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

**issued by**

**CLIMATE PREDICTION CENTER/NCEP/NWS**

**10 July 2008**

**[Synopsis:]{.underline} ENSO-neutral conditions are expected to
continue into Northern Hemisphere Fall 2008.**

A transition from La Niña to ENSO-neutral conditions occurred during
June 2008, as sea surface temperatures (SSTs) returned to near-average
across the central and east-central equatorial Pacific Ocean (Fig. 1).
Also, positive SST anomalies continued in the eastern equatorial
Pacific. Consistent with this pattern, the latest weekly SST index was
-0.1°C in the Niño-3.4 region, and +0.4°C in the Niño 1+2 region (Fig.
2). The subsurface oceanic heat content (average temperatures in the
upper 300m of the ocean, Fig. 3) and patterns of subsurface temperature
anomalies (Fig. 4) also reflected the transition to ENSO-neutral
conditions. Positive heat content anomalies were associated with
above-average temperatures at thermocline depth across the entire
equatorial Pacific, while small negative subsurface temperature
anomalies persisted near the Date Line between the surface and 75m
depth.

Similar to past transitions, La Niña continues to linger in the
atmospheric circulation, but with diminishing strength. Enhanced
low-level easterly winds and upper-level westerly winds remain across
the central equatorial Pacific, while convection continues to be
suppressed in the central equatorial Pacific and slightly enhanced over
the far western Pacific. Collectively, these atmospheric and oceanic
anomalies are consistent with a return from La Niña to ENSO-neutral.

Most of the recent dynamical and statistical SST forecasts for the Niño
3.4 region indicate ENSO-neutral conditions (−0.5 to 0.5 in the Niño-3.4
region) will continue through Northern Hemisphere Winter 2008-09 (Fig.
5). Despite this model consensus, the possible development of El Niño or
La Niña cannot be ruled out due to uncertainty in model forecasts and
because ENSO events often form during the second half of the year. Based
on current atmospheric and oceanic conditions, recent trends, and model
forecasts, ENSO-neutral conditions are expected to continue into
Northern Hemisphere Fall 2008.

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 7 August 2008. 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="3.316666666666667in"}

Figure 1. Weekly sea surface temperature (SST) anomalies (°C) centered
on 2 July 2008. Anomalies are computed with respect to the 1971-2000
base period weekly means (Xue et al. 2003, *J. Climate*, **16**,
1601-1612).

![](media/image2.png){width="6.0in" height="6.75in"}

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

![](media/image3.png){width="6.0in" height="2.95in"}

Figure 3. 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/image4.png){width="6.0in" height="2.375in"}

Figure 4. Depth-longitude section of equatorial Pacific upper-ocean
(0-300m) temperature anomalies (°C) centered on the week of 27 June
2008. The anomalies are averaged between 5°N-5°S. Anomalies are
departures from the 1982-2004 base period weekly means.

![](media/image5.png){width="5.998611111111111in"
height="5.180555555555555in"}![](media/image6.wmf){width="1.0479166666666666in"
height="0.28055555555555556in"}

Figure 5. 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 18 June 2008.