Do LP and HP supercells produce violent tornadoes?

[Thomas Loades]

Tom Grazulis's 2001 booklet F5/F6 Tornadoes notes that "HP supercells are NOT the ones that produce F5 tornadoes. Too much rain is not good for the updraft."

Obviously this isn't a case of HP supercells not producing F5 tornadoes, period — the 1990 Plainfield, IL, tornado shows that — and this comment was in regard to global warming increasing the incidence of violent tornadoes (that there could be an increase in moisture in the air, thus more HPs . . . alternately, he says, it could just as soon be hot but dry and so nary a supercell).

At any rate, the Plainfield tornado was not all that long-lived: its path was 16 miles long. And while it was the last of a family of about 4 tornadoes, the others weren't very long-lived (or violent) either. So, as Karen alluded earlier, it may be that because of its less stable updraft, an HP can produce violent tornades without sustaining them.

It is possible that the 1925 Tri-State tornado was spawned by an HP, but the only real evidence is that no-one could really see a tornado — that's pretty shaky evidence. THis lack of visibility may have had more to do with the size of the tornado (i.e. it wasn't a "classic" funnel or anything) or intervening microbursts.

 

[Karen Politte]

Karen,
Actually, the mid-upper level winds were stronger over OK. The jet streak axis was centered right over centerl OK. For example, at 300mb, DDC had 65kts, while OUN sounding had 90kts... At 500mb, OUN may have been a shade stronger with 45kts, compared to likely the low 40s in souther KS.

See the 500mb, 300mb, and 250mb graphics at http://www.spc.noaa.gov/exper/archive/even...0529/index.html

For this particular event, I still haven't really figured out why the central OK storm was as HP as supercells get, while the southern KS storm was classic. My only observation was that there was stronger/more CINH down in central OK (see OUN sounding) than was the case in southern KS.

Jeff -

You got me going, so I've been digging around for data from May 29th. I was privy to a private discussion between Louis Wicker and others who came to the near-solid conclusion that the northern Oklahoma/southern Kansas conditions were much more favourable than central Oklahoma that day - mainly in CAPE but also in wind fields.

Trouble is - your link above shows the 0Z May 30th OUN sounding, but not the special sounding released from LMN (Lamont) that date at that time (there WAS one - that's why others managed to come to the conclusion of why the southern-KS storm was Classic and the OKC storm was horridly HP).

As soon as I find the LMN sounding - I will post it here, along with perhaps a few of the conclusions of the aforementioned discussion.

I saw Greg Stumpf raise his head in this thread. Greg - care to digress on the May 29th differences????

KR

 

[Shane Adams]

IMO the windfieilds in S Kansas were almost perfect for classic mode. Great directional and speed shear combo, plus the added bonus of awesome vent winds - which is what I based my target decision on. The windfields were equally good in W OK that day for sups too, but the convective temp was 91 degrees - with upper 60s/low 70s dews, I was afraid any storm that could break through would be extremely high-based (20+ spreads are iffy). When we left Norman for N OK that day, I would've bet the farm nothing would go south of Enid, OK. I was wrong about my OK forecast, but fortunately I was right for my KS one.

Main thing I remember about forecasting that morning was automatically shunning N Kansas/SE Nebraska due to weaker mid-level winds; I feared a slopfest was in short order once initiation got underway up there.