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Synopsis: La Niña is expected to continue through the Northern Hemisphere spring 2008.
Current atmospheric and oceanic conditions indicate that La Niña has continued to strengthen in the tropical Pacific. By the end of January 2008, equatorial SST anomalies were more than 2.0�C below average across parts of the central and east-central equatorial Pacific (Fig. 1). Other than the far eastern Niño-1+2 region, the magnitude of the cold anomalies in the Niño region indices increased during the past month with the latest weekly values near -1.5�C (Fig. 2). The upper-ocean heat content (average temperatures in the upper 300m of the oceans) also decreased further during January (Fig. 3), and negative subsurface anomalies between -2�C to -5�C expanded westward towards the Date Line (Fig. 4). Consistent with these oceanic conditions, stronger-than-average low-level easterly 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 recent dynamical and statistical SST forecasts for the Niño 3.4 region indicate a moderate-to-strong La Niña through the rest of the Northern Hemisphere winter, with the likely continuation of a weaker La Niña through April-May-June (Fig. 5). Thereafter, there is considerable spread in the models, with approximately one-half indicating La Niña could continue well into the Northern Hemisphere summer. Current atmospheric and oceanic conditions and recent trends are consistent with the likely continuation of La Niña through the Northern Hemisphere spring 2008.
Expected La Niña impacts during February-April 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, the Pacific Northwest, and the Ohio and Tennessee Valleys. Below-average precipitation is expected across the South, particularly in the southeastern states.
This discussion is a consolidated effort of NOAA and its
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). Forecasts for the evolution of El Niño/La Niña are updated monthly in the
Forecast Forum section of CPC's Climate
Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 6 March 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.
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