Persistent Overshooting Tops with Non-Supercells?

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Alex Dashevsky

Sep 19, 2019
Chisinau, Moldova
I've read in many sources that persistent (>20 min.) overshooting tops are quite a strong indicator that a convective storm is severe and, frequently, a supercell. This makes sense for me because supercells are associated with strong, long-lived updrafts which produce long-lived overshooting tops. But I've seen some cases when multicells anchored to outflow boundaries, breeze fronts or terrain whose OTs exhibited very similar behavior.

The question is: how reliable are OTs as satellite clues of mesocyclones/supercells? Ideally, some statistics of persistent OTs for a region, like the percent of them linked to supercells, would be very helpful.

The main reason I'm asking this question is that I've read many times in Russian/CIS severe weather discussions written by amateurs and even qualified meteorologists that long-lived OTs are a 100% indicator of a mesocyclone. Based on this "criterion", many isolated long-lived orographic storms in Crimea and North Caucasus regions developing in very weak deep layer shear (20 kt or even less than 10 kt) are labeled as supercells. Perhaps orography modifies the local wind field so much that the deep layer shear can increase by 10-15 kt or more, and this process is not captured well even by mesoscale models?