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:
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—Anna Quindlen (b. 1952)
“Though an unpleasant sort of person, and even a queer threatener withal, yet, if one meets him, one must get along with him as one can; for his ignorance is extreme. And what under heaven indeed should such a phantasm as Death know, for all that the Appearance tacitly claims to be somebody that knows much?”
—Herman Melville (1819–1891)
“The actor is too prone to exaggerate his powers; he wants to play Hamlet when his appearance is more suitable to King Lear.”
—Sarah Bernhardt (1845–1923)