The onset of monsoon over Kerala is likely to take place around June 3, India Meteorological Department (IMD) said on Monday, adding that monsoon presently was crossing Sri Lanka and had been there for two days.
As per the latest meteorological indications, the southwesterly winds could strengthen gradually from June 1, resulting in an increase in rainfall over Kerala.
“It has been raining over Kerala but we cannot announce monsoon onset until all parameters are met. They are likely to be met in the next couple of days. We are monitoring continuously,” M Mohapatra, director general, IMD said.
“Monsoon is now over Sri Lanka. The very next point will be Kerala. Rains had reduced over Kerala in the past two days. Westerly winds are picking up now,” added DS Pai, scientist and head of climate research services at IMD Pune.
“@Indiametdept will never manipulate data or make statements to justify their forecasts. They admit forecast failures with humility. In weather & monsoon forecasts, no one can be perfect. We are also accountable to Indian tax payers. We show respect to our country,” M Rajeevan, secretary, ministry of earth sciences tweeted on Monday referring to the lag in monsoon onset compared to IMD’s forecast.
IMD said on May 28 that the onset of monsoon was likely over Kerala on June 31, a day ahead of its normal date. IMD in its monsoon forecast on May 14 also predicted that monsoon is likely to arrive over Kerala on May 31 with a possible error margin of plus/minus four days.
After Very Severe Cyclone Yaas weakened, scientists had said that the cyclone over Bay of Bengal had helped strengthen monsoon winds. But the monsoon’s progress slowed from May 29.
“Probably we need to consider exceptional cases when cyclones occur very close to the monsoon onset, interacting with the monsoon? In such cases, a classical onset may not happen as we expect,” tweeted Roxy Mathew Koll, climate scientist, Indian Institute of Tropical Meteorology.
According to IMD’s monsoon onset parameters, after May 10, 60% of the available 14 stations enlisted–Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu and Mangalore should report rainfall of 2.5mm or more for two consecutive days, depth of westerlies should be maintained upto 600hPa; outgoing longwave radiation (OLR) value should be below 200wm-2 ( watt per sq metre).
OLR represents the total radiation going to space emitted by the atmosphere or extent of cloudiness.
Southwest monsoon normally sets in over Kerala around June 1. It advances northwards, usually in surges, and covers the entire country around July 5.
Skymet Weather, a private weather forecasting company, however, announced the onset of monsoon on Sunday–May 30, two days ahead of normal monsoon onset date of June 1.
A cyclonic circulation over eastcentral Arabian Sea off the Karnataka coast is likely to meander over the region during the next four days. Southwesterly winds are also likely to strengthen during the next 2-3 days. Under the influence of these and other favourable meteorological conditions; scattered to fairly widespread rainfall/thunderstorm activity is likely over Karnataka and Kerala and Mahe, and isolated to scattered rainfall/thunderstorm over remaining parts of south peninsular India during the next 4-5 days.
Moderate to extremely heavy rain was recorded over many parts of east and northeast India including East Garo Hills (32cm); Bhalukpong (13cm); Lakhimpur (11cm); Jamshedpur (17cm); Pollur, Tikrikilla, Dhemaji, Kolar (9cm); Barpeta (8cm); Uthiramerur, Dharamsthla, Vellore, Matheran, Shanti Niketan, Itanagar, Cherrapunji, Kokrajhar, Nongstoin (7cm) each.
Extremely heavy rainfall (over 20cm) was recorded at isolated places over Assam and Meghalaya; heavy to very heavy rainfall at isolated places over Jharkhand and Arunachal Pradesh and heavy rainfall over Gangetic West Bengal, north Konkan, coastal and south Interior Karnataka, Tamil Nadu, Puducherry and Karaikal.
A western disturbance, as a trough in mid and upper tropospheric westerlies, is affecting the Western Himalayas. There is lower level moisture incursion from north Arabian Sea to the plains of northwest India and is very likely to continue during next 3-4 days. Under its influence, no significant change in maximum temperatures is likely during next 3 days. Scattered rainfall/thunderstorm activity is likely over the Western Himalayan region and adjoining plains of northwest India during next three days.