Butterflies in your stomach
a feeling of being very nervous or frightened about something
Science says there are multiple reasons for “Butterflies in Stomach” though more often than not it is associated with a period of anxiety and nervousness. For the weather bloggers of Chennai possibly the closest feeling to butterflies in the stomach is when the satellite images & weather model outputs start to indicate the seasonal wind change, the change of winds from West to East, as this for all practical purposes is the time to look forward to Northeast Monsoon. With the signs now showing up for a seasonal wind change it is time to also do a bit of crystal ball gazing on what could be in store during this year’s Northeast Monsoon season.
Please note this outlook is completely based on our understanding of current conditions along with our estimate of how intra-seasonal oscillation could behave to get a fair idea of how events could pan out over the next few weeks. While it is tough to pick past years that might match closest to how things are evolving in the current year more so considering the evolution of El Nino this year has been of a flavor that is not often seen. Similarly unlike most years when Positive IOD peaks during the second half of Southwest Monsoon season this year we might see Positive IOD peak during Northeast Monsoon season.
In order to make a meaningful estimate we have decided to add more weightage to Multivariate Enso Index rather than opt for Oceanic Nino Index and SOI as individual factors in understanding the state of El Nino. Similarly the lagged peak of Positive IOD may make the numerical based IOD index less relevant to 2023 when comparing past episodes. One another conscious call that has been adopted while trying to understand past years is to avoid going back too long as over the past couple of decades there are factors like Urban Heat Island that have altered the monsoon dynamics over places like Chennai.
With focus primarily on intra seasonal oscillations there is a fair degree of confidence 2023 may be closer to 2006 and 2002, both years with normal or slightly above normal Northeast Monsoon season for Chennai and near normal seasonal rainfall for Tamil Nadu and Pondicherry Subdivision.
The Summary of Northeast Monsoon 2023 Outlook
- There is a slight chance for a possible onset during the 3rd week of October, if that window is missed then onset could happen during 1st week of November
- Most parts of Tamil Nadu to see near normal Northeast Monsoon
- Northwest Interior Tamil Nadu and adjoining interior Peninsular India may see below normal NEM
- South Tamil Nadu and adjoining South Kerala may see above normal NEM season
- The first half of the season (up to 2nd week of November) could be weak and sub par
- Number of disturbances during the NEM 2023 season (LPA or stronger) is estimated to be between 4 and 6 with Arabian Sea likely to host a greater number of disturbances
- Number of cyclones during NEM 2023 Season is estimated to be between 1 and 3
- Southern Ghats may come under one or two extreme rainfall episodes during late November / early December