Monday, June 13, 2016

Yesterday's Strong Storms

After doing a post yesterday on some of the subtleties of convection during the morning and early afternoon yesterday (see prior post The Unusual Distribution of Cumulus Clouds Today), Mother Nature decided to crank things up and give us some strong storms later in the day.

The afternoon sounding from the Salt Lake City International Airport sets the stage.  With daytime surface heating and abundant atmospheric and soil moisture, the surface-based convective available potential energy (CAPE, a theoretical measure of the amount of energy a parcel of air would have if lifted vertically) was 2277 J/kg, a remarkably high value for northern Utah.  Mixing out the shallow surface layer gives lower values, but this is a sounding consistent with deep convection and strong updrafts.

Source: SPC
And we got some strong storms, some of which were long lived.  Perhaps the most impressive was the cell that tracked from the West Desert, across I-80, over the Great Salt Lake, and eventually to Willard, following the green line below.

KMTX 0.5º Radar Reflectivity at 0046 UTC (1846 MDT) 12 June

KMTX 0.5º Radar Reflectivity at 0259 UTC (0859 MDT) 12 June

Intrepid University of Utah storm chaser Sara Bang tweeted the photo below showing golf-ball sized hail that she intercepted along I-80.

Based on the time of her tweet, the hail was likely produced by the storm in the radar images above, which eventually produced 1.5 inch diameter hail in Willard and Perry as it crossed I-15 near Willard Bay.

Source: NWS
I suspect that there will be some dents on vehicles in these areas.

The Salt Lake Valley got some hail as well, although the largest report I saw was dime sized.  The storm that produced the hail was well-developed, with the visual characteristics of a weak mesocyclone.  From my house in the Avenues, looking southwest toward the southern Oquirrhs, the storm featured a well-developed wall cloud, characterized by a locally low cloud base, and a precipitation shaft consistent with the forward-flank downdraft.

I'm no convective storm chaser, so feel free to comment on this interpretation.  The anvil trained off downstream and produced some mammatus over the University of Utah.

More storms are likely today.  Although the shear is less favorable for such strong storms, the CAPE looks to be high.  Keep an eye to the sky and an ear out for watches and warnings as discerning between thunderstorms and severe thunderstorms is notoriously difficult in our part of the world.

1 comment:

  1. The convection that day was fairly impressive, with cloud features that remind me of the few dryline storms I have had the chance to see in the Plains region. I had some small hail at my house and noticed some impressive mammatus and the low-based wall cloud type features. It looked like the directional wind shear was weak (and reversed near the surface) so only some modest rotation, but it was noticeable.