Forecasts and Planning Tools

Seasonal to Interannual Forecasts

Climate Outlook

Archive copy - April 2007

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.

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What's Next for the Pacific Northwest?

April 2007
Updated April 3, 2007 (posted 4.3.07)

The climate outlook is reviewed after the 20th of each month and updated as needed.

Since mid-January the weather has been more seasonable. For February and March averaged together, temperatures were slightly above the long-term average around much of the Pacific Northwest with more moderate anomalies in SE Oregon through southern Idaho. With the exception of western Washington, precipitation has been below to much below average at most locations in the Pacific Northwest, especially in eastern Oregon. Mountain snowpack, which got off to a good start, has not been building well since February and was below average in most of the interior Pacific Northwest as of April 3. Basins were reporting at 70-87% of average in the Oregon Cascades; 40-72% of average in eastern Oregon; 57-79% of average in southern Idaho; 76-81% of average in north Idaho; 81-99% of average in eastern Washington; and 91-110% of average in the Washington Cascades.

Wasn't the El Niño supposed to bring warmer and drier conditions? Generally speaking, warm ENSO conditions in the tropical Pacific often bring the Pacific Northwest a milder, drier winter, but the typical pattern isn't guaranteed. While ENSO is the strongest determinant of how our winter climate varies from one year to the next, it does not explain even half of how one winter differs from another. This year's El Niño was not accompanied by the persistently shifted storm track and associated patterns of precipitation and temperature changes that have been observed in many past El Niño winters.

Current indicators for Pacific climate

El Niño/Southern Oscillation (ENSO). During January, the El Niño event was substantially weakened as an equatorial oceanic Kelvin wave pumped cold water to the surface in the eastern Pacific, leading to a rapid transition to ENSO-neutral conditions. Current model forecasts of ENSO from 21 different prediction tools show ENSO possibilities for the next year, with most forecasts suggesting ENSO neutral conditions for the rest of 2007, and about 1/3 of the forecasts calling for the development of La Niña conditions by summer. ENSO forecasts issued in the spring generally have the lowest skill, so it is prudent to continue monitoring conditions in the tropical Pacific and not place too much emphasis on this latest round of ENSO forecasts. ENSO forecasts issued in the summer and fall have historically been much more accurate than those issued in spring.

Pacific Decadal Oscillation (PDO). The Fall PDO index values were negative with respect to the 1900-93 mean, but are now neutral, and are likely to remain small now that El Niño is gone (more information on PDO forecasting).

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

The Climate Prediction Center's outlook for April-May-June is for a greater than 33% chance of warmer than normal temperatures for much of Oregon and Idaho, and equal chances for above, below, or near normal temperatures in norwest Oregon, the northern tip of Idaho and all of Washington. The near-term precipitation forecast is equal chances for above, below, or near normal precipitation throughout the Pacific Northwest. The CPC 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.

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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)
• 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)

State Climatologist Offices

• Idaho State Climate Services
• Oregon Climate Service
• Office of the Washington State Climatologist

Special Areas

• Monthly climate information digest (from the International Research Institute for Climate Prediction)
• Drought in central and southwest Asia (from the International Research Institute for Climate Prediction)