THE MERIDIONAL GROWTH OF SQUALL LINES

Abstract

Squall lines that form ahead of an accelerating cold front are sometimes observed to grow in length. In this paper an attempt is made to explain this interesting property of squall lines, and to deduce a mathematical formula by which this growth may be forecasted. The idealized model is based on the following assumptions: (1) the ground on which the flow occurs is horizontal and devoid of any elevations; (2) there is an inversion layer above the lower surface flow; (3) the acceleration of the cold front is constant; (4) no lateral velocities are produced because of the motion of the cold front. On the basis of these assumptions, and with use of the method of characteristics, a formula is derived for the formation and growth of a squall line. A numerical example is given to clarify the method.