As stated above, gustnadoes frequently spin up along the leading edge of the bow echo. At the ends of the bow echo, some areas may spin. Squall Line Terminology • Squall Line : a relatively narrow line of thunderstorms, often fast moving • Bow Echo: line of thunderstorms shaped like a “bow”, frequently produces damaging winds • Derecho: a fast moving line of thunderstorms that produces widespread, significant wind damage (long track, duration Bow echoes tend to develop when moderate to strong wind shear exists in the lower 2 to 3 km of the atmosphere. They're usually produced by one or more curved lines of thunderstorms known as a bow echo or squall line. Cross Section of a Squall Line. Put simply, a bow echo is the “signature” you see on radar when the winds associated with a squall line (line of storms) are not uniform. Since the downdraft from a squall line approaches the earth's surface at an angle, the faster the downdraft winds the faster the storms may migrate forward. Such development occurred with the " I-94 Derecho " over the north-central United States on July 19, 1983 (see Fig. ... a line of severe thunderstorms with damaging winds raced east-southeast at a … As the bow echo matures, the locally intense rear-inflow jet descends to the … 4. Bow echoes are relatively small (20-120 km [10-65 nm] long), bow-shaped systems of convective cells that are noted for producing long swaths of damaging surface winds. Below is an example of a bow echo: BOW ECHO The next example is that of a bow echo with a line-end vortex on the north side of the squall line: LINE-END VORTEX These are known as bookend vortices. Bow echo formation begins shortly after the merger as a local strengthening of the cold pool and rear-inflow jet cause the squall line to surge forward just south of the merged supercell. The most damaging winds are typically felt at the apex of the bow, but wind damage may occur along the entire line of thunderstorms. This is a very large bow echo, covering many dozens of miles. What's the strongest? The vortex as the northern end of the bow echo rotates cyclonically while the one at the southern end rotates anticyclonically. They are observed both as relatively isolated convective systems and as sub-structures within much larger convective systems such as a squall line. When the derecho tore ... A key difference between hurricanes and derechos is the amount of advanced notice people receive. Another bow echo. Accompanied by conceptual animations, numerical simulations, and case studies, Mesoscale Convective Systems: Squall Lines and Bow Echoes presents strategies with which the forecaster can identify the potential for long-lived MCSs and attendant severe weather. The line of thunderstorms of a progressive derecho often begins as a single bow echo that evolves into a short squall line, typically with more than one embedded bowing segment. 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