Modes of Supercell Initiation along the Dryline

摘要

Supercells have long been recognized as producers of severe weather, and the dryline has long been recognized as a preferred region of thunderstorm (including supercell) development. However, the modes of initial formation of these dryline supercells have yet to be examined. Radar microfilm of selected dryline supercells has been studied and the following six modes of initial development have been determined: isolated; pair; line segment; cluster; merger; and squall line. Characteristics of storm evolution such as splitting, backbuilding, and the orientations of cells compared to shear vectors were also examined (through the time of severe weather occurrence). Soundings from the proximity of each storm were used to estimate a sounding representative of the environment at the time and location of each storm's first echo. These estimated environmental soundings were then plotted (including hodographs) and many sounding and hodograph parameters (such as CAPE, BRN, LMS, etc.) were computed. A previously unstudied parameter of severe storms, the time from first echo to the time of first severe weather occurrence, has been determined for each of the storms. This should be useful information to nowcasters and mesoscale modelers as they attempt to predict specific 'storm day' evolutions.