CPC and the contributors to the Forecast Forum caution potential users of
this predictive information that they can expect only modest skill.
transition from La Niņa to ENSO-neutral conditions is possible during June-
Niņa continued to weaken during April 2008, as reflected by changes in sea
surface temperatures (SSTs) across the equatorial
Negative SST anomalies in the central and east-central equatorial Pacific
have weakened, while positive SST anomalies are confined to parts of the eastern
equatorial Pacific (Fig. T18).
The latest monthly SSTs in the westernmost Niņo-4 and Niņo-3.4 regions
are near 1°C below average, while departures in the easternmost Niņo-3 and Niņo-1+2
regions are −0.2°C and 0.4°C respectively (Table T2).
subsurface ocean temperatures at thermocline depth have continued to increase in
central and east-central equatorial Pacific (Fig. T17).
While this increase has resulted in positive heat content anomalies
(average temperatures in the upper 300m of the ocean), a shallow layer of
negative anomalies in the central Pacific continues to persist between the
surface and 100m. Despite these
changes, SSTs remain sufficiently cool to maintain the persistent atmospheric
anomalies associated with La Niņa. Enhanced
low-level easterly winds and upper-level westerly winds continued across the
central equatorial Pacific (Figs. T20 and T21), convection remained suppressed throughout the central equatorial
Pacific, and enhanced convection covered the far western Pacific (Fig.
Collectively, these atmospheric and oceanic conditions indicate an
ongoing La Niņa.
majority of the recent dynamical and statistical SST forecasts for the Niņo
3.4 region indicate La Niņa will persist through
May-June-July 2008 (Figs. F1- F13). Thereafter,
there is considerable spread in the forecasts, with the majority reflecting ENSO-neutral
conditions (−0.5 to 0.5 in the Niņo-3.4 region) during the second half of
the year. However, the spread of the
models spans the possibility of a return to La Niņa or even an El Niņo by the
end of 2008. Based on current
atmospheric and oceanic conditions and recent trends, a transition from La Niņa
to ENSO-neutral conditions is possible during June- July 2008.
updates of oceanic and atmospheric conditions are available on the Climate
Niņo/La Niņa Current Conditions and Expert Discussions).