Representational Image.Reuters

The Indian Meteorological Department (IMD) has announced that the southwest monsoon is likely to set over Kerala on 5 June.

"Conditions are favourable for the onset of southwest monsoon over Kerala and its further advance into some more parts of south Arabian sea, remaining parts of MaldivesĀ­ Comorin area, some parts of Tamil Nadu and some more parts of Bay of Bengal during next 48 hours," IMD said in its weather bulletin.

The IMD also stated that the "conditions are also favourable for advance of southwest monsoon into some parts of northeastern state during the next 72 hours."

Last month, the department had announced that the monsoon will hit Kerala on 5 June with a model of error of +/- four days. It also mentioned that the normal date of onset of monsoon over Kerala is 1 June. However, since 2005 till 2013, the monsoon has set over Kerala only once on 1 June. During other years, the arrival of the monsoon has been delayed or advanced by a few days.

Year Actual Onset Date Forecast Onset Date
2005 7 June 10 June
2006 26 May 30 May
2007 28 May 24 May
2008 31 May 29 May
2009 23 May 26 May
2010 31 May 30 May
2011 29 May 31 May
2012 5 June 1 June
2013 1 June 3 June

The weather department has been issuing operational forecasts for the date of monsoon onset over Kerala using a statistical model which uses six indicators - minimum temperature over North-west India, pre-monsoon rainfall peak over south Peninsula, outgoing long wave radiation (OLR) over south China Sea, lower tropospheric zonal wind over southeast Indian ocean, upper tropospheric zonal wind over the east equatorial Indian Ocean and outgoing long wave radiation (OLR) over south-west Pacific region.

The onset of southwest monsoon over Kerala indicates the beginning of the rainy season in India. The monsoon is the main source of irrigation for India's 235 million farmers and agriculture represents about 14 percent of the Indian economy, according to Bloomberg.

In the recent times, there have been concerns about the impact of El Nino (an abnormal warming of sea surface temperatures in the eastern tropical Pacific) on the Indian monsoon. El Nino, a weather condition, can create adverse impacts such as floods and droughts in different parts of the world. The IMD has projected a 60 percent probability of El Nino this year and also forecast below-normal rainfall. This has sparked fears that EL Nino might trigger drought-like conditions this year in India.

Below-normal rainfall might cause trouble to agriculture, as its fate is determined by the monsoon rains. The IMD's first forecast had given 33 percent probability to "below normal" monsoon (90-96 percent of Long Period Average) and 35 percent chances of "normal" monsoon (96-104 percent of LPA). The forecast has also mentioned a 23 percent chance of a drought, reported Financial Express.

The Met department will be issuing another forecast later in June. It will be more definitive as the forecast will be given after the onset of the southwest monsoon.