Published in the Experimental Long-Lead Forecast Bulletin, December 1995
The El Niño forecasts are part of an ongoing research effort at COLA, and do not represent official forecasts. These forecasts should not be used as the basis of any commercial, policy, or other decisions. They are strictly research tools for advancing the understanding of the ocean-atmosphere system.
Below, we show the horizontal structure of the SSTA
correlation averaged over lead times of 10 to 12 months. The top
panel shows the correlation for 60 forecasts and the
bottom panel shows the correlation for the corresponding 60
persistence forecasts. The persistence forecast is made by persisting
the observed SSTA at the initial time for all lead times. The
dynamical prediction system yields correlations that are greater than
0.6 over a sizable region of the tropical Pacific. The correlation is
largest between 5S and 5N in the central and eastern Pacific, but
falls off rapidly near the coast of South America. The persistence
forecasts, on the other hand, have near zero or negative correlation
throughout most of the equatorial Pacific.
The top panel shows the correlation between the predicted
and observed sea surface temperature anomalies averaged over lead
times of 10 to 12 months for all 60 forecasts. The bottom panel
shows the correlation between the corresponding 60 persistence
forecasts with lead times of 10 to 12 months.
The top panel of the figure below shows the NINO3 time series of the
predicted SSTA for three forecasts initialized on September 1, 1995,
October 1, 1995 and November 1, 1995, respectively. Each forecast is
18 months in duration. The September forecast indicates near normal
conditions for most of the forecast with very weak warming in the
boreal summer of 1996 and weak to moderate cooling in the boreal
winter of 1996-97. The forecasts initialized in October and November
are similar to each other, but are different from the September
forecast. Both the October and November forecasts indicate cooling
during boreal winter 1995-96 and warming during the boreal fall 1996
and winter 1996-97. The ensemble mean (average of all three
forecasts) horizontal structure of the predicted SSTA for the boreal
fall of 1996 and the boreal winter of 1996-97 are shown in the middle
and bottom panels respectively. The ensemble averaged
forecast indicates warm SSTA beginning in the boreal fall of 1996 with
anomalies in excess of 1 degree Celcius over much of the central
Pacific between 5S-5N during the boreal winter of 1996-97. Warm El
Niño conditions are predicted for the boreal fall of 1996 and winter
of 1996-97.
The top panel shows the time evolution of the NINO3 SSTA
forecast. The solid curve corresponds to the forecast initialized in
September, the dotted curve corresponds to the October forecast and
the dashed curve corresponds to the November forecast. The middle
panel shows the ensemble mean SSTA averaged from September 1996 to
November 1996. The bottom panel is the ensemble mean SSTA averaged
from December 1996 to February 1997.
