Sunday, December 2, 2012

A Blustery Fall Day

Wave clouds over the Wasatch at Sunrise
I love days when I wake up to a rattling house and wave clouds over the Wasatch.  Today we have a cold front moving into the western United States, with a very strong low-level pressure gradient moving into northern Utah.  

1200 UTC 2 Dec 2012 IR satellite imagery and sea level pressure analysis
In this case, that pressure gradient is oriented in a way that will drive strong flow in the primarily north-south oriented valleys of northern Utah.  Indeed, one can see a southerly low-level jet, with a peak wind speed of more than 40 knots, centered at about 800 mb (about 700 m above the valley floor) over the Salt Lake Valley in this morning's sounding.  

Winds will pick up this morning as the surface warms and turbulence mixes down some of that stronger flow.  So, if you haven't bothered to rake your lawn, your leaves should be in for an interesting ride.  


  1. Cool photo... I ended up taking essentially the same one, from a different angle. It looks to me like this is the type of front that may generate a good deal of strong convection, because the mid/upper level cold pool and baroclinic zone moves through faster than the surface front can keep pace with. This could generate forward-tilting portions with pockets of stong CAPE. You can see this hinted at in the convective panel display, and also in theta-e time height where potential temp is inverted up to 700 mb this evening. Anyone want to make bets on a lightning show nearby (particularly from SLC northward)?

  2. With the windstorm events of last year on everyone's mind the last few days, I was wondering how rare of an instance it is to have those downslope winds that were so damaging, and what needs to be in place for them to happen? I believe a strong inversion and pressure gradient is key, but what is missing on days like today that keep it from escalating to the point it did last year?