This foreshadow needs to be taken cautiously because we are right now in the phase of 'spring predictability barrier'. And outlooks do change when the Summer sets in. April outlooks are the most accurate. But with this, the following can be concluded:
This year's Monsoon will most probably not experience a La-Nina year (this phenomena correlates well with excess rainfall). Therefore, there is a lesser chance of excess rain. The chances of below normal rainfall are slightly higher than normal as of now.
In the last decade, 2002, 2004 and 2009 were drought years due to emergence of EL-Nino these years. Monsoon rain was -22% under the normal in 2002, while in 2004, it was -17% under the normal. In 2009, during which India faced one of the biggest droughts in recent years, monsoon rain was -27% under the normal. The year 2012 was also a El-Nino year which witnessed -7% rainfall under the normal.
El-Nino is a phenomenon which emerges after a gap of every 3 to 7 years and affects rainfall in India during monsoon. Due to more heating, warm waters off Western coast of South America increase the sea surface temperatures above normal by 0.5oC.
This process leads to diversion of flow of moist winds from the Indian Ocean towards the western coast of South America, thus reducing the amount of rainfall in Indian sub-continent during the year of its emergence.
During La-Nina, which is just the opposite of El-Nino, less heating leads to colder sea waters off Western South America coast, thus making it a high pressure zone which pushes the moist sea winds towards Indian Ocean therefore increasing chances of normal or excessive rainfall in the Indian sub-continent.