Current ENSO Information
Summary of ENSO Model Forecasts
16 October 2002
Note on interpreting model forecasts
The following graph and table show forecasts made by dynamical and statistical
models for SST in the Nino 3.4 region for nine overlapping 3-month periods.
Note that the expected skills of the models, based on historical performance,
are not equal to one another. The skills also generally decrease as the
lead time increases. Thirdly, forecasts made at some times of the year
generally have higher skill than forecasts made at other times of the year--namely,
they are better when made between June and November than when they are
made between January and May. Differences among the forecasts of the models
reflect both differences in model design, and actual uncertainty in the
forecast of the possible future SST scenario.
Discussion of current forecasts
The set of dynamical and statistical model forecasts issued during late
October and early November shows a range of possible sea surface temperature
conditions for the coming 2 to 8 months (November- December-January 2002-03
through July-August- September 2003). Nearly all models are indicating
a continuation of warm conditions. Most of the models forecast warming
sufficient to be called an El Nino (e.g., warming to 0.7 degrees C or more
above average in the Nino 3.4 region for the December-January-February
seasonal average). Only one is forecasting ENSO conditions in the neutral
category--less than 0.7 degrees C away from normal. The warmest forecast
for the December-January-March period comes from the Lamont-Doherty (LDEO)
simple coupled model from Columbia University, U.S. (1.8 degrees C above
normal), and the coldest one is from the NOAA CDC's statistical Linear
Inverse Model, calling for SST anomalies of 0.1 degrees C below normal.
The SST anomalies forecast by the models for December-January-February
tend to be forecast also for slightly later periods, such as February-March-April
2003, although a decline toward normal in indicated by many models by that
time. For this later time, 14 of the 15 models still suggest El Nino conditions
(0.6 degrees or more for that season): the NASA/NSIPP, the NCEP, JMA, Scripps,
LDEO, BMRC, CSIRO, ECMWF, Korea SNU, CPC Markov, CPC Constructed Analogue,
CPC-CCA, Colorado State CLIPER, and the UBC nonlinear CCA. The CDC Linear
Inverse model predicts SSTs in the neutral category for February-March-April.
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