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

**issued by**

**CLIMATE PREDICTION CENTER/NCEP/NWS**

**6 March 2008**

**[Synopsis:]{.underline} La Niña is expected to continue through the
Northern Hemisphere spring 2008.**

Atmospheric and oceanic conditions during February 2008 continued to
reflect a strong La Niña. Equatorial SSTs were more than 2.0°C below
average across large portions of the central and east-central equatorial
Pacific (Fig. 1), and the corresponding weekly values of the Niño-4 and
Niño-3.4 indices remained between −1.6°C and −2.1°C during the month
(Fig. 2). In contrast, SSTs in the far eastern equatorial Pacific were
above average during February 2008, in association with a warming trend
that began in mid-December. The upper-ocean heat content (average
temperatures in the upper 300m of the oceans between 180° - 100°W)
remained below average across the equatorial Pacific during February
(Fig. 3), with the largest temperature anomalies averaging −2°C to −6°C
at thermocline depth (Fig. 4). Consistent with these oceanic conditions,
stronger-than-average low-level easterly winds and upper-level westerly
winds persisted across the central equatorial Pacific, convection
remained suppressed throughout the central equatorial Pacific, and
enhanced convection covered the far western Pacific. Collectively, these
oceanic and atmospheric conditions are similar to those accompanying the
last strong La Niña episode in 1998-2000.

The most recent dynamical and statistical SST forecasts for the Niño 3.4
region continue to indicate a moderate-to-strong La Niña through March
2008, and a weaker La Niña through April-May-June 2008 (Fig. 5).
Thereafter, there is considerable spread in the forecasts, with
approximately one-half indicating that La Niña could continue into the
Northern Hemisphere fall. Current atmospheric and oceanic conditions and
recent observed trends support the likely continuation of La Niña
through the Northern Hemisphere spring 2008.

Expected La Niña impacts during March-May 2008 include a continuation of
above-average precipitation over Indonesia and below-average
precipitation over the central equatorial Pacific. The above average
SSTs in the eastern equatorial Pacific may result in increased rainfall
over Ecuador and northern Peru, similar to the evolution during the
1998-2000 La Niña episode. Compared to the Northern Hemisphere winter,
La Niña impacts over the United States in spring are typically less
pronounced. The primary springtime signal for the contiguous United
States is an increased probability of below-average precipitation across
the South, particularly in the Southeast.

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 10 April 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="3.477777777777778in"}

Figure 1. Sea surface temperature (SST) anomalies (°C) during 3
February - 2 March 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="7.2in"}

Figure 2. 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 from the
1971-2000 base period weekly means (Xue et al. 2003, *J. Climate*,
**16**, 1601-1612).

![](media/image3.png){width="6.0in" height="3.1in"}

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="2.6222222222222222in"}

Figure 4. Depth-longitude section of equatorial Pacific upper-ocean
(0-300m) temperature anomalies (°C) centered on the week of 22 February
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="5.9944444444444445in"
height="5.199305555555555in"}

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 20 February
2008.![](media/image6.wmf){width="1.0479166666666666in"
height="0.28055555555555556in"}