Forecasts and Planning Tools

Seasonal to Interannual Forecasts

Climate Outlook

Archive Copy - July 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?

July 2007
Updated July 11, 2007 (posted 07.17.07)

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

June continued the May pattern of near-normal temperatures (1971-2000 mean) over the northern portion of the Pacific Northwest (Idaho, Oregon, and Washington), and warmer than normal temperatures in the southern portions of Oregon and Idaho (UW/NOAA Joint Institute for the Study of the Atmosphere and Ocean (JISAO)). Boise, Idaho, experienced a mean temperature of 70.6°F (1.8°C above the 1971-2000 normal), and 11 days with hourly temperatures > 90°F (National Weather Service (NWS)). Satellite estimates of June sea surface temperatures (SST) indicate a narrow region of colder than normal water along the Washington and Oregon coasts, and a broader region of cold water along the California coast (NOAA Pacific Fisheries Environmental Laboratory (PFEL)). Ship-of-opportunity SST estimates for March-April-May show the region of cold water to extend quite some distance offshore earlier in the year (JISAO).

June was generally drier than normal in what is climatologically a dry month. Seattle, Portland, and Spokane were about 1cm drier than their 1971-2000 normals, which range from 3 to 4.5cm, and Boise was 0.5cm wetter than it's 1.9cm normal (NWS). Both precipitation and temperature variations contribute to an ongoing drought and high fire potential in the eastern portions of Oregon and Washington and the southern part of Idaho: U.S. Drought Monitor for 10 July (NOAA Climate Prediction Center) | Fire Incidents on 11 July (USDA Forest Service)

Current indicators for Pacific climate

El Niño/Southern Oscillation (ENSO). June continued the pattern of colder than normal eastern equatorial Pacific sea surface temperatures (SST), warm anomalies in the west, and normal conditions in the central equatorial Pacific (1971-2007 mean), where the correlation of SST and PNW climate is strongest (JISAO). The 20 June forecast of 13 models summarized by the IRI is for near normal to weak cold ("La Niña") ENSO conditions for this summer through next winter. Historically, the next few months are a favorable period for the development of La Niña conditions, so careful monitoring this summer should provide valuable guidance on the evolution of ENSO over the next year (CPC ENSO Discussion).

Pacific Decadal Oscillation (PDO). The PDO index value was small and negative in May with respect to the 1900-93 mean. NOAA's Earth System Research Laboratory is now producing experimental Pacific SST forecasts, including forecasts for the PDO index, at lead times of 3 to 12 months into the future. The forecast for next winter is for weak cold conditions along the west coast of North America (negative PDO value), which would be consistent with a weak, cold ENSO during the intervening months. Details on methods and the forecasts are available here.

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

The Climate Prediction Center's outlook for July-August-September (temperature | precipitation) is for a greater than a 40% chance of a warmer than normal season in the region, with the percentages approching 50% in southeastern Oregon and southern Idaho, and a greater than 33 chance of drier than normal season over the entire region, and 40% probabilities of the same in eastern Oregon and southwestern Idaho (NOAA Climate Prediction Center). In the absence of strong ENSO conditions, the CPC precipitation forecast has negligible skill. 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.

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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 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)

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)