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Seasonal to Interannual Forecasts

Climate Outlook

ARCHIVE COPY - JANUARY 2008

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The Climate Impacts Group (CIG) translates global-scale climate forecasts and conditions into regional-scale climate forecasts for Pacific Northwest (PNW) resource managers and the general public. The El Niño/Southern Oscillation (ENSO) is the most important factor for seasonal forecasting, changing the odds for different types of winter and spring weather (e.g. warmer/drier, cooler/wetter) in the PNW. Another important climate variable for Pacific Northwest climate is the Pacific Decadal Oscillation (PDO). The climate outlook also provides the basis for natural resource forecasts, including the CIG's annual streamflow forecasts.


What's Next for the Pacific Northwest?

Winter 2007-08
Updated January 24, 2008 (posted January 28)

The climate outlook is reviewed monthly and updated as needed.

During December 1-3, a series of storms moved through the Pacific Northwest (PNW) bringing snow, strong winds, heavy rainfall, landslides, and major flooding. Over the 3-day period, strong winds in excess of 80 mph battered much of the Oregon and Washington coast. Winds in several locations, including Hoquiam, which recorded a maximum gust of 81 mph, were the strongest since the Columbus Day storm of 1962. (More on the Great Coastal Gale of December 1 - 3, 2007).

The most significant event of this period was the heavy rainfall around western Washington on December 3, which resulted in major flooding. According to the United States Geological Survey (USGS), major flooding was observed in southwest Washington and moderate flooding in central western Washington. Three rivers -- the Elwha, Skokomish, and the Chehalis -- reached all-time flood levels. The high water from Chehalis river led to widespread flooding for much of the central Chehalis valley, including a 20-mile stretch of Interstate-5. Preliminary estimates indicate that 24-hour precipitation amounts were near 100-year rain frequency levels. Bremerton broke its all-time daily maximum rainfall record on December with 7.50" of rain, breaking the old record of 5.62" set December 10, 1921. (Additional rainfall totals)

As December 2007 drew to a close, the monthly precipitation totals were above the 1971-2000 normal in western Oregon and Washington, the eastern flank of the North Cascades, the Spokane area, and northern Idaho (totals, percentage of normal, High Plains Regional Climate Center). December temperatures were near normal over the region, as were precipitation and temperature averaged over October, November, and December (not shown).

Coastal sea surface temperatures (SSTs) continued to be below normal in December, with SSTs at least 1C below normal along the Washington coast, and at least 2C below normal along the Oregon and much of the California coast (figure, 1985-97 climatology, NOAA Coastwatch). This pattern of colder than normal west coast SSTs is consistent with the cold ENSO conditions that have dominated the equatorial Pacific in the last several months (figure, 1982-96 climatology, NOAA Earth System Research Laboratory).

Mid-January 2008 brought cold, dry conditions to the Pacific Northwest and much of the U.S. (7-day averages for the PNW and U.S.), but the average temperature for the last 30 days remains near normal for the PNW (figure). The Snotel snow water content, as reported on 23 January, is at or above the 1961-90 normal for much of the PNW, and in the 75-90% range in southeast Oregon and southern Idaho (figure). A comparison with the 20 December 2007 analysis reveals how much the values can change at this time of year (figure, Western Regional Climate Center).

Current indicators for Pacific climate

El Niño/Southern Oscillation (ENSO). Cold ENSO continues in the equatorial Pacific, with mean October-November-December sea surface temperatures (SSTs) 1.48°C below the 1971-2000 normal in the Niño 3.4 region (5N-5S, 170-120W), the coldest temperatures at this time of the year since 1988 (figure) and the 6th coldest in the 58 year record. As of 10 January, NCEP characterized this as a moderate "La Niña" (cold ENSO) episode (discussion). The cold conditions are forecast to remain strong through the remainder of the December-January-February season, with diminished cold ENSO conditions persisting through June-July-August (18 forecast models).

Pacific Decadal Oscillation (PDO). The existing pattern of colder than normal SSTs along the west coast of North America and on the equator, and warmer than normal SSTs in the central north Pacific is characteristic of the cold polarity of the PDO phenomenon (figure). The amplitude of this pattern in September, October, November, and December was -0.36, -1.45, -1.08, and -0.58, respectively, indicating that the PDO has diminished in strength since October. One of the conceptual models for PDO variability is that the seasonal and longer term fluctuations in the PDO are produced by ENSO, so the forecast of continued cold ENSO is consistent with the PDO to remain negative in the coming months. The NOAA Earth System Research Laboratory experimental SST forecast is for the PDO pattern to remain negative through the rest of 2008.

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What does the outlook mean for the PNW in coming months?

The Climate Prediction Center's outlook for January-February-March temperature and precipitation is for equal chances of above, below, or normal temperatures for the PNW, with the exception of the southeast corner of Idaho which has a 33% chance of above normal temperatures. Precipitation probabilities are for a greater than 40% chance of above normal precipitation for southeast Washington, northeast Oregon and central Idaho, and a greater than 30% chance of above normal precipitation in the rest of the region.

The forecasts should be interpreted as the tilting of odds towards general categories of conditions, and should not be viewed as a guarantee that the specified conditions will be realized. The forecasts tend to have most skill in years of significant warm or cold ENSO conditions, like this one. Historically, La Niña conditions have favored cooler than average winter temperatures around western Washington and western Oregon. However, the combination of long-term warming trends with the La Niña influence supports the CPC forecast for “equal chances” for above, below, and average winter temperatures in the PNW region.

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Pacific Northwest Resource Outlooks

Climate Prediction Resources

The links below provide access to the latest information on the current state of global and regional climate, as well as links to global and regional climate predictions.

The Current State of the Tropical Pacific

Predictions of Tropical Pacific and North Pacific Conditions

The Current State of the Globe

Current and Predicted U.S. Conditions

Pacific Northwest Conditions

State Climatologist Offices

Special Areas