Tuesday, September 13, 2016

Last Night's Brief But Intense Dust Storm

Late in the day yesterday, a cold front pushed into northern Utah, ushering in a period of strong northerly winds and blowing dust.  The plot below shows the situation at 9 PM MDT (0300 UTC), with sustained winds on top of Fremont Island of 46 mph and strong flow across much of the Great Salt Lake and adjoining salt playa.  Strong flow also penetrated into the western Salt Lake Valley.  At this time, the area around the University of Utah was relatively protected, with lighter winds.

Source: Mesowest
Colleagues at the University of Utah are operating an observing site on the playa just east of Antelope Island.  The flow at this site was northerly to north-northeasterly for most of the afternoon, but increased dramatically at about 1900 MDT (7 PM) to about 25 mph with higher gusts.  The temperature at this time also dropped dramatically.  

Source: MesoWest
The Great Salt Lake is currently remarkably low with a great deal of exposed playa.   MODIS imagery from Sunday shows that nearly the entire northeast arm, with the exception of Willard Bay (a reservoir) and perhaps some of the wildlife refuges, as well as most of Farmington Bay, to be water free.  Vast areas around the western and northern side of the lake are also exposed.  

Source: NASA
While remote dust sources are often important during wind events in Utah, last night appears to be a case we were dealing with dust primarily from the exposed playa surrounding the Great Salt Lake.  PM2.5 levels were especially high just behind the front.  The image below shows values along the TRAX line from 8:20-9:20 PM, with a peak of over 80 ug/m3.  

Source: MesoWest
Sorry east benchers, but there was no escape for you.  Peak concentrations at Olympus Cove reached almost 110 ug/m3, much higher than observed during most wintertime inversions, although fortunately the event was short lived.  

Source: Mesowest
On the plus side, I did hear rain drops pitter-pattering last night, with the airport recording .02" of rain.  Will miracles never cease!


  1. At the current rate, assuming the current drought persists, how long would it take to the lake to dry out?

    1. That I don't know the answer to and I don't think I can provide a reasonable guess. Best to say I don't know.