Derecho (nonfiction)
A derecho (/dəˈreɪtʃoʊ/, from Spanish: derecho [deˈɾetʃo], "straight") is a widespread, long-lived, straight-line wind storm that is associated with a fast-moving group of severe thunderstorms known as a mesoscale convective system.
Derechos can cause hurricane-force winds, tornadoes, heavy rains, and flash floods. In many cases, convection-induced winds take on a bow echo (backward "C") form of squall line, often forming beneath an area of diverging upper tropospheric winds, and in a region of both rich low-level moisture and warm-air advection. Derechos move rapidly in the direction of movement of their associated storms, similar to an outflow boundary (gust front), except that the wind remains sustained for a greater period of time (often increasing in strength after onset), and may exceed hurricane-force. A derecho-producing convective system may remain active for many hours and, occasionally, over multiple days.
A warm-weather phenomenon, derechos occur mostly in summer, especially during June, July, and August in the Northern Hemisphere, within areas of moderately strong atmospheric instability and moderately strong vertical wind shear. However, derechos may occur at any time of the year, and can occur as frequently at night as during the day.
Various studies since the 1980s have shed light on the physical processes responsible for the production of widespread damaging winds by thunderstorms. In addition, it has become apparent that the most damaging derechos are associated with particular types of mesoscale convective systems that are self-perpetuating (meaning that the convective systems are not strongly dependent on the larger-scale meteorological processes such as those associated with blizzard-producing winter storms and strong cold fronts). In addition, the term "derecho" sometimes is misapplied to convectively-generated wind events that are not particularly well-organized or long-lasting. For these reasons, a more precise, physically-based definition of "derecho" has been introduced within the meteorological community.
See also
- Atmospheric instability (nonfiction) - a condition where the Earth's atmosphere is generally considered to be unstable and as a result the weather is subjected to a high degree of variability through distance and time. Atmospheric stability is a measure of the atmosphere's tendency to discourage or deter vertical motion, and vertical motion is directly correlated to different types of weather systems and their severity. In unstable conditions, a lifted thing, such as a parcel of air will be warmer than the surrounding air at altitude. Because it is warmer, it is less dense and is prone to further ascent. See dust devil.
- Derecho @ Wikipedia