Our Bureau
NEW DELHI, May 25
CONFOUNDING the doomsayers, the India Meteorological Department (IMD) has forecast a `normal' South-West monsoon for 2000, making it the 13th consecutive year since 1988 in which India would be receiving normal-to-excess rainfall during the four month period from June to September.
As per the IMD's long-range forecast released here today, the total rainfall for the country as a whole in the coming monsoon season would be 99 per cent of its long-period average (LPA), rendering it `normal' in overall terms.
A monsoon is considered `normal' if the total rainfall over the June-September period ranges between 90 per cent and 110 per cent of the LPA. The latter, in turn, is taken to be the average historical rainfall received by the country for the period 1901-70, amounting to 88 cm.
Thus, while rainfall of over 96.8 cm (110 per cent of LPA) is tantamount to an `excess' monsoon, any figure below 79.2 cm (90 per cent of LPA) is deemed to be `deficient'. A 99 per cent of LPA forecast being made this time round would, therefore, translate into a country-wide average rainfall of above 87 cm. This is slightly below the LPA of 88 cm, but it is nevertheless `normal'.
In fact, going by the IMD's forecast, this year's monsoon is going to be better than that of last year, which saw an overall average precipitation of 96 per cent of the LPA (see Table). Of course, forecasts can go awry, as it happened last time, when the IMD predicted a rainfall level of 108 per cent of LPA, which turned out to be only 96 per cent.
The IMD's own forecasting model has an estimated prediction error range of plus or minus four per cent, which was widely transgressed last year, forcing the department to rework some of model parameters this time round.
The IMD Director-General, Dr. R.R. Kelkar, told presspersons that the S-W monsoon would hit the Kerala coast around its normal date of June 1. So far, the progress has been as per schedule, with the monsoon arriving over the south Andaman Sea on the usual date of May 15 and maintaining its further advance over the Bay of Bengal and the north Andaman Sea. Further, there has been good pre-monsoon rainfall activity over the North-Eastern region, which is likely to continue.
In the normal course, the monsoon would cover the entire southern, eastern and north-eastern States, apart from Maharashtra and parts of Madhya Pradesh, by June 10. It would advance to Gujarat around June 15 and to the rest of central India and Uttar Pradesh by June 20. The northern States, including Delhi, would receive their first monsoon showers towards the month-end. While the Kutch and eastern Rajasthan regions have to wait till the first week of July, the due date is as late as July 15 for the severely drought-prone Western Rajasthan.
Dr. Kelkar admitted that while forecasting monsoon trends for the country as a whole was a relatively simpler affair, its actual spatial and temporal progress was virtually impossible to predict. Thus, in 1991, the monsoon hit Kerala around its normal time, whereas it could arrive in Delhi only by July 14, as against the scheduled date of June 29.
``Once the monsoon arrives, its further progress depends on a host of short-term fluctuating factors, which makes it difficult to come out with precise forecasts for each State or region'', he added.
At the same time, the IMD has released specific forecasts of monsoon rainfall for the country's three broadly homogeneous meteorological regions, comprising Peninsular India (the southern States plus Gujarat, Maharashtra and MP), North-West India (J&K, Himachal Pradesh, Punjab, Haryana, UP, Rajasthan and Delhi) and North-East India (West Bengal, Orissa, Bihar, Andamans and the north-eastern States).
As per these forecasts, the monsoon rainfall will be 98 per cent of the LPA for the Peninsula, while being 102 per cent and 100 per cent of the LPA over the North-West and North-East regions respectively.