IMD scales down monsoon forecast

Monsoon clouds gather over Vallangy near Palakkad on Friday. Monsoon will be normal this year but with less heavier rains, the weather office said on Friday. Photo: K.K. Mustafah

The India Meteorological Department has revised its estimate for rainfall during the current south-west monsoon to 96 per cent of the long period average (LPA) from 99 per cent predicted in April.

Releasing the new forecast on Friday, Minister of State for Science and Technology Ashwani Kumar stressed there was no need for alarm since the new estimate too put the monsoon in the normal category.

The new outlook is based on the fresh data that have come in since April for various parameters considered for the long-range forecast.

In keeping with its annual routine, the IMD also issued rain forecasts for July and August: the rain would likely be normal, at 98 per cent in July and 96 per cent in August.

Asked about reports that there was a possibility of El Nino adversely affecting the monsoon in August-September, D.S. Pai, Director of the Pune-based National Climate Centre and lead forecaster, said there was a “substantial” possibility — 36 per cent — of an El Nino condition emerging in August. But it was likely to be weak and, if at all, might have an adverse effect on rains at the tail end of the season, in September.

Furthermore, the IMD issued season-wide forecasts for different homogenous regions.

The north-east region, comprising West Bengal, Bihar, Jharkhand, Assam and other north-eastern States, is estimated to benefit the most this year with a rainfall of 99 per cent of the LPA.

In contrast, the north-west region is expected to be at the bottom of the table with a rainfall of 93 per cent of the LPA. This region is composed of Delhi, Haryana, Punjab, Chandigarh, Uttar Pradesh, Uttaranchal, Jammu and Kashmir, Himachal Pradesh and Rajasthan.

The southern peninsular region — of Tamil Nadu, Andhra Pradesh, Karnataka, Kerala, Puducherry, Lakshadweep and the Andaman and Nicobar Islands — and central India, comprising Maharashtra, Gujarat, Goa, Orissa, Madhya Pradesh and Chhattisgarh, are likely to come in between, with rainfalls of 95 per cent and 96 per cent.

All the forecasts come with riders, to account for any error in the models. The forecast for the all-India seasonal rainfall comes with a margin of error of plus or minus four per cent, while the estimate for July and August has a margin of error of plus or minus nine per cent. The forecast for the region-wise rainfall has a margin of error of plus or minus eight per cent.