Date of this Version
2004 American Meteorological Society
Recently, three distinct archetypes for midlatitude linear mesoscale convective systems (MCSs) have been identified. This article focuses on the fundamentals of two of these archetypes: convective lines with trailing stratiform (TS) precipitation and convective lines with leading stratiform (LS) precipitation. Both the TS and LS modes typically exhibit quasi-2D reflectivity patterns and quasi-2D environmental storm-relative wind fields. Ongoing work has revealed that there are three common flow structures for these quasi-2D MCSs: front-fed TS systems (which are sustained by front-to-rear storm-relative inflow), as well as front-fed LS and rear-fed LS systems (which are sustained by rear-to-front storm-relative inflow). This paper summarizes the observed structures of the front-fed TS, front-fed LS, and rear-fed LS modes, and then outlines an idealized numerical experiment in which these modes were simulated. The authors analyze the basic simulated kinematic and microphysical structures and provide a framework in which to analyze the dynamics of the modeled systems. To a large degree, the organizational modes of developing quasi-2D MCSs may be anticipated by considering the magnitudes and preferred directions of the horizontal pressure gradient accelerations associated with a surface cold pool [whose strength is largely related to the environmental humidity and convective available potential energy (CAPE)] and an updraft in the mean environmental wind shear profile. In this regard, the lower-tropospheric shear is of prime importance, although the middle- and upper-tropospheric shear provide for additional, nontrivial accelerations.