NEM 2023 update

Global weather and climate models are expecting a below normal Northeast Monsoon this year due to large scale suppression arising as result of strong Positive IOD (Indian ocean dipole) .This year the period between October to December 2023 will have larger dry periods and shorter rainfall periods due to suppression. But if we analyse the past data whenever the atmospheric conditions of strong El-Nino coupled with strong positive IOD, it resulted in good rainfall during northeast monsoon period over Tamil Nadu and AP areas. For eg if we take the year 1997 and 2015 we had seen a strong El Nino atmosphere coupled with positive IOD conditions which indeed brought excess rainfall during northeast monsoon period in Tamil Nadu and Andhra. But we cannot take these factors alone into the account. We also have to see the MJO ( Madden Julian Oscillation) – The Rain maker/Master wave’s progression, duration of the visit Indian Ocean Basin (P2&P3) as well.

So what can we expect this year for TN and AP areas?

Most of the major global models such as ECMWF, CFS, NMME, Canips are going with below normal to near normal NEM rainfall (Oct – Dec 2023) for TN and AP. Only South TN is shown in above normal to excess shade.

To Sum up:

• Northeast Monsoon Rainfall may commence between October 23 to 28 over TN and AP.
• Numerical Weather Models are expecting a Low pressure area to develop out of a large broad area of trough in south Bay of Bengal between oct 22 to 24. It is still unclear that in which area of trough and part of BOB will the LPA develop and move(This would decide the onset of NEM 2023)
• Most Parts of TN will see close to normal rainfall this NEM, and southern districts will see above normal monsoon, this would depend on the MJO progression and duration of stay in P2, P3 and P4
• Monsoon is expected to be weak till Mid November, after which it will pick up its pace over TN and AP.
• Arabian sea will be more active this NEM Compared to our Bay of Bengal.
• Compared to well organized systems, we are expecting that there would be more No of Easterly waves bringing rains to TN Coast.
• KTCC(Kanchipuram, Thiruvallur, Chennai and Chengalpattu) will see close to normal NEM this year.