Appearance
At ground level, shelf clouds and roll clouds can be seen at the leading edge of outflow boundaries. Through satellite imagery, an arc cloud is visible as an arc of low clouds spreading out from a thunderstorm. If the skies are cloudy behind the arc, or if the arc is moving quickly indicate that high wind gusts are likely behind the gust front. Sometimes a gust front can be seen on weather radar, showing as a thin arc or line of weak radar echos pushing out from a collapsing storm. The thin line of weak radar echoes is known as a fine line. Occasionally, winds caused by the gust front are so high in velocity that they also show up on radar. This cool outdraft can then energize other storms which it hits by assisting in updrafts. Gust fronts colliding from two storms can even create new storms. Usually, however, no rain accompanies the shifting winds. An expansion of the rain shaft near ground level, in the general shape of a human foot, is a telltale sign of a downburst. Gustnadoes, short-lived vertical circulations near ground level, can be spawned by outflow boundaries.
Read more about this topic: Outflow Boundary
Famous quotes containing the word appearance:
“Look into the world—how often do you behold a sordid wretch, whose straight heart is open to no man’s affliction, taking shelter behind an appearance of piety, and putting on the garb of religion, which none but the merciful and compassionate have a title to wear.”
—Laurence Sterne (1713–1768)
“The aim of science is to apprehend this purely intelligible world as a thing in itself, an object which is what it is independently of all thinking, and thus antithetical to the sensible world.... The world of thought is the universal, the timeless and spaceless, the absolutely necessary, whereas the world of sense is the contingent, the changing and moving appearance which somehow indicates or symbolizes it.”
—R.G. (Robin George)
“The President has paid dear for his White House. It has commonly cost him all his peace, and the best of his manly attributes. To preserve for a short time so conspicuous an appearance before the world, he is content to eat dust before the real masters who stand erect behind the throne.”
—Ralph Waldo Emerson (1803–1882)