Скачать или смотреть Radar Loop, KPUX, 5/15/2021

This radar loop shows the lifecycle of the storms I observed on 5/15/2021, both of which involved bow-head mesocyclones. Both started out as rather disorganized clusters of storms, but as one storm became dominant and developed a mesocyclone, the structure quickly evolved into a bow-echo system with the rotating storm becoming the bow-head. The first storm, over the Raton Mesa, actually had a stronger rotation signature on radar, but it was the second one that produced the tornado - and also became the bow-head/bookend vortex of a much larger-scale bow echo. These evolutions can be seen in the radar loop. The first five images show the first storm complex, near the bottom of the image just south of the CO-NM state line. The storm reaches peak intensity in the second image, at which time it coverd U.S. 64 southeast of Raton, NM with 1-inch hail. It also had its strongest rotation at this time. It is not quite a true bow-head storm yet, but by the next (3rd) image, it has made this transition. After this, the bow-head cell, which had been nearly stationary, moved pretty much due north across the state line to just west of Branson, CO, weakening after that. But the other storms down the line continued, and expanded southward. Eventually these storms became part of the second bow-echo line of storms, but I am getting ahead of myself here.

The last eight images in the loop show the evolution of the new bow echo which developed between Branson and La Junta, CO, and eventually combined with the remaining storms down the line of the first bow echo. In the first of these images, the 6th image in the overall sequence, new cells have developed northeast of Trinidad, south of U.S. 350. These cells seem to have formed on the outflow from the original bow echo. To the east, there are other storms, some of which form on a pre-existing frontal boundary extending from SE Colorado to the ENE into Kansas - the boundary SPC was looking at when they upgraded part of the existing Severe Thunderstorm Watch to a Tornado Watch. In following frames, the cells northeast of Trinidad move north toward U.S. 50, with a new cell forming over Rocky Ford initially ahead of the others. This storm quickly became supercellular, and was the one that produced the tornado - around the time of the 00:25 frame in the video. As this occurred, the disorganized cluster of cells transitioned into a bow echo, with the tornadic cell becoming the bow head. This is largely evident in this frame, and totally so in the next one, which shows a classic bow-echo structure. And from this point on, the storms in far SE Colorado and well down into New Mexico that had started out as part of the previous bow echo are now part of the new one.