June 13, 2016

Team Duck's Forecast:

"Day 1 Synopsis: An approaching southern stream shortwave will track into Colorado/WY today, fostering an environment characterized by deep layer shear AOA 40-50 knots. At the same time, moist upslope flow vectors will develop in response to a Denver Cyclone development by mid afternoon, with climatologically high values of the upper 50s to lower 60s, with several stations in SE Colorado reporting 60s and numerous stations in western KS low-mid 60s. Low level flow and hence helicity will be more marginal until the lee low develops, which will limit the tornado threat to some extent, however, given the degree of mid-layer shear, supercells will form the initial developmental mode. Unfortunately, as Skip intimated, capping looks to break early over the high terrain suggesting a quick upscale growth, both west of Denver, and near the Raton Mesa based on the latest CAMS. There are also a few veer-back-veer type soundings popping up further north as well, suggesting the further issues with modal developing.

However, both 4km NAM and HRRR intimate that a gap will exist between the initiated clusters, primarily on or around I70 or slightly south thereof, possibly on the edge of capping. While HRRR cynically turns everything in SE CO into an MCS, and north of I70 (but leaves an impressive helicity swath on Tail-end Charlie of the north line) runs of the NAM have been more hopeful, with potentially discrete storms firing in this less cluttered window, or possibly a TEC scenario off the northern squall. Various WRF flavors paint a range of scenarios from mess to discrete, though some indications from the WRF-NSSL indicate the potential for some fairly potent supercells to develop along the line end near I70. The way I see it - the favorable DLS shear should lead to early supercells coming off the front range if the cells don’t congeal before they get up, with upscale growth within 2 hours for this initial development. This suggests a couple of tornadic windows along the I70 corridor, and possibly points further into SE CO if modal evolution is discrete - 1. Associated with initial supercell development off the Palmer and Front Range, including spout potential. 2. With a discrete SC or TEC type storm charging east along I70.

In view of this, I think heading to Bennett by 17:30Z and assessing the next move will be important, with a play around the Limon, CO region as a target most likely, and concur with Skip that we should be watching points further south for discrete development. "

Team Woodchuck's Forecast:

"Great discussions from Skip and John, and I agree that the setup is anything but obvious for the best tornado play today. Looking at 16Z observations and satellite, and a check of the 12Z NAM draws my attention to the southern side of the Palmer Divide and Arkansas Valley for the peak “magic time” play around 00-01Z this evening. This may be in the form of a tail-end Charley as John suggested. Before then, I feel a bit clueless so reckon that Bennett on down to Limon keeps us in play for various options without drawing us far from the later, more optimized potential in SE Colorado. The early convection over the mountains does seem likely to cast shadows over much of NE Colorado, reducing heating. Also, I note something of a CAPE-robber in the upper air data and predicted soundings that reduces CAPE until later this afternoon, when the height falls and upper cooling act to ramp up the instability quite rapidly.

The 16Z surface plot and NAM soundings near Lamar from 21Z and 00Z are copied below for reference. "

Team Duck's Summary:

"A strong coffee set us on our way this morning. High dew points associated with moist upslope flow in CO were expected to yield a favourable environment for tornadoes and supercells, however an MCS off the front range in the morning hours heavily depreciated the environment over northern CO, leaving the environment more favourable further south. Stronger vertical wind shear was expected to arrive with the short wave trough in the early afternoon, but initial storms formed south toward the Raton Mesa, so we decided to head for these with hopes of reaching them before they went upscale. Unfortunately, after we started in that direction, the storms continually congealed, leaving northern targets looking more favourable. These proceeded to grow upscale then fall apart also, leaving no viable dataset targets. Due to fatigue and distance to the next day’s target, we called the chase to get an early night on our way to the next day."

Team Woodchuck's Summary:

"Regarding yesterday’s post-operations action, Team Woodchuck enjoyed one heck of a storm along and north of US-34. The initial development ahead of the convective line around Akron yielded zero-zero whiteout conditions as we punched it from the rear, such that we could not see the lines on the road more than 10 feet from our car. Absolutely wild! Once we broke free the views were spectacular. Something kept the storm from evolving into a major supercell. A glance at the 00Z upper air observations tells me that the absence of 50 kt mid-level flow, advertised by the morning models, never materialized, yielding only modest hodographs in the otherwise favorable environment. Still, a great storm and a spectacular ride for sure."

After our earlier targets failed to materialize we were just about to call the chase in Anton when a robust storm went up to the north-northwest. We double backed for the intercept noting a gorgeous updraft.

A scuddy lowering that looked like a wall cloud with RFD clear slot appeared well to the north as we got under the low clouds. The storm even picked up a tornado warning for us.

It even took on a well developed cyclindrical shape and I thought we were about to get a gorgeous supercell chase and maybe even a tornado.

It gusted out almost immediately, however. We called the chase in Akron, driving out from under the dramatic looking gust front and started heading for Colby, KS