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 to prevail during the northern summer (June-August).
and subsurface water temperatures increased in the eastern equatorial Pacific
during April (Table T2, Fig. T5),
associated with the arrival of the downwelling phase of a strong oceanic
Kelvin wave (Fig. T17). By
the end of April positive
equatorial SST anomalies greater than +0.5°C (~0.9°F) were observed in most
eastward to the South American coast
(Fig. T18). The increase in SST
anomalies in the eastern equatorial Pacific during April was reflected by an
increase in the SST anomalies in the Niño 3 and Niño
1+2 regions (Table T2) and by an
increase in the upper-ocean heat content in the eastern half of the
equatorial Pacific (Fig. T15).
Subsurface cooling and a decrease in upper-ocean heat content have
been evident in the central equatorial Pacific, associated with the upwelling
phase of the Kelvin wave (Fig. T17).
cooling is expected to propagate eastward, reaching the eastern equatorial
Pacific during May. Thus, the effects of the warming along the west coast of
should be brief.
precipitation and low-level winds displayed considerable week-to-week
variability during the month, associated with strong MJO activity (Figs. T11,
T12 and T13). For the
month as a whole, enhanced precipitation (negative OLR anomalies) prevailed
over the western Pacific (Fig. T25),
accompanied by stronger-than-average low-level easterly winds over the
central equatorial Pacific and anomalous low-level westerly winds over the
extreme western equatorial Pacific (Fig. T20).
Continued strong week-to-week variability in the patterns of tropical
atmospheric circulation and precipitation is likely during May.
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 2005 is +0.3°C,
which does not satisfy the NOAA operational definition of El Niño
for the first time since May-July 2004. Consistent
with this, a majority of the statistical and coupled model forecasts
F2, F3, F4a,
F4b, F5, F6,
F7, F8, F9,
F10, F11, F12
indicate that ENSO-neutral conditions will prevail during the northern summer
(June-August). The spread in the forecasts indicates increasing
uncertainty during the last half of 2005.
updates of SST, 850-hPa wind, OLR and features of the equatorial subsurface
thermal structure are available on the