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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

February 2012
Updated 31 January 2012 (posted 08 February)

The 90 days ending on January 28 were cooler than normal for the western coast of the US, with few large temperature anomalies in the Pacific Northwest. (Figure 1) shows the temperature departure from the 1971-2000 normals illustrating that most of the Pacific Northwest was within 2°F of normal for the last 90 days. Western OR and most of WA State were cooler than normal by about 2°F. Eastern OR and most of ID were on the warm side, with temperatures between 1 and 3°F warmer than normal. The most extreme temperature departure for the western states in the last 90 days occurred in eastern MT, where temperatures were between 6 and 9°F above normal.

Precipitation during the last 90 days was generally below normal throughout the western US, especially in CA and NV, as shown in the precipitation percentages of normal, where 1971 - 2000 average conditions serve as the baseline (Figure 2). For the Pacific Northwest, the driest areas were in east-central WA, south-central OR, and near Dubois, ID, receiving between 25 and 50% of normal precipitation in the last 90 days. These dry conditions in combination with the dry autumn conditions prompted the US Drought Monitor to label some of these areas with moderate drought. Dry conditions prevailed elsewhere in the Pacific Northwest as well with areas of eastern WA, eastern OR, and central ID receiving between 50 and 70% of normal precipitation during the same time period. Some locations fared better in the last 90 days, with most of western WA and western OR receiving between 70 and 90% of normal precipitation. A few locations even received above normal precipitation – parts of the Willamette Valley in OR, along the I-5 corridor in southwest WA, parts of Okanogan County in WA, and southern ID.

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ENSO Conditions

According to the Climate Prediction Center (CPC), the weak-to-moderate La Niña is still present in the equatorial Pacific Ocean. The La Niña Advisory issued by the CPC in early September is still in effect. Negative sea-surface temperature anomalies in the Pacific Ocean have strengthened in the last 90 days, as well as the temperatures in the upper 300 meters of the ocean. These changes were expected, as an ENSO event is typically its strongest during the winter months. A majority of the ENSO forecast models indicate a continuation of the current La Niña into the spring with some weakening, followed by near-normal conditions in summer and autumn of 2012.


Climate Outlook

What's next for the Pacific Northwest? La Niña conditions tilt the odds toward wetter and cooler winters, but so far only the latter portion of that typical situation has come into fruition. The CPC outlook continues to rely heavily on the statistical relationship between La Niña events and cooler and wetter conditions in the Pacific Northwest for the seasonal outlook. The CPC three-class February-March-April (FMA) temperature outlook (Figure 3) has chances of below normal temperatures exceeding 33% for WA, the western half of OR, and the ID panhandle. Eastern OR and southern ID have equal chances of below, equal to, or above normal temperatures for FMA. The FMA precipitation outlook (Figure 4) calls for at least a 33% chance of above normal precipitation for all of WA, the western half of OR, and the northern two thirds of ID. The latest model runs from NCEP's coupled forecast system (CFS) provide a somewhat different perspective. These simulations, which constitute just one piece of the information used in the CPC seasonal outlooks, suggest that February may be warmer than normal for much of the Pacific Northwest. The CFS model indicates a return to relatively cool temperatures for March and April, as is typical during La Niña. How the February-March-April period will play out remains to be seen, of course, and will be addressed in the next CIGnal issue.

 

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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