Maritime meteorological conditions in the Pacific Ocean and Indian Ocean have large influence on Indian Monsoon. ENSO and IOD mostly remained out of phase with each other during the core monsoon months of July and August, more so in the latter month. MJO also pushed the surge of cloud and rains to arrest the seasonal deficiency during last 7days.
ENSO: ENSO neutral conditions are present. Equatorial sea surface temperatures (SST’s) are near to below average across most of the Pacific Ocean. ENSO neutral conditions are likely for the month of September. Conditions are building up for emergence of La Nina towards fall of year and winter months. La Nina watch has already been announced by the ENSO alert system.
Nino 3.4 index is considered as a principal measure for monitoring , assessing and predicting ENSO. La Nina is characterized by a negative ONI less than or equal to -0.5°C. The seasonal projection suggest La Nina episode to continue well in to next year.
Historically speaking, El Nino and La Nina events develop during the period April-June and they tend to reach their maximum strength during October- February. Typically, these episodes persist for 9-12 months, though occasionally last up to 2 years.
IOD: IOD ( Indian Ocean Dipole) is also termed as Dipole Mode Index (DMI). Intensity of DMI is represented by anomalous SST gradient between Western Equatorial Indian Ocean and Southeastern Equatorial Indian Ocean. When DMI is +ve, then the phenomenon is named as +ve IOD event and similarly for the -ve episode. IOD is a coupled ocean-atmosphere phenomenon and is linked with the performance of monsoon season. The month of August started with -ve IOD, but now it has consistently shifted within the threshold of neutral bounds ( +/- 0.4°C).
IOD is expected to remain neutral in the month of September and therefore helpful for enhancing monsoon rains over the country. Persistent -ve IOD during the core monsoon month July, lasting till 3rd week of August has corrupted the seasonal rains leading to large deficiency.
MJO: Madden Julian Oscillation is a transitory oceanic factor circumventing the globe in the equatorial belt. It is a pulse of clouds and rains enhancing oceanic activity in their area of influence. MJO is loitering over the Indian Ocean in a favorable phase 1,2 and 3 and is likely to escalate formation of weather system in the Bay of Bengal during the 1st week of September. This might as well be its last appearance over the Indian Ocean and may shift over the maritime continent during the 2nd half of September.
All the three oceanic parameters getting aligned will enhance the monsoon activity. September rains look promising and active monsoon conditions are likely to prevail over most parts, albeit in a sequential pattern.