Wasatch Weather Weenies

It appears that our current cold front moved discretely across Nevada as observed during the 2006 Saints and Sinner storm (see Steenburgh et al. 2009 ).  In other words, the leading edge of the cold air didn't simply slide across Nevada as a material surface.  A new cold front developed ahead of the decaying Pacific cold front. Click on the image below for a loop of the RUC2 analysis.  In particular, note how a new trough, cyclonic wind shift, and absolute vorticity maximum develop over northeast Nevada in advance of the trough, cyclonic wind shift, and absolute vorticity maximum over northwest Nevada.  If you doubt the discrete propagation, just watch how the position of the cyclonic wind shift jumps from the -2 C isotherm at 1700 UTC to the +2C isotherm at 2100 UTC. RUC2 800-mb geopotential height (black contours), absolute vorticity (red contours), wind (vectors), and temperature (color fill).  Click to expand and animate. Cool stuff, and anothe...

As anticipated, a strong Intermountain Front is now pushing into Utah.  Note the temperature contrast along I-80.  From 51F to 34F between stations.  Yes, that is a 50 knot sustained wind immediately ahead of the front. Check out the Meteogram from the Dugway I-80 site (DPG 17).  The temperature fell like a stone with frontal passage from 53F to 42F in 5 minutes (that's the resolution of the data) and to 38F in 10 min. Wind?  Ya Betcha.  Gust to 63 mph immediately after frontal passage. Some lowland gusts over 70 mph reported so far today to MesoWest (Note: Subject to quality control verification): West Salt Flat: 70 mph Sherwood Hills: 71 mph US-6 Eureka: 80 mph Orem: 71 mph The peak gust thus far at KSLC is 56 mph and at the University of Utah is 49 mph.  

As pointed out by one of our readers, a couple of dust sources can be seen in the latest MODIS overpass.  First, the dust near Wendover originates along the Utah-Nevada border perhaps a few miles south of Wendover. One can also see a source north of Delta between the Fumarole Butte and Little Sahara. Look for the plume where it crosses the Sheeprock Mountains.   There appears to be little dust emission over the Sevier Lake Bed and environs.  I also can't see evidence of dust from the Milford area.  This is a nice "null case" for dust emission and transport as it contrasts with windstorms last Spring that produced large dust plumes from the Sevier Lake and Milford Flats area. With regards to the dust in Salt Lake, the optical depth may be too small to see in these visible images.  It's difficult to say for sure, but careful inspection suggests there may be a plume originating near Point of the Mountain (gravel quarry?) that extends northward up the I-15 c...

For your afternoon enjoyment, watch the wind take out the stop sign along US-6 in Eureka, Utah.  Now you see it. Now you don't.

As noted by one of our readers, there is some dust in the air now over the Salt Lake Valley, as well as near Wendover where the visibility is more strongly reduced. UDOT Traffic Cam I-80 MilePost 1, Wendover, UT, 1320 MST 16 Feb With a careful look, you can make out some dust emission sources and plumes in the West Desert.  That being said, we are not seeing large dust emissions from the usual suspects in southern Utah, despite the fact that winds appear to be strong enough (27 mph gusting to 39 mph at near Delta at 1359 UTC).  The meteorology is right, but perhaps the land-surface is not ready to go so early in the year. Meanwhile, a healthy cold front has developed in eastern Nevada.  It is 53F presently in Wendover with a south wind, but 30F at the Elko airport with a west wind. MesoWest surface map at 2120 UTC Update 2:29 PM: I just looked out the window and there is lots of dust!  Where is it coming from?  Inquiring minds want to know.

The sun is now high enough that we are getting some good visible satellite images for examining dust emissions and transport.  Fortuitously today, there are few cirrus clouds over the Intermountain West, so we have a birds eye view. At 1630 UTC, there appears to be little if any dust emissions from the Sevier Lake bed, Sevier Desert, and Milford Flat fire scar. Visible satellite image at 1630 UTC 16 Feb That being said, the surface winds in this region are just beginning to exceed the minimum speed needed for dust emission.  At Delta, UT (KU24) at 1647 UTC, for example, the temperature is still only 48F, with sustained winds of 21 knots (10.5 m/s).   As the convective boundary layer continues to grow, surface winds should increase dramatically in the next couple of hours, so the meteorology should be in place soon.  Stay tuned and we'll see if the land surface cooperates.

Morning has broken, the south wind is blowing, and change is coming to the Wasatch Front. At 1500 UTC 16 Feb, we have a deep upper-level trough centered off the California coast with southwesterly 700 mb flow over California and the Intermountain West.  That 700 mb flow reaches over 50 knots over the Sierra and portions of southern and western Utah.  At the moment, it is -2C at 700 mb over Salt Lake City, but a broad baroclinic zone lies upstream over western Nevada and northern California.  Note that the skies are clear on the warm side of the baroclinic zone, but cloudy within the baroclinic zone. 1500 UTC 16 Feb IR Satellite Image with RUC 700-mb Temperature and Wind Over the next several hours, strong frontogenesis will occur over Nevada as the upper-level trough and low-level baroclinic zone move eastward.  Several processes contribute to this frontogenesis.  As can be seen in the NAM model forecast valid 0000 UTC 17 Feb (5 PM MST), strong confluenc...