The Role of Multiple Vortex Tornado Structure in Causing Storm Researcher Fatalities

[TropicalAnalystwx13]

Interesting journal from Josh Wurman, Karen Kosiba, and Paul Robsion.

 

Abstract:
 

"A large and violent tornado/multiple vortex mesocyclone (MVMC) / tornado tracked east and northeastward near El Reno, Oklahoma on 31-May-2013, causing eight fatalities, including storm-chasers/researchers attempting to deploy in-situ instrumentation. Sub-vortices moved within and near the MVMC, some in trochoidal-like patterns, with ground-relative translational velocities ranging from 0-79m/s, the fastest ever documented. Doppler On Wheels (DOW) measurements in one of these sub-vortices exceeded 115m/s at 114m AGL. With assumptions concerning radar-unobserved components of the velocity, peak wind speeds of 130-150m/s are implied, comparable to the strongest ever measured. Only Enhanced Fujita Scale-3 (EF-3) damage was documented, likely due to a paucity of well-built structures and the most intense winds being confined to small, rapidly moving, sub-vortices resulting in only sub-second gusts. The region enclosing the maximum winds of the tornado/MVMC extended ~2km. DOW measured winds >50m/s (>30m/s) extended far beyond the radius of maximum winds (RMW) extending >5km(7km), comparable to the widest ever documented. A strong multiple-vortex anticyclonic tornado with dual-polarization debris signatures is documented.

A sub-vortex tracking eastward within the larger tornado/MVMC intensified, moved north, then northwestward, becoming briefly nearly stationary near/over a research team’s vehicle, transporting it ~600 m generally eastward, killing the team. An experienced media team’s vehicle was destroyed inside the tornado/MVMC, resulting in injuries. The circumstances leading to these incidents are analyzed using DOW data. The anomalous, and likely unpredictable in real-time, path of the interior sub-vortex likely contributed to these deaths and 3 injuries. The risks associated with chasing and scientific missions near, and particularly inside, large and complex MVMC/tornado vortices are discussed."

 

http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-13-00221.1

[WEATHER53]

I often wonder just how small and how many of these small vortexes exist within a storm. The scouring that we see on F-5 almost makes me think of something like a mop with all those individual strands just whirling at incredible speeds, sorta like a weed wacker.