Second 3 Monthly Season With La Nina Threshold – Overall ENSO Neutral Conditions At End Of October 2016

ENSO Status on 5th November 2016

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 improved homogeneous historical SST analyses (Extended Reconstructed SST – ERSST.v4). The SST reconstruction methodology is described in Huang et al., 2015, J. Climate, vol. 28, 911-930).
CPC uses current Climatology based on 1986-2015 which has recently been changed from base years 1981-2010. Explanation about Climatology base years change is given here.

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 current El Nino event ended at the end of July 2016. Due to change in Climatology from 1981-2010 to 1986-2015 there was a change in the date as to when a full fledged El Nino was confirmed which was at the end of February 2015 considering the SST departures from average in the Niño 3.4 region based on Extended Reconstructed SST – (ERSST.v4). The graph below shows that at the end of October 2016 there have been two 3-monthly seasons JAS 2016 at -0.6ºC & ASO 2016 at -0.7ºC having La Nina threshold. Technically a full fledged La Nina can not develop during the year 2016, relying on the official NOAA definition for La Nina, because there are now only two 3-monthly seasons left after October 2016.

Latest Oceanic Nino Index (ONI) Graph till October 2016

The Table below shows the monthly SST of Nino3.4 Region and the Climate adjusted normal SST and SST anomaly for last two years. Climate Base 1986-2015.

Period    Nino3.4 ClimAdjust
YR   MON  Temp.ºC Temp.ºC ANOM ºC


2014  10   27.25   26.91    0.34
2014  11   27.51   26.88    0.63
2014  12   27.40   26.80    0.61
2015   1   27.22   26.61    0.61
2015   2   27.25   26.80    0.45
2015   3   27.79   27.32    0.47
2015   4   28.59   27.86    0.73
2015   5   28.83   27.98    0.85
2015   6   28.70   27.76    0.94
2015   7   28.50   27.37    1.13
2015   8   28.47   27.02    1.45
2015   9   28.62   26.94    1.68
2015  10   28.86   26.91    1.95
2015  11   29.14   26.88    2.25
2015  12   29.04   26.80    2.24
2016   1   28.94   26.61    2.33
2016   2   28.89   26.80    2.09
2016   3   28.87   27.32    1.55
2016   4   28.97   27.86    1.11
2016   5   28.60   27.98    0.62
2016   6   27.82   27.76    0.06
2016   7   26.99   27.37   -0.38
2016   8   26.39   27.02   -0.63
2016   9   26.22   26.94   -0.72
2016  10   26.06   26.91   -0.84

Oni Index for JAS 2016 was -0.5ºC and ONI Index for ASO 2016 as -0.7ºC, both are below -0.5ºC, the La Nina threshold which has been reached for just two consecutive 3-monthly seasons. Overall ENSO neutral conditions prevail till end of October 2016.

CPC considers El Niño or La Niña conditions to occur when the monthly Niño3.4 OISST departures meet or exceed +/- 0.5°C along with consistent atmospheric features. These anomalies must also be forecast to persist for 3 consecutive months.

Southern Oscillation Index

As per BOM, Australia:

The latest 30-day Southern Oscillation Index (SOI) to 3rd November is -5.0 within the neutral ENSO range. SOI values have been plummeting from the high of +14 reached in first week of October 2016. Currently there is a disconnect between SST anomaly and SOI.

Sustained positive values of the SOI above +7 typically indicate La Niña while sustained negative values below −7 typically indicate El Niño. Values between about +7 and −7 generally indicate neutral conditions.

SOI Monthly graph up to October 2016 as per The Long Paddock – Queensland Government.

SOI was -4.51 at the end of October 2016 and -4.44 on 4th Novemberr 2016 as per The Long Paddock – Queensland Government.

Summary by: Climate Prediction Center / NCEP Dated 31st October 2016

ENSO Alert System Status: La Niña Watch ENSO-neutral conditions are present.* Equatorial sea surface temperatures (SST) are below average in the central and east-central Pacific Ocean. La Niña is favored to develop (~70% chance) during the Northern Hemisphere fall 2016 and slightly favored to persist (~55% chance) during winter 2016-17.*

* Note: These 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

As per BOM -Australia 25th October 2016

Pacific remains ENSO-neutral – A La Niña WATCH remains in place.

The tropical Pacific Ocean remains El Niño–Southern Oscillation (ENSO) neutral.

Most climate models predict SSTs will remain cooler than average, but ENSO-neutral, through until the end of the 2016–17 summer. Only two of eight models suggest brief, weak La Niña levels may occur towards the end of 2016. The ENSO Outlook remains at La Niña WATCH.

Full Fledged La Nina Not Possible During 2016 Based On NOAA Criteria