mesocyclone tornado Vs. non-mesocyclone tornado

[Karen Politte]

What if a "gustnado" (horrible term - use eddy-whirlwind instead!) forms along the leading edge of the RFD, and then gets spun-up?

I always thought that GUSTnadoes - by their very name - only formed on the leading edge of a gust front. That is how they are characterized - as ground-level eddies that form on the leading edge of outflow from a thunderstorm. Given this description - I don't think that true gustnadoes can be confused with vortices that form on an RFD boundary but I don't know how to categorize the latter, either.

I guess my problem is that for gustnadoes to form they have to be on a gust front - and if they are on a gust front that precludes any tornadic/tornado possibilities as the parent storm has probably already been undercut and is a big windy mess.

Landspouts and waterspouts must fall under the heading of tornadoes according to the NWS definition of the term because they are underneath a cumuliform cloud. As this is the only "official" definition of the word TORnado - there is a pretty large catchment area for what is considered a tornado.

Therein lies one of our problems in defining these phenomena. Due to the official definition being so broad, there is a necessity to "split up" what is considered a tornado into many smaller categories - hence landspout, waterspout, tornado, non-mesocyclonic tornado, non-supercell tornado etc. etc. I think so far the handiest category for me has proved to be tornado vs. non-mesocyclonic tornado - as both can be and have been formed by tornadic supercells.

KL

 

[Paul Knightley]

Do you think, though, that research should try to find out how a tornado actually develops beneath an updraught, but in the first instance, put the type of updraught to one side - there must be a chance that the actual process of getting tornadogenesis to occur is the same, whatever the nature of the updraught above (i.e. conservation of angular momentum, etc). Although the type of updraught is probably very important for many aspects of a tornado's character, the actual formation might be the same.

Just a thought anyway!

p.s. on a personal note, I think the word 'tornado' should suffice...it is the same phenomenon, whatever the type of updraught, and whatever surface it moves over.

 

[mike scantlin]

i always understood gustnadoes to be along any thunderstorm-wind gust, whether rfd, gust front, or anything else. it doesnt have to be a gust front to be a gust does it? just my peices of copper.

 

[Paul Knightley]

They are basically eddy-whirlwinds - you see them all over the place, not just along thunderstorm gust fronts.

 

[Kevin Scharfenberg]

Much of the reason for this taxonomy is to help the forecasters responsible for issuing warnings to better understand the physical processes behind the formation and maintenance of the vortex. If I'm sitting at a radar desk and I hear a chaser say "tornado" - my first question is whether the chaser is seeing a classic supercell tornado with RFD, clear slot, under a large updraft base, etc., or is it a "landspout" along a flanking line towering cumulus, or a spin up on surging outflow ("gustnado"). The answer will make a big difference on whether I'm worried about a violent, long-track tornado or something weaker and more transient.

 

[Paul Knightley]

That's a fair point Kevin - I'm just thinking that in the wider view of why tornadoes form, there may well be some connection between the various modes.