What kind of Storm is a derecho storm?
What kind of Storm is a derecho storm?
A derecho (pronounced similar to “deh-REY-cho”) is a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms. Although a derecho can produce destruction similar to the strength of tornadoes, the damage typically is directed in one direction along a relatively straight swath.
How are bow echoes related to derecho development?
Derecho development is necessarily tied to the formation of bow echoes. A bow echo usually arises from a cluster of thunderstorms, but also may evolve from a single strong storm. Bow echoes most frequently occur when atmospheric winds are relatively strong and unidirectional (i.e., they vary little in direction with height but increase in speed).
What kind of weather does a derecho need?
Below is an image depicting favorable weather patterns for derecho formation. A progressive derecho needs a very unstable (hot and moist) environment with relatively strong winds aloft.
What is the definition of straight line wind damage?
As a result, the term “straight-line wind damage” sometimes is used to describe derecho damage. By definition, if the wind damage swath extends more than 240 miles (about 400 kilometers) and includes wind gusts of at least 58 mph (93 km/h) or greater along most of its length, then the event may be classified as a derecho.
How big does a derecho wind gust have to be?
As mentioned above, by the present definition, derecho winds must meet the National Weather Service criterion for severe wind gusts (greater than 57 mph) at most points along the storm path. But in stronger derechos, winds may exceed 100 mph.
What happens to power lines during a derecho?
In addition to posing a direct hazard to anyone caught below the falling lines, derecho damage to overhead electric lines sometimes results in massive, long-lasting power outages. Hundreds of thousands of people may be affected; in the worst events, power may not be restored for many days.
What was the wind speed of a derecho in 1977?
But in stronger derechos, winds may exceed 100 mph. For example, as a derecho roared through northern Wisconsin on July 4, 1977 , winds of 115 mph were measured.