Seasonal to Interannual Forecasts
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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 March 3, 2009 (posted March 12)
The climate outlook is reviewed monthly and updated as needed.
The NOAA Climate Prediction Center March-April-May forecast is for a greater than 33% chance of below normal temperatures north and west of Boise, Idaho, with the probabilities exceeding 40% in northern Oregon, northernmost Idaho, and all of Washington. The precipitation forecast is for a greater than 33% chance of below normal precipitation in southern Idaho, and an even chance of below, equal to, and above normal precipitation throughout the rest of the Pacific Northwest. These forecasts represent a continuation of the recent drier and cooler than normal conditions described below.
The seasonal 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. The precipitation forecasts only have skill in years of significant warm or cold ENSO conditions.
For More Information
The Pacific Northwest (Oregon, Washington, and Idaho; PNW) was significantly drier and slightly cooler than normal in the 30 days ending 1 March (1971-2000 mean) (precipitation total, departure, percent normal; temperature departure; WRCC). The precipitation totals were less than 50 percent of normal in northwest Oregon, western Washington, the eastern flank of the north Cascades (Okanogan and Chelan), eastern Oregon, and Idaho. This pattern is a continuation of the weaker than normal wet season that the West has experienced this water year (beginning 1 October) (map). Consistent with the deficit in precipitation, the snow pack, as measured by snow water equivalent, is near normal to 50-70% of normal throughout the Columbia basin (3 March, map legend, today; NWRFC).
The ocean surface temperatures along the Oregon and Washington coasts were near the 1985-97 normal during November and December (not shown), and became colder than normal during January and February (PFEL). The anomalously cold ocean surface temperatures along the Oregon and Washington coasts extend north through the Gulf of Alaska (February-mean analysis, ESRL), and are part of a pattern of negative surface temperature anomalies along the North American coast and positive temperature anomalies in the central north Pacific that has been present since September 2007. This pattern is the negative phase of the Pacific Decadal Oscillation. The negative temperature anomalies on the equator in the Pacific are associated with a weak, cold El Niño/Southern Oscillation episode.
El Niño/Southern Oscillation (ENSO). The phase and strength of the El Niño/Southern Oscillation phenomenon is characterized by the average sea surface temperature (SST) anomaly over 5°N-5°S, 170-120°W in the equatorial Pacific, in what is called the "Niño 3.4" region (NOAA El Niño definition). Niño 3.4 SST anomalies in November, December, and January were -0.24, -0.78, and -0.96°C, respectively (1971-2000 mean), indicating that cold ENSO conditions were developing. The average of the three monthly values is -0.66°C, which just exceeds the NOAA -0.5°C criterion for this to be a cold ENSO episode.
ENSO forecasts are made with statistical models, which employ statistics of past variability to predict the future, and mechanistic models, which solve equations for ocean and atmosphere motions, that forecast the future from present conditions. Agreement of the forecasts from these two types of models increases our confidence in the forecast. The International Research Institute for Climate and Society polls the results of 23 models, both statistical and mechanistic, that are produced by research institutions around the world. The 23 forecasts, which were initialized with January ocean and atmosphere conditions, predict a March-April-May Niño 3.4 value of -0.4°C -- a lessening of the cold ENSO towards normal conditions. Conditions are expected to return to normal (a Niño 3.4 value anomaly of zero) in June-July-August.
Pacific Decadal Oscillation (PDO). The PDO has exhibited negative monthly values since September 2007 (digital values), with values in excess of -1 standard deviation from April through November of 2008 and again in January 2009. [For a normally distributed variable, only 32% of the values exceed one standard deviation in magnitude.] The present weak "La Niña" (cold ENSO) conditions are consistent with the development or continuation of negative PDO values.
The NOAA coupled forecast system model (a mechanistic ocean-atmosphere model) predicts significant cold anomalies along the west coast of North America through April-May-June (forecast), diminishing to zero or even slightly negative by July-August-September. April-May-June is the time of the year for the transition from downwelling to upwelling along the Oregon and Washington coast, and the above forecast is consistent with an enhancement of or early transition towards upwelling.
For More Information
- Current conditions: Weekly NRCS drought monitor/snowpack update reports
- Read the latest expert analysis of the current state of ENSO from NOAA's Climate Prediction Center
- European Centre for Medium-Range Weather Forecasts ENSO forecast
- View the International Research Institute for Climate Prediction's ENSO QuickLook
- How is an El Niņo/La Niņa event defined?
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)
- NOAA El Niño and La Niña definitions (from NOAA’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 Niño3.4 sea surface temperature anomaly plume forecasts (from the European Center for Medium-Range Weather Forecasts)
- 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)
- The North Atlantic Oscillation (NAO) (from NOAA’s Climate Prediction Center)
- 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)
- State of the Climate report (from the National Climatic Data Center)
- Northern Hemisphere snow report (from the National Climatic Data Center)
- 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.
- Large fire incidents (from the National Interagency Fire Center)
- 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
- Temperature and precipitation maps (from the Western Regional Climate Center)
- Temperature and precipitation maps (from the High Plains Regional Climate Center)
- Western Washington water and snowpack (from Seattle City Light)
- Seattle water supply conditions and outlook (from Seattle Public Utilities)
- Wildland fires (from the Northwest Interagency Coordination Center)
- Coastal conditions (from NOAA’s CoastWatch)
- monthly snowpack maps for the region (from the National Resource Conservation Service)
State Climatologist Offices
- Drought in central and southwest Asia (from the International Research Institute for Climate Prediction)