Southwest Monsoon hits Kerala; Met dept's region-wise forecast today

The Met also says that there is 71 per cent probability of the rains being normal to excess while just 29 per cent probability of it being below normal to deficient

The southwest monsoon has arrived over Kerala, marking the start of a four-month long rainfall season, said the India Meteorological Department (IMD) said on Monday.

The four-month monsoon season from June to September accounts for 75 per cent of rainfall in the country.

Private forecaster, Skymet Weather on May 30 had declared arrival of monsoon, but the IMD had differed, saying conditions were not ripe then for such an announcement.

IMD will on Monday release the second stage forecast for the 2020 monsoon season, which will detail the region-wise forecast and also how the rains will perform in the four months of June, July, August and September. "The southwest monsoon has set in over Kerala today, 1 June 2020,” the IMD said in a statement.

The IMD, in its first stage forecast for 2020 released in April, had said that rain this year is expected to be ‘normal’ at 100 per cent of the Long Period Average (LPA).

The LPA of the season rainfall over the country as a whole for the period 1961-2010 is 88 cm.

The Met also said that there is 71 per cent probability of the rains being normal to excess while just 29 per cent probability of it being below normal to deficient.

Not only this, the dreaded El Nino phenomenon which is known to negatively impact the performance of the southwest monsoon is not only expected to remain ‘neutral’ during the four-month monsoon season that starts from June but according to some forecasting models might as well turn into a La Nina during the latter half of the four-month season.

The El Nino is defined as an increase of Eastern Tropical Pacific's sea surface temperature (SST) of 0.5 degree centigrade from long term average while its reverse La Nina is defined as a decrease of SST over the same area by -0.5-degree C from long term average.

El Nino plays a big role in the performance of India’s southwest monsoon season that runs from June to September as data studied by private weather forecasting agency Skymet shows that in the last 135 years starting from 1880 to 2014, about 90 per cent of all evolving El Nino years have led to below normal rainfall, while 65 per cent of evolving El Nino years have brought droughts.

If that’s not all, the Indian Ocean Dipole (IOD), another factor which has a bearing on the performance of south-west monsoon in India is expected to remain neutral during most of the forecasted period.