A proposed method for objectively identifying and characterizing frontal zones
Abstract
Presented here is a method to objectively identify and characterize thermal frontal zones from gridded datasets. The detection scheme identifies frontal zones based upon a thermal definition: two thermal parameters are utilized, virtual potential temperature and equivalent potential temperature. Minimum strength and size constraints are implemented to exclude frontal zones that are thermally weak and too small in size to be considered synoptic frontal zones. The resulting near-surface frontal zones are then characterized according to type, and additional frontal attributes may be obtained. Additionally, the extension of the procedure to multiple levels in the vertical demonstrates the unique examination of the frontal zones in three-dimensions. An evaluation of the overall technique indicates that a reasonable agreement between objective and subjective analyses may be obtained, though the minimum strength criterion is tuneable and can vary between synoptic situation and seasons. Further, the applicability of the objective frontal zone detection method as a forecast tool for convective mode prediction is investigated. The premise of the implementation utilizes the relationship between the orientation of the deep-layer shear vector—perpendicular, oblique, or parallel—with respect to the initiating boundary (e.g. cold front or dryline) to evaluate the likely convective evolution of storms within a short time after initiation. To this end, a procedure was developed to quantify the angle between the linear boundary and the deep-layer shear vector. Results from several cases of severe weather during 2011 have suggested that reasonable approximations of the deep-layer shear angle across the initiation boundary are obtainable, and that the overall relationship may provide useful insight to forecasters regarding short-term convective mode evolution.
Degree
M.S.
Advisors
Trapp, Purdue University.
Subject Area
Meteorology
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