Editing Squall line (section)

=== Derecho ===
{{Main|Derecho}}
[[File:DangerousShelfCloud.jpg|thumb|[[Shelf cloud]] on the leading edge of a derecho as photographed in [[Minnesota]]]]

A derecho (''from Spanish'': "[[wikt:derecho|derecho]]" meaning "straight")<ref>Merriam-Webster's Spanish/English Dictionary (2009). [http://www.merriam-webster.com/spanish/derecho Derecho.] Merriam-Webster, Incorporated. Retrieved on 2009-05-03.</ref> is a widespread and long-lived, violent convectively induced straight-line windstorm that is associated with a fast-moving band of severe thunderstorms usually taking the form of a bow echo. Derechos blow in the direction of movement of their associated storms, similar to a [[outflow boundary|gust front]], except that the wind is sustained and generally increases in strength behind the "gust" front.  A warm weather phenomenon, derechos occur mostly in summer, between May and August in the [[Northern hemisphere]].  They can occur at any time of the year and occur as frequently at night as in the daylight hours.<ref name="noaa">{{cite web| url= http://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm | title = About Derechos | publisher = [[Storm Prediction Center]] of the [[National Weather Service]] | author1 = F. Corfidi | author2= Jeffry S. Evans | author3= Robert H. Johns | access-date = March 5, 2015 |date= Feb 1, 2015}}</ref>

The traditional criteria that distinguish a derecho from a severe thunderstorm are ''sustained'' winds of {{convert|58|mph|km/h}} during the storm as opposed to gusts, high or rapidly increasing forward speed, and geographic extent (typically {{convert|250|nmi|sigfig=1}} in length.)<ref name="noaa" />  In addition, they have a distinctive appearance on radar (bow echo); several unique features, such as the rear inflow notch and bookend vortex, and usually manifest two or more downbursts.  Although these storms most commonly occur in North America, derechos occur elsewhere in the world.  Outside North America they may be called by different names.  For example, in [[Bangladesh]] and adjacent portions of India, a type of storm known as a "Nor'wester" may be a progressive derecho.<ref name="noaa" />