Darren Addy
EF5
I believe the Latin meso ("middle") refers to scale, not location within a thunderstorm. Cyclonic rotation ranges from the very large (i.e. wave cyclones) to the very small (tornadoes and even smaller suction vortices). Mesocyclones fall somewhere in the middle of that spectrum.
While you are not incorrect, Bob, the AMS would seem to point out that a mesocyclone is more than that:
(It should be noted that a mesocyclone is not just any cyclone on the mesoscale; it refers specifically to cyclones within convective storms.)
The AMS definition does shed more light, but also still highlights my main question. Again, correct me if I'm wrong, but I get the impression that stormchasers seem to think that a supercell (by definition) must contain a mesocyclone. But the AMS definition specifically says "Mesocyclones are frequently found in conjunction with updrafts in supercells." (emphasis mine) I'd also note that "in conjunction with updrafts" is not the same as "the entire updraft" (stated in the Scientific American quote from the OED, above). From this, I would tend to lean toward the position that the Scientific American definition (incorrectly?) broadened Fujita's original definition.
I also think that, as Glen pointed out, the AMA separation of the mesocyclone signature from the mesocyclone itself, is more precise. I believe that the NOAA Storm Spotter Glossary should be changed (and "mesocylone signature" added) to make the differentiation clear.
Darren Addy
Kearney, NE