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ARCHIVE - March 2009

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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?

March 2009
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.

More on recent Pacific Northwest climate and recent and projected changes in key indicators for Pacific Northwest climate is provided below.

For More Information

Recent Pacific Northwest Climate

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.

Sources:

  • Western Regional Climate Center (WRCC)
  • NOAA Northwest River Forecast Center (NWRFC)
  • NOAA Pacific Fisheries Environmental Laboratory (PFEL)
  • NOAA Earth System Research Laboratory (ESRL)


    Recent and Projected Changes in Key Indicators for Pacific Climate

    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

    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 and North Pacific Conditions

    The Current State of the Globe

    Current and Predicted U.S. Conditions

    Pacific Northwest Conditions

    State Climatologist Offices

    Special Areas