The Surface-Wind Response to Transient Mesoscale Pressure Fields Associated with Squall Lines

Abstract

Abstract The two most prominent surface pressure features associated with squall lines are 1) a surface mesohigh, centered within the heavy-rain region, and 2) a wake low, located at the back edge of the trailing area of light rainfall. The surface flow near these features is often highly unbalanced due to propagation and transience of the pressure fields. Centers of surface divergence and convergence are typically displaced rearward of the mesohigh and wake-low axes, respectively. In an attempt to explain the basic mesoscale characteristics of the surface flow in the vicinity of squall lines, a simplified model of a propagating mesohigh-wake-low couplet is developed using a one-dimensional slab model of the boundary layer. The component of the flow normal to the squall line is predicted, with advective and frictional effects included but the Coriolis force neglected. Model results are compared to the observed airflow near the mesohigh and wake low associated with an intense squall line that moved through...