Much-Awaited La Niña Unlikely in 2024; La Niña Threshold Not Expected During Indian Southwest Monsoon
Enso Status on 6th September 2024
Ashok Patel’s Analysis & Commentary :
ONI Data has been obtained from CPC – NWS – NOAA available here
The Oceanic Niño Index (ONI) has decreased to +0.1°C for the JJA 2024 season, indicating that the Third ENSO Neutral threshold was maintained through the end of August 2024, indicating ENSO Neutral conditions continued. To achieve a La Nina threshold, an ONI should at least drop to -0.5°C for JAS 2024. This requires the combined Niño3.4 SST for July, August, and September 2024 to total at least -1.36°C. The Niño3.4 SST was 0.05°C for July 2024 and -0.07°C for August 2024, therefore, the September SST would need to drop to -1.34°C to meet the required three-month total. However, current weekly Niño3.4 data suggest that it is unlikely the September SST will reach -1.34°C. Consequently, ENSO Neutral conditions are expected to persist through the JAS 2024 season.
Based on the above analysis and NOAA criteria, ENSO Neutral conditions are expected to persist through the JAS 2024 season, which coincides with the end of the Indian Southwest Monsoon. Much-awaited La Nina is unlikely in 2024 since after the Monsoon only three months would remain; even if the La Niña threshold is reached during any of these remaining months.
How ONI is determined:
The ONI is based on SST departures from average in the Niño 3.4 region, and is a principal measure for monitoring, assessing, and predicting ENSO. Defined as the three-month running-mean SST departures in the Niño 3.4 region. Departures are based on a set of further improved homogeneous historical SST analyses (Extended Reconstructed SST – ERSST.v5).
NOAA Operational Definitions for El Niño and La Niña, El Niño: characterized by a positive ONI greater than or equal to +0.5ºC. La Niña: characterized by a negative ONI less than or equal to -0.5ºC. By historical standards, to be classified as a full-fledged El Niño or La Niña episode, these thresholds must be exceeded for a period of at least 5 consecutive overlapping 3-month seasons.
CPC considers El Niño or La Niña conditions to occur when the monthly Niño3.4 OISST departures meet or exceed +/- 0.5ºC along with consistent atmospheric features. These anomalies must also be forecast to persist for 3 consecutive months.
The Climate Prediction Center (CPC) is a United States Federal Agency that is one of the NECP, which are a part of the NOAA
Latest Oceanic Nino Index Graph Shows Enso Neutral
Conditions Prevail At The End Of August 2024
The Table below shows the monthly SST of Nino3.4 Region and the Climate adjusted normal SST and SST anomaly from February 2023. Climate Base 1991-2020. ERSST.v5
Period Nino3.4 ClimAdjust YR MON Temp.ºC Temp.ºC ANOM ºC 2023 2 26.30 26.76 -0.46 2023 3 27.19 27.29 -0.11 2023 4 27.96 27.83 0.14 2023 5 28.40 27.94 0.46 2023 6 28.57 27.73 0.84 2023 7 28.31 27.29 1.02 2023 8 28.21 26.86 1.35 2023 9 28.32 26.72 1.60 2023 10 28.44 26.72 1.72 2023 11 28.72 26.70 2.02 2023 12 28.63 26.60 2.02 2024 1 28.37 26.55 1.82 2024 2 28.28 26.76 1.52 2024 3 28.42 27.29 1.12 2024 4 28.60 27.83 0.78 2024 5 28.17 27.94 0.24 2024 6 27.91 27.73 0.18 2024 7 27.34 27.29 0.05 2024 8 26.79 26.86 -0.07
Indications and analysis of various International Weather/Climate agencies monitoring Enso conditions is depicted hereunder:
Summary by: Climate Prediction Center / NCEP Dated 3rd September 2024
ENSO Alert System Status: La Niña Watch
Synopsis: ENSO-neutral is expected to continue for the next several months, with La Niña
favored to emerge during September-November (66% chance) and persist through the
Northern Hemisphere winter 2024-25 (74% chance during November-January).
Note: Statements are updated once a month (2nd Thursday of each month) in association with the ENSO Diagnostics Discussion, which can be found by clicking here.
Recent (preliminary) Southern Oscillation Index values as per The Long Paddock – Queensland Government.
30 Days average SOI was +8.53 at the end of August 2024 and was +7.91 on 5th September 2024 as per The Long Paddock – Queensland Government and 90 Days average SOI was +0.18 on 5th September 2024.
As per BOM – Australia 3rd September 2024
- ENSO is currently neutral.
- The Bureau’s model indicates a neutral but cooler than average ENSO state. Of the remaining 6 international models surveyed by the Bureau, 3 indicate SSTs in the central tropical Pacific remaining within historically ENSO-neutral values (between −0.8 °C to +0.8 °C), and 3 indicate SSTs exceeding the La Niña threshold (below −0.8 °C) from October.
- Historically, the ENSO forecast skill is high at this time of year for up to 4 months ahead.
