Things started pretty quickly once we got out to Eastern Colorado yesterday. Cells fired due to upslope flow, but they started sticking together and could not produce tornadoes at that point:
We watched these storms form just east of Denver and then we let one pass over us so that we could get south of it. Marble-sized hail fell brutally upon our vehicle, but nothing was big enough to cause damage. What did cause some problems was the amount of hail that stayed on the ground minutes after the storm passed:
I-70 east of Denver was covered with hail and we lost traction at least twice while braking. The air temperature also dropped to a frigid 39 degrees as the hail fell, down from around 65 just minutes earlier. We went to the tail-end of this now conjoined storm system to see if anything would intensify, but nothing was happening.
That's when a little cell near Pueblo, CO started making itself known on radar. It was unknown how this cell would develop, but after a few minutes of radar observation it became clear that this cell was going to be a good one. We made the drive down to the Pueblo area and found an intense supercell that was dropping a wall cloud. A second one formed just to the south of the first after a few minutes and then both started to fluctuate and join. This joined supercell was absolutely enormous and gave chasers (including VORTEX2, the TIV, and The Weather Channel) a few hours of absolute action. We even found the TIV (Tornado Intercept Vehicle) and took some very close-up pictures! Unfortunately it did not put down a tornado, but we did see a brief rope funnel (2:34 in video below). Here's a video of the cell from its early stages to sunset:
Here are some pictures: