The Meteorology of the Seattle Crane Collapse

Important New Information:  An unofficial report from the weather station at the very close Center for Wooden Boats noted a gust to 35 mph at 3:26 PM on Saturday.
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A crane collapsed in Seattle around 3:30 PM yesterday (Saturday) at the site of the new Google facility (Fairview and Mercer).  Tragically, four people lost their lives and several more were injured.

The failure was coincident with the passage of a wind shift and surge in winds associated with the southward passage of a Puget Sound convergence zone.   This wind shift/strengthining was associated with a dark cloud feature and some light rain...something that was evident from a sequence of images from the Seattle PanoCam ( a sequence from 3:10 through 3:40 PM is shown below).

The weather radar image from Camano Isl at 3:26 PM showed light to moderate precipitation associated with the convergence zone.

While the Doppler radar velocity indicted a strengthening of the wind (gray color indicates little velocity towards or away from the radar, the light yellow about 20 kt).

One of the nearest observing sites was near Eastlake Ave. (see map--the oval is the accident site)

 The observations at this site showed a gust to 25 mph just at the time of the incident.  The winds were from the north.  Look at the temperature trace (red line).  There was a large (roughly 10F) drop)in temperature with the wind event--consistent with the increase in clouds and onset of precipitation (note that the dew point (green line) rose at the same time, consistent with a moistening of the air).

Even better perhaps was a site right on the lake (see map)..

Its winds gusted to 23 mph around 3:30 PM.

Other nearby sites were consistent with this wind evolution, but slightly weaker.  The site in question could have had stronger winds (5-10 mph more) because it was upstream of the relatively smooth/low drag Lake Union.

The development of strong northerly winds on Saturday afternoon was expected, with the model and NWS forecasts clearly predicting it (see sample below).  Seattle WindWatch was sending out messages for days.

I will let others evaluate whether an increase in winds to around 30 mph should have taken down the crane.

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The Northwest Weather Workshop on May 3-4

There is one local gathering each year in which regional meteorologists and interested layman get together to talk about our weather and its impacts:  the Northwest Weather Workshop.  This meeting is open to everyone.

The workshop this year will be on May 3-4 at the NOAA/NWS Sand Point facility in north Seattle.

The first day will include a session on Northwest wildfires--their prediction, the smoke, the associated meteorology and more.    That evening there will be banquet and a special speaker from Washington Department of Transportation, talking about dealing with the cold and snow in February.  Saturday will have sessions on OLYMPEX (a weather field experiment in the Olympics),  advancing weather modeling, the cold/snow of February, and much more.  Lunch Saturday is included in the modest registration fee.  There are special rates for students.

Typically, about 120-150 folks attend the meeting, which is held in Bldg. 9 of the NOAA Sand Point facility just north of Magnusson Park.  Folks often want to know where you have to be a meteorologist to come.   My answer is that 70-80% of the talks should be perfectly accessible to lay people.

You can view the detailed agenda here.  If you want to go to the meeting you must register in advance.  To register or learn more about the workshop, please go to this website: https://atmos.washington.edu/pnww/