Three important oceanic parameters El Nino Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Madden Julian Oscillation (MJO) get aligned for the first time in this season. Together, the trio has enhanced the monsoon activity to go vigorous over the east and central parts of the country. This breaks the jinx of August which was constantly scoring below normal rains between 01st and 17th August. Surplus rainfall has been recorded for 4 consecutive days and possibly more in the offing for another couple of days.
ENSO: The ENSO phenomenon contributes significantly to seasonal climatic fluctuations in many regions of the globe. Indian Summer Monsoon Rainfall (ISMR) displays an effective correlation with the East Pacific Ocean thermal conditions. In the last 4 weeks, Sea Surface Temperatures( SST’s) have been mostly near or below average across most East-Central Pacific Ocean, especially in the Nino 3.4 region.
ENSO remains neutral and La Nina component indicates a spike towards the fall of the year. El Nino probability continues to be minimal (<10% ) till the end of the year. ENSO maintains a favorable phase for enhancing monsoon activity during the remaining period of the season.
IOD: The IOD is defined by the difference in SST’s between the eastern and western Indian Ocean. A -ve phase is known to corrupt the monsoon rains, while the +ve one supports wetter than normal season. Since the inception of the Monsoon season 2021, the IOD index has generally been below the -ve threshold (-0.4°C) since mid-May. First time in this season, the has risen to fall within the threshold of normal (+/- 0.4°C). The latest weekly value of the Indian Ocean Dipole to 15thAug was -0.37°C. It is likely to retain this status.
MJO: A well-defined MJO nearly completed a circumnavigation of the global tropics since early July. Presently, MJO continues to sail in the favorable phase 2&3 and is expected to last till the end of August. It is expected to support the monsoon systems over the Bay of Bengal and escalate the rainfall activity. It is likely to shift to Maritime Continent in phase 4&5 during 1st week of September.
MJO is a transitory pulse of rain and clouds and may not visit the Indian Ocean again during the monsoon period. However, subject to ENSO and IOD remaining in sync, September can make a decent beginning to wipe out the scar of August.