What's Next for the Pacific Northwest?
El Niño Conditions
El Niño conditions are weakening in the tropical Pacific Ocean, and sea-surface temperature (SST) anomalies have cooled substantially in the last month. The weekly SST anomalies in the four Niño regions at the time of this writing are at about 0.5 degrees Celsius above normal throughout the tropical Pacific, though much of the atmosphere is still reflecting an El Niño pattern. The "El Niño Advisory" that was released on March 5, 2015 is still in effect, but the El Niño is expected to continue to weaken and be in a neutral state by the May-July period. Models indicate that La Niña conditions will develop by late summer and persist through the winter of 2016-17. At this time, the strength of the La Niña is uncertain, but a "La Niña Watch" has been released.
What does this mean for Washington in the coming months?
El Niño doesn't typically have a large impact on our summer weather. Still, there are other forecasting tools available to make a seasonal forecast. The CPC three-class summer (June-July-August; JJA) temperature outlook has increased chances of above normal temperatures for the entire state, with chances exceeding 50% on the three-tiered scale for most of the state. There is not much indication of how precipitation will turn out for JJA. The CPC outlook has equal chances of below, equal to, or above normal precipitation for the entire state.
The outlook for July-August-September (JAS) is also indicating above normal temperatures statewide. There is a slight tilting of the odds toward below normal precipitation for southern WA in locations such as Walla Walla, for example. The remaining majority of WA state is split into equal probabilities of below, equal to, or above normal precipitation.
Remember that these outlook percentages are based on a tercile system, and therefore the chances of below, equal to, or above normal temperatures or precipitation are split into equal probabilities of 33%. When there is a greater than a 33% chance of an occurrence, it should be looked at as a slight tilting of the odds in favor of that outcome.
Last Updated: 5/19/2016
Climate Prediction Resources
NWS Local 3-Month Temperature Outlook
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