Denver convergence vorticity zone

The Denver Convergence Vorticity Zone (DCVZ) is an orographically-induced atmospheric phenomenon characterized by convergent winds east of the Denver metropolitan area, typically 50 to 100 km in length and oriented in a north-south direction. This meteorological feature was subject to academic scrutiny following a large outbreak of Denver-area tornadoes in 1981 and has been used to explain the propensity of the area to spawn landspout (misocyclone) and supercell (mesocyclone) tornadoes. The DCVZ is often associated with the Denver Cyclone effect, although the Denver Cyclone is considered a distinct atmospheric phenomenon by some scientists.

DCVZ conditions form when a low-level moist, southeasterly flowing air mass meets the Palmer Divide, a ridge that extends east of the Colorado Front Range. If the moist air lifts over the ridge and meets northwesterly winds originating in the Rocky Mountain foothills, winds may converge to create enhanced cyclonic vorticity. A study conducted between 1981 and 1989 demonstrated that the DCVZ formed on one-third of all days during the convective season (May through August).

DCVZ conditions are often associated with the Denver Cyclone effect, which is characterized by the formation of a large gyre near the city center.

Several studies have documented the role of the DCVZ in tornado outbreaks across the Denver area. Using climatic data from the 1980s, one researcher has suggested that the presence of a strong June DCVZ has been associated with a 70% chance of zone-area tornado formation.

...
Wikipedia