Office of the Washington State Climatologist

Climate Outlook

What’s Next for the Pacific Northwest?

Neutral El Niño-Southern Oscillation (ENSO) Conditions

According to the latest ENSO forecast from the Climate Prediction Center (CPC), La Niña conditions are expected to last through the winter in the equatorial Pacific.  Since mid-May, cooler than normal sea surface temperatures (SST) have been pushing west from the Pacific Coast of South America and have halted at 160 ˚E in October.  Easterly trade winds have been stronger than normal as consistent with the strengthening of the Walker Circulation in La Niña conditions.  SSTs range between 0.5 to 1.5 ˚C in the western equatorial Pacific. While SST anomalies of -1.0 to -2.0 ˚C exist in the eastern equatorial Pacific, this region has undergone warming over the past month with the Oceanic Niño Index (ONI) having increased to -1.2 from  -1.6 ˚C.  Even though SST might have slightly warmed over the past couple of weeks, sub-surface sea temperatures continue to drop in the eastern equatorial Pacific further solidifying La Niña conditions. Of the 23 La Niña events that have occurred since 1950, SSTs in October were cool enough to rank this event as the 8th strongest in the ERSSTv5 record. CPC forecasts place a 54% chance of an ONI value below -1.5 ˚C for November-December-January, which would qualify as a strong La Niña.  ENSO models favor neutral conditions to return to by April-May-June of 2021 with odds at 55%.

What does this mean for Washington in the coming months?

The CPC December temperature outlook has increased chances of below normal temperatures statewide with slightly greater chances in the northwest pocket of the state. The precipitation outlook matches the La Niña pattern with increased chances of above normal precipitation across the state.

The CPC three month (December-January-February) temperature outlook has slightly favored chances of below normal temperatures in the southeastern half of the state with greater chances existing in the northwestern half. With similar correspondence to the December outlook, above normal precipitation is favored statewide with the greatest odds in the 40 to 50% range in eastern Washington.

Last Updated: 11/19/2020

Climate Prediction Resources

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