Closings & Delays across the Tennessee Valley

Mesoscale convective vortex (MCV) spinning much needed rain into the Tennessee Valley

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Animation of a mesoscale convective vortex (MCV) moving into the Tennesse Valley Sunday morning, July 10, 2016.

Animation of a mesoscale convective vortex (MCV) moving into the Tennessee Valley Sunday morning, July 10, 2016.

A mesoscale convective vortex (MCV) is spinning its way through northeastern Mississippi into northwestern Alabama and south-central Tennessee, as of 10 a.m. Sunday morning.

An MCV is a meteorological term for a relatively medium scale (“mesoscale”) low pressure system that pulls air inward into a circular loop (“vortex”) that is generating showers and thunderstorms where it is located (hence why it’s considered “convective”, because it is causing air to rise and fall as it moves through the region).

Valley rainfall deficit as of July 10, 2016.

Valley rainfall deficit as of July 10, 2016.

As of 10 a.m., the MCV is producing heavy rain in Franklin, Colbert and Lauderdale counties, a section of the Tennessee Valley that is in great need of rain. In fact, the latest rainfall climatology analysis shows that the Muscle Shoals climate station is reporting a rainfall deficit of nearly 8.5 inches for the year.

MCVs are usually located within a larger mesoscale convective system (MCS), which is a cluster of thunderstorms that move over a region as a collective system. According to the National Severe Storms Laboratory, MCSs can last more than 12 hours as they move across entire states.

Within an MCS, an MCV can pull air and rain into its signature circling pattern, which creates the embedded vortex within the overall thunderstorm system. This causes the circular pattern that is usually between 30 to 60 miles wide but can last for as long as 12 hours.

When MCVs form over land, they can sometimes generate strong to severe thunderstorms. When the move from land to over tropical waters like the Gulf of Mexico or the Atlantic Ocean, MCVs can serve as the catalyst for tropical depressions, tropical storms or even hurricanes.