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IRI/CPC ENSO Quick Look | Download PDF version
CPC/IRI ENSO Update / Forecast
Technical ENSO Update
IRI/CPC Plume-Based ENSO Forecast
CPC/IRI Consensus Probabilistic ENSO Forecast
IRI/CPC ENSO Predictions Plume
Individual Model View, last 22 months
Monthly archive
ENSO Update
16 February 2011
Summary
NOTICE: This "IRI ENSO Update/Forecast" is now supplanted by
the NOAA/Climate Prediction
Center ENSO Diagnostic Discussion, issued early in the month. The IRI Technical ENSO Update
is still issued by the IRI near the middle of the month. The probabilistic ENSO forecast created
at mid-month is now an objective rendering directly from the IRI/CPC ENSO prediction plume,
using equal weighting for all plume models and using a Gaussian probability density function
centered on the multi-model mean prediction. Probabilistic ENSO forecasts having an additional,
and possibly beneficial, influence from the forecasters' judgement, are made jointly by IRI and
CPC at the beginning of the month and are accessible from the above-mentioned NOAA/ Climate
Prediction Center's ENSO Diagnostic Discussion. These early month probabilities are to be
considered the official CPC/IRI probabilistic ENSO forecast product. The thresholds for
El Niño and La Niña are plus and minus 0.45 C Nino3.4 SST anomalies, respectively,
as used historically by NOAA/Climate Prediction Center, rather than the seasonally varying
quartile-based values used by IRI through 2011. The implication of the approximately
half-degree anomaly thresholds is that non-neutral ENSO conditions are expected to occur
with greater than 25% frequency during northern autumn and early winter, and slightly less
than 25% frequency during northern spring and early summer. Specifically, the climatological
probabilities of La Nina, neutral, and El Nino conditions for each 3-month season using
the 0.45 C thresholds are as follows:
----- LN N EN -----Climatological Probabilities
DJF 37 28 35
JFM 34 37 29
FMA 30 48 22
MAM 26 54 20
AMJ 24 54 22
MJJ 25 51 24
JJA 25 50 25
JAS 27 46 27
ASO 29 40 31
SON 32 34 34
OND 34 31 35
NDJ 37 27 36
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