India may set a new date with her monsoon

PUNE: During the regime of the new government , India may get a new set of ‘normal onset dates’ of monsoon, 60 years after they were first determined in 1943. A committee is working on re-determining the normal onset dates of monsoon as the actual arrival of monsoon is delayed by almost 15 days in central and north west India as compared to the normal dates. However,the normal date of arrival of monsoon in Kerala will remain unchanged as June 1.

The India Meteorological Department (IMD) had determined the onset dates for different cities in India in 1943 based on rainfall data from 1901 to 1940 collected from 149 stations. The normal time for the south westerly rain bearing winds to hit the mainland is June 1 in Kerala. Moving northward, it covers the entire country by July 15.

So, the current normal onset date of monsoon in Varanasi, represented by Prime Minister Narendra Modi, is June 15 while the study has suggested it to be delayed by 10 days to June 25. Onset dates are useful for the planners for agricultural operations and for management of the water resources. A late onset of monsoon can be devastating for agriculture even if the rainfall is normal.

A study carried out by six meteorologists of IMD New Delhi and IMD Pune three years ago had suggested a set of new normal onset dates for different cities in India. The new normal has been derived using rainfall data of 569 stations from 1971 to 2000. A committee is studying the recommendations of this study. A high-level source in the central government said: “The committee has not completed the revision of onset dates.

Work is till going on. There is a need to revise the onset dates as IMD is at present using the dates determined long time back. We need to revise and we will come out with the new dates very soon.” There is no change suggested in the normal onset date of June 1 for onset over the mainland at Kerala. However, there is huge difference in the current normal onset dates in central India and north west India.

“Considerable difference in the existing date and the re-determined date of monsoon has been observed over parts of south Peninsula and western parts of central and adjoining north west India where the re- determined dates are advanced by 1 to 3 days and delayed by 10 to 15 days respectively with respect to normal dates of onset of monsoon,” says the paper.

The IMD has suggested that the normal onset dates were delayed by 14 days in Jhansi, 11 days in Lucknow, 10 days in Varanasi , 12 days in Gwalior, 7 days in Kolkata and by 12 days in Jaipur. The delay in the onset of monsoon over central and north west India has been attributed to a hiatus in advance of monsoon and often these regions not receiving rainfall from the monsoon spell causing onset over Kerala. The study had called for a periodic revision of the onset dates.