**EL NIÑO/SOUTHERN OSCILLATION (ENSO)** **DIAGNOSTIC DISCUSSION**

**issued by**

**CLIMATE PREDICTION CENTER/NCEP/NWS**

**8 November 2007**

**[Synopsis:]{.underline} La Niña will likely continue into early
2008.**

La Niña continued to strengthen during October 2007, as equatorial sea
surface temperature (SST) anomalies became increasingly negative from
170ºE to the South American coast (Fig. 1). The latest 4-week analysis
shows the largest SST departures (−2ºC to −3ºC) located between 140ºW
and the South American coast, with departures of −0.5°C to −1°C observed
near the Date Line (Fig. 2). All of the Niño region indices, except for
Niño-4, remained lower than −1.0°C (Fig. 3) indicating that La Niña is
approaching moderate-strength (3 -month running mean value of the Niño
3.4 index below −1.0°C).

Also during October, 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 (Fig. 4), with temperatures
ranging from 2°C to 6°C below average at thermocline depth (Fig. 5).
Consistent with these oceanic conditions, the low-level easterly winds
and upper-level westerly winds remained stronger than average across the
central equatorial Pacific, convection remained suppressed throughout
the central and eastern equatorial Pacific, and an area of slightly
enhanced convection covered parts of the far western Pacific.
Collectively, these oceanic and atmospheric conditions reflect La Niña.

The recent SST forecasts (dynamical and statistical models) for the Niño
3.4 region indicate a continuation of La Niña into early 2008 (Fig. 6).
Over half of the models indicate at least a moderate La Niña through
December, followed by gradual weakening thereafter. Current atmospheric
and oceanic conditions and recent trends are consistent with the model
forecasts.

Expected La Niña impacts during November -- January include a
continuation of above-average precipitation over Indonesia and
below-average precipitation over the central equatorial Pacific. For the
contiguous United States, potential impacts include above average
precipitation in the Northern Rockies, Northern California, and in
southern and eastern regions of the Pacific Northwest. Below-average
precipitation is expected across the southern tier, particularly in the
southwestern and southeastern states.

This discussion is a consolidated effort of the National Atmospheric and
Oceanic Administration (NOAA), NOAA's National Weather Service, and
their funded institutions. Oceanic and atmospheric conditions are
updated weekly on the Climate Prediction Center web site ([El Niño/La
Niña Current Conditions and Expert
Discussions](http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml)).
Forecasts for the evolution of El Niño/La Niña are updated monthly in
the [Forecast
Forum](http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/bulletin/forecast.shtml)
section of CPC\'s Climate Diagnostics Bulletin. The next ENSO
Diagnostics Discussion is scheduled for 6 December 2007. To receive an
e-mail notification when the monthly ENSO Diagnostic Discussions are
released, please send an e-mail message to:
<ncep.list.enso-update@noaa.gov>.

Climate Prediction Center\
National Centers for Environmental Prediction\
NOAA/National Weather Service\
Camp Springs, MD 20746-4304

![](media/image1.png){width="6.0in" height="6.741666666666666in"}

Figure 1. Time- longitude section of weekly SST anomalies (°C) averaged
for the latitude band 5ºN-5ºS. Time increases downward and longitude
ranges from Indonesia on the left to South America on the right. SST
anomalies are departures are from the 1971-2000 base period weekly means
(Xue et al. 2003, *J. Climate*, **16**, 1601-1612).

![](media/image2.png){width="6.0in" height="3.7416666666666667in"}

Figure 2. Sea surface temperature (SST) anomalies (°C) during the period
7 October- 3 November 2007. SST anomalies are computed with respect to
the 1971-2000 base period weekly means (Xue et al. 2003, *J. Climate*,
**16**, 1601-1612).

![](media/image3.png){width="6.0in" height="7.166666666666667in"}

Figure 3. Time series of area-averaged sea surface temperature (SST)
anomalies (°C) in the Niño regions \[Niño-1+2 (0°-10°S, 90°-80°W), Niño
3 (5°N-5°S, 150°W-90°W), Niño-3.4 (5°N-5°S, 170°W-120°W), Niño-4
(150ºW-160ºE and 5ºN-5ºS)\]. SST anomalies are departures are from the
1971-2000 base period weekly means (Xue et al. 2003, *J. Climate*,
**16**, 1601-1612).

![](media/image4.png){width="6.0in" height="3.283333333333333in"}

Figure 4. Area-averaged upper-ocean heat content anomalies (°C) in the
equatorial Pacific (5°N-5°S, 180º-100ºW). Heat content anomalies are
computed as departures from the 1982-2004 base period weekly means.

![](media/image5.png){width="6.0in" height="2.525in"}

Figure 5. Depth-longitude section of equatorial Pacific upper-ocean
(0-300m) temperature anomalies (°C) centered on the week of 25 October.
The anomalies are averaged between 5°N-5°S. Anomalies are departures
from the 1982-2004 base period weekly means.

![](media/image6.png){width="5.9944444444444445in"
height="5.199305555555555in"}

Figure 6. Forecasts of sea surface temperature (SST) anomalies for the
Niño 3.4 region (5°N-5°S, 120°W-170°W). Figure courtesy of the
International Research Institute (IRI) for Climate and Society. Figure
updated 16 October
2007.![](media/image7.wmf){width="1.0479166666666666in"
height="0.28055555555555556in"}