On the afternoon of March 24, 2016, a stunning mesoscale convective vortex (MCV) formed within a mesoscale convective system as it moved over southern Alabama. I created the animation below using a sequence of radar images provided by the College of DuPage.
What is an MCV (Mesoscale Convective Vortex)?
An MCV is an area of low pressure that develops aloft within a large, organized, and long-duration complex of thunderstorms known as a mesoscale convective complex (MCC). The low pressure is a result of the tremendous amount of latent heat released through vapor condensation and ice nucleation which warms the core of the convective complex. This warming causes the air within the cloud layer to expand, reducing the air pressure. As the pressure drops, the surrounding wind field responds by turning inward toward the developing area of low pressure (air flows from high pressure to low pressure). Eventually, a local minimum in air pressure exists (closed low) and a circulation becomes evident. This circulation is not a tornado or mesocyclone; an MCV has nothing to do with either of those.
A convectively induced vortex can actually exist in the atmosphere long after the thunderstorm complex that created it has dissipated. Forecasters will continue to monitor a lingering MCV in the days ahead for potential thunderstorm development. A lingering mesoscale convective vortex can even serve as the impetus for tropical cyclone formation if they move offshore during the hurricane season. In fact, an MCV shares some similar characteristics of tropical cyclones, particularly its warm-core low.
Note: An MCV is NOT a “land hurricane” although some have historically – and incorrectly – referred to them as such.