• A friendly and periodic reminder of the rules we use for fostering high SNR and quality conversation and interaction at Stormtrack: Forum rules

    P.S. - Nothing specific happened to prompt this message! No one is in trouble, there are no flame wars in effect, nor any inappropriate conversation ongoing. This is being posted sitewide as a casual refresher.

2014-05-21 REPORTS: CO

Good day all,

Better late than never ... Below is my chase log for May 21, 2014 in Colorado from near and east of the Denver area.

Summary: May 21 was to be the greatest chance at seeing tornadoes (out of my chase trip from May 19-22), and a trip to NE Colorado was part of the days plan. I forecasted and found the best area anywhere from north of Denver, Colorado and points eastward. The SPC had this area in a slight risk outlook, with a 10% tornado, 15% wind, and 30% (hatched) hail probabilities for an area bulls-eyed just north and east of Denver. I left Ogallalla, Nebraska and headed west on I-80 then I-76, reaching Brighton, Colorado by noon local time. This area seemed to be the place to be, and storms began initiating near Golden, Colorado / Denver to the SW. This storm was the main tornadic supercell of the day, and was tracked from near Denver International Airport and eastward along Bromley Lane to Highway 79 south (and along farm roads), eventually winding up heading east on Highway 36. The chase ended on Highway 71 north of Last Chance, Colorado. After I was done chasing, I headed back along Highway 36, taking a detour to the hail swath and flooding to the north of Byers, then resumed west on Highway 36 to I-70, and west into the city, and south on I-255 for the night in Aurora.


Above: In the graphic above, the SPC tornado outlook of 10% is shown in the left image, bulls-eyed over NE Colorado. This area was in a slight risk outlook, with an additional 15% wind and 30% (hatched) hail probability. In the middle image, the mesoscale discussion (MCD 636) is shown, with the greatest tornado threat near the Palmer Divide east of Denver, and a lesser threat area extending into Wyoming due to upslope wind flow and an outflow boundary. Despite tornadic storms forming east of Denver that day, another tornado developed well to the north near Chugwater, Wyoming (just north of the 2% outlook on the left image in Wyoming). The right image is the incredible NWS radar (base reflectivity) presentation of the tornadic supercell moving across Denver and Arapahoe Counties, and over Denver International Airport, during the late afternoon. The "hole" of the radar image is the "cone of silence" directly above the radar antenna, which cannot "look" straight up. The actual tornado, if any, is rain wrapped and should be just west (left) of the cone of silence "hole".


Above: Heading east out of Brighton with an incredible radar presentation of the storm on my screen!


Above: Funnel cloud / possible firsrt tornado from the supercell over Denver International Airport (reported near Towers road).


Above: Hail fall covers ground with some stones up to 2 inches near Commerce City, Colorado just west of Denver International Airport.


Above: The melting hail and passage of a tornadic HP supercell leaves its mark on the landscape. This caused a massive hail fall and flash flooding north of Byers, Colorado.


Above: From Highway 36 near Byers, Colorado ... The hail "swath" is pretty ominous 2-3 hours after an HP supercell dumped nearly a half foot of hail on the landscape!

Full report on this storm (May 21, 4:00 PM): Observation and indirect penetration of an extremely severe and tornadic thunderstorm in Adams County, Colorado from near I-76 and Brighton and eastward past Denver International Airport, and finally into Bennett and Byers along Highway 36. The storm was an HP supercell with violent rotation. A very large wall cloud and some small tornadoes were observed with this storm. The storm became outflow dominant and merged with a line segment during the end of its lifecycle north of Byers. Large hail was observed with this storm, with some pieces near 2" (the core had at least 3"). 70 MPH winds, frequent lightning, and heavy rains were also encountered with this storm. The hail left a large area with significant accumulations and flash flooding was observed in rural areas after passage of the supercell. Conditions causing the storms were surface heating, a low pressure trough, upper trough, and upslope wind flow. A 2009 Ford Escape was used to chase the storms. Documentation was digital stills and HD video. A tornado watch was also valid for the area until 8 PM MDT.
Last edited by a moderator: