Starting in late 1995 and continuing throughout much of 1996, a weak to moderate La Niña event occurred in the equatorial Pacific (Halpert et al. 1996). By late 1996, the SST values had returned to near average values with the exception of cooler than normal waters in the Niño 1+2 region. However, the SOI remained slightly positive and substantially drier than normal conditions continued (as measured by the outgoing longwave radiation), thus the weak La Niña-type regime has continued. Input values for the pool of ENSO-CLIPER predictors on 1 December, 1996 were as follows:
Initial Niño 1+2 conditions (1, 3, 5 m) = -1.1, -0.9, -1.0° C
Trend of Niño 1+2 conditions (1, 3, 5 m) = -0.3, +0.2, -0.3° C
Initial Niño 3 conditions (1, 3, 5 m) = -0.4, -0.3, -0.2° C
Trend of Niño 3 conditions (1, 3, 5 m) = -0.2, -0.1, +0.1° C
Initial Niño 3.4 conditions (1, 3, 5 m) = -0.2, -0.2, -0.1° C
Trend of Niño 3.4 conditions (1, 3, 5 m) = 0, -0.1, +0.2° C
Initial Niño 4 conditions (1, 3, 5 m) = 0, +0.1, +0.1° C
Trend of Niño 4 conditions (1, 3, 5 m) = -0.1, 0, +0.3° C
Initial SOI conditions (1, 3, 5 m) = -0.2, +0.3, +0.4 Std. Dev.
Trend of SOI conditions (1, 3, 5 m) = -0.6, -0.4, -0.1 Std. Dev.
Employing these predictors in the ENSO-CLIPER model yields the forecasts for December 1996-February 1997 (zero season lead) out through September-November 1998 (seven season lead) shown in Fig. 6. The adjusted RMSE is also plotted as horizontal bars, indicating the degree of uncertainty associated with each forecast though the true RMSE will not be known until after verification (a function of both the ENSO-CLIPER model forecast ability and the annual cycle of variability). All predictands are forecast to return to near neutral by winter-spring 1997 and then progress to moderate El Niño warm conditions during late 1997 and early 1998.