1983 ENSO

[Ptarmigan]

I looked at 1983, which was a strong El Nino year, prior to 1997-98 and it showed this:
2.3
2.0
1.5
1.2
1.0
0.6
0.2
-0.2
-0.6
-0.8
-0.9
-0.7

http://www.cpc.noaa.gov/products/analys ... ears.shtml

Looks like towards to end of 1983, it went into La Nina. If I am correct, a value +/-0.5 is El Nino/La Nina.

DESCRIPTION: Warm (red) and cold (blue) episodes based on a threshold of +/- 0.5oC for the Oceanic Niño Index (ONI) [3 month running mean of ERSST.v3b SST anomalies in the Niño 3.4 region (5oN-5oS, 120o-170oW)], based on the 1971-2000 base period. For historical purposes cold and warm episodes (blue and red colored numbers) are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons.

I wonder why it is not considered that in 1983.

[brunota2003]

Wouldn't it be considered a Neutral year?

[Macrocane]

Because it was below -0.5 °C for only 4 consecutive overlapping seasons