One year lead-time experimental streamflow forecasts for the Columbia River at The Dalles
Past Forecast Performance
What is the Performance Record of the ENSO Forecasts since 1998?
This figure from the data archives of the IRI
shows the time history of the NINO3.4 time series (sea surface temperature
anomalies in degrees C). The retrospective definition of ENSO state that
we use for forecasting is based on 0.5 standard deviations from the long-term
mean (+/- 0.47 degrees C) of the NINO3.4 index averaged from December
to February (PDO ENSO Tables). We have been
interpreting ENSO forecasts delivered in about the first week of June
ENSO forecasts for water year 1998, 1999, 2000, 2002, and 2003 (warm,
cool, cool, neutral, warm respectively) made in June proved accurate.
The ENSO forecast for 2001 predicted the highest likelihood of ENSO neutral
conditions in June, but during the winter the sea surface temperatures
exceeded the threshold for the cool ENSO category, so our interpretation
of the ENSO forecast in June was in error. The streamflow forecast for
2001 would have been even more in error if we had had a correct forecast
of cool ENSO, so the incorrect ENSO forecast was not the predominant source
of forecast error in 2001 as it turned out.
For water year 2004, the ENSO forecast available in June 2003 for the
winter 2003-2004 proved to be incorrect. By October 1, however, an updated
forecast of ENSO neutral conditions was released. This forecast proved to
How did we do in 2003 and 2004?
The long-range streamflow forecast in for water year 2003 was very skillful,
with the observations very closely matching the ensemble mean. In the
2004 water year, the observed streamflow (through August 2004) was near
the bottom of the forecast ensemble. These conditions may be partly explained
by the wide spread drought occuring over much of West, the cause of which
is only partly understood.
For more details, see Forecast Archive.
August 25, 2005