38 years ago today, Hurricane force winds sank the Hood Canal Bridge
Feb. 13, 1979 was the great "Hood Canal Bridge Storm" -- so named because winds reaching hurricane force strength tore apart critical parts of the floating bridge, causing part of the bridge to sink.
According to noted local windstorm researcher Wolf Read, the storm was estimated to have a central pressure of about 968 mb (28.58") when it passed a buoy 315 miles west of Aberdeen, then followed a classic track, moving along the Washington coast, making landfall in southern Vancouver Island.
The peak of the storm hit that morning with the greatest wind speeds in a narrow area between Tacoma and Bellingham. Olympia's peak gust was just 44 mph, but Tacoma hit 53, Sea-Tac hit 60 and Bellingham hit 75.
But it was even worse along the northern edge of Kitsap County and the Hood Canal area, where southwest gusts reached over 80 mph, and some estimates are speeds hit up to 120 mph! Read calls it "one of the greatest storms to strike the upper Kitsap region." Making it worse, the winds were perfectly aligned with the Hood Canal, turning it into wind tunnel, aligned perpendicular to the bridge span.
Read, going off his memory, says he thinks the force of the winds and waves knocked the bridge into a list, and the theory goes that it exposed the pontoon's hatches to the pounding waves, which sheared the hatches clean off. The opening allowed water to flood into the pontoons, sinking the west and of the bridge. Another part of the bridge broke free and floated up the canal for a bit before sinking. No one was reported hurt in the collapse.
Read, quoting a WSDOT site, said the bridge was closed for 3 1/2 years and it cost $143 million (in 1982 dollars) to replace.
The name's Lee. Lee Low.
What made this storm so terrible for the Hood Canal when other great Western Washington windstorms (such as the Inauguration Day, Columbus Day and Hanukkah Eve Day) storms haven't been as bad? This particular storm was aligned in such a way as to create what's called a "Lee low" (or sometimes called a "lee trough").
When the deep center of the low was due northeast of the Olympic Mountains, it was pulling tremendous amounts of air toward its center from the southwest. As the air rose over the Olympics and sank down the northeaster side, it creates a localized area of low pressure to form on the lee side of the mountain -- thus the term "lee trough" or "lee low". This secondary low can cause extreme pressure differences over a short distance, creating its own intense wind tunnel.
This is why the bridge closes now in gusty winds:
Once the bridge reopened in 1982 -- now with heavier anchors -- the WSDOT implemented new safety procedures to close the storm during wind storms. Today, the bridge will close to traffic and open the drawspan to relieve pressure on the bridge when winds hit 40 mph for 15 minutes or more. In fact, that was required just this past Thursday as winds hit the mark. Here's video showing the power of Mother Nature's fury on the bridge -- and remember, this was only about half as bad as it was during that storm in 1979.