independent weather analyst.

"The phenomenon is also believed to be the principal trigger for the monsoon anomaly on a national scale - flood in some states and drought in others," said Gokul Chandra Debnath, the director of Regional Meteorological Centre, Alipore.

MJO, which has no regular cycle of occurrence, comes in the form of alternating cyclonic and anticyclonic formations, which move eastward along the Equator. Originating in the Indian Ocean near East Africa and moving towards the Pacific, the MJO usually lasts between 30 and 60 days.

"It can influence rainfall by adding moisture to the system during its wet or cyclonic phase and reducing convection during its dry or anticyclonic phase," said an official from the India Meteorological Department in Pune.

Weather analysts said MJO hit the Indian Ocean during a cyclonic phase around August 24, affecting monsoon activities over the Bay of Bengal and resulting in heavy showers throughout September as well as the extended stay of rains.

According to meteorologists, the departure of the monsoon from the state - scheduled for October 7-8 - is likely to be delayed by a week

This is the latest MJO forecast for next 30 days.

And MJO suggest bad news for the entire NE monsoon.