Thiruvananthapuram, May 31 (IANS): Kerala witnessed showers Friday. The first showers here at the end of May signal that it is time for the onset of the southwest monsoon, which the IMD forecast Friday could arrive in the state in three to four days.

The director of the India Meterological Department (IMD) here, K. Santhosh, told IANS that conditions for the onset of the monsoon are now favourable.

"This is all I can say now, as the analysis is going on," Santhosh said.

The southwest monsoon normally sets in over Kerala around June 1, and advances northwards, usually in surges, covering the entire country by mid-July.

From 2005 onwards, the IMD has been issuing operational forecasts for the monsoon's onset over Kerala using an indigenously developed statistical model with a model error of four days.

The forecasts of the monsoon in the past eight years - 2005 to 2012 - have been on the dot.

In 2012, the monsoon arrived June 5; in 2005, it arrived only on June 7; in 2009, it came rather early, on May 23.

According to guidelines laid down for the purpose, the monsoon's onset is declared depending on certain weather conditions, including an analysis of the situation as read from 14 different weather stations in the Lakshadweep, Kerala and Mangalore.

IMD officials monitor the rain starting May 10. If 60 percent of the stations or more record 2.5 mm of rain for two continuous days, then criteria for declaring that the monsoon has arrived are said to have been met. Wind strength is also measured as part of this exercise.

The IMD has forecast a normal monsoon this year.