Seasonal to Interannual Forecasts
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
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.
For More Information
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.
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.
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
- Real-time data from moored ocean buoys (NOAA’s TAO array)
- ENSO diagnostic discussion (NOAA’s Climate Prediction Center)
- Weekly ENSO update (NOAA’s Climate Prediction Center)
- ENSO Quick Look (International Research Institute for Climate and Society
- Monitoring El Niño/La Niña (NOAA’s Climate Prediction Center)
Predictions of Tropical Pacific and North Pacific Conditions
- Seasonal Niño3.4 sea surface temperature anomaly plume forecasts (European Center for Medium-Range Weather Forecasts)
- Statistical Probabilistic ENSO Predictions (International Research Institute for Climate and Society)
- Sea surface temperature forecasts (International Research Institute for Climate and Society)
- Experimental PDO and Pacific Seasonal Forecasts (NOAA's Earth System Research Laboratory)
The Current State of the Globe
- Climate diagnostics bulletin (NOAA’s Climate Prediction Center)
- The North Atlantic Oscillation (NAO) (NOAA’s Climate Prediction Center)
- Accumulated daily precipitation time series graphs (NOAA’s Climate Prediction Center)
- Daily global and regional precipitation analysis (NOAA’s Climate Prediction Center)
- Index of Climate Prediction Center’s climate monitoring activities and data
Current and Predicted U.S. Conditions
- Monthly to seasonal climate outlooks (NOAA’s Climate Prediction Center)
- State of the Climate report (National Climatic Data Center)
- Northern Hemisphere snow report (National Climatic Data Center)
- Spring and summer streamflow forecasts (USDA Natural Resources Conservation Service)
- Drought in the US
- Water supply forecasts and snowpack conditions for the Western U.S.
- Large fire incidents (National Interagency Fire Center)
- Experimental seasonal fire risk forecasts (U.S. Forest Service)
- Western U.S. climate conditions and forecasts (Western Regional Climate Center)
- Monthly temperature and precipitation maps (National Climatic Data Center)
Pacific Northwest Conditions
- Temperature and precipitation maps (Western Regional Climate Center)
- Temperature and precipitation maps (High Plains Regional Climate Center)
- Western Washington water and snowpack (Seattle City Light)
- Seattle water supply conditions and outlook (Seattle Public Utilities)
- Monthly snowpack maps for the region (National Resource Conservation Service)
- Snotel River Basin Snow Water Content (Western Regional Climate Center)
- River forecasts (NOAA Northwest River Forecast Center)
- Wildland fires (Incident Information System -- InciWeb)
- Oregon and Washington wildland fires (Northwest Interagency Coordination Center)
- Coastal conditions (NOAA’s CoastWatch)
State Climatologist Offices
- Drought in central and southwest Asia (International Research Institute for Climate and Society)