Hi Squawk7777
I like you had the impression 'the book' says not associated....
Found these on a quick search:-
"A non-frontal band or sold line of thunderstorms which typically produce strong winds" <a href="http://www.wrh.noaa.gov/cgi-bin/Greatfalls/gettext.pl?glossary/glossary.html" target="_blank"><here></a>. This seems to suggest 'not connected'.
"Cold fronts move at speeds from 10 to 50 knots. In winter they are 2 or 3 times faster than in the summer. A fast-moving cold front may be preceded by a squall line, a roll of black, threatening clouds with violent storms. Wind shifts suddenly along the front, and wind velocities increase dramatically. Behind the squall line are heavy rains, then clearing, and gusty winds, usually followed by several days of clear, cool weather." <a href="http://www.boatwashington.org/weather.htm" target="_blank"><here></a> which seems to suggest they are related.
This looks the most plausible model readily available:-
<a href="http://www.usatoday.com/weather/tg/wsqualin/wsqualin.htm" target="_blank">http://www.usatoday.com/weather/tg/wsqualin/wsqualin.htm;</a>
But wait! Hows about:-
"A squall line is a line of thunderstorms that have a common lifting mechanism. Lifting mechanisms tend to occur in bands. Examples of banded lifting mechanisms include fronts, large outflow boundaries, gravity waves, and isentropic lifting associated with CSI. The classic squall line will develop out ahead of and parallel to a cold front or dry line boundary. The storms first develop where there is the best combination of moisture, instability and lift. The storms will continue to evolve and new cells will develop (commonly toward the south and east). The squall line will sustain itself by producing its own lift due to outflow boundaries. As long as instability and moisture remain present out ahead of the squall line, the squall line will continue to propagate." found <a href="http://theweatherprediction.com/habyhints/150/" target="_blank"><here></a>
That sounds like good stuff to me. I think therefore we can conclude that they are said not to be associated with fronts as they are created by anything generating a line of unstable air. However, as a front will often generate this in advance of it, then they are often found ahead of one.
Hows that for bull****? I'm going to lie down <img src="smile.gif" border="0">
[ 20 December 2001: Message edited by: vanman ]</p>