Today is the first day of Autumn and the latest Japanese long-range forecast model just came out with its September through November predictions for Sea-Surface-Temperature-Anomalies (departure from average). The image above shows that the all important warm pool of sea surface temperatures (also referred to as a Positive PDO) is forecast to remain well entrenched along the Alaskan, Canadian and northwestern coast of the United States.
Why do we care so much about Sea Surface Temperatures?
Ocean temperatures directly impact the behavior of the Jet Stream. A warm PDO favors a ridge of high pressure remaining mostly entrenched across the western third of the Nation and favors more dips in the Jet Stream across the Eastern United States.
The following two images are from the same long-range forecast model predicting surface temperature and precipitation anomalies through November 2016:
Surface Temperature Anomalies (September, October and November):
- Here in the Washington Region I expect a slow start to Fall with more periods of mild temperatures (Indian Summer) versus frequent blasts of arctic air.
Precipitation Anomalies (September, October and November):
- Near normal to below normal precipitation is currently forecast during the next 60 days across the Washington Region.
Will the warm phase of the PDO hold through the upcoming Winter of 2016-17?
The image above (if it is accurate) from the same model predicts the warm PDO to remain in tact across the same area through the upcoming Winter.
The same model shows Winter starting out with a weak La Nina that may weaken further into neutral conditions as we head toward February.
- The Blue line above is showing the current El Nino/La Nina (Nino) conditions (currently temperatures are running about a half degree cooler than average which is indicative of a weak La Nina).
- The red line is the mean or middle ground forecast which basically shows a very weak La Nina (at best) continuing through the upcoming Winter. However, some of the grey lines do indicate the possibility of the SSTA (Sea Surface Temperature Anomalies) in this region warming a bit toward neutral conditions (neither El Nino the warm phase, or La Nina the cool phase).
The upcoming Winter Forecast is going to be more challenging if we do in fact head into neutral conditions.