Forecasts and Planning Tools

Seasonal to Interannual Forecasts

Climate Outlook

ARCHIVE - MARCH 2008

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?

Spring 2008
Updated March 6, 2008 (posted March 10)

The climate outlook is reviewed monthly and updated as needed.

Strong winter storms in early January and late January/early February dumped heavy amounts of snow on the mountains in the Pacific Northwest (PNW). Most notably, the February 1 snow depth totals in the central and southern Cascades of Washington were the highest in over 30 years, with record snow on White Pass. However, mountain snowpack has not been building well since the development of a strong ridge of high pressure off the west coast, which has steered much of the moisture away from the PNW. Precipitation totals for the month of February were below normal (defined as the 1971-2000 mean) with the percentage of normal precipitation ranging from less than 50% for much of Oregon, central Washington, and the Olympic Mountains to less than 90% most elsewhere. A few exceptions include the northern Cascades in Washington (at 100-120% of normal) and the Magic Valley area in Idaho, up to 300% above normal. Even with the low precipitation amounts, mountain snowpack remains healthy throughout the PNW with March 1 snowpack at or above average (current basin snow water content).

Cooler than normal temperatures in January gave way to near normal temperatures in February. The temperature departure from the 1971-2000 mean was near to slightly above average for Washington, northern Oregon, and the Idaho Panhandle, with near to slightly below average temperatures elsewhere.

Coastal sea-surface temperatures (SSTs) gradually cooled and spread westward during January and February. February SSTs along the Oregon coast were 3°C below normal, with temperatures of 2°C below normal along the Washington and California coastlines. Beyond the coastline, temperatures were at least 3°C below normal farther west (February anomalies, NOAA Coastwatch). This pattern of colder than normal west coast SSTs is consistent with the cold ENSO conditions (La Niña) that have dominated the equatorial Pacific in the last several months (Dec 2007-Feb 2008 anomalies, NOAA Earth System Research Laboratory).

Current indicators for Pacific climate

El Niño/Southern Oscillation (ENSO). Cold ENSO continues in the equatorial Pacific, with mean November-December-January sea surface temperatures (SSTs) 1.4°C below the 1971-2000 normal in the Niño 3.4 region (5N-5S, 170-120W). The current cold ENSO conditions are characterized as a strong "La Niña" episode as defined by NCEP and are expected to diminish some through Spring. Thereafter, the majority of the models are suggesting weak La Niña to neutral ENSO conditions through Summer.

Pacific Decadal Oscillation (PDO). The pattern of colder than normal SSTs along the west coast of North America and on the equator, and warmer than normal SSTs in the central north Pacific is characteristic of the cold polarity of the PDO phenomenon. The amplitude of this pattern diminished some in November (-1.08) and December (-0.58) and strengthened in January (-1.00). One of the conceptual models for PDO variability is that the seasonal and longer term fluctuations in the PDO are produced by ENSO, so the SST forecast of continued cold ENSO is consistent with the forecast for a continued negative PDO pattern through 2008 (NOAA Earth System Research Laboratory experimental SST forecast).

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

The Climate Prediction Center's (CPC) outlook for Spring (March-April-May) temperature is for slightly increased odds of below normal temperatures along the Oregon coast and western Washington, with equal chances of above, below, or normal temperature conditions around the rest of Washington, Oregon, and northern and central Idaho. Southern Idaho has increased odds (a 33% chance) for above normal temperature in this period. The typical pattern of above average precipitation often associated with La Niña is expected to diminish during Spring with the PNW CPC precipitation outlook calling for equal chances of above, below, and normal precipitation.

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. The forecasts tend to have most skill in years of significant warm or cold ENSO conditions, like this one. Historically, La Niña conditions have favored cooler than average winter temperatures around western Washington and western Oregon (mapping tool). However, the combination of long-term warming trends with the La Niña influence supports the CPC forecast for “equal chances” for above, below, and average winter temperatures in much of the PNW region.

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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)
• NOAA El Niño and La Niña definitions (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 Niño3.4 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.
• 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

• Drought in central and southwest Asia (from the International Research Institute for Climate Prediction)