canonical correlation analysis (CCA) forecast of SST in the central Pacific
(Barnett et al. 1988, Science, 241, 192‑196; Barnston and
Ropelewski 1992, J. Climate, 5, 1316‑1345), is shown in Figs.
F1 and F2. This forecast
is produced routinely by the Prediction Branch of the
. The predictions from the National Centers for
Environmental Prediction (NCEP) Coupled Forecast System Model (CFS03) are
presented in Figs. F3 and F4a,
from the Markov model (Xue, et al. 2000: J. Climate, 13,
849‑871) are shown in Figs. F5 and F6.
Predictions from the latest version of the LDEO model (Chen et al.
2000: Geophys. Res. Let., 27, 2585‑2587) are shown in Figs.
F7 and F8.
Predictions using linear inverse modeling (Penland and Magorian 1993:
J. Climate, 6, 1067‑1076) are shown in Figs. F9
and F10. Predictions from the Scripps / Max
Planck Institute (MPI) hybrid coupled model (Barnett et al. 1993: J.
Climate, 6, 1545‑1566) are shown in Fig. F11.
Predictions from the ENSO‑CLIPER statistical model (Knaff and
Landsea 1997, Wea. Forecasting, 12, 633‑652) are shown in
Niño 3.4 predictions are summarized in Fig. F13,
provided by the Forecasting and Prediction Research Group of the IRI.
The CPC and
the contributors to the Forecast Forum caution potential users of this
predictive information that they can expect only modest skill.
ENSO-neutral conditions are expected during the
next 3-6 months.
The 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
which is reflected in the near zero departures observed in all of the Niño
regions, except for Niño 1+2 (Table T2
and Fig. T5).
During the month, negative SST departures developed in the extreme eastern
equatorial Pacific (Fig.
T18), which is a reversal from
conditions observed during February-March (Table T2).
During April above-average precipitation (negative OLR anomalies) 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 (Fig. T25).
Slightly stronger-than-average low-level (850-hPa) easterly winds
persisted over the central equatorial Pacific (Figs.
T7 and T20),
and anomalous upper-level (200-hPa) cyclonic circulation centers were
observed in both hemispheres (Fig.
Although these atmospheric features are lingering effects of the La Niña,
they are weaker than in previous months. The equatorial subsurface
temperature anomaly pattern featured negative anomalies in the eastern
Pacific and positive anomalies in the western and central Pacific during
April 2006 (Fig. T17). Since February the area
of positive anomalies at depth has expanded to the east (Fig.
T15), and the basin-wide upper
ocean heat content has increased. Collectively, these atmospheric and oceanic
features are consistent in indicating the demise of La Niña and a return to
The value of the Oceanic Niño Index (ONI; 3-month running mean average of SST anomalies in
the Niño 3.4 region – computed
using the Extended Reconstructed SST version-2 data set) for February
- April 2006 is -0.4°C, which
indicates ENSO neutral conditions. Most
of the statistical and coupled
model forecasts indicate ENSO-neutral conditions in the tropical Pacific
through the end of 2006 (Figs. F1,
F2, F3, F4a,
F4b, F5, F6,
F7, F8, F9,
F10, F11, F12
spread of these forecasts (weak La Niña to weak El
Niño) indicates considerable uncertainty in the outlook for the last half of
updates of SST, 850-hPa wind, OLR and features of the equatorial subsurface
thermal structure are available on the
Center homepage at: