Derecho Storms

10/31/2019 (Permalink)

Black Shelf Cloud, cloud beneath storm,Derecho approaching

Derecho Storms

Derechos are home to the most incredible shelf clouds nature can produce. A shelf cloud is a thick cloud that juts down from the sky, like a shelf hanging beneath the bottom of the storm. There are two different types of derechos. The most dangerous type is a progressive derecho. This is the kind of storm you see in the summer that speeds across entire states and leaves tornado-like damage in its wake. A serial derecho forms along a cold front.  Serial derechos are most common during the fall and winter months. 

Derechos are associated with bands of rapidly moving showers or thunderstorms variously known as bow echoes, squall lines, or quasi-linear convective systems.  The winds associated with derechos are not constant and may vary considerably along the path it takes.  Sometimes the winds are below severe level reaching 57 mph or less.  Severe winds from this storm can be from 75 mph to greater than 100 mph.

Derechos are most common in the central United States, but they can form just about anywhere around the world that experiences severe thunderstorms. A relentless summertime heat wave can trigger multiple derechos in one week if conditions are just right. They can leave behind more damage than a tornado, yet they're relatively unknown by anyone other than weather enthusiasts.

One of the reasons derechos can wreck such havoc is because they come on suddenly.  There usually isn’t much of a buildup to the strongest winds before they hit.  Conditions can go from calm to chaos in a matter of seconds.  The abruptness with which the winds can hit can even snap off the tops of trees.

The aftermath of many derechos looks like what you would see after a hurricane or tornado.  The winds destroy roofs, structures, barns and can cause wide spread power outages. The storm can produce wind damage over 200 miles long and last over 6 hours.  

Those involved in outdoor activities during the hot summer months are at a greater risk.  Campers or hikers in forested areas are vulnerable to being injured or killed by falling trees.  Occupants of cars and trucks also are vulnerable to falling trees and utility poles.  Even those indoors may be at risk from falling roofs.  Mobile homes in particular may be overturned or destroyed. 

Derechos are very powerful, destructive wind storms. The derecho initially starts as a cluster of storms that forms a squall line. This line of storms can eventually show a bowing structure, indicating stronger storms and more concentrated winds in those areas.  During the summer months when storms are predicted stay weather alert and move your activities inside if any way possible.  These storms are fast moving and approach suddenly.