Massive Supercell question

[Howard Robinson]

I remember hearing something about a massive supercell that had updrafts as strong as an F4. Does anyone know about this? This happen recently as well.

 

[Jeff Snyder]

Hmmm ... I know of storms (not particularly, but inferred from hail size) that likely had updrafts from 100-140mph with baseball and softball sized hail. I'm thinking the Aurora mega-stone probably came from the storm with a mega-strength updraft, but I'm almost certain that storm structure played a very large role in the growth of that stone, rather than updraft strength alone (hailstone trajectory usually plays a decent roll anyways). But ok, take a 230/250
mph updraft...

Wmax (IDEAL Updraft strength) = SQRT (2*CAPE)

Usually, this is actually: Updraft = [SQRT (2*CAPE)]/2... in other words, in the real world, the actual updraft speed can be / is usually one-half of the square of two times CAPE. Now, this updraft speed in the above formula is in m/s ... So, with the proper conversion, 250mph is about 103 m/s...

Solving for CAPE....

CAPE = (2*Updraft speed)^2 / 2

CAPE = (2*103)^2 / 2 = 21,218 J/KG ...

Yep, that means to support an updraft of 230mph with ONLY bouyancy/CAPE, which isn't exactly fair, the CAPE in the environment must be 21,218 J/KG ... I'll just leave it at that...

Now, there is another signficant source for updraft strength other than bouyancy/instability (CAPE) -- updraft rotation. With a rotating updraft, vertical pressure perturbations, the updraft tends to be 'stronger' than a non-rotating updraft... Thus a supercell in a 4000 CAPE environment (with it's rotating updraft / mesocyclone) can and will have a stronger updraft than a non-supercell in the exact same environment... Thus the reason why the vast majority of "very large" hail reports, say >2.0", are produced from supercells.

EDIT: This only applies to vertical updraft velocity... Check out http://meted.ucar.edu/mesoprim/cape/print.htm points 6-9 (I think) for other factors that contribute or detract from the CAPE-vertical velocity estimation equation given in this post...

 

[Jason_Politte]

I remember hearing something about a massive supercell that had updrafts as strong as an F4. Does anyone know about this? This happen recently as well.

Here's the thread:

http://stormtrack.org/forum/viewtopic.php?t=3357

and the case study of the Superior, NE supercell:

http://ams.allenpress.com/pdfserv/i1520-04...085-08-1095.pdf

Jason

 

[Jeff Snyder]

I remember hearing something about a massive supercell that had updrafts as strong as an F4. Does anyone know about this? This happen recently as well.

Here's the thread:

http://stormtrack.org/forum/viewtopic.php?t=3357

and the case study of the Superior, NE supercell:

http://ams.allenpress.com/pdfserv/i1520-04...085-08-1095.pdf

Jason

OOOOOOOOOOOOOOH...

I was thinking in terms of updraft vertical velocity, not mesocyclone rotational velocity ...

 

[Glen Romine]

I remember hearing something about a massive supercell that had updrafts as strong as an F4. Does anyone know about this? This happen recently as well.

It wasn't the updraft speed that was this large, but the differential horizontal velocity across the very large mesocyclone of the Superior, NE supercell - well off the surface. Actual winds, relative to the ground, were only about half this intense.

Glen