DYNAMIC INTERPRETATION OF NOTCHES, WERS, AND MESOCYCLONES SIMULATED IN A NUMERICAL CLOUD MODEL.

Radar reflectivity fields frequently exhibit notches, weak echo regions (WER), or bounded weak echo regions (BWER) at mid-levels in strong convective storms. These features have most often been observed in supercell storms, where Doppler radar analyses have shown them to be within strong updrafts and mesocyclones. In fact, the appearance and subsequent persistence of the BWER on conventional radars or of the mesocyclone in conjunction with a BWER on Doppler radars has become one of the more definitive criteria for identifying a supercell storm. Numerical simulations discussed in this paper are produced using the Klemp-Wilhelmson numerical cloud model. Storms are initiated with a single symmetric bubble of warm air in an initially horizontally homogeneous environment, characterized by vertical profiles of wind, temperature, and moisture appropriate to the particular case being studied. Refs.