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Seasonal to Interannual Forecasts

Climate Outlook

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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.

Recent PNW Climate

August 1 2011
Updated 1 August 2011 (posted 4 August)

The 90 days ending on July 25 were cooler than normal across the entire Pacific Northwest. Figure 1 shows the temperature departures from the 1971-2000 normal (in Fahrenheit) for the western US, indicating that much of the Pacific Northwest was between 2 and 4°F cooler than normal. A few locations were even cooler than that, specifically parts of eastern WA and the OR Cascades, ranging between 4 and 6°F below normal. These negative temperature anomalies represented a continuation of relatively cool temperatures for the region beginning in February 2011.

The distribution of precipitation in the Pacific Northwest during the last 90 days, in a relative sense, is shown in Figure 2. Most locations had close to normal precipitation, but a few areas were wetter than normal. Central WA and southwestern and southeastern OR, for example, received between 150 and 200% of normal precipitation. There were some drier than normal spots as well, such as south central OR and eastern ID. These locations ranged between 33 and 91% of normal precipitation. The source of both temperature and precipitation data presented here are from The Western Regional Climate Center.

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ENSO Conditions

The equatorial Pacific is now in an ENSO-neutral state, according to the Climate Prediction Center. Figure 3 shows the sea surface temperature (SST) anomalies for several regions of the equatorial Pacific since August 2010. In recent months, the SSTs have been very close to normal except for the easternmost portion of the tropical Pacific (Niņo 1+2 region) where SSTs have been warmer than normal. As for the state of ENSO for winter 2011-12, a majority of the models indicate a continuation of ENSO-neutral conditions. A just-released run of the Coupled Forecast System (CFS) model, however, indicates an ensemble mean with weak La Niņa conditions for the 2011-12 winter. These results point towards a higher likelihood that the equatorial Pacific will be on the cool side and a lower likelihood of an El Niņo developing for next winter. These predictions will be fine-tuned in the coming months and by early fall, more definitive forecasts for ENSO should be available.


Climate Outlook

What's next for the Pacific Northwest? Despite the cooler than normal conditions that have persisted, the Climate Prediction Center (CPC) August-September-October (ASO) seasonal temperature outlook (Figure 4) has equal chances of below, equal to, or above normal temperatures for most of the region. In other words, the probability is split evenly into a 33% chance for each of the three outcomes. The exception is most of western OR in which there is an increased likelihood of below normal temperatures.

The ASO precipitation outlook also has equal chances of below, equal to, or above normal precipitation for most of the region (Figure 5). Southeastern OR and southwestern ID have a slightly greater than 33% chance of below normal precipitation for the period, tilting the odds towards drier conditions there.

 

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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