Organizational Modes of Midlatitude Mesoscale Convective Systems

Abstract

This paper discusses common modes of mesoscale convective organization. Using 2-km national composite reflectivity data, the authors investigated linear mesoscale convective systems (MCSs) that occurred in the central United States during May 1996 and May 1997. Based upon the radar-observed characteristics of 88 linear MCSs, the authors propose a new taxonomy comprising convective lines with trailing (TS), leading (LS), and parallel (PS) stratiform precipitation. While the TS archetype was found to be the dominant mode of linear MCS organization, the LS and PS archetypes composed nearly 40% of the studied population. In this paper, the authors document the characteristics of each linear MCS class and use operational surface and upper air data to describe their different environments. In particular, wind profiler data reveal that the stratiform precipitation arrangement associated with each class was roughly consistent with the advection of hydrometeors implied by the mean middle-and upper-tropospheric storm-relative winds, which were significantly different among the three MCS modes. Case study examples are presented for both the LS and PS classes, which have received relatively little attention to this point. As well, the authors give a general overview of the synoptic-scale meteorology accompanying linear MCSs in this study, which was generally similar to that observed by previous investigators.

A 10‐year spatial climatology of squall line storms across Oklahoma

“…Although past studies (e.g. Parker and Johnson, 2000;Burke and Schultz, 2004) have utilized composites or merged reflectivity to identify large convective systems and bow echoes, individual radar sites proved useful in this study due to the focus on a relatively small geographic domain. Level-II radar data were acquired for sites nearest storm report locations for each separate event.…”

“…Burke and Schultz (2004) focussed on the climatologies of bow echoes during the typically lower-frequency cool season and found similar spatial patterns as revealed in several derecho studies. Other studies such as Hilgendorf and Johnson (1998) and Parker and Johnson (2000) have focussed on the organizational characteristics, modes, and evolution of mesoscale convective systems (MCSs) as observed in radar data in an effort to better understand the dynamics of specific MCS modes. Cumulative weather event climatologies such as these are invaluable to the advancement of forecasting techniques and event recognition by illustrating where, when, and under what conditions severe events have occurred in the past.…”

On Polarimetric Radar Signatures of Deep Convection for Model Evaluation: Columns of Specific Differential Phase Observed during MC3E*

“…3) with strong upper-tropospheric westerly and southerly winds. Such a wind profile has been shown to favor linear squall line development with leading stratiform precipitation (Parker and Johnson 2000), and the storms that developed in southern Oklahoma were indeed of this type. However, the storms of interest were located in northern Oklahoma to southern Kansas, and developed along a weak low-level baroclinic zone.…”

The evolution of an MCS over southern England. Part 1: Observations

“…In particular, consistent with the strongly sheared environment, it has much in common with the parallel stratiform systems of Parker and Johnson (2000) and Parker (2007b) which develop three-dimensional structure due to the propagation of the cold pool perpendicular to the upperlevel shear. However, the development of the observed system appears to have some differences.…”

“…However, since the initial Line B is approximately aligned with the strong shear vector and there is some low-level shear between the surface and about 900 hPa with component normal to the line, it is likely to be more helpful to discuss the structure in terms of the 'parallel stratiform' systems identified by Parker and Johnson (2000) and analysed in more depth by Parker (2007b). In fact, the wind profile has much in common with the control simulation of Parker (2007a).…”