Reviewing the 2019 January 5/6 “Epiphany” Windstorm

The strongest storm thus far of the 2018-2019 storm season brought a brief but intense blow to many areas last night, with many locations in the Willamette Valley and Puget Sound experiencing 50 mph gusts and a few locations even hitting 60! I’ve heard that some folks are calling this storm the “Epiphany Storm” since the peak gusts for Washington occurred on 1/6, which is Epiphany 2019 (the 12th day after Christmas). The peak gusts occurred late 1/5 for most of Oregon, but the “Epiphany Eve/Epiphany Storm” is a bit verbose, so for the purposes of this blog, we’ll just call it the Epiphany Storm.

Note the widespread 40-50+ mph gusts throughout Western Washington and Oregon in the map below, with South Seattle in particular getting hammered. Some of the strongest winds occurred over the most populated regions, which explains the 300,000 power outages across the region even though many susceptible branches/trees had been “pruned” by the storms we saw in mid/late December.

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

Compare the structure of this storm to one on 12/20 that also knocked out power to 300,000 people, though it did so over a wider geographical region. That storm wasn’t picture-perfect either, but it at least had some sort of bent-back occlusion (the clouds wrapping around the center) and a pronounced “dry slot” near the low pressure center.

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

First, the storm took a nearly perfect track for high winds through the Willamette Valley and especially the Puget Sound region. As the graphic below shows, 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.

This slideshow from my HRRR graphics shows the track/winds with the storm as it moved through the region. Note the near-perfect track for strong winds over Central/South Puget Sound.

Second, there were strong hourly 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.

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.

My mom took some photos of the damage from this storm around the Madrona neighborhood of Seattle. The first picture shows a fallen tree on the Lake Washington Blvd. switchbacks in the Denny Blaine neighborhood of Seattle, and the second picture shows a Seattle City Light employee restoring power near McGilvra Elementary School, which is near Madison Park. If you can believe it, I actually slept through the storm; a very unweather-geeky thing to do. However, I did not see any damage in my neighborhood (Old Town/Chinatown in Portland) and I did not lose power.

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, atypical squall line/north-south oriented, bowing Puget Sound Convergence Zone 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.

Thanks for reading, and I hope you enjoyed the storm! I’m actually in Phoenix this week for the 99th annual American Meteorological Society Conference, so I’ll try to write some posts to share my adventures with y’all.

Have a great week!
Charlie