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).
Role in Denver area tornado formation
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.
- Szoke, Edward J. (8 Nov 2006). "The Denver Cyclone and Tornadoes 25 Years later: The Continued Challenge of Predicting Non-supercell Tornadoes". 23rd Conf Severe Local Storms. St. Louis, MO: American Meteorological Society.
- Egger, Crystal. "Colorado's Front Range: Understanding Tornadogenesis In relation to the Denver Cyclone". Retrieved 2014-05-30.
- Pietrycha, A. Email correspondence quoted by Sam Barricklow, http://www.k5kj.net/DCVZ.htm
- Szoke, E.J., and J.A. Augustine, 1990: An examination of the mean flow and thermodynamic characteristics of a mesoscale flow feature: The Denver Cyclone. Fourth Conference on Metroscale Processes, Boulder, American Meteorological Society
- Szoke, E.J., and J.A. Augustine, 1990: A decade of tornado occurrence associated with a mesoscale flow feature: The Denver Cyclone. 16th Conference on Severe Local Storms, Alberta, Canada, American Meteorological Society, 554-559.