Radar observations and analysis of misocyclones along Spring 2012 West Texas drylines
Prososki, Paul F.
MetadataAfficher la notice complète
The dryline is a non-frontal boundary common to West Texas and Oklahoma in the spring time, and is associated with severe weather and much of the precipitation this region receives throughout the year. Although these associations have long been known, one of the most difficult forecasts operational meteorologists face today is predicting if and when convective initiation (CI) will occur. Various boundaries such as cold fronts, sea-breeze fronts, and drylines all have been observed to contain propagating vertical vorticity maxima known as misocyclones. Though the finescale kinematics and processes affecting misocyclones are poorly understood, misocyclones are believed to be a possible connection to enhanced upward motion along the boundary, and subsequently, also CI. It is also known that secondary boundaries, such as horizontal convective rolls, that intersect the boundary can be regions of elevated convergence and may be associated with clouds. For these reasons, this thesis seeks to observe in high detail the development and life cycle of dryline misocyclones as well as intersections of any secondary boundaries with the dryline. Specifically, the goals of this study are to observationally confirm that horizontal rolls can be tilted to enhance vertical vorticity maxima along the dryline and test whether cross-dryline horizontal shear also affects misocyclone development. Furthermore, satellite data exceeding 1-km resolution is obtained in an attempt to associate cloud locations with significant dryline features in the vorticity, convergence, and reflectivity fields. Two dryline cases are analyzed in this thesis, 30 April 2012 and 19 May 2012. This study confirms that the intersection of the dryline and other ancillary boundaries are preferred locations for the genesis of misocyclones. Furthermore, it is observed that misocyclones can remain fixed at these locations while most dryline misocyclones are propagating. Horizontal shear appears to be significant in the amplification of misocyclones on the 19 May dryline, but results failed to be generalized by the 30 April case. Clouds are observed on the 30 April case to be located near significant structural features along the dryline, including misocyclones and the aforementioned boundary intersections with the dryline.