Mothership Madness - Apex Chase August 6th, 2019 Part II - Arrival
Mar 5, 2020 | By: Storm Chase Tour Of The Great Plains
Part II - An early evening mothership ballet
As we continued onto the second phase of our August 6th event, we encountered a defining moment that every storm chaser dreams of. Intercepting a long track beautiful mothership supercell with a great road network, little traffic and plentiful escape routes. Today's second part recalls the science and observations of our 2019 apex Mothership interception in South Dakota on an incredible early evening.
Recalling our exit from our first encounter with a high precipitation monster near Gettysburg, South Dakota. The majority of that first part of the chase was plagued with road construction, a fast moving HP supercell and near constant lightning. As we chased south for the next 30 miles nearing Blunt, SD, the storm grew in intensity and became outflow dominant. We scrambled to leave the town of Blunt, SD just before the core and its monster 3" destructive hail hit, having escaped the road construction delays that impeded our chase.
Shortly after exiting the outskirts of town, we made our way east away from the storm, where we continued to observe frequent cloud to ground lightning near and far from our position. We knew that the hail core was not far behind, as the radar showed very high reflectivity almost on top of our position. However, with every minute and mile that passed as we pushed eastward on Highway 14, it seemed more likely that we might just make it out of this unscathed. Suddenly, we were startled by an extremely loud crack as a golf ball size hail stone landed directly between the hood and the windshield of the vehicle. Luckily, this would be our only close encounter with hail on this particular chase. Unfortunately for the towns, vehicles and crops in Blunt, Agar, Onida, and Harrold, South Dakota, the hail created havoc with some reports as big as 3 1/2".
the hail path. Red indicates 2"+ hail
A new mesoscale discussion was issued by the SPC warning a significant area of our chase parameter of incoming severe weather with all dangers associated including large hail, lightning, flooding and tornadic activity well into the late evening hours.
At this point of our chase, we briefly considered chasing on a more southerly route, staying ahead of the monster. Most chasers opted to fall back behind the storm, exiting to the west. We shed the majority of them while exiting onto Highway 14 and plotted our route to refuel, and attempt to catch the storm again near sunset. Our plan was to get south so that we could intercept the storm as it continued to move to the southeast nearing I-90, our original staging location. As we stopped for a quick refueling at Max's corner gas station in the town of Stephan, SD, we noted continuous thunder as the lightning was nearly constant in the very spread out and defined anvil cloud directly overhead. At about that time, the storm that we had been chasing for the last two hours was beginning to morph from an HP Monster into a classic style thunderstorm beauty. As we approached the Missouri river crossing our view of the storm base was improving by the minute. Our decision to go east instead of south was about to pay off tremendously.
As we crossed the bridge crossing along the Missouri river near the town of Fort Thompson, SD, we were in a position allowing us to see that the storm was venting its precipitation off to the ESE away from the updraft tower giving us an obstructed view of its increasingly sculpted base. Approaching what was now a very different looking storm than what we had seen earlier in the day, we were amazed by what we were witnessing. Before us was a storm structure that resembled a flying saucer with what was becoming an increasingly well-defined RFD cut. We decided to continue a little further south near the town of Reliance, SD in order to get in front of this incredible storm and capture it on camera. It was at that moment we found ourselves caught between freshly burned memories and anticipation of the chase to come before sunset.
Our first moments with the mothership
Looking back at that first iconic moment witnessing that mothership as it churned and spun, its hard not to feel tremendous emotions in fond recollection. For both of us, this moment was something we had deigns on capturing and experiencing for both of our careers. For Steve, the captured imagination of beautiful mechanics and structure was one that rarely gets seen in person on this magnitude, and for Bryan, the shapely sculpted cloud formations and color brought a palette that rivaled anything captured in all his years of grandscape photography. We both knew that this moment was an unspoken peak and a day that we would never forget.
Intercepting the Mothership
Within a few minutes of stopping south of Reliance, SD to capture stunning pictures of the increasingly beautiful mothership, the storm drew close and was practically on top of us so we could document every facet of its motion, light and color. It was time to continue south so that we could stay in front of it despite our amazing vantage point. The structure of the storm continued to improve as the minutes passed.
As we were heading south our forecaster Steve Saviano had time to read through the SPC mesoscale discussion for our area. Dew points in the area were fairly high being in the mid 60s, thus providing ample low level moisture for the storm to feed on for the rest of the evening. It appeared that our storm was also taking advantage of mild warm advection out of the southwest at the 850 mb level. This provided a lifting mechanism in lower levels of the atmosphere along with enhancement of bulk shear values aiding with further development despite the loss of daytime heating. All of these ingredients combined to create an incredible setup that not only maintained but also enhanced storm development.
By 7:40 local time we had reached our next pull off near the town of Iona, SD and immediately began photographing what was now a fully developed mothership supercell. The base of the storm was very round with notable sculpted features such as plates and bands along with Kelvin-Helmholtz waves. It appeared that the storm was taking full advantage of the its local environment where SR bulk shear was around 60kts, SR helicty of >200m^2/s^2 and MU CAPE values in excess of 3000 j/kg. It was quite simply one of the most spectacular supercells that we could have dreamed of and the setup continued to provide ample opportunity to document until sunset.
Incredible 66,000' Foot Tops to our storm
The exhilaration of documenting a perfect mesocyclone for those short moments before sunset became dream-like for our chase team. Somehow, all other chasers and their dots had disappeared from the area, leaving us with a silent and peaceful experience that was an absolute rarity. In fact, other that the cows, crows and occasional critter, our lonely stretch of empty road was truly isolated in a sea of late summer prairie grasses, wheat fields and slow moving rivers as the storm danced overhead. When we finally did see a human again it became a defining moment during our chase. It was a farmer, near the front entrance to his property right off the highway, grabbing his mail and staring with awe at the impending arrival of the mothership as it descended to our position. His expression was so noteworthy, hands on hips, head arched back and in complete bewilderment at something so beautiful and scary at the same time that we can still clearly remember that moment. Surely the locals must witness severe storms in this area often, but even on that late afternoon, it commanded attention to the few souls who witnessed it.
Our chase 08-06-19 The RFD cut was incredible! Textbook RFD as sunset approaches
We documented each location as long as we could and watched the storm draw in light that illuminated from the horizon near sunset. Directly to our west, the last rays of sunlight began to paint all levels of the storm structure with different tones as the mothership crossed slightly to our east. For the rest of our daylight chase, we were now able to witness the shifting colors of the front-lit storm as we sat safely to the west of the storm path.
Kelvin-Helmholtz Waves embedded in the storm Pezman in front of the camera instead of behind for a changeThe entirety of our storm from initiation well into the next day as an MCS event into Kansas and Missouri and beyond Our storm at its peak. Note the sudden new initiation behind it right at dark... something nasty lurking
We prepared to end our chase once the last flicker of sunlight flashed on the quickly moving storm. But, mother nature had other plans for us and we began to document a blue hour lightning event from our storm that kept us tracking and documenting from a distance. To our north, hardly noticeable at first, we became aware of a rapidly developing cell behind our mothership event. Something powerful, dark, brooding and dangerous began to take hold over the atmosphere as the last light faded.... An embedded Tornado signature began to exhibit on radar as we approached the town of Burke, SD...