The Anatomy of a Tornadic Supercell
Updated: Jun 14, 2022
Before I worked alongside Ben, Fred & Drew on-air, my sole role on team was the Radar technician - I made sure our live, dual-pol doppler radar located at our studios here in Lawrenceburg was running up to par, and I typically steered it during severe weather, tucked away behind the scenes. This sector of meteorology that I specialize in is known as Radar Meteorology. Like so many in this sector, I have to admit: I am obsessed with how I can use this to see severe weather phenomena in the highest fidelity possible, revealing it's smallest structures – let's take a look at what that entails.
The Forward Flank
First, we’ll take a look at the portion of the supercell that, most of the time, takes up the most space – what we call the the forward flank. The forward flank, also often called the forward flank downdraft, contains a vast, vast majority of the precipitation and hail, and damaging straight line winds. Although not the most spectacular part of the storm, the FFD can and often is easily denoted by a shelf cloud (often confused with a wall cloud!) on the leading edge, produced by interactions between the precipitation within the cell and warmer and moist air outside of the cell. In standard, NE-moving supercells, this is the first sign of significant weather approaching a given location.
The Tornado, Inflow, and Rear Flank downdraft
On small scales, a tornadoes structure can be considered somewhat akin to a hurricane. With proper equipment, you can see the “eye” of the tornado itself, such as in this example. Although still up for debate, some suggest that, like a hurricane, a tornado has a calm center. That said, there are some key differences. The tendril-like perturbations on the right side of the eye that you see in the above image are small regions of precipitation being ingested into the tornado through a process known as inflow. Along side that, the clear region just above the eye is known as the Inflow notch. Inflow as a process is actually pretty common; it is the act of a fluid flowing into a larger region of the same type of fluid – in this case, inflow can be considered moist, warm air flowing into a supercell feeding the updraft. When close to a tornado, inflow itself can present dangers on its own – wind speeds within regions of inflow often reach 60+mph, which makes damage assessment often difficult for meteorologists due to the possibility of widespread damage across large areas.
This curly-Q shape that is so iconic and presentable in the image is due to a process known as Rear Flank Downdraft. This, in essence, is a large dry region of air that wraps around the tornado and wall cloud itself that originates from the highest levels of the supercell - the RFD, like the inflow region and tornado, can present dangers in and of itself. In a great many cases, the winds within the RFD can exceed 100mph, alongside large hail being lofted within and around the mesocyclone. This is one of the many reasons it is EXTREMELY important to heed tornado warnings, even if you can see for yourself the tornado is not close to you - the extent of the damaging winds that help feed it's lifecycle can be just as deadly.
Why some supercells become tornadic and some don’t is all but a mystery, and research continues to discriminate between cells that are more or less likely to become tornadic within its lifespan. Here at Tennessee Valley Weather, we hope that our suite of tools helps provide the best insight into these storms possible, helping us keep everyone safe and perhaps, if we find ourselves in the right place in the right time, gleaming valuable insights into these beasts of nature.