Impact of El-Nino & Warm PDO on Summertime Wind in the Pacific Northwest

The warm phases of the El-Nino Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) have combined to make the 2019 warm season very unusual for wind forecasting in the coastal waters and inland waterways of the Pacific Northwest and northern and central California. El Nino is encouraging the southward displacement and intensification of the Pacific storm track while the Warm PDO and its’ associated pool of cooler sea-surface temperatures in the central Pacific are acting to weaken and enlarge the climatologically-favored North Pacific surface high, leading to a host of changes to seasonal wind patterns in the Columbia River Gorge, the San Francisco Bay region, and the Puget Sound and Georgia Strait.

Using observations from publicly available gridded reanalysis and climate records and the WeatherFlow™ network of weather stations we discuss changes from the historical record with a particular focus on the impacts of larger shifts in the general circulation on winds in areas with high sensitivity to microclimate influencers like nearby terrain, coastal upwelling, and prevailing ocean currents.

We find four particularly prominent phenomena that impact local seasonal wind regimes noticeably. There has been a significant uptick in the presence of the San Francisco Bay area coastal marine eddy, which we find to be tied to both the weaker North Pacific High and warmer waters in the Alaskan coastal currents, that has drastically changed coastal wind and fog distributions. The marine influence on the Columbia River Gorge has thinned and become more unstable, which has caused the normally ubiquitous steady west winds between Stevenson, OR and Hood River, OR to lull more often. The southward displacement of the storm track has made the usually reliable daily winds at Squamish Spit, BC exceptionally unstable and difficult to forecast. And increased troughiness across the interior Northwest US and British Columbia has kept temperatures well below normal across the Columbia River Basin in Washington, leading to unusually frequent outbreaks of stiff westerlies in the eastern Columbia Gorge. We show visual evidence of the changes in cloud formation patterns, statistical summaries of wind data at key locales in the summer of 2019 compared to averages from the prior 15 years, and general circulation composite analyses and make the case that the ENSO+/PDO+ blend may give hints as the likely impact of increasing global temperatures on wind patterns in the coastal Pacific Northwest going forward.