Wednesday, May 18, 2011

2011-05-18: SE Colorado Cyclic Supercell & Tornado

I pretty much had abandoned all hope of convective initiation in SE CO, but resolved to stay put until after the 5pm hour (superstition). While I was busy posting about how bummed I was about storms not forming while sitting in La Junta, CO, storms erupted directly to my west.

From the get-go, a single cell on the eastern fringe of Pueblo Cty took on very characteristic visual cues that it would rapidly become severe and likely would sustain itself. This particular cell had unimpeded 25kt easterly winds and was rapidly consuming cells forming to its west and one cell to its south. As it did so, despite 30+ deg dew point depressions, the cell developed impressive laminar-appearing inflow bands from the south (which I suspect were actually failed updrafts) and a classic midlevel feeder band from the east and the LCLs began dropping immediately. I even was treated to a few horseshoe vortices along the beaver tail.

What was impressive was how rapidly this all occurred. The cell went from CI to classic supercell within an hour. The storm entered a perfect steady state and pulsed only a few times before it began to show visual cues of splitting. An RFD cut could be seen splitting the updraft as I proceeded north on CO 109.

As the RFD cut tightened the circulation on the northern-appearing split, massive amounts of hail began falling from the southern circulation. I still had internet access, so reported the hail (which varied from dime-to-nickel size, but managed to cause immediate hail fog). On radar the cell looked single cellular, but visually there were two updraft bases with the northerly one persistently with the stronger midlevel feeders.

Getting through the hail at 2330z, I managed to get under the northern cell's rain free base and for a short time got to enjoy warm easterly winds. By 2350z, the southern cell pulsed visually and formed a pretty impressive high based wall cloud. At first I thought this was due to outflow from the RFD cut, but got a terrific vantage to see the storm develop a brisk easterly sfc-level inflow jet. This was unmistakable, as was the westerly winds coming from the back of the cell from the RFD (which itself set off a westerly inflow jet/outflow boundary).

For more scientific purity, here it is the same shot with most labels removed.

I was approximately 5 miles WSW of Arlington on US 96 when the southerly storm developed sfc-level rotation under the wall cloud. At 2355z I was confident I wasn't looking at a gustnado, and data on radar suggested significant rotation at all levels, so I felt confident that this was a true mesocyclone storm tornado.

Note: above photo hasn't yet been fully processed. However, above the dust whirl, note the faint tube extending to near cloud base. Similar findings in the images below:

The tornado stayed over open land only 1 mile south of me, and it remained stationary under the southern updraft, but then obtained a brief dual vortex (both appeared slowly rotating and nonviolent), and the two vortices briefly "danced" around each other before the tornado dissipated at 0000z exactly. This was the only definite tornado I witnessed today, and it wasn't particularly pretty, but man did it feel nice to have a forecast verify when I had all but given up on the day.

By that time, the southern cell became undercut by very cold outflow from the RFD and remained undercut for the remainder of the subsequent hours. The northern cell rapidly became the dominant cell but was outflow dominant and only rarely re-ingested easterly wind. The cells both put out astounding dusty outflow and had beautiful gust fronts while periodically the northerly cell would redevelop impressive inflow bands at the midlevels and would take on classic supercell characteristics.

The gustfronts were intense and frequently developed very low LCLs, occasionally being only maybe 100ft AGL, and once had me terrified I'd misinterpreted the storm visually and it was about to put down a tornado right next to me. But the cold westerly winds and the fact the rotation lacked inflow to the east left me pretty convinced that it was part of the gust front, it just was so damned close to the ground.

I'll note that the supercell was staggeringly the big show with the tornado being merely icing on the cake. Data network availability throughout Kiowa Cty still remains pretty spotty in places, but I was reasonably impressed today with the strange places I suddenly had terrific cellular signal (try County Road E west of Galatea--huh?).

Today also marked my first chase with my new digital SLR (the Canon T2i). Since I had the original Canon Digital Rebel SLR (from my parents in 2003), the advance in technology coupled with a pretty snazzy new Canon EFS 18-200mm...the photos are already just lightyears better even preprocessing. Can't wait to share them very soon.

***Addendum to above: still have a lot to learn about the camera, sorry the quality is subpar. :)

***Addendum to addendum: I have some terrific artistic photos, but will due to me having been driving/chasing for the past 18 hours, I need some sleep. I'll also have had a chance to post-process quite a bit soon, which will enhance the photos a lot. Today's addenda were for documentation purposes, largely.


Tom Magnuson said...


I am the WCM at NWS Pueblo. Great details in your account. Question...You said you saw the tornado 5 WSW of Arlington and it was 1 mile south of you. Was that 5 WSW of Haswell? Would you mind if I link to your blog on my Met. Tom Magnuson Facebook page?

Tom Magnuson said...
This comment has been removed by the author.
Tom Magnuson said...

Did the tornado start at 555 and last 'til 600 p.m.?