Day 2: A Carousel of Mesocyclones

Tuesday was, without a doubt, the best storm chasing day of our lives. Although we didn’t see a tornado, we saw multiple incredible mesocyclones, which are the rotating updrafts affiliated with all tornadic thunderstorms. Moreover, these mesocyclones occurred within the same thunderstorm complex and were rotating in opposite directions. It was a truly incredible experience we will all keep with us for the rest of our lives.

A rapidly rotating mesocyclone has a very characteristic appearance, with broad, striated cloud bands spiraling along a predominantly vertical axis. These mesocyclones are often called “motherships” by weather geeks, and by taking a look at the gif below, I’m sure you can see why.

Mesocyclones are formed when strong wind shear in the lower atmosphere creates a rotating cylinder of air parallel to the ground. This vortex is then lifted into an upright column by an updraft, thus becoming a rotating updraft/mesocyclone. Interestingly, this process actually forms two mesocyclones, one that travels clockwise and to the left and one that travels counterclockwise and to the right. Though the right-moving, counterclockwise-rotating mesocyclone is favored for creating tornadoes and the left-moving, clockwise-rotating one usually dissipates quickly, it can also produce tornadoes. The above mesocyclone above was rotating clockwise and presumably moving to the left, though the structure with this particular storm was convoluted and it was tough to identify how the storms were moving on radar.

To form a rotating updraft, you need wind shear and lots of it. When there is enough wind shear, a vortex of air parallel to the ground is formed. This vortex is then lifted into an upright column by an updraft in the unstable atmosphere, and this rotating column of air becomes the rotating updraft.

This wind shear was clearly visible on satellite imagery. Note the lower-level, cumulus clouds over East Texas/Oklahoma arriving from the ENE and higher, cirriform clouds over the Texas Panhandle arriving from the west.

Though the conditions on our second day weren’t as good as the ones on Monday when we flew in (and unfortunately were unable to get to the best chase areas), things were still looking pretty darn stormy, as a remnant shortwave trough and associated surface low gave us a combination of warm, moist, southeasterly surface flow from the Gulf of Mexico and strong, westerly winds at upper-levels. We started out our morning by heading south from Perryton, Texas to Woodward, Oklahoma. This area had the highest wind shear, CAPE, and helicity (the tendency of an air parcel to move in a corkscrew/helix-like fashion) on the models, all of which are key for tornado formation.

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After hanging out in Woodward for the afternoon, we headed 12 miles south to Sharon, OK to get a view of some altocumulus castellanus (also known as accas) clouds coming in from the south, which are mid-level, vertically stacked cumulus clouds that mark the location of updrafts in the atmosphere. Accas indicate the atmosphere is moist and primed for strong thunderstorms but still has a “capping” inversion preventing full-blown cumulonimbus clouds from developing. As the inversion erodes throughout the day, these altocumulus castellanus clouds will rise higher and higher, and when one of them reaches the LFC (level of free convection – the point at which a rising air parcel is warmer than the surrounding atmosphere… read more here), it will rise freely until it reaches the tropopause, potentially creating a strong thunderstorm in the process.

Here’s a nice timelapse looking south towards some incoming altocumulus castellanus. This was taken near Sharon, OK.

We soon saw some storms developing to our south near Wheeler, Texas, with one of them quickly earning itself a severe thunderstorm warning. After a friendly debate on whether to wait in our current region of more favorable dynamics or chase these with the knowledge that they could fizzle by the time we got there, we decided to head south around 5:10 on Highway 40 and chase them. And boy oh boy, am I glad we did. This cell soon developed a well-defined hook echo on radar and was given a tornado warning at 5:51. Unfortunately, I’ve so far been unable to access the archived NEXRAD 2 radar imagery of this storm from NOAA, but here’s a “placeholder” picture of a storm with a well-defined hook echo. This storm spawned the Bridge-Creek/Moore tornado of 1999, which had wind speeds of 301 mph, the highest ever recorded (in this instance, inferred via doppler radar) on Earth.

GOES-16 caught some amazing imagery of this storm. Again, notice the wind shear at different levels of the atmosphere.

#GOES16 view of the tornado-warned supercell in the eastern #Texas panhandle #txwx – (the loop is from 4:34 pm until 6:14 pm CDT) pic.twitter.com/j3rjd33vVS

— Dan Lindsey (@DanLindsey77) May 29, 2018

Here’s some footage of us getting hyped and chasing this storm. There were some some chasers who caught up from behind us and were probably hitting triple digits. We were anxious to get to this storm, but felonies aren’t our cup of tea. Oh, and we didn’t see a tornado, we were just excited. You would be too.

This cell lost its tornado warning by the time we got there, but it still had an absolutely unbelievable amount of rotation associated with it… at least compared to anything we had seen. When we finally got onto the south side of the storm and had a clear view of the updraft/mesocyclone without the downdraft and associated rain/hail obscuring our view, we were mesmerized by its structure and beauty.

We pulled off on road E0470, (a dirt road slightly north of I-40) and snapped some absolutely incredible pictures. The picture with the single lightning bolt was one of the very first pictures we took and had  a 1/10th second exposure, so we got pretty darn lucky!

Here’s a cheesy picture of me at E0470 pretending I’m actually responsible for all of these amazing photos. My smile turned in to a shocked surprise a split second after this photo was taken as a lightning bolt lit up a tree several hundred yards away, so we dashed back towards the car. And it was here that our real adventure began.

The storm’s powerful downdraft was closing in on us fast, and seeing as we weren’t super keen on getting hit by the baseball-sized hail that was initially reported with the storm when it had the well-defined hook echo, we headed east to keep ahead of the clockwise-rotating mesocyclone and, more importantly, the storm’s downdraft. We stopped for a few pictures along the way both of the mesocyclone and the shelf cloud that marks the leading edge of the downdraft. The one below is another mesocyclone photo and is particularly cool because you can see a green tint in the mesocyclone. Green clouds mean the thunderstorm is very tall/deep, and, as such, are often associated with severe weather.

The next part should be the most memorable part of the evening, but it is mostly a blur simply because of how chaotic it was. Around 7:45, we got turned around while heading east and actually headed west directly into the storm’s downdraft. We were greeted by extremely heavy rain and strong winds, and we even saw some cows running for cover. When cattle are running, much less running to take shelter, it means that you need to get away from your current location as fast as you can.

Once we had gotten a safe distance away from the storm, we stopped at the intersection of Highway 34 and F CR 1330 around 8:30 to document the “corkscrew of death.” This is not a funnel cloud… just another example of an area of locally stronger rotation within a broadly rotating storm.

We pulled off again on I283 to take a few shots of some beautiful mammatus clouds at sunset and struck up a conversation with another fellow storm chaser from Garden City, Texas. We had quite a bit in common, he helped set up wind mills at the wind farms across the region and was also originally from Seattle. It would have been nice to shoot lightning again, but we were absolutely exhausted and decided to call it a night around 9:45 and stayed at the Days Inn in Erick. We’re looking forward to that Continental Breakfast tomorrow morning.

Joey was Johnny on the Spot through the entire time and took some incredible footage. Unfortunately, we didn’t get any footage when we were in the downdraft, but we were more concerned with simply getting reoriented at that time. Here’s the rest of his footage from our stop at E0470 onward. Before 2:17, most of the footage is of the mesocyclone and rotating updrafts, and after 2:17, most of the footage is of an incoming shelf cloud ahead of the downdraft.

Thanks for reading! This was a long blog… if we are ever so lucky to top this day on this trip, expect a novel.

Charlie, Joey, and Chris