Weather conditions and the tragic Seattle crane collapse
Apr 29, 2019, 3:12 PM
A University of Washington weather expert says that wind forecasts were known a day ahead of the tragic crane collapse in Seattle on Saturday.
“An important issue is the forecastablity of this,” UW Climatologist Cliff Mass told KIRO Radio. “And the forecasts were out for 20-30 mph winds for that period. So the forecasts a day before were quite good at predicting the strengthening of the winds on Saturday.”
The exact cause of the crane collapse in Seattle’s South Lake Union neighborhood Saturday is under investigation.
RELATED: SPU student among 4 killed in Seattle crane collapse
In a recent blog post titled “The meteorology of the Seattle crane collapse,” Mass explains that the winds were fairly strong that afternoon, according to measuring devices around Lake Union. The closest device to the scene was an anemometer (which measures wind speed) near the Center for Wooden Boats. Gusts around 25-35 mph were recorded around 3:30 p.m., Mass says. That’s 10-15 mph stronger than originally thought.
“They had an anemometer which measured 35 mph gusts,” Mass said. “The winds might have been revved up a bit because the winds had to pass over the building. But I think 25-35 mph is pretty consistent with that observation. There was a 25 mph wind further up the lake, not too far from Gasworks Park, so a number of locations reported this surge of northerly winds that pushed down from the north into the Seattle area.”
One thing Mass notes is that a “microburst” was not a factor in Saturday’s incident, as some have speculated. A microburst is a very localized downdraft of air, usually within a storm.
Instead, a few conditions came together to send winds into South Lake Union. Wind factors can vary from location-to-location, especially depending on the terrain or how rough the surface is. This location is down from Lake Union, which is fairly smooth.
“It was kind of a bad location if you don’t like strong northerly winds,” he said. “Water is aerodynamically smooth, so you don’t have all the drag from trees and buildings and stuff like that. So winds can get stronger over the water than they are over land.”
