Current 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 eight 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 October than when they are made
between January and April. 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
September and early October shows a range of possible sea surface temperature
conditions for the coming 3 to 8 months (November-December-January 2002-03
through June-July-August 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). A small number are 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. (1.78 degrees C above normal), and the coldest one is from the NOAA
CDC's statistical Linear Inverse Model, calling for SST anomalies 0.1 to
0.2 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, 12 of the 14
models that forecast to that long a lead time still suggest El Nino conditions
(0.6 degrees or more for that season): the NASA/NSIPP, the NCEP, JMA, Scripps,
LDEO, BMRC, CSIRO, Korea SNU, CPC
Markov, CPC-CCA, Colorado State CLIPER, and the UBC nonlinear CCA.
The CPC Constructed Analogue and CDC Linear Inverse models predict SSTs
that fall short of El Nino levels for February-March-April.
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