Tornado Production of Southernmost Supercells (a.k.a. "Tail-End Charlie")

[Alex Elmore]

A study was published in the Electronic Journal of Severe Storms Meteorology yesterday that took a statistical look at the tornado production of the southernmost supercell in a line of storms/supercells, which is commonly referred to as the "tail-end charlie" storm by forecasters and chasers:

www.ejssm.org/ojs/index.php/ejssm/article/view/167/117

I know I've been guilty of thinking a tail-end storm has better tornado potential, but *spoiler* that appears to not be the case.

 

[Ethan Lang]

This surprised me also, I can count a number of times that I have seen tornadoes with tail-end charlies . In fact there was one I particular that I chased pre-frontal supercells all day and saw nothing then got two nighttime tornadoes on the tail end of a developing MCS. In this case the LLJ ramped after dark as is common in the plains during the spring.

 

[Andy Wehrle]

Just anecdotally I know on Moore day in 2013 a lot of chasers were further south on storms near the Red River and while some produced tornadoes, none were anything like the one to the north.

Rochelle day in 2015, the monster EF4 was produced by the northern-most storm in the warm sector because it was the one that latched on to the warm front, cells to the north had crossed into the cooler air while ones to the south were in veered surface flow.

On May 24, 2011 there was a group of three closely spaced supercells in central OK, all producing violent tornadoes. The northernmost one turned out to be the strongest and longest-tracked but also quite heavily rain-wrapped for much of its life.

I'm sure there are plenty of days where Tail-End Charlie has turned out to be the storm of the day, but there's obviously much more to it than that.

 

[Spencer Dant]

The storm that dropped Rochelle also formed off of some sort of outflow boundary and it seemed to have that sort of enhancement going for it into the tornadogenesis cycle. It was plenty isolated when it initiated. In this sense, it's probably an outlier.

The reason that I often go for a TEC play when chasing a semi- or completely linear system is because I know that that storm can be productive given that it has the opportunity to draw in clear inflow, whereas other storms in the system very well may but also may not. I don't know which ones will or won't, and I would rather not jump up and down the line constantly after new, seemingly random inflow notches when I can simply stay just south of the southern end, have clear and constant visual on the storm I am chasing as well as new initiation latching onto the southern end of the line, and shuffle my position accordingly. Scientifically, the tail end may not be any more prolific than any other embedded structure, but it's much more chaseable.

 

[Dave C]

"Adjacent mesocyclones had to be <75 km from each other in order to ensure that the adjacent cells within the line were close enough potentially to impact each other through processes such as precipitation fallout, outflow boundaries, etc."

75km/45 miles or less? That's like opening a hanger door to park a bike. I exaggerate but the call to chase a tail end storm is most intelligent with closer spacing than that if we are talking discrete supercells. Selecting only storm lines within 45 degrees N-S shows the researcher is bounding relative to the compass and not relative to wind fields and frontal or boundary placement, even if 45 degrees facilitates event selection and covers the majority of lines.

Despite somewhat arbitrary criteria prior to statistical analysis, there was enough rigor in the paper that their claim is somewhat validated. In a coarse sense, the southern storm is not always best. One has to wonder though, who drops south all the time, for any line without reason? I'd say most do it when storms are being starved of inflow or destructively interfered with by neighbors or a forming MCS- and that is the real criteria.

"Thus, the main question is: Does this tactic actually work? Will storm chasers be more likely to observe a tornado by targeting the southern-end storm?"

Anecdotally, I can think of many instances when the tail end storm was the only storm able to get clear inflow or stay isolated long enough to organize. It's also a favorable position for not getting squeezed into evolving clusters, as others have mentioned. The decision is not made in a vacuum without considering several factors and variables relative to each other that paint a big picture. I don't know many chasers who always go south without looking at what is going on first. If storms are being starved, then you might move. Maybe others do it differently but I have never had any blanket rule.

 

[Greg McLaughlin]

It has been my experience that tail-end charlie storms are your best bet on veer-back setups.