IMD scales down its forecast for monsoon

The South-west monsoon season this year may not be as bountiful as was expected earlier.

The India Meteorological Department on June 21  announced that latest analysis showed that rainfall during the four month season would be only 95 per cent of the long period average [LPA] subject to a model error of plus or minus four per cent.

In its earlier forecast made on April 19, the IMD had predicted a rainfall of 98 per cent of the LPA subject to a model error of plus or minus five per cent.

The IMD also announced that the rainfall during July and August could be well below normal this year. According to the Department, rainfall during July is likely to be 93 per cent of the LPA for that month, and that for August 94 per cent of the LPA for that month.

(These estimates are subject to a model error of plus or minus nine per cent).

Asked specifically about rains during July, which is crucial for the agricultural sector, IMD Director General, Ajit Tyagi, said the system was likely to be weak during the first half of the month and pick up later.

Stressing that strong and weak phases were a common feature of monsoon, he pointed out that the system had remained robust ever since its onset over Kerala on May 29.

``The system is expected to remain robust and cover most parts of the country except for a small area in the extreme north-west region by the end of this month, before entering into a weak phase''.

On onset over Delhi, he said, indications were that it would set in over the capital around the normal date of June 29.

The IMD also announced that the overall rainfall is likely to be the worst in the southern peninsular region this year. It is likely to get a rainfall of only about 94 per cent of its LPA for the season as a whole. [The region is composed of Kerala, Karnataka, Andhra Pradesh, Tamil Nadu, Pondicherry, Lakshadweep and Andaman and Nicobar islands]

In contrast, the north-west region, which is likely to top the table, is forecast to get a rainfall of 97 per cent of its LPA for the season. [The region consists of Delhi, Haryana, Punjab, Chandigarh, Uttar Pradesh, Uttaranchal, Himachal Pradesh, Jammu and Kashmir and Rajasthan].

The north-east and the Central India regions are likely to fall in between, with a rainfall of 95 per cent of their LPA for the season. [While the north-east region consists of Bihar, Jharkhand, West Bengal and Sikkim besides the seven north-eastern States, Central India region consists of Gujarat, Maharashtra, Madhya Pradesh, Orissa, Goa and Chattisgarh].

Releasing the new forecasts, Union Science and Technology, Pawan Kumar Bansal, stressed that there was no need for any panic.

``There is no doubt a scaling down of the estimates. But, a rainfall of 95 per cent [for the country as a whole and for the season in its entirety] will not be that bad. It will be just below normal. There is absolutely no cause for panic''.

Senior IMD officials said the forecast has been scaled down as some of the parameters for which data became available after the last forecast were found to be not favourable.

In all, six predictors are used for the forecast: north-Atlantic sea surface temperature in December and January, equatorial south east Indian Ocean sea surface temperature in February and March, east Asia mean sea level pressure again in February and March, central Pacific sea surface temperature tendency from March to May, the north Atlantic mean sea level pressure in May and north central Pacific zonal wind in May.

In other words the data for the last three predictors are available only between March and May. Out of the three, the data for the central Pacific sea surface temperature tendency and the north Atlantic mean sea level pressure were found to be unfavourable to the monsoon this year.

The data for the first three predictors, which went into the making of the earlier forecast, on the contrary, were either favourable or neutral.