Seasonal to Interannual Forecasts
November 2004 archive copy
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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. 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?
Fall 2004 -Winter 2005
Updated November 5, 2004
Current ocean conditions
A variety of El Niño/Southern Oscillation (ENSO) forecast models continue to predict a weak-to-moderate intensity warm phase of ENSO for now through the end of winter 2005. Recent observations support these forecasts. Sea surface temperatures in the central and western tropical Pacific have been mostly warmer than average since May 2004 and, after some delay, have been spreading eastward to the coast of South America since early October.
Seasonal to interannual forecasts of the state of the Pacific Decadal Oscillation (PDO) 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 and, more importantly, what triggers PDO regime shifts. However, the relative persistence of PDO phases over the 20th century and new evidence pointing to a statistical relationship with the state of ENSO provides a reasonable basis for providing seasonal projections of the PDO state.
The PDO index for sea surface temperatures in the north Pacific has been in a moderate warm phase since August 2002. Given this and the forecast for a moderate El Niño this winter, the CIG projects continuation of a weak to moderate warm phase PDO for winter 2004-05. There are presently no indications that a PDO phase shift will take place in the next year.
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What will it mean for the PNW in coming months?
Because of the high confidence that we're likely to continue experiencing a mild-to-modest intensity warm phase ENSO event for the remainder of this fall and winter, NOAA predicts that the higher than average odds for anomalously warm and dry fall and winter weather in the PNW. Conversely, NOAA predicts lower than average odds for a cool and wet fall and winter in the PNW. An additional factor informing the current one year lead time climate forecast for the U.S. is the clear trend to warmer fall and winter temperatures in the western part of the country (e.g., 8 of the last 10 winters have been at least 1 ° F warmer than "normal" in Washington state).
Like the ENSO forecast, the PDO forecast also affects the odds for certain climatic conditions in the PNW. A warm phase PDO typically increases the odds for warmer (by about 1°F on average) and drier (by about -10% on average) winter conditions in the PNW. It should be noted, however, that other factors coming into play in the 1990s may be affecting this relationship. Recent observations highlight an increased importance for a second major pattern of North Pacific sea surface temperature variations, the Victoria Pattern. More research is needed to determine if and how the Victoria Pattern affects PNW climate. For more information on the Victoria Pattern, please see Bond et al. 2003 and McKinnel 2003.
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In summary, expectations for continued mild warm-phase ENSO conditions, along with observed temperature trends, combine to support a forecast that has increased odds for mild temperatures and less than average precipitation for the PNW region.
It is critical to note that these climate forecasts indicate relatively subtle shifts in the odds for warmer/cooler temperatures and more/less precipitation in the PNW rather than a deterministic (or exact) climate prediction for the next 2 seasons. Simply stated, expectations for continued El Niño conditions in the tropics and trends for warmer winter PNW temperatures yield a climate outlook for the PNW that has higher than average odds for a warm and dry fall and winter, and lower than average (but not zero!) odds for a cool and wet fall and winter.
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)