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Seasonal to Interannual Forecasts

Climate Outlook

March 2010 - Archive Copy

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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 2010
Updated 19 March 2010 (posted March 24)

The climate outlook is reviewed monthly and updated as needed.

The 4 March NOAA El Niño Southern Oscillation (ENSO) diagnostic discussion characterizes present conditions in the tropical Pacific as warm ENSO (El Niño) and anticipates a diminution of the phenomenon through Northern Hemisphere Spring. A review of tropical Pacific observations and more recent ENSO forecasts is found below.

The NOAA Climate Prediction Center (CPC) April-May-June temperature forecast is for the likely continuation of the warmer than normal conditions the PNW has experienced this calendar year. In particular, the CPC temperature forecast is for a greater than 50% chance of above normal temperatures over Oregon, Washington, and western Idaho; with the probabilities of the same diminishing to 33% in southeastern Idaho. The CPC precipitation forecast for April-May-June is for an equal chance of below, equal to, or above normal precipiation for this period over the PNW. ENSO variability is less able to affect Northern Hemisphere extratropical climate during April-May-June than during the previous months, and the above forecasts, when viewed over the contiguous U.S., are consistent with a weaker ENSO influence.

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 during significant ENSO conditions.

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Recent Pacific Northwest Climate

The 30 days ending 17 March saw temperatures above the 1971-2000 normal in Washington, northern Oregon, and northern Idaho; with temperature departures in excess of 2 °F (1 °C) in eastern Washington and northern Idaho (WRCC). The southern portions of Oregon and Idaho experienced cooler than normal temperatures in the same period, with temperature departures in excess of -2 °F (-1 °C) in the eastern Snake River Valley (Pocatello daily temperatures, NCEP). The February-average Washington and Oregon state-average temperatures were in the 96th and 83rd percentile, respectively (NCDC).

Precipitation summed over the 30-days ending 17 March was 50-75% of normal and drier over most of the PNW (total, departure, percent normal). The continuation of mild, generally drier than normal conditions again led to below normal snow pack over much of the Columbia Basin (Snow Water Equivalent (SWE) on 19 March, legend; today; NWRFC). The snowpack, as of 19 March, is near to slightly below normal SWE (75-90%) in the Canadian portion of the Columbia Basin and the Columbia Mts. of northeastern Washington; and 50-75% of normal throughout northern Idaho and northwest Montana. The eastern Snake River Valley, which extends into southwest Montana and northeast Wyoming, is at 25-75% of normal SWE.

The snow pack in the Cascade Mts. of Washington and Oregon is generally 25-75% of normal SWE with the exception of several stations on the eastern flank of the Washington Cascades, which are near to slightly above normal. The normal to above normal SWE between Yakima and Omak is consistent with the above normal recent precipitation in this region (above). [See article in the Wenatchee World.] The northeast Olympic Penninsula continues to experience generally above normal SWE. The long-lived drought conditions to the east of Cascades persists with a slight decrease between Yakima and Omak (23 February, 16 March Drought Monitor).

Strong southerly winds associated with the January storms (described in the February Outlook) produced warmer than normal sea surface temperatures (SSTs) along the west coast of Washington, Oregon, and California, and in the Salish Seas (1985-97 mean, PFEL). Coastal SST anomalies in excess of 1 °F (0.5 °C) are observed from Vancouver Island to just north of Cape Mendocino in northern California (40 °N), and in excess of 2 °F (1 °C) between northern Oregon and central Vancouver Island. The mean Pacific SST anomalies for the 30-days ending 13 March (analysis, 1982-96 mean; ESRL) documents small SST anomalies near the coast and cool anomalies centered at 30°N to the west of 130°W.

Sources:

  • Western Regional Climate Center (WRCC)
  • National Centers for Environmental Prediction (NCEP)
  • National Climatic Data Center (NCDC)
  • Northwest River Forecast Center (NWRFC)
  • Drought Monitor
  • 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 employs 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, as a key indicator of tropical Pacific climate. The Nino 3.4 SST anomaly for November, December, January, and February was 1.65, 1.78, 1.58, and 1.24 °C, respectively, and the February value represents a further weakening of the warm ENSO.

    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 model forecasts are summarized by the International Research Institute for Climate and Society. The December-January-February mean Nino 3.4 SST was 1.53°C, and the models are initialized with ocean and atmosphere data through February. The models exhibit a consensus that the present warm ENSO episode will diminish in the coming months, with a mean forecast April-May-June Nino 3.4 SST of 0.4°C. If this forecast verifies, the NOAA "El Niño advisory" will be over in April-May-June.

    Pacific Decadal Oscillation (PDO). Much of the past 2.5 years has seen strong negative PDO values relative to the 1900-93 mean, which was manifested by colder than normal temperatures along the North American coast. This run ended in July of 2009, and the index was small in magnitude and usually positive through the remainder of 2009. The January and February 2010 index values are 0.83 and 0.82 standard deviations, respectively, which are consistent with the strong west coast storms and above normal coastal SST anomalies in these months (historical digital values in units of standard deviations). [For a normally distributed variable, only 32% of the values exceed one standard deviation in magnitude.]

    The present "El Niño" (warm ENSO) in the equatorial Pacific and its forecast persistence through the Northern Hemisphere Spring is consistent with the development of a PDO warm phase in the coming months. The NCEP coupled forecast system, a mechanistic ocean-atmosphere model, predicts warm SST anomalies along the Washington, Oregon, and California coasts through June-July-August. The warmest anomalies, in the range 0.5-1°C, are forecast for along the Oregon, Washington, British Columbia, and eastern Gulf of Alaska coasts through May-June-July. The current cool SST anomalies offshore (above, centered at 30 °N, and west of 130 °W) are predicted to persist through the forecast period. This pattern of SST anomalies is consistent with the positive phase of the PDO (19 March 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