ENSO-neutral conditions are expected to prevail
during the next 3-6 months.
The current patterns of anomalous ocean
temperatures are consistent in indicating a return to ENSO-neutral conditions
in the tropical Pacific. During April SSTs were close to average at most locations between
Indonesia and 90ºW (Fig. 1), which is reflected in the near zero departures observed in all of
the Niño regions, except for Niño 1+2 (Fig. 2). During the month, negative
SST departures developed in the extreme eastern equatorial Pacific, which is
a reversal from conditions observed during February-March.
April above-average precipitation (negative OLR anomalies, Fig.
3, top panel)
was observed over portions of Indonesia and northern Australia, while
below-average precipitation (positive OLR anomalies) was observed over the
central equatorial Pacific and the eastern tropical Pacific between the
equator and 20ºN. Slightly stronger-than-average low-level (850-hPa)
easterly winds (Fig. 3, middle panel) persisted over the central equatorial
Pacific, and anomalous upper-level (200-hPa) cyclonic circulation centers
were observed in both hemispheres (Fig. 3, bottom panel). Although these
atmospheric features are lingering effects of La Nina, they are weaker than
in previous months. Since February the basin-wide upper ocean heat content
has increased, becoming slightly positive in April (Fig.
these atmospheric and oceanic features signal the demise of La Niña and a
return to ENSO-neutral conditions.
the statistical and coupled models predict ENSO-neutral conditions in the
tropical Pacific through the end of 2006 (Fig. 5). However, the spread of these forecasts
(weak La Niña to weak El Niño) indicates considerable uncertainty in the outlook for the last
half of the year.
This discussion is a consolidated effort of NOAA and its funded institutions. Weekly updates for
SST, 850-hPa wind, OLR and features of the equatorial subsurface thermal structure are available on the Climate
Prediction Center web page at http://www.cpc.ncep.noaa.gov (Weekly Update). Forecasts for the evolution of El Niño/La Niña are updated monthly in the
Forecast Forum section of CPC's Climate
Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for