Seasonal to Interannual Forecasts
ARCHIVE COPY - AUGUST 2006
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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?
Updated August 24, 2006
The climate outlook is reviewed after the 10th of each month and updated as needed.
July continued the exceptionally warm conditions throughout the Pacific Northwest, with a mean temperature of 70.2F, almost 4 degrees warmer than the long term mean, and in the 96th percentile in the 112 year record. The warmer than normal conditions began in April with temperature percentiles of 74, 82, 93, and 96% for April, May, June, and July, respectively; and are responsible for a year-to-date mean temperature in the 93rd percentile. July 2006 is the fifth consecutive July with temperatures at least 2F above normal. Julys for years before 2002 were closer to the long term mean, and recent Junes have been cool and warm. The precipitation averaged over May, June, and July has been slightly less than normal (42nd perentile). Eastern Idaho is experiencing "abnormally dry" although not "drought" conditions. Forest fires are occurring in Oregon, Washington, and Idaho..
Current indicators for Pacific climate:
El Niño/Southern Oscillation (ENSO). "[ENSO] neutral conditions exist in the tropical Pacific. As of mid-August sea surface temperatures are near 0.5C above average through much of the equatorial Pacific, and are approximately 1C above average near the dateline. There appears to be a warming trend in the equatorial Pacific over the last couple of months; however, it is still uncertain whether temperatures will warm to the level of an El Niño event in the the coming seasons." The forecast is for the tropical Pacific to remain in ENSO-neutral conditions through spring of 2007, with the following probabilities:a 60% chance of ENSO neutral conditions, a 35% chance of an El Niño, and a 5% chance of a La Niña; and the probability for La Niña increasing a little in the late Winter.
Pacific Decadal Oscillation (PDO). North Pacific SST anomalies trended towards the negative PDO pattern in September, October, and November 2005, but the PDO index has been of small magnitude and positive sign in December 2005 through July 2006. The expected continuation of ENSO-neutral conditions through spring 2007 suggest that the PDO will remain near neutral through this forecast period (see note on PDO forecasting).
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What will it mean for the PNW in coming months?
The seasonal outlooks through spring 2007 suggest a tilt in the odds towards a continutation of warmer conditions throughout the region with a probability in excess of 33% through winter, and probabilities in excess of 40% in the spring. In the absence of strong El Niño or La Niña conditions, the forecast models offer only marginal skill in predicting precipitation, and so no guidance is provided here.
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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)