Forecasts and Planning Tools

Seasonal to Interannual Forecasts

Climate Outlook

Archive Copy - August 2005

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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?

Summer/Early Fall 2005
Updated August 19, 2005
The climate outlook is reviewed monthly and updated as needed.

Current indicators for Pacific climate:

El Niño/Southern Oscillation (ENSO). NOAA's latest expert assessment states that ENSO-neutral conditions are expected for the next 3-6 months. Current climate conditions in the tropical Pacific are near average, also indicating ENSO-neutral conditions.

Pacific Decadal Oscillation (PDO). Seasonal to interannual forecasts for the state of the PDO index (based on a pattern of North Pacific sea surface temperatures (SSTs)) are an emerging science. A major source of uncertainty in developing PDO forecasts is our lack of understanding of what causes the observed multi-year persistence in the PDO index and, more importantly, what triggers PDO regime shifts. However, a strong tendency for year-to-year persistence of the PDO index along with a well-established statistical relationship with the state of ENSO provides a means for making skillful 1-year projections of the PDO index. (For more information on this one-year lead-time PDO forecast method, see Newman, M., G. P. Compo, and M. A. Alexander, 2003. ENSO-forced variability of the Pacific Decadal Oscillation, Journal of Climate 16: 3853-3857)

North Pacific SSTs have projected onto the warm (positive) phase of the PDO pattern for every month in 2005 (January-July), although the trend since May has been to weaker positive values. Notably, nearshore ocean temperatures off the coast of southern British Columbia to central California cooled considerably from exceptionally warm levels in May through mid-July to near average and even below average values from late July through present (August 18) (read related Seattle Post-Intelligencer story).

If ENSO forecasts favoring ENSO-neutral conditions in the next 3-6 months are correct, the ENSO influence on North Pacific SSTs should be expected to contribute to a continuation of recent trends toward near-zero values of the PDO index for the next 3-6 months.

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What will it mean for the PNW in coming months?

The combined expectations for ENSO-neutral conditions over the next 3-6 months, a weak PDO pattern in North Pacific SSTs, and persistence of recent surface air temperature trends over the past 15 years favor increased odds for above average air temperatures for the next 3-6 months in western Washington and Oregon, and for the entire PNW region for Aug-Sep-Oct and December-May. There is no indication of a shift in the odds towards above or below normal precipitation in this period (i.e, the probability for above-normal, normal, or below-normal precipitation is statistically equal). For a more complete discussion of the latest seasonal climate forecasts for the U.S., see the Climate Prediction Center's discussion.

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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 Conditions

The Current State of the Globe

Current and Predicted U.S. Conditions

Pacific Northwest Conditions

State Climatologist Offices

Special Areas