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 predictions from the National Centers for
Environmental Prediction (NCEP) Coupled Forecast System Model (CFS03) are
presented in Figs. F3 and F4. Predictions
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
Predictions using linear inverse modeling (Penland and Magorian 1993:
J. Climate, 6, 1067-1076) are shown in Figs. F9 and
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 Fig. F12.
Niņo 3.4 predictions are summarized in Fig. F13, provided by the
Forecasting and Prediction Research Group of the IRI.
CPC and the contributors to the Forecast Forum caution potential users of
this predictive information that they can expect only modest skill.
conditions are expected to continue through August 2007, with a slightly greater
than 50% chance of La Niņa developing during the next couple of months.
conditions continued in the tropical Pacific during July 2007, with average to
below-average sea surface temperatures (SSTs) extending from the date line to
the west coast of South America (Fig. T18).
The July SST departures were negative in the Niņo 1+2 ("1.6ēC), Niņo 3
("0.8ēC), and Niņo 3.4 ("0.3 ēC) regions, and positive in the Niņo
4 (+0.2ēC) region (Table T2).
Thus, while SSTs in the eastern equatorial Pacific have been cooler than average
for the last six months, the departures continue to fall short of the threshold
for La Niņa (3-month running mean value of "0.5 ēC for the Niņo 3.4
region: 5°N-5°S, 120-170°W).
Despite not meeting the SST threshold for La Niņa, recent atmospheric
circulation and tropical convection patterns are consistent with the evolution
toward La Niņa conditions. For example, the low-level easterly winds remained
stronger than average in the west-central equatorial Pacific (Fig.
T20), convection remained suppressed across most of the equatorial
Pacific, and a weak area of enhanced convection covered parts of Indonesia and
the far western equatorial Pacific (Fig.
T25). Also, the upper-ocean heat content (average temperatures in the
upper 300 m of the ocean) in the central and east-central equatorial Pacific
remained below-average, but the magnitude of the departures continued to exhibit
intraseasonal fluctuations. Collectively, the oceanic and atmospheric conditions
reflect a continuation of ENSO-neutral conditions.
of the ENSO models predict below-average SSTs in the Niņo 3.4 region for the
remainder of the year (Figs. F1-F13). The spread of the recent model
forecasts range from ENSO-neutral to La Niņa, with a majority of dynamical
models indicating a more immediate transition to La Niņa. However, over the
last several months, the dynamical models have consistently predicted a stronger
and more rapid cooling than has actually occurred. In contrast, a majority of
the statistical models indicate a continuation of ENSO-neutral conditions, but
some forecast weak La Niņa conditions during the fall or winter. When
considered collectively, recent atmospheric conditions and model forecasts
suggest a slightly greater than 50% chance of La Niņa developing during the
next couple of months. Historically, the early fall season
(August-September-October) has been a critical period for the onset of La Niņa
updates of oceanic and atmospheric conditions are available on the
Niņo/La Niņa Current Conditions and Expert Discussions).