Hazards Associated with Supercells
Supercells make up only a small proportion of all deep moist convection, but they are responsible for a disproportionate fraction of high-end severe convective weather. Dudha and Gallus (2010) state that supercells produce severe weather more frequently than other storm types, and also produce more intense severe weather. In their study, supercells accounted for over half of all storm reports in the U.S., with about 91% of supercells producing severe weather.
Destructive Winds
Supercells, on average, produce more severe wind reports, ~6 reports per event, than any other storm type, except Bow Echoes (~15 reports). Destructive winds should be considered over damaging winds due to the supercellular classification (except: if you can confidently diagnose an elevated supercell the downdrafts of which are well insulated from the surface by a deep layer of potentially cold air).
Large Hail
Supercells produce more than two-thirds of all hail reports. Supercells average the highest amount of severe hail reports per hail event, especially for hail greater than 2.5 cm. The particularly strong and longer-lived updraft has good potential to produce large hail by allowing riming to take place within hail growth layer, -10º to -30ºC, for an extended period of time. Some consideration to giant hail should be given when dealing with supercells.
Flash Flooding
Heavy rainfall resulting in flash flooding is not an automatic hazard associated with supercells, in particular for smaller or faster-moving storms. Supercells tend to have a comparatively low precipitation efficiency, but also process inordinate amounts of water vapour. The result of these two opposing drivers for heavy rainfall is that flash flooding is more likely with larger and/or slower-moving supercells.
Tornadoes
The average number of tornadoes produced by supercells is much greater than that from any other storm type. About 15-30% of supercells are tornadic (for example, Dudha and Gallus 2010; Trapp et al. 2005a). However, a higher proportion, 20% to 40%, of low-level mesocyclones are associated with tornadoes. Stronger low-level mesocyclones, especially when embedded in tornadogenesis-supporting storm environments, warrant consideration of a tornado warning.