Monday, August 17, 2009
The Marks of Wind
A squall line is a line of severe thunderstorms that can form along and/or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. It contains heavy precipitation, hail, frequent lightning, strong straight line winds, and possibly tornadoes and waterspouts. Severe weather, in form of strong straight-line winds can be expected where the squall line in areas where the line itself is in the shape of a bow echo, in the portion of the line most bows out. Tornadoes can be found along waves within a line echo wave pattern, or LEWP, where mesoscale low pressure areas are present. Some bow echoes which develop within the summer season are known as derechos, and they move quite fast through large sections of territory. On the back edge of the rain shield associated with mature squall lines, a wake low can be present which are sometimes associated with a heat burst.
Lenticular clouds are stationary lens-shaped clouds that form at high altitudes, normally aligned perpendicular to the wind direction. Lenticular clouds can be separated into altocumulus standing lenticularis (ACSL), stratocumulus standing lenticular (SCSL), and cirrocumulus standing lenticular (CCSL).