La Niña expected to produce above-average precip through spring, 2008

The National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center has released its forecast for the spring 2008 season. As La Niña continues in the western equatorial Pacific with cooler than normal sea surface temperatures, the winds will continue to stall in the western Pacific, likely bringing drought to southern North America and wetter than normal conditions to the northern-tier states, including Oregon. Here’s what the diagnostic discussion said specifically:

Sea surface temperatures October 2007-January 2008. Graphic courtesy of NOAA/NWS.“Expected La Niña impacts during January-March include a continuation of above-average precipitation over Indonesia and below-average precipitation over the central and eastern equatorial Pacific. For the contiguous United States, potential impacts include above-average precipitation in the Northern Rockies, the Pacific Northwest, the Ohio and Tennessee Valleys, and parts of the Great Lakes region. Below-average precipitation is expected across the South, particularly in the southeastern states. Recent Madden-Julian Oscillation (MJO) activity has contributed to short-term fluctuations in low-level winds and convection over the equatorial Pacific, which has acted to modify some of the typical La Niña impacts on a sub-seasonal timescale.”

In short, while the December Storm brought tremendous rainfall to the region, we can expect to see more chances of above-average precipitation and increased chances of below-normal temperatures, particularly as the northerly jet stream brings more arctic-origin storms to the PNW coast. Keep your hatches battened down and your winter coats handy. Storm-track trends are illustrated in the animated graphic (courtesy of NOAA) below.

Storm Tracks--courtesy of NOAA/NWS Climate Prediction Center

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