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: La
transition to ENSO-Neutral
conditions is expected by June 2011.
Niña weakened for the third consecutive month, as reflected by increasing
surface and subsurface ocean temperatures across the equatorial Pacific Ocean (Figs.
T9 and T15).
All four Niño indices ranged between –0.4°C and –1.0°C for the
moth of March
(Table T2). Subsurface
oceanic heat content anomalies (average temperatures in the upper 300m of the
ocean) became weakly positive in response to the continued eastward progression
of a strong oceanic Kelvin wave, which has begun to shoal in the eastern Pacific
(Fig. T17). However, the basin wide
extent of negative SST anomalies remained considerable throughout the month (Fig.
Also, La Niña impacts on the atmospheric circulation remained strong
over the tropical and subtropical Pacific. Convection
remained enhanced over much of Indonesia and suppressed over the western and
central equatorial Pacific (Fig. T25).
Also, anomalous low-level easterly and upper-level westerly winds have
persisted in this region (Figs. T20
Collectively, these oceanic and atmospheric anomalies reflect a weakening
La Niña, but with ongoing global impacts.
all of the ENSO models predict La Niña to continue weakening in the coming
months, and the majority of models indicate a return to ENSO-neutral by
May-June-July 2011 (three month average in the Nino-3.4 index between –0.5°C
and +0.5°C; Figs. F1-F13).
While there is confidence in ENSO-neutral conditions by June 2011, the
forecasts for the late summer and beyond remain highly uncertain.
At this time, all of the multi-model forecasts suggest ENSO-neutral
conditions will persist from June through the rest of the year.
However, the spread of individual model forecasts and overall model skill
at these lead times leaves the door open for either El Niño or La Niña
conditions by the end of 2011.
updates of oceanic and atmospheric conditions are available on the Climate
Niño/La Niña Current Conditions and Expert Discussions).