Seasonal to Interannual Forecasts
ARCHIVE COPY - JANUARY 2007
On This Page
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?
Final update January 23, 2007 (posted 1.26.07)
The climate outlook is reviewed after the 10th of each month and updated as needed.
A windy December
The December climate in western Washington and northwestern Oregon was dominated by an extreme windstorm the night of 14-15 December with peak gusts in excess of 60 mph in the population centers. Nearly 1.5 million households and businesses lost electrical power, and numerous trees were downed throughout Washington and Oregon. The breadth of the damage was such that many electricity customers were without power for a week, and there were nine carbon monoxide fatalities as homeowners ran gasoline-powered electricity generators indoors in their effort to stay warm during the seasonal cold temperatures. The Governor of Washington proclaimed a state of emergency for 17 counties. (Read more on the December 14-15 wind storm from Wolf Read)
The December temperature and precipitation averaged over Oregon, Washington, and Idaho were near the long term means, and the precipitation summed for October through December was in the 90th percentile, owing to the exceptional November precipitation. The snow pack, as measured as snow water content at the SNOTEL stations, is near to just below normal in Oregon and Idaho, and 20 to 40% above normal in the Washington Cascades in observations through 17 January. The potential for flooding exists throughout the winter season and users should to check the flood watches or warnings provided by the River Forecast Center and the United States Geological Survey. The Pacific/North American atmospheric circulation index, an indicator of the strength of the climatological atmospheric ridge that dominates the region's winter weather, was significantly positive during December. Positive values of this index usually indicates no snow in the Puget Sound Lowlands, but snow it did in December.
Wasn't the El Niño supposed to bring warmer and drier conditions? Yes, in a typical warm ENSO episode the Pacific Northwest often experiences a milder, drier winter. ENSO is the strongest determinant of how our winter climate varies from one year to the next, but it does not explain all or even half of how one winter differs fron another. In addition, this year's ENSO episode is moderate in magnitude, and so it's effect on our climate is weaker than in a stronger ENSO episode.
Current indicators for Pacific climate
El Niño / Southern Oscillation (ENSO). Ocean temperatures averaged over the Nino 3.4 region of the tropical Pacific during October-November-December are 1.1°C above the 1971-2000 mean. From an historical perspective, about 18% of the 3-month seasons since 1895 exceeded the present value in magnitude. The size of this anomaly is such that it is considered a moderate warm ENSO episode. The anomalously warm tropical Pacific conditions associated with ENSO normally peak during November-December-January, and this year is forecast to be similar, with anomalies diminishing in in magnitude through Nothern Hemisphere spring (forecast).
Pacific Decadal Oscillation (PDO). The Fall PDO index values were almost a half degree negative with respect to the 1900-93 mean, but are now neutral, and are expected to become positive in the coming months due to the effect of the warm ENSO conditions (more information on PDO forecasting)
For More Information
What does the outlook mean for the PNW in coming months?
The Climate Prediction Center's outlook for February-March-April is for a greater than 33% chance of warmer temperatures than normal for western Washington and central and western Oregon, and a greater than 40% chance of warmer than normal temperatures in Idaho, eastern Washington, and eastern Oregon. The precipitation forecast is for a greater than 33% chance of drier than normal conditions in Idaho. The temperature forecast is typical of a warm ENSO episode. The forecasts should be interpreted as the tilting of odds towards warmer and drier conditions, and not viewed as a guarantee.
For More Information
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)
- 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 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)
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)