Supercell Research

[Trey Alvey]

I'm doing research on some of the supercells from April 27th and am trying to find a good set definition for a supercell. I'm having some trouble classifying supercells via radar observation (and staying consistent with how each is analyzed). I know not all supercells are the same, but I'm trying to find some way to distinguish the storms when they're in the developing stage from when they become supercells and staying consistent with how I analyze each storm (or defined as a supercell). For example, a storm via radar observation has shown >40 knots of GTG shear on 2+ tilts for 20+ minutes; therefore, it is now a supercell. Any help with this is greatly appreciated. Thanks!

 

[Jason Mills]

I'm down here in Alabama and I will remember that sad sad day forever, but a supercell is defined as just a storm that has a violent/rotating updraft, there is really no set "number" that makes it a supercell. There are 2 different kinds of supercells, LP (Low Precipitation) and HP (High Precipitation) and they both look very different on radar. (Sorry if you already know this, I sometimes get carried away.) A LP supercell has a very defined hook and there is little rain around the tornado, this means there is no downdrafts around the updraft. All of the 4/27/11 tornadoes were classic supercells which are just regular supercells and are kinda between LP and HP. HP is ALOT harder to recognize because the signature is hidden in the precip in the radar signature. HP are VERY dangerous to chase because you just plain cant see the tornado. If you want me too I will post pictures of both. If you need anymore help just ask, I'm doin my own little research!!!

 

[Jason Mills]

There are just 2 supercell classifications, LP and Hp, Sorry, my bad.

 

[rdale]

There are just 2 supercell classifications

3.

Classic.

Nice intro at http://facstaff.unca.edu/cgodfrey/courses/atms103/ppt/supercell.pdf

 

[Skip Talbot]

A LP supercell has a very defined hook and there is little rain around the tornado, this means there is no downdrafts around the updraft. All of the 4/27/11 tornadoes were classic supercells which are just regular supercells and are kinda between LP and HP.

You probably meant classic supercells here, as there are three kinds as RDale pointed out. LPs don't even have to display a hook on the radar. In fact sometimes they show up as little more than a circular blip. LPs do have downdrafts including rear flanking downdrafts that wrap around the updraft. If its showing up at all on the lowest radar tilts, its got some sort of downdraft.

HP is ALOT harder to recognize because the signature is hidden in the precip in the radar signature. HP are VERY dangerous to chase because you just plain cant see the tornado.

HPs often exhibit dramatic mesocyclones on radar. The precip doesn't hide the meso from the radar like it does a tornado from our eyes, in fact it gives the radar more material to work with to measure the precip's velocity. HP hooks are also quite prominent, they usually just appear a lot fatter, with the storm looking like a kidney bean or a blob with an inflow notch.

As for Trey's original question. I was hoping someone more knowledgeable than me would chime in, but I would try to find some algorithms that the 88D's level 3 storm attributes are using to mark mesocyclones.

 

[rdale]

Thanks for bumping this - but the easy answer is "there is no algorithmic definition." The 88D algorithms look for areas of rotation, but they are not defining some rotations as supercells and some as non-supercell rotations.

http://cimms.ou.edu/~doswell/Conference_papers/SELS96/Supercell.html is probably a better way to standardize if needed. My guess is that the best way to define supercell in your research the same way you'd apply this definition operationally. Make your research have a real-world application for something you can plot on GR2AE and you'll have a winnter.

 

[Dean Baron]

For example, a storm via radar observation has shown >40 knots of GTG shear on 2+ tilts for 20+ minutes; therefore, it is now a supercell. Any help with this is greatly appreciated. Thanks!

That is true but I would not hold these stats as the criteria for considering a supercell or not. It's hard to explain but as you gain experience in radar interpretation you will be able to easily identify supercells. The only time I look at GTG shear is when I know there is a particularly strong tornado already on the ground. Many supercells don't exhibit a ton of shear even on level 3 velicities (not sure about level 2, never used it). Also, not all supercells have to be surface based. Seems like a lot of prolific hail producers are elevated sups.

 

[rdale]

Even elevated supercells would show rotation... But it's true that GTG shear would not be what you want - look at a broadscale rotation.

 

[Dean Baron]

Even elevated supercells would show rotation... But it's true that GTG shear would not be what you want - look at a broadscale rotation.

True, and I didnt mean to imply they don't. It was more to emphasize that there can be supercells that have very slim chance of putting down a tornado.

 

[Jeff Duda]

You can use previous research to back up any methodology you choose to use for defining a supercell. Here's what I used in my WAF paper from a couple years ago. Read specifically through section 2 and one paragraph near the end of section 1. Also consider looking through the references cited in those sections.

Duda and Gallus (2010)

 

[Bob Hartig]

You may want to give this paper in the EJSSM a read. It's the second of a two-part article, so you may wish to read part one first; it lays a historic foundation on supercell morphology and classification that part two builds on.