A Review of the 2019 Epiphany Windstorm

The strongest storm thus far of the 2018–2019 storm season brought a brief but intense blow to the Pacific Northwest on January 5/6, with south/central Puget Sound (including the Leschi area) experiencing 50–60 mph winds and worst damage. I’ve heard that some folks are calling this storm the “Epiphany Storm” since 1/6 was Epiphany 2019 (the 12th day after Christmas).

A toppled tree just east of Leschi Elementary on Lake Dell Ave. Image courtesy Sara Robertson.

As far as wintertime midlatitude cyclones go, the Epiphany Storm was relatively weak. Based on observations near Long Beach in far SW Washington, it looks like the central pressure dropped to 982–983mb, which is strong but nothing out of the ordinary. On satellite, the storm resembled a “glob of clouds” rather than a well-defined, hook-shaped midlatitude cyclone.

However, the Epiphany Storm had two distinct features that helped it deliver a solid, region wide below despite its small size.

First, the storm took a nearly perfect track for high winds in Puget Sound. It raced NNE from just off the Oregon Coast to Cape Disappointment and eventually across the Strait of Juan de Fuca towards the US/Canada border. As it did so, it dragged a small region of intense pressure gradients across the highly populated I-5 corridor, knocking out power to hundreds of thousands of people and causing one injury in the process.

Second, there were strong pressure rises at most stations with the passage of this storm. The NNE (as opposed to more easterly) track, the moderate/fast speed and the intense pressure gradients to the south of the low-pressure center all played a role. Most stations saw their strongest winds during the time of maximum pressure rise immediately after the center of the storm had passed.

The University of Washington WRF-GFS model did a fantastic job modeling this storm. After several “so-so” or downright poor forecasts for major windstorms in recent years (the 2016 Ides of October storm comes to mind!), it’s refreshing to absolutely nail a forecast, especially with all the uncertainty that existed even 24 hours away from landfall due to differences in various models.

Most Pacific Northwest windstorms create a surge of westerly winds down the Strait of Juan de Fuca as they depart, and this storm was no exception. Not only did many locations throughout Island and San Juan Counties experience 60+ mph gusts from this westerly surge, but an intense squall line formed over Southern Whidbey Island and extended north all the way into Bellingham. The forecasters at the Seattle NWS office issued a rare Severe Thunderstorm Warning for 60 mph winds and penny-sized hail associated with this feature.

We can still get windstorms in February, March and even April, but they are more rare and generally weaker than the storms we see from November through January. So, while windstorm season is far from over, the chances of us seeing a storm stronger than the 2019 Epiphany Storm this winter/spring are quite low.

~Charlie Phillips

Charlie Phillips, a Madrona resident, received his B.S. in atmospheric sciences from the University of Washington and works in Portland as a meteorologist. Check out his weather website at charlie.weathertogether.net.