DOW Arrives at the U!

The Center for Severe Weather Research Doppler on Wheels arrived on the University of Utah campus early last night for this month's Outreach and Radar Education in Orography (OREO) field campaign.

The visit of the DOW, made possible by the National Science Foundation and Center for Severe Weather Research, will give University of Utah students a hands-on education in radar operations and interpretation, mountain and lake-effect precipitation processes, and the use of mobile observing platforms for field research.

We will exhibit the DOW at the Natural History Museum of Utah this Saturday, November 4, as part of their "Behind the Scenes" Weekend.  This is the best opportunity for the general public to check out this unique weather instrument.

My students have been working the past couple of weeks on plans to deploy the DOW for field research in northern Utah.  They plan to focus on five areas:

  1. The spillover of orographic (i.e., mountain enhanced) precipitation into the lee of a mountain barrier.  This work will concentrate on the northern Wasatch near Huntsville and the southern Wasatch near Heber.  
  2. Multirange effects.  This work will examine how upstream ranges affect precipitation on downstream topography, such as the Oquirrh Mountains affecting the Wasatch.  A number of possibilities exist depending on the flow dynamics.  
  3. Lake effect.  Always of interest, but one never knows if this fickle phenomenon will show its face.  We'll see if Mother Nature cooperates.
  4. Front-Mountain interactions.  What happens on small scales when a front plows into a mountain?  The students hope to find out.
  5. Polarimetric adventures.  The DOW is a polarimetric radar, which means that it transmits and receives radar horizontally and vertically polarized radar signals (this capability now also exists in National Weather Service radars).  Such information can be used in a number of ways, including to characterize the types of particles in precipitating clouds and to improve radar estimates of precipitation rate. 
This week focuses on training some of the students in DOW operations.  It's not quite as easy as piloting the Starship Enterprise and one also needs to learn how to configure the scanning strategies of the radar in an effective way to address key scientific objectives.  Our currently benign, warm weather is actually perfect for such training.  

After Saturday's exhibit, we will be using the DOW for a variety of teaching endeavors, both near campus and at sites across northern Utah to address the areas above.  Much depends on the weather and the teaching requirements.  Stay tuned to this blog for updates.

Snow Expected over Western Washington

The first real blast of cold air will reach western Washington with substantial snow in the mountains, where the snow level will descend to approximately 1000 ft.   There could even be some snow reaching sea level in some very favored locations, such as Bellingham and Port Angeles, downstream of the Fraser River Gap in the Cascades.

In any case, this will be the coldest air over the region since last January, so be prepared.

During the past week, high pressure has dominated our region, producing warmer than normal conditions and lots of sun.    But everything is changing now.  By Thursday morning (5 AM, see below) the upper level ridge (high pressure) area will move westward towards the Aleutians, while a potent trough of low pressure is moving towards the Northwest.  If this was one month later, there would be a serious threat of snow over Seattle.  Real serious.

The forecast of sea level pressure (solid lines) and low-level temperatures (colors) shows very cold air (blue) over British Columbia and a low pressure center (associated with upper trough) over southern Vancouver Island.  An intense pressure difference (or gradient) is found north of the border.  This is when the JAWS music starts.

One day later (Friday, 5 AM), the low has moved to the mouth of the Columbia River and cold air starts pushing into northern Washington State.  With the large pressure difference along the border,  strong and cold northeasterly flow will be moving through the  Fraser River Valley into Bellingham and over the San Juan Islands.
With cold air moving in aloft and upward motion/precipitation from the upper level trough, the Pacific Northwest will not only be wet, but snow will fall in the mountains and in areas cooled by the Fraser River outflow.

Next, let me show you the 24h snowfall maps during the next few days.  For the 24h ending 5 PM Thursday, significant snow will fall in the Cascades, with some locations getting a foot.  Lots over NE Washington.

 The next 24h, with cold air coming through the Fraser River Valley,  shows light snow over some parts of NW Washington and heavier snow over the northern side of the Olympics (down to sea level) as northeasterly flow from the Fraser outflow winds ascends that mountain range.

The 72 hr total snow over the region is impressive, with higher elevations getting 1-2 feet.  Snow in eastern Oregon as well.  Skiers should be excited...we will get a good start on base for this winter.    Snow shoeing will be viable by the weekend.

And yes, don't forget the winds.  Expect strong (30-50 mph) northeasterly wind gusts from Bellingham, across the San Juans to the Olympics (see map for 8 PM Thursday).
The pattern this week is a classic one for a La Nina will be interesting to see if this configuration is repeated soon.