Forecasts and Planning Tools

Seasonal to Interannual Forecasts

Climate Outlook

ARCHIVE COPY - SEPT/OCT 2008

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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.


What's Next for the Pacific Northwest?

September/Ocotber 2008
Updated October 1, 2008 (posted October 8)
Reviewed October 24 (no further updates made)

The climate outlook is reviewed monthly and updated as needed.

The Pacific Northwest (PNW) experienced near-normal temperatures and precipitation during June-July-August (JJA) and September, as shown below.

  June-July-Aug September
Temperature total, departure total, departure
Precipitation total, departure total, departure

Table 1. Comparison of average Pacific Northwest temperature and precipitation for June-August 2008 and September 2008. Departures are relative to 1971-2000. Source: High Plains Regional Climate Center.

In contrast to the climate over land, ocean surface temperatures both along the coast and over the north Pacific exhibited large magnitude anomalies during the past 12 months. Washington and Oregon coastal sea surface temperatures (SSTs) were characterized by large cold anomalies from September 2007 through July 2008, with more normal conditions in August 2008 (animation; NOAA Coastwatch). Consistent with these temperature anomalies has been strong upwelling, as documented in satellite wind estimates (animation; red for bringing cold water to the surface) and pressure-based alongshore upwelling indices (Washington [positive values for bringing cold water to the surface]; Oregon; NOAA Pacific Fisheries Environmental Laboratory).

The anomalous coastal conditions have contributed to a strong cold polarity of the Pacific Decadal Oscillation (SST anomaly map, PDO definition), with 12 consecutive months of negative PDO values, and the last five months with PDO values exceeding one standard deviation in magnitude (digital values, 1900-93 climatology). [For a normally distributed variable, only 32% of the values exceed one standard deviation in magnitude.].

Current indicators for Pacific climate

El Niño/Southern Oscillation (ENSO). Last winter's cold ENSO peaked in February (Niño 3.4 (5N-5S, 170-120W) SST anomaly of -1.85°C, 1971-2000 climatology), and it diminished in amplitude in subsequent months. The August and June-July-August mean SST anomalies are 0.21 and 0.02°C, respectively. The NOAA Climate Prediction Center, on 11 September, characterized the present conditions as "ENSO-neutral" (definition, latest report). Seventeen of the 20 ENSO forecast models polled by the International Research Institute for Climate and Society predict a continuation of ENSO-neutral conditions through the end of the forecast period (May-June-July of 2009).

Pacific Decadal Oscillation (PDO). The cold polarity of the PDO has been present since September 2007, and has intensified in amplitude during the last five months (April through August) (see above). Both the July and August values exceed 1.5 standard deviations in magnitude. The NOAA Earth System Research Laboratory's statistical Linear Inverse Model PDO forecast is for continued cold polarity, but of smaller magnitude, through the end of the forecast period (September 2009) (forecast).

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What does the outlook mean for the PNW in coming months?

The seasonal climate forecast by the NOAA Climate Prediction Center is for a greater than 33% chance of above normal October-November-December temperatures in Idaho, eastern Oregon, and eastern Washington; and an equal chance of below, equal to, or above normal temperatures for the remainder of the PNW. The precipitation forecast for the same period is for an equal chance of below, equal to, or above normal precipitation. The skill of the precipitation forecast derives from ENSO-related changes in precipitation. The model precipitation forecast has no useful skill in ENSO neutral years, like this one. The forecasts should be interpreted as the tilting of odds towards general categories of conditions, and should not be viewed as a guarantee that the specified conditions will be realized.

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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