Applications of the Term "Pulse” as a Thunderstorm Mode Descriptor

Ordinary single-cell thunderstorms are a staple feature of summertime convection in the southeastern United States. According to the National Weather Service (NWS) glossary, these storms are to be termed “pulse” storms if they are associated with severe weather. However, this characterization is commonly violated by both operational products and research publications whereas the term sometimes goes altogether unmentioned in educational meteorology texts. Ultimately, the ambiguity of the term “pulse” poses a hazard for the consumers of the weather products that reference this thunderstorm mode.

This study examines a large number operational and academic texts to determine the different uses of this term. Operationally, thousands of Storm Prediction Center (SPC) mesoscale discussions and convective outlooks were mined for uses of “pulse.” The term's appearance in operational products closely resembled traditional expectations for this storm mode. Usage peaked in products issued in the late afternoon during the summer months, and declined sharply after sunset. Meanwhile, dozens of journal articles, government reports, and conference papers were consulted for examples of research applications.

In general, two distinct applications were apparent. With the first, a “pulse” thunderstorm is clearly linked to the manifestation of severe weather. However, with the second application, “pulse” is seemingly employed as a synonym for generic, benign air mass thunderstorms. Some alternative forms such as “pulse severe” alleviate this confusion, but also cast doubt on whether “pulse” alone is meant to communicate storm severity. The discontinuity between these two applications can lead to unnecessary confusion amongst consumers of these products. Most troubling is that the primary ambiguity relates to whether or not “pulse” implies an expectation of severe weather – an immediate threat to the lives and property of the product's consumers. This study proposes that a standard definition be adopted by operational and research meteorologists to facilitate a more streamlined communication of summertime severe weather hazards to the public.