Seasonal to Interannual Forecasts
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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?
Updated December 21, 2007
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)
In November, temperatures in the PNW were near normal throughout much of the region, with slightly below normal temperatures in western Oregon and Washington and slightly above normal temperatures elsewhere. In a normally wet month, strong ridging over the region led to below normal precipitation throughout much of the PNW, with the exception of the Yakima Valley, central Oregon, and the Blue Mountains around Washington and Idaho, which received above normal precipitation.
With below normal November precipitation and the melting that resulted from the December 1-3 storms, mountain snowpack is off to a slow start. Current (as of December 20th) river basin snow water content is 70-80% of average for most basins. The only basin above average is the Olympic Mountains at 102% of average.
Current indicators for Pacific climate
El Niño/Southern Oscillation (ENSO). Cold ENSO conditions are present across equatorial Pacific. The November temperature anomaly in the Niño 3.4 region was -1.45°C, classifying this season's conditions as a moderate La Niña. Model forecasts suggest the continuation of La Niña through February with over half suggesting moderate-to-strong La Niña conditions. The cold ENSO conditions are expected to gradually warm up during Spring, returning to normal by early Summer (May-June-July).
Pacific Decadal Oscillation (PDO). The PDO index values in September, October, and November were -0.36, -1.45, -1.08 respectively (with respect to a 1900-93 climatology), consistent with changes in the northeastern Pacific temperatures described above (digital values). The ongoing cold ENSO can be expected to contribute to continued negative PDO values (cold along the coast). NOAA's Earth System Research Laboratory experimental Pacific SST forecasts suggest that the PDO pattern will likely remain negative through the forecast period (through November 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 | precipitation) is for equal chances of above, below, or normal temperature conditions for southern Idaho and 33-40% chance for normal temperatures for the remainder of the PNW. Precipitation probabilities for the period are for a 33-40% chance of above average precipitation in the PNW.
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
- Water Resources Forecasts (streamflow and other hydrologic conditions)
- Salmon survival forecast
- Forecast of extreme weather events
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
- Real-time data from moored ocean buoys (from NOAA’s TAO array)
- ENSO diagnostic discussion (from NOAA’s Climate Prediction Center)
- NOAA El Niñ:o and La Niña definitions (from NOAA’s Climate Prediction Center)
- Weekly ENSO update (from NOAA’s Climate Prediction Center)
- ENSO Quick Look (from the International Research Institute for Climate Prediction)
- Monitoring El Niño/La Niña (from NOAA’s Climate Prediction Center)
Predictions of Tropical Pacific and North Pacific Conditions
- Seasonal Niño3 sea surface temperature anomaly plume forecasts (from the European Center for Medium-Range Weather Forecasts)
- ENSO forecast forum (from NOAA’s Climate Prediction Center)
- Statistical Probabilistic ENSO Predictions (from the International Research Institute for Climate Prediction)
- Sea surface temperature forecasts (from the International Research Institute for Climate Prediction)
- Experimental PDO and Pacific Seasonal Forecasts (from NOAA's Earth System Research Laboratory)
The Current State of the Globe
- Climate diagnostics bulletin (from NOAA’s Climate Prediction Center)
- Monitoring climate in the Extratropics and Tropics (from NOAA’s Climate Prediction Center)
- The North Atlantic Oscillation (NAO) (from NOAA’s Climate Prediction Center)
- Monthly climate information digest (from the International Research Institute for Climate Prediction)
- Accumulated daily precipitation time series graphs (from NOAA’s Climate Prediction Center)
- Daily global and regional precipitation analysis (from NOAA’s Climate Prediction Center)
- Index of Climate Prediction Center’s climate monitoring activities and data
Current and Predicted U.S. Conditions
- Monthly to seasonal climate outlooks (from NOAA’s Climate Prediction Center)
- Northern Hemisphere snow report (updated monthly by NOAA/NCEP)
- Spring and summer streamflow forecasts (from the USDA Natural Resources Conservation Service)
- Drought in the US
- Water supply forecasts and snowpack conditions for the Western U.S.
- Experimental seasonal fire risk forecasts (from the U.S. Forest Service)
- Western U.S. climate conditions and forecasts (from the Western Regional Climate Center)
Pacific Northwest Conditions
- Western Washington water and snowpack (from Seattle City Light)
- Seattle water supply conditions and outlook (from Seattle Public Utilities)
- Coastal conditions (from NOAA’s CoastWatch)
- Data on PNW snowpack (from the Western Regional Climate Center)