4/11/12 Texas Panhandle Storm Chase and Gustnado

by John Farley

Due to a variety of competing commitments, my ability to get out and chase in April and May of this year is more limited than usual, especially for any multi-day chase trips during this time frame. So I was pleased to see that a chase opportunity was shaping up on April 11 fairly close to my location in Santa Fe, as a somewhat diffuse dryline was forecast to set up across eastern NM, with a back-door cold front approaching from the northeast, moving across Oklahoma toward the Panhandles. With a weak shortwave approaching from the west, there would be decent directional shear in the afternoon (though not particularly storng wind fields), with surface winds from the southeast across eastern NM and the Panhandles veering with height to southwesterlies in the upper winds. In the area between the two aforementioned features, there would also be decent instability, with CAPE forecast to range from around 750 to 1500 across eastern NM and the Panhandles, as warm, moist gulf air would be advected into the area by the southeasterly low-level winds. Here is what I wrote about the day on the Stormtrack forecast thread the preceding day:

"It won't be a huge day, but certainly could be worth chasing if you're close, which I am in Santa Fe. Dryline will set up a little farther west than usual in SE Colorado and eastern New Mexico. There will be sufficient instability for strong storms and good directional shear along and east of the dryline, although the wind fields are rather weak. Still, I think the combination of instability and shear will be enough to get some supercells in the early stages of the event, although they may evolve with time into a more linear organization as they move east into the Panhandles. I think the place to be is along the dryline by the time of initiation, likely to be around mid-day or early afternoon. Not totally sure I will chase this event yet, but if I do, my preliminary target based on what I am seeing now would be around Tucumcari, NM. The tornado potential is not high with this, but with the directional shear present a tornado or two is certainly possible, and the likelihood of supercells appears quite good."

I knew there would probably be better days later in the week, but this was the day I could chase and as noted, it looked like there would at least be a good chance for supercells. By the morning of the event, it was apparent that 1) the dryline was even more diffuse than had been earlier predicted, and also farther west, with fairly high (for NM) dewpoints in the 40s and 50s over all of NM east of the central mountain chain, and that 2) the backdoor cold front, or more correctly, an outflow boundary created by overnight storms along the front, which had now become the effective position of the front, would be farther southwest than had earlier appeared, making the front a more significant player in this event. (As it turned out, most of the significant storms formed along the front, not the dryline, except in southern and southeastern NM, well south of my target area.) I headed out a little after 9 a.m., figuring on a target area somewhere between Tucumcari, NM and Dalhart, TX. I was still hoping that storms might initiate near Tucumcari, but figured the best action would be farther northeast.

As soon as I was heading southeast from Santa Fe toward Clines Corners to pick up I-40, it was apparent that the atmosphere was dynamic, as weak elevated convection, much producing just virga but some producing precipitation reaching the ground, was scattered in most directions, some but not all occuring over the mountains. A cluster of such convection slightly more robust than some of the others, but still weak, was located southeast of Clines Corners. This picture was taken about 15 miles east of Clines Corners near the Flying C travel center, looking south. I wondered if this might strengthen and become more surface-based once it reached the more moist, unstable air farther east and perhaps evolve into the main show, but that was not to be. I reached Tucumcari and stopped for lunch and data around 11:30. Earlier, the models had predicted a north-south line of storms over eastern NM, but now the RUC was suggesting the more robust storms would be farther northeast, over the TX Panhandle. I would have to go farther east, unless something initiated soon near Tucumcari. On the upside, the SPC Mesoanalysis data were indicating that CAPE had already reached 2000 across most of the area around Tucumcari eastward toward Amarillo - more instability than had been predicted the night before. I noticed that some weak convection I had noticed visually, off to my northeast near the TX-NM state line had now become more robust, both visually and on radar. In fact, a large area of convection was now rapidly developing near the back-door front, in an east-west allignment from near Nara Visa, NM eastward to north of Amarillo. Clearly, I had to get northeast, toward the Dalhart target.

I had intermittent data problems as I headed northeast on route 54 through Logan and Nara Visa, but fortunately I could see the storms well, as this picture shows. Radar, when I could get it, indicated an east-west cluster of storms from around Nara Visa eastward to around Channing, TX, with one strong cell (which was visible to me at times in the form of an overshooting top) farther to the ESE of Channing. That cell was more isolated and stronger than the others, but would be harder for me to reach, and I thought the others farther west might intensify once the better dynamics approaching from the west moved into the area. The storms had moved into TX a bit, and I was catching up to the back edge arount 10 miles or so into TX, so I stopped at a roadside rest area to watch for a while. Lightning and thunder were frequent, but there was not any real structure of interest. Also now I was in the rain-cooled air, with the temperature having fallen into the 60s from the upper 70s a few miles back. Looking at the map, I noticed that I was near an east-west road that would take me to Channing. This would allow me to travel just to the south of the east-west line of slow-moving storms, and possibly offer a chance to catch the stronger, more isolated storm farther to the east.

As I headed east, I noticed both visually and on radar that the storms to my north were intensifying, and appeared to be evolving into one main cell. Around 2:30, the first of two significant weather advisories for this storm was issued, indicating potential for 50 mph wind and penny-sized hail. About halfway to Channing, perhaps 20 miles west of there, I suddenly noticed a rapidly-swirling column of dust about a mile to my north. I stopped quickly, snapped one picture, then switched to video. Here is the picture:

The time stamp on the picture indicates that it was taken at 3:11 p.m. At first I was not sure whether this was a gustnado (which seemed most likely), a tornado, or a dust devil. I eliminated the possibility of tornado by looking at the clouds above, and seeing that there was no rotation and no feature vaguely resembling a funnel. Clearly the rotation did not extend to the cloud base. In fact, I was so nearly under the edge of the clouds that I even wondered (as you can hear on the video) whether it could have just been a dust devil. However, the answer - it was clearly a gustnado, though a somewhat unusual one - became apparent to me shortly after the feature disappeared. I realized that the temperature had now jumped back up to 78 - it had been in the 60s shortly before I noticed the feature - and I was being pummeled by strong inflow from the south. What clearly happened was that the swirl had spun up on the surface boundary between the rain-cooled air to the north and the warm inflow surging in from the south. This was a little different than many gustnadoes in that the dominant wind feature along the boundary where it formed appeared to be the warm, juicy inflow from the south, not the cool outflow from the north, but clearly it spun up from the ground on the boundary between the inflow and the rain-cooled outflow. It was quite large, spinning intensely, and at times lofted dust at least 100 feet in the air, maybe more. For a variety of reasons too complicated to explain, the only camera I had on this trip was my iPhone, which I used for both the still photos in this report and the video. I used my video editor to zoom as much as I could, but the limitations of the iPhone for getting video of a feature a mile away from me and moving away are apparent. Nonetheless, the video is sufficient to illustrate the general idea of what was going on:

The gustnado lasted for about 2 minutes after I first saw it; I have about a minute and 15 seconds of it on video though some of that is edited out of the video linked above. I don't know how long it was there before I saw it. After the gustnado dissipated, I continued eastward just to the south of the slow-moving storm. The storm appeared to be intensifying, and I was blasted a couple times by strong inflow, perhaps around 40 mph, which occasionally created considerable blowing dust crossing the road from south to north. The storm formed what looked like the beginnings of a wall cloud, as it seemed to be trying to become supercellular:

Notice the two pronghorn antelope in the picture also; at the time I was so focused on the storm that I did not notice them - until I looked at my pictures, that is; they are in a few that I took from that location.

I continued eastward to the road that goes north toward Hartley, and then turned north and went a couple miles and stopped to watch the storm. The storm again appeared to be on the verge of becoming supercellular and also had a bit of a rainfoot, as can be seen in this picture. A second significant weather advisory, again mentioning potential for penny-sized hail and 50 mph wind, was issued around 3:30. Very quickly the storm formed what I initially thought was an inflow band, but in retrospect I think it was more of an outflow feature, something of a roll cloud that soon evolved into a shelf cloud. Here is a panorama photomerge of the storm, made from pictures taken around the time the roll-cloud featured formed, about 3:37 p.m.:

Within a few minutes, this evolved into a very impressive shelf cloud:

This was about as good as it got, however, at least as far as viewing the storm from the south went. After this, the outflow surged forward, and the storm visually appeared to be turning outflow dominant. I think what really was happening may have been that the storm was evolving into an HP supercell structure, with a meso forming well to my northeast, on the east edge of the storm, perhaps in the area behind the shelf cloud and heavy precipitation in the picture above. It did get a couple TVS structures on radar between 4 and 5:30, and finally got its first and only SVR warning at 5:50, after I broke off because from my location, I could see nothing but rain and outflow. I briefly once again considered making a move for the supercell to the southeast of this storm, which I had been thinking about going after when the storm closer to me intensified and produced the gustnado. But I decided it would be too hard to get ahead of that storm in an area with limited road network, despite the slow movement of that storm, which was not just northeast of Amarillo but in a rather roadless area where eastward access was blocked by a body of water. Additionally, I had to get back to Santa Fe that night due to commitments the next day, so I did not want to go even farther east. Turns out it would have been even harder than I thought to get to the southeastern storm, since flooding caused by the storm forced the closure of route 287, the main highway between Amarillo and Dumas, the route I would have taken to get in position. That storm would have been something to see, though, as it produced hail so copious that in some areas, hail drifts 3 to 5 feet were found after the storm. A link to a newspaper photo gallery of the massive hail accumulation and resulting flooding and road closing can be found here. A storm survey by the Amarillo NWS can be found here.

I noticed on radar that some storms were forming north of Tucumcari, so I decided to start back west toward Santa Fe and check those storms out along the way. I turned north at San Jon and went to Logan and a bit northeast of there to view the storms. I had hoped that the storms might pulse up with the stronger dynamics coming into the area, but by now the drier air had mixed eastward, and the storms were very high-based and not doing anything interesting, so I called it a chase and returned to Santa Fe. It was a lot of driving for a one-day chase, but the gustnado and the storm structure made it a very worthwhile chase nonetheless.

Total chase distance: 601 miles.

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