The India Meteorological Department (IMD) said on Sunday that the arrival of the southwest monsoon in Kerala will be delayed by at least a week beyond the normal of June 1. However, a top official said while this could lead to reduced rainfall in June, it would not affect the overall quantum of rains across the country.
This widely diverges from a forecast earlier this week by Noida-based forecaster Skymet, that the monsoon would set in over Kerala between May 28 and 31.
“The statistical model forecast suggests that the monsoon onset over Kerala in this year is likely to be slightly delayed. The southwest monsoon is likely to set in over Kerala on June 7,” the IMD said in a press statement. The IMD’s model has an inbuilt error of four days which means the monsoon rains could set in as early as the June 3 or as late as June 11.
Crucial for kharif
June accounts for only 18 to 20 per cent of the monsoon rains but it marks the beginning of the kharif sowing season. July and August account for about two-thirds of monsoons and are critical for a good harvest. According to the IMD, there is no correlation between the quantum of monsoon rains in June and July or the date of onset and the performance of the monsoon. Last year, the monsoon arrived at the Kerala coast on June 5, later than the agency’s predicted date of May 30. This was the only time, the IMD claims, its monsoon onset model failed to get the date within the model’s error margin since it began issuing such forecasts in 2005.
According to the IMD’s press statement, the monsoon is expected to set in at the Nicobar islands around May 17, and set in substantially over the Andamans by May 20. It’s the timing of its subsequent journey into Kerala that’s in doubt.
Exceeding April forecast
Delay notwithstanding, monsoon rains could be better than what the IMD forecast in April. Madhavan Rajeevan, Secretary, Ministry of Earth Sciences and Ocean Development, said there were “better chances” of heavy rains in August and September than the agency’s initial estimate. “The cooling of the Pacific waters has been better than expected and we expect the La Nina to set in slightly earlier around the second half of monsoon,” he told The Hindu .
The IMD is expected to announce a crucial update — specifying how the monsoon will distribute across the country between July and August and how much rain is expected in July — in the first week of June.
The delay in onset over Kerala is because of the El Nino, which, though waning, is still strong, and the waters of the Indian Ocean being warmer than usual for this time of the year. Generally rain-bearing winds begin to be drawn across the equator by this time of the year.
Remnants of El Nino holding up monsoon
The El Nino refers to a cyclical warming of the Central and Eastern Equatorial Pacific that frequently corresponds to a drought in India. The La Nina is the converse of the El Nino and brings good rains over the subcontinent.
Generally rain bearing winds begin to be drawn across the equator by this time of the year. These so-called cross equatorial flows haven’t developed substantially for this time of the year and even the IMD doesn’t yet have a clear explanation for this phenomenon.
While it has been steadily raining over Andamans — a meteorological thumb-rule that the monsoon is on track —they are likely to peter out because they aren’t sufficiently fuelled by the crossequatorial flows.
“There is a lag in the seasonal transition. Usually there are cyclones in May and we haven’t seen one so far,” said D.S. Pai, Chief forecaster, IMD. “Also, different models are showing different things and we are waiting and watching.”
Pre-monsoon rains
There will be rains over Tamil Nadu and Kerala in and around June 1 but these would be pre-monsoon rains, Mr. Rajeevan added.
The IMD has an elaborate set of criteria to officially declare the monsoon’s onset over Kerala. These include at least 8 of 14 specified locations in Kerala and Karnataka receiving a minimum quantity of rains over two days, and a specific range of land temperatures and windspeeds.
‘No change in forecast’
“We are not changing our forecast,” said Mahesh Palawat of Skymet, “because our model indicates consistent rain over Kerala beginningMay 28. Also there have been instances in the past when IMD has declared monsoon even when some of their own parameters haven’t been met. It’s a subjective declaration.”
In April, the IMD had said that India's monsoon rains would be “above normal” and 106 per cent of 89 cm. This is cheerful news on the back of two consecutive years of drought in 2014 and 2015 and severe water shortage in several parts of the country. Policy makers relying on a good monsoon to bolster economic growth and consumption.
Corrections & Clarifications:
The article has been corrected for a factual error.
