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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 is now provided by the Office of the Washington State Climatologist on a quarterly basis with the CIG newsletter.

Recent PNW Climate

November 2011
Updated 19 October 2011 (posted 10 November)

The 90 days ending on October 15 were relatively warm for most of the western US, as shown in the temperature departure from the 1971-2000 normals (Figure 1). Most of WA and OR were within 2°F of normal while southeastern OR and much of ID was between 2 and 4°F warmer than normal. The warmer than normal temperatures are in contrast to the below normal temperatures experienced by the Pacific Northwest on average during the first half of the year.

The precipitation during the last 90 days is also in contrast to anomalies seen in previous months. Precipitation was generally below normal for the Pacific Northwest, as shown in Figure 2, the precipitation percentages of normal (baseline: 1971-2000). Parts of eastern WA, northwest OR, parts of south central OR, and southwestern MT were especially dry, only receiving between 25 and 50% of normal precipitation. Central ID and the southern WA Cascades were the exceptions, with wetter than normal conditions for the last 90 days.

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ENSO Conditions

La Niņa conditions are present in the equatorial Pacific Ocean, and the Climate Prediction Center (CPC) released a La Niņa Advisory in early September that is still in effect. Figure 3 shows the sea surface temperature (SST) anomalies for several regions of the equatorial Pacific since November 2010. All of these regions have had below normal SSTs in recent months. It is worth noting that the SST anomalies are not as strong this year as they were at this point last year. With back-to-back La Niņa events, it is common for the 2nd event to be weaker than the 1st. A majority of the ENSO forecast models indicate a continuation of below normal equatorial SSTs, resulting in a weak-to-moderate La Niņa event for the winter.


Climate Outlook

What's next for the Pacific Northwest? The projection of continued La Niņa conditions tilts the odds towards relatively cool and wet winter. The wetter conditions usually occur in the early part of the wet season (October through December) while the colder conditions tend to occur later in the winter (January through March). The current CPC outlook reflects this. The CPC three-class November-December-January (NDJ) seasonal temperature outlook (Figure 4) has equal chances of below, equal to, or above normal temperatures for the Pacific Northwest. In other words, the probability is split evenly into a 33% chance for each of the three outcomes. On the other hand, the NDJ precipitation outlook (Figure 5). has the chances of above normal precipitation exceeding 33% for most of the Pacific Northwest, with chances exceeding 40% for WA, the ID panhandle, and northwestern OR.

 

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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