MEMPHIS, Tenn. (WMC) - While the tornado threat goes down during the summer months, the damaging wind threat tends to stay present, but why is that?
In this episode of the breakdown we explain why damaging wind storms are more likely in June.
Mesoscale Convective Systems (MCS), are thunderstorm clusters that are smaller than a low-pressure system with cold and warm fronts, but larger than any single thunderstorm.
A MCS can grow large enough to affect the weather for the next day in the surrounding area.
First identified back in the 1970s from infrared satellite imagery, they gained the name mescal convective complexes, simply larger versions of MCSs described by the areal coverage and persistence of their satellite signature, according to the AMS Meteorology Glossary.
This type of system is common in many parts of the world, including the central and southern United States.
A typical MCS will develop int he nations heartland in late spring and summer, usually at night and will continue into the early morning hours. These systems will have extreme lightning and loud crashes of thunder, usually keeping people awake at night.
Cooler air near the ground at night will help intensify a jet stream much lower to the ground, only 1,500 to 3,000 feet, this low-level jet will ride atop cooler air near the ground, which then feeds storms humid air to a developing MCS.
As the low-level jet collides with the rain-cooled outflows from thunderstorms that formed earlier in the night, new thunderstorms will form and the process will continue over and over again.
The MCS will be stronger overnight thanks to the increased instability from the cooler at the cloud-top level. As the clouds lose energy into space, there is no solar radiation absorbed, that along with heat giving off from condensation of water vapor into the clouds.
An MCS can track over hundreds of miles and last for around 12 hour or more. While MCS can produce hail and tornadoes there are three main impacts that occur with this system in the U.S.
Flooding Rain, if an MCS stalls form over slowly, it can cause flash flooding. This is caused by upper level winds at the jet stream are weak.
Damaging Winds, when a MCS is pushed by a more strong upper level jet stream. When this happens, straight-line winds can down trees and power lines, in the heat of the summer. Usually this occurring during the night hours.
A more extreme version of this is called a derecho. This MCS will feature swaths of wind damage 250 miles long, often with gusts of wind over 75 mph.
The lightning strike rate will also rise with the formation of these storms as they carve a path of damage across the storms path.