Thursday, 30 October 2008
Madison Ballroom (Hilton DeSoto)
The body of knowledge on Deep, Moist Convection now includes a host of newly documented archetypes. However, the convective storm classification system that is used in forecast discussions and taught in both pre-professional and professional education has remained relatively unchanged over the past two decades. The current scheme segregates storms into single, ordinary cells, multicell clusters, multicell lines and supercells with an implication of ascending organization in the same order. When delving into the descriptions of each, there are often serious problems evident in the scheme. For instance, consider that supercells exhibit pulse-like behavior, and contain multiple mesocyclones with their own locally intense updrafts in different stages of development. None of this is mentioned in the current classification. Consider that the common descriptions of multicells, even the AMS glossary definition, only describe multicells as existing with new cell development initiating from the cold pool. Those multicell descriptions ignore a large number of cell groups existing with no identifiable cold pool. We also have no way to account for the fractal behavior of convection in our classification scheme, or in other words, that small multicells are embedded in larger multicells. A better classification scheme would help forecasters recall the most appropriate conceptual model of an observed convective storm and then potentially make a better forecasts of motion and impacts. Likewise, spotters would be more able to effectively convey the observed behavior of convective storms from a field perspective. One way to do this is to have an operationally useful classification scheme so that naming the type of convective storm conveys it's most likely expected behavior in a useful forecast period. In this paper, we will describe the reasons why a classification scheme is needed, limitations of the current classification scheme, and propose an improved scheme.
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