Precipitation in rear-flank-downdrafts.

[David Draun]

Several of the supercells I witnessed last week in KS/OK/TX had precip, sometimes heavy, in the RFD regions of the storms. I also know that some RFD's are dry as well. Does this conincide with supercell morphology i.e. LP/Classic/HP? Does it have to do with the wind-fields in the storm-environments? Also, can the prescence of precipitation in the RFD hamper tornadogenesis by making the RFD too cold?

I hope someone can enlighten me.

 

[cdcollura]

Good day,

In the case of an HP supercell, the RFD is normally filled with heavy precipitation. In an LP supercell, there is essentially a dry RFD (in most cases). Classic supercells can be a balance between the two, especially when in the process of evolving to LP (drier RFD) or HP (wetter RFD).

A warm RFD aids more in tornadogenesis as warm air is buoyant compared to a cold RFD. It is hard to answer whether the tempoerature of an RFD is dependant on how much precipitation is in it. A drier RFD tends to be warmer, but not always (as in the case a cold front is behind the supercell storm = cold RFD opposed to a dryline = warmer RFD).

 

[Ben Baranowski]

David,

I've heard/read some research from the Bluestein/Wurman/Markowski group and they've seen precip. in nearly all of the RFDs they've sampled. Many times the particles are so large that the RFD looks precip-less. This was a bit suprising to me since RFDs actually look clear to me, but they're the ones with the radars.

Ben

 

[Paul Knightley]

The May 22nd storms in KS were interesting to me w.r.t their RFDs...the updraught region which spawned the tornado I saw initially started out as a major, opaque core with plenty of heavy precip in it...it seemed like as the rotation increases, or perhaps as the meso descended, alot of the precip got cleared away, and in the end, the occluding meso produced a (fairly) brief tornado...now it may have produced before the precip cleared, but it seemed in a much better position to do so once the precip had gone.