TRACKING THE RAINS

88.11cm The total rainfall that India is likely to get between June and September this year. That’s 99 per cent of the average annual rainfall.

88.11cm The total rainfall that India is likely to get between June and September this year. That’s 99 per cent of the average annual rainfall.

Monsoon? Isn’t that just rain?
In general, monsoon refers to any wind pattern that reverses its direction seasonally. In India, this refers to the moisture-laden winds traveling southwest from the Arabian Sea that cause a huge amount of rain over most of the country. At India’s southernmost point, it gets split and travels over the Bay of Bengal towards the northeastern states.

Why is it important?
India receives more than 80 per cent of its rains during this four-month monsoon period. With an overwhelming proportion of India’s population still dependent on agriculture, and over 60 per cent of cultivable area dependent on rains for irrigation, it is not difficult to see why monsoons are so important. It’s not just extremely vital for a good agricultural produce but also one of the most important factors in economic planning of the government. Additionally, it offers people welcome relief from the extreme heat prevailing in the northern and peninsular parts of the country.

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The calendar
The monsoon season is from June to September. Typically, the monsoon winds reach the Kerala coast on June 1 and then travel upwards causing heavy rains along India’s western coast. It reaches Delhi around the first week of July.

Average rainfall during this season:
89 cm (This is the average of annual rainfall from the period 1941 to 1990, and referred to as Long Period Average of LPA).

Forecast schedule
IMD makes a seasonal forecast of the monsoon rainfall in the middle of April every year and updates its prediction in June. The April forecast gives only an overall prediction while the one in June also gives the expected regional distribution. These forecasts are observed with keen interest by the government as well as industry as a good monsoon generally drives consumption patterns and leads to healthy growth.

Parameters for April prediction
North Atlantic sea surface temperature in December and January
Equatorial South Indian Ocean sea surface temperature in February and March
East Asia mean sea level pressure in February and March
North West Europe land surface air temperature in January
Equatorial Pacific warm water volume in February and March

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Parameters for June prediction
North Atlantic sea surface temperature in December and January
Equatorial South Indian Ocean sea surface temperature in February and March
East Asia mean sea level pressure in February and March
Central Pacific (Nino 3.4 region) sea surface temperature tendency for judging El Nino or La Nina factor
N Atlantic mean sea level pressure in May
North Central Pacific wind at 1.5 km above sea level in May