Monsoon arrives in Kerala, good rainfall distribution this year: IMD

Kerala has been reporting continuous heavy rainfall over the last three days, mainly associated with the depression that has formed over the southeast Arabian Sea, off Kerala coast. Some locations in Kozhikode and Thiruvananthapuram districts, here, recorded rainfall close to 90mm till 8.30 am on Monday.

IMD declares onset of the monsoon onset over Kerala when the rainfall recorded over 14 stations – Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu and Mangalore is 2.5mm or more for two or more consecutive days. Besides, IMD also factors-in desired criteria including depth acquired by the westerly winds, the values of Outgoing Longwave Radiation (OLR) for the monsoon onset.

Onset dates over Kerala 2010 – 2020:

Source: IMD

The country is expected to receive normal rainfall during June to September season this year, with the season’s rainfall expected to be 102 per cent of the Long Period Average (LPA), said M Rajeevan, Secretary, Ministry of Earth Sciences (MoES). He made the announcement during the release of the second stage Long Range Forecast (LRF) prepared by India Meteorological Department (IMD) on Monday.

Between the June-September months, the rainfall recorded over the country is 88 cm calculated for the period 1961-2010.

“There will be good rainfall distribution over all the homogeneous regions of the country. We expect normal rainfall this season, with a model error of +/- 4 per cent,” said Rajeevan.

Dr. Rajeevan further added that IMD expects a “good spatial distribution’’ of rainfall across the country. The northwest region in India is expected to receive 107 per cent LPA, the central region 103 per cent, the Southern Peninsula 102 per cent and the North-Eastern region (which also includes states like West Bengal and Jharkhand) will receive slightly less rainfall than the rest of the country of 96 per cent LPA.

The Southwest monsoon which hit Kerala on Monday, has already covered most past of the southern State on the day of its onset, said Mrutyunjay Mohapatra, Director General, IMD.

On rainfall distribution over the country during the season ahead, Mohapatra said, “Except for the Northeast, rainfall over remaining parts of the country would be either normal or above normal. Since a few years, rainfall over the Northeast has shown a declining trend, which is expected even this year.”

Accordingly, the rainfall forecast over the four homogeneous regions this season is – Northwest India – 107 per cent of LPA ; Central India – 103 per cent of LPA ; South Peninsular India – 102 per cent of LPA and Northeast India – 96 per cent of the LPA.

According to the senior Met officials, a weak La Nina is likely to develop during the latter half of the season. La Nina is the abnormal cooling of the equatorial and east-central Pacific Ocean. La Nina is good for the Indian monsoon, experts said.

Yet another atmospheric factor that influences the monsoon, the Indian Ocean Dipole (IOD), will remain neutral during the entire monsoon season, the LRF said.

“Many atmospheric variables over the region indicate ENSO (El Nino) neutral to cool ENSO neutral conditions over the region. The latest forecasts from MMCFS and other global models, as well as our own, together indicate cool ENSO neutral conditions are likely to prevail during most part of the monsoon season. However, a few other climate models indicate the possibility of development of weak La Nina conditions in the latter part of the season or thereafter. These also create favourable conditions for a good monsoon,’’ said DG IMD Dr. Mohapatra.

The rainfall during July and August stand crucial for the country, as it is the time for major Kharif season cultivation. 70 per cent of the season’s rainfall is recorded during July and August.

“In July, which is a crucial month for farmers, we expect an LPA of 103 per cent across the country, which dips slightly to 97 per cent in August, which is a little less than normal. According to our data, we have a high probability of a normal monsoon at 41 per cent, while the chances of a deficient monsoon are low at 5 per cent. Our data shows that this will be a good monsoon year for us. The chances of an above-normal monsoon are 25 per cent and excess rainfall monsoon is 14 per cent,’’ Rajeevan added.

This year, rainfall in July is projected to be 103 per cent of the LPA whereas rainfall during August is expected to be 97 per cent of the LPA, the second-stage LRF stated.

(Inputs from ENS)