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Kinematic Observations of Misocyclones along Boundaries during IHOP

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  • 1 Department of Meteorology, The Pennsylvania State University, University Park, Pennsylvania
  • | 2 Center for Severe Weather Research, Boulder, Colorado
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Abstract

During the International H2O Project, mobile radars collected high-resolution data of several 0.5–2-km-wide vertically oriented vortices (or misocyclones) along at least five mesoscale airmass boundaries. This study analyzes the properties of the misocyclones in three of these datasets—3, 10, and 19 June 2002—to verify findings from finescale numerical models and other past observations of misocyclones and to further the understanding of the role that they play in the initiation of deep moist convection and nonsupercell tornadoes. Misocyclones inflect or disjoint the swath of low-level convergence along each boundary to varying degrees depending on the size of their circulations. When several relatively large misocyclones are next to each other, the shape of low-level convergence along each boundary is arranged into a staircase pattern. Mergers of misocyclones are an important process in the evolution of the vorticity field, as a population of small vortices consolidates into a smaller number of larger ones. Additionally, merging misocyclones may affect the mixing of thermodynamic fields in their vicinity when the merger axis is perpendicular to the boundary. Misocyclones interact with linear and cellular structures in the planetary boundary layers (PBLs) of the air masses adjacent to each boundary. Cyclonic low-level vertical vorticity generated by both types of structures makes contact with each boundary and sometimes is incorporated into preexisting misocyclones. Intersections of either type of PBL structure with the boundary result in strengthened pockets of low-level convergence and, typically, strengthened misocyclones.

Corresponding author address: James N. Marquis, 503 Walker Building, University Park, PA 16802. Email: jmarquis@met.psu.edu

Abstract

During the International H2O Project, mobile radars collected high-resolution data of several 0.5–2-km-wide vertically oriented vortices (or misocyclones) along at least five mesoscale airmass boundaries. This study analyzes the properties of the misocyclones in three of these datasets—3, 10, and 19 June 2002—to verify findings from finescale numerical models and other past observations of misocyclones and to further the understanding of the role that they play in the initiation of deep moist convection and nonsupercell tornadoes. Misocyclones inflect or disjoint the swath of low-level convergence along each boundary to varying degrees depending on the size of their circulations. When several relatively large misocyclones are next to each other, the shape of low-level convergence along each boundary is arranged into a staircase pattern. Mergers of misocyclones are an important process in the evolution of the vorticity field, as a population of small vortices consolidates into a smaller number of larger ones. Additionally, merging misocyclones may affect the mixing of thermodynamic fields in their vicinity when the merger axis is perpendicular to the boundary. Misocyclones interact with linear and cellular structures in the planetary boundary layers (PBLs) of the air masses adjacent to each boundary. Cyclonic low-level vertical vorticity generated by both types of structures makes contact with each boundary and sometimes is incorporated into preexisting misocyclones. Intersections of either type of PBL structure with the boundary result in strengthened pockets of low-level convergence and, typically, strengthened misocyclones.

Corresponding author address: James N. Marquis, 503 Walker Building, University Park, PA 16802. Email: jmarquis@met.psu.edu

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