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Seasonal to Interannual Forecasts

Climate Outlook

ARCHIVE COPY - JUNE 2010

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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?

June 2010
Updated 22 June 2010 (posted June 25)

The climate outlook is reviewed monthly and updated as needed.

The 3 June NOAA El Niño Southern Oscillation (ENSO) diagnostic discussion indicates favorable conditions for a "transition to La Niña conditions during June - August 2010." This discussion is updated early in each month. A review of tropical Pacific observations and more recent ENSO forecasts is found below.

The NOAA Climate Prediction Center (CPC) July-August-September temperature forecast is for a greater than 33 percent chance of above normal temperatures in southern Idaho, and an equal chance of below, near, and above normal temperatures in the remainder of the PNW. The CPC precipitation forecast for the same period is for an equal chance of below, near, and above normal precipitation throughout the western U.S. The precipitation forecasts have only marginal skill during periods like the present when the tropical Pacific climate is near normal (ENSO neutral, CPC tools discussion).

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.

For More Information

Recent Pacific Northwest Climate

The Pacific Northwest experienced cooler and wetter than normal conditions in the last 90 and 30 days, respectively, with Portland establishing a new June record precipitation total of 4.24 in. (10.8 cm) in just the first 16 days of the month (daily totals, NCEP; "Oregon Live" article). The average June precipitation for the Rose City is 1.59 in. (4.0 cm).

The average temperature departure for the 30 days ending on 14 June continued a pattern of below normal temperatures that began in March (20 March through 18 April and 18 April through 17 May averages, WRCC). Temperatures during 16 May through 14 June were typically 2 to 4 °F (1 to 2 °C) below the 1971-2000 mean over the PNW, California, Nevada, Montana, and western Wyoming. Large cold departures, in excess of -4 °F (-2 °C), were observed in the Oregon Cascades, the Okanogan region of Washington, and the Snake River Valley of Idaho (Boise, Pocatello). The temperature departures in the coastal regions of Washington and Oregon were slightly cooler than the 1971-2000 mean (departures smaller than 2 °F (1 °C)).

The precipitation for the 30 days ending 14 June is characterized by totals that are betweeen 2 to 4 times normal over the Snake River Valley in Idaho, Washington, northern and coastal Oregon, and coastal northern California (total, departure, percent normal). The largest magnitude excesses, between 4 and 8 in. (2 and 4 cm), were observed to the west of the Cascades. The above normal precipitation contributed to water levels on the 21st of June that were 80% and higher of bankfull on the eastern slopes of the Washington Cascades, including the Stehekin, Methow, and American Rivers; the Oregon Wallowas; and in western Montana rivers that feed the Columbia (21 June analysis, legend; today's analysis; NWRFC).

The additional precipitation and cooler than normal temperatures in the PNW contributed to an easing of drought conditions throughout the PNW and a declassification of drought status in Washington, north and central eastern Oregon, and the southwest corner of Idaho (15 June, 18 May, Drought Monitor). Consistent with this there are no "large wildland fires" (fire area > 100 acres) in the PNW on 22 June (today's analysis for Oregon and Washington (NICC) and Idaho (InciWeb).

May coastal sea surface temperature (SST) anomalies made for the second month of below normal temperatures (April) with anomalies at the coast typically 1 °C below the 1985-97 normal and temperatures between 1 and 2 °C below normal within 15 degrees longitude of the coast (PFEL). The meridional winds along the Oregon coast, which drive upwelling, document periods of upwelling-favorable northerly winds in April and May, and strong and unseasonable downwelling-favorable winds in the more recent period from mid-May through early June (James Johnstone, UW). On a broader scale, negative Pacific SST anomaliess in excess of -0.5 °C were observed to the east of Hawaii and in the Gulf of Alaska for the period 16 May through 12 June (1982-96 mean, ESRL).

Sources:

  • National Centers for Environmental Prediction (NCEP)
  • Western Regional Climate Center (WRCC)
  • Northwest River Forecast Center (NWRFC)
  • Drought Monitor
  • National Interagency Coordination Center (NICC)
  • Incident Information System (InciWeb)
  • Pacific Fisheries Environmental Laboratory (PFEL)
  • Earth System Research Laboratory (ESRL)

  • Recent and Projected Changes in Key Indicators for Pacific Climate

    El Niño/Southern Oscillation (ENSO). The NOAA El Niño Southern Oscillation (ENSO) diagnostic discussion, issued 3 June, indicates favorable conditions for a "transition to La Niña conditions during June - August 2010." The average SST anomaly averaged over 5°N-5°S, 170-120°W in the equatorial Pacific, in what is called the "Niño 3.4" region, is employed as a key indicator of tropical Pacific climate in the discussion. The Nino 3.4 SST anomaly peaked in December at 1.78°C, declined in magnitude in subsequent months, and became slightly negative (-0.02°C) in May. The early weeks of June have seen the development of significant cold SST anomalies in the equatorial Pacific (animation).

    NOAA employs mechanistic and statistical models to forecast how ENSO will evolve over the next several seasons. Mechanistic models solve equations for ocean and atmosphere motions, and precipitation and radiative processes to forecast the future from present conditions. Statistical models, on the otherhand, are constructed from observations of past climate, and apply regression coefficients to present climate conditions to forecast the future. Agreement of the forecasts from these two types of models increases our confidence in the forecast.

    The ENSO models are initialized with ocean and atmosphere data through May and the forecasts are summarized by the International Research Institute for Climate and Society. Twenty of the twenty-three models forecast the further development of cold Nino 3.4 SST anomalies during July-August-September, with a clustering of seventeen forecasts for Nino 3.4 SST between -0.4 and -1 °C, or moderate cold ENSO. The cold conditions are forecast to continue through the winter, with the predicted mean Nino 3.4 SST anomaly for October-November-December and January-February-March at -0.8 and -0.6 °C, respectively.

    Pacific Decadal Oscillation (PDO). The PDO index became positive in December 2009 and, beginning in January, values have been typically around 0.7 standard deviations (1900-90 reference period, PDO values). Positive PDO values are consistent with above normal SST anomalies along the eastern portion of the north Pacific and negative SST anomalies in the central north Pacific. [For a normally distributed variable, only 32% of the values exceed one standard deviation in magnitude.] The existence of warm ENSO during June 2009 through April 2010 in the equatorial Pacific is consistent with the development of a PDO warm phase.

    NOAA employs both statistical and mechanistic models to forecast the PDO and coastal ocean conditions. The statistical linear inverse model forecasts the PDO to be weak and negative through the end of the forecast period in Spring 2011. The NCEP coupled forecast system, a mechanistic ocean-atmosphere model, predicts a continuation of the present pattern of north Pacific SST anomalies, with cold SST anomalies along the eastern boundary and positive anomalies in the central north Pacific, through the end of the forecast period in December-January-February. This pattern is consistent with a weak, negative PDO later this year (22 June forecast, more recent forecasts).

    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