MJO, Madden Julian Oscillation is always surrounded with an aura among the weather bloggers and for that matter many professionally trained meteorologists across the globe for being the King among all tropical waves. When one goes through the rainfall patterns during Northeast Monsoon over the years it has always been linked with how MJO has behaved during the months of October to December. Two consecutive years 2015 & 2016 that sit on two extreme sides of the rainfall scale is classic example of how NEM is linked with MJO behavior.
Thiruvalluvar wrote கெடுப்பதூஉம் கெட்டார்க்குச் சார்வாய்மற் றாங்கே எடுப்பதூஉம் எல்லாம் மழை on how important rains are but it may not be very untrue if the same is rewritten as “கெடுப்பதூஉம் கெட்டார்க்குச் சார்வாய்மற் றாங்கே எடுப்பதூஉம் எல்லாம் MJO”
MJO is now seen over the African Continent & a quick analysis shows the prevailing amplitude is one of the strongest in recent times to be seen over this part of the Globe during the preceding months of Southwest Monsoon. After 2008 we are seeing one of the strongest signals of MJO travelling through African Continent during the month of April / May and is likely to move into Indian Ocean without much of drop in intensity over the next few days. With ITCZ straddling the equator the arrival of MJO over Indian Ocean in a few days time will drag the ITCZ further across the Equator enhancing the rainfall prospects over Indian Sub Continent.
The light rains today morning in a few places along the coast of Tamil Nadu is an indicator of how crucial the location of ITCZ is in rainfall prospects. Despite being the early days of May & Easterlies not bringing active moisture like NEM days still many places got light to moderate rains on the back of ITCZ being close to Equator.
As the Easterlies push moisture into interior areas and along the Western Ghats it is likely to trigger convective thunderstorms today over many places of South TN today. Few places along the Ghats may see moderate to intense spell of rains at times during late afternoon / evening today. There is a slight chance for coastal places like Chennai to catch a spell or two of light rains during the night / morning hours, while some places to the west of Chennai may catch a burst of thunderstorm activity during afternoon hours.