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 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.
For More Information
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.
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
- 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)