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Seasonal to Interannual Forecasts

Climate Outlook

ARCHIVE - JULY 2008, part 2

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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?

July 2008
Updated July 21, 2008 (posted July 25)

The climate outlook is reviewed monthly and updated as needed.

The cooler than normal temperatures that dominated the Pacific Northwest (PNW) during March through May (more information) were replaced in late June by normal and well above-normal temperatures throughout the region (temperature, departure; High Plains Regional Climate Center). July PNW temperatures through 7/17 were in excess of 1 and 2°C above the 1971-2000 normal and they, along with the absence of rainfall (total, departure), contributed to 1) several wildland fires along the eastern sides of the Cascade range and north of Spokane (July 18, USDA Forest Service; Northwest Interagency Coordination Center), and 2) drought conditions in central Washington, central Oregon, and southern Idaho (July 15, Drought Monitor). Normal and below normal temperatures are observed along the Washington and Oregon coasts.

The coastal ocean temperatures continue to be exceptionally cold (1985-97 climatology, animation; NOAA Coastwatch). June SST anomalies exceeded -2°C along the Washington coast and -4°C along the Oregon coast. Pressure-based upwelling indices through 18 May show April and May upwelling (positive values) that exceed the typical range (blue shading) along the Washington and Oregon coasts (NOAA Pacific Fisheries Environmental Laboratory). The cooler than normal coastal conditions are part of a pattern of basin-scale anomalies that has been present since last Fall and Winter (15 June through 12 July, 21 October 2007 through 19 January 2008; NOAA Earth System Research Laboratory).

Current indicators for Pacific climate

El Niño/Southern Oscillation (ENSO). Last winter's cold ENSO peaked in January (Niño 3.4 (5N-5S, 170-120W) sea-surface temperature (SST) anomaly of -1.86°C, 1971-2000 climatology), and it has been diminishing in amplitude in subsequent months. The June Niño 3.4 value is -0.31°C, and the April-May-June mean is -0.58°C, which the NOAA Climate Prediction Center is characterizing as "ENSO-neutral" (10 July). Fourteen of the 20 models polled by the International Research Institute for Climate and Society predict a continuation of ENSO-neutral conditions through at least December-January-February (Niño 3.4 <0.5°C in magnitude).

Pacific Decadal Oscillation (PDO). The cold polarity of the PDO has been present since September 2007, and has intensified in amplitude during the last 3 months (April-May-June), consistent with the cold coastal anomalies described above. PDO index values for April, May, and June were -1.52, -1.37, and -1.34 standard deviations, respectively (based on 1900-93 climatology; note that values greater than a standard deviation in magnitude are larger than 68% of the values for a normally-distributed variable). The NOAA Earth System Research Laboratory's statistical Linear Inverse Model PDO forecast is for a continuation of cold PDO throughout the rest of 2008 (forecast).

For More Information

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

The seasonal climate forecast by the NOAA Climate Prediction Center is for a greater than 33% chance of below normal August-September-October temperatures for western Oregon and Washington, a greater than 40% chance for below normal temperatures at the Oregon coast, and an equal chance of below, equal to, or above normal temperatures for the remainder of the PNW. The precipitation forecast for the same period is for a greater than 30% chance of below normal precipitation over much of the region, exceeding 40% in eastern Oregon and Washington, and western Idaho. Southeast Idaho, northwest Oregon, and western Washington are forecast to have an equal chance of below, equal to, or above 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 precipitation forecasts have marginal skill during ENSO neutral seasons like this one.

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