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Seasonal to Interannual Forecasts

Climate Outlook

ARCHIVE - JULY (part 1) 2008

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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 1, 2008 (posted July 3)

The climate outlook is reviewed monthly and updated as needed.

Spring (March-May) was unseasonably cool throughout the Pacific Northwest (PNW). The average temperature for March-May was 43.6°F, 1.9°F cooler than the 20th century average and the 15th coldest on record. In many parts of the PNW, Spring temperature departures were generally 2-3°F below normal (1971-2000 average) with greater departures of 4-5°F in parts of central Oregon and southern Idaho. While many daily low maximum temperatures were set, Spring was not without its usual heat waves. Snowmelt from one such heat wave in May resulted in flooding for parts of eastern Washington and Northern Idaho, washing out roads and a dam along Strong Creek.

Cool weather continued through the first half of June, which began by setting a record for the coldest first week of June in Seattle. In the Washington Cascades, snowplows were clearing snow on the major highways around June 10th as an unseasonably cool storm system brought several inches of snow to the mountains and eastern Washington (Pullman, WA reported 1.5" of snow while Oroville, WA reported 3.0"). At the time, June was on track to be one of the coldest June's on record, but that was before summer weather arrived and a dominant ridge of high pressure moved over the area. Temperature departures for the month of June were generally 1°F below average throughout the PNW, with greater departures of 2-4°F in western Washington and Oregon.

While Spring weather was mostly cool and cloudy, Spring precipitation was below normal throughout the PNW. Only a few areas received above normal precipitation, with most of the region below 70% of normal. Thunderstorms in parts of eastern Washington, northeast Oregon, and northern Idaho resulted in above normal June precipitation in those areas. Others areas that received above normal precipitation include northwest interior Washington, the Washington Cascades, and parts of the Washington and Oregon coast. Central Washington, eastern Oregon, and southern Idaho are being monitored closely for the development of a drought due to the continued lack of precipitation in these areas. Currently, southern Idaho and southeast Oregon have been classified as moderate drought areas by the Drought Monitor.

Strong coastal upwelling winds (ERD Coastal Upwelling Indices, WA & OR) led to exceptionally cold ocean temperatures (4-6°F departures) along the Washington and Oregon shores in May and June. Elsewhere, coastal sea-surface temperatures (SSTs) along the west coast remain anomalously cool with temperature departures of 1-2°F. The pattern of colder than normal west coast SSTs is consistent with the cold ENSO conditions that have dominated the equatorial Pacific this year (April-June 2008 anomalies, NOAA Earth System Research Laboratory).

Current indicators for Pacific climate

El Niño/Southern Oscillation (ENSO). Since late February, Niño 3.4 (5N-5S, 170-120W) sea-surface temperatures (SSTs) in the tropical Pacific have been gradually warming up. The current Niño 3.4 region SSTs are 0.3°C below average and, as the majority of models suggested earlier this year, ENSO neutral conditions are present. According to the latest model forecasts, ENSO neutral conditions are expected to remain through August. Thereafter, considerable uncertainty exists, with some models suggesting the development of warm ENSO and others suggesting the return of cold ENSO.

Pacific Decadal Oscillation (PDO). The cold polarity of the PDO has been present since September 2007 and was -1.52 and -1.37 in April and May, respectively. 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).

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

Temperatures for western Oregon and Washington will likely remain below normal for the next three months (greater than a 33% chance) according to the Climate Prediction Center's (CPC) temperature outlook for July-August-September. However, in southern Idaho and southeast Oregon, the CPC outlook calls for an increased probability of above normal temperatures (greater than a 33% chance) with equal chances elsewhere in the region. There is an increased chance of below average precipitation through summer for much of the PNW, with a greater than a 40% probability in Idaho and greater than 33% in Oregon and eastern Washington. The only exception is western Washington, where equal chances of above, below, and normal precipitation exist.

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 in ENSO neutral seasons, like this one.

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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