Why do LP supercells generally not produce tornadoes?

[Andrew Clope]

I was thinking about this tonight, and was wondering if it's because the LP supercells do not produce enough rain cooled air/precip, to wrap around the updraft (RFD) and tighten rotation?

 

[Stan Rose]

RFD role might be a factor. Also, a generally higher cloud base. Not sure if it's ever been quantified, since ive seen plenty of pics of LPs producing tornadoes.

 

[Bob Schafer]

Tornadogenesis can't occur until mesoscale rotation is transferred to the ground. It's a battle between that and the ambient flow. Even with a landspout there must be cooperation at near-sfc level or there is disruption.

LP's are (generally) simply weaklings compared to a classic sup, high-based or not, so the probability of tornadogenesis is reduced.

 

[Jeff Duda]

RFD role might be a factor.

I agree that this probably has a significant impact.

Additionally, the reduced size/strength of the FFD cold pool probably also plays a big role since it serves as a mechanism for generating horizontal vorticity through baroclinicity. I think the current thinking among most tornado researchers are that there is more than one way for tornadoes to form from supercell storms. If it's true that there really are fewer tornadoes from LP storms, and if someone can get enough thermodynamic measurements through transects of the FFD and inflow air to verify these hypotheses, I think you'd find that this particular mechanism (low-level baroclinically generated horizontal vorticity from the FFD) of getting tornadoes is probably a popular mechanism. That would help explain the paucity of tornadoes.