CPC and the contributors to the Forecast Forum caution potential users of
this predictive information that they can expect only modest skill.
Alert System Status: El
transition to ENSO-neutral conditions is expected by June 2010, which will
continue into the Northern Hemisphere summer 2010.
Niņo weakened during April 2010 as positive surface temperature (SST) anomalies
decreased across the equatorial Pacific Ocean.
However, SST anomalies still exceeded +0.5°C across most of the Pacific
at the end of the month (Fig. T18,
Table T2). Since the end of February,
subsurface heat content anomalies (average temperatures in the upper 300m of the
ocean) have decreased steadily in association with the expansion and
strengthening of below-average temperatures at depth (25-200m; Fig. T17).
Also, enhanced convection developed over Indonesia, while suppressed
convection strengthened and expanded over the tropical Pacific, south of the
equator (Fig. T25). The
low-level equatorial trade winds remained near-average, and anomalous
upper-level westerly winds prevailed over the central Pacific during much of
April (Figs. T20, T21). Collectively, these oceanic
and atmospheric anomalies reflect a weakening El Niņo.
all models predict decreasing SST anomalies in the Niņo-3.4 region through the
Northern Hemisphere summer 2010 (Figs. F1-F13).
Most models predict a transition to ENSO-neutral conditions during
April-June 2010, followed by ENSO-neutral conditions through the end of the
year. However, by July-September
2010, the envelope of model solutions includes a significant number (nearly a
third) indicating the onset of La Niņa conditions.
Even though ENSO-neutral conditions are most likely during the second
half of the year, the general tendency of the models in recent months has been
toward increasingly negative SST anomalies in the Niņo-3.4 region.
These forecasts, in addition to various oceanic and atmospheric
indicators, indicate a growing possibility of La Niņa developing during the
second half of 2010.
updates of oceanic and atmospheric conditions are available on the Climate
Niņo/La Niņa Current Conditions and Expert Discussions).