Weather forecast to feature monsoon phases

P. Sunderarajan

The India Meteorological Department is set to introduce an additional feature to its forecasts during monsoon.

Shailesh Nayak, Secretary, Ministry of Earth Sciences, said here on Tuesday that from this year, farmers would also get forecasts of active and break phases of monsoon 10-15 days in advance.

Till now, the Department has been issuing forecasts for five days and an outlook for the next two days. From this year’s monsoon, it will issue forecasts for one week and an outlook for the next. Notes on the possibilities of changes in the monsoon activity — from the active phase to the break phase or from the break phase to the active phase would be part of these advisories.

Scientists of the Meteorological Department have been working on forecasts on the active and break phases for the past three years. The forecasts would primarily be based on Madden Julian Oscillation. This phenomenon is an equatorial travelling pattern of anomalous rainfall that is planetary in scale. It is characterised by an eastward progression of large regions of both enhanced and suppressed tropical rainfall, observed mainly over the Indian and Pacific Oceans.

The anomalous rainfall is usually first evident over the western Indian Ocean and remains evident as it spreads over the very warm ocean waters of the western and central tropical Pacific. This pattern of tropical rainfall generally becomes nondescript as it moves over the cooler ocean waters of the eastern Pacific, but reappears over the tropical Atlantic and Indian Oceans. The wet phase of enhanced convection and precipitation is followed by a dry phase, in which thunderstorm activity is suppressed. Each cycle lasts 30 to 60 days.

Speaking at a plenary session of the 97th Indian Science Congress, Dr. Nayak disclosed that recent studies indicated that the level of the Indian Ocean had risen by 9 mm between 2004 and 2009. Describing it as “not an unusual phenomenon” since a raise of 3 mm a year was observed in the Pacific and Atlantic Oceans between 1993 and 2003, he said it could be due to several reasons, including the 2004 tsunami.