![]() Pulse thunderstorms are generally not tornado producers (relative to supercell thunderstorms), but their associated large hail and high wind threats can be particularly troublesome to diagnose. While most disorganized thunderstorms cause relatively little human inconvenience, the strongest cells can produce surface conditions exceeding severe weather warning criteria. These cloud formations are almost a daily feature of the southeastern U.S. Typically lasting between 30 min and 1 h, each cell consists of a three-stage life cycle (i.e., the cumulus, mature, and dissipating stages) first described by Byers and Braham (1949) during the Thunderstorm Project. Fueled by the diurnal instability, short-lived, isolated convection generally forms during the afternoon in hot, humid, summertime air masses. These storms are a staple feature of the summer climate across the central and eastern United States. ![]() Meanwhile, broadcast meteorologists frequently opt for the phrase “pop up” or “popcorn” thunderstorm to communicate this convective mode to their audiences. “Airmass,” “ordinary,” “garden variety,” and “single cell” are all commonly used to indicate unicellular, nonsupercellular convection. Aside from pulse (and its sister term “pulse type”), the weather nomenclature also contains several other words to describe disorganized convection (see for a description of “organized” versus “disorganized” thunderstorms). Though its applications vary, contemporary uses of “pulse” broadly reference a small, short-lived, and isolated updraft forming in a weakly sheared environment. “Pulse thunderstorm” is a widely recognized term within the meteorological lexicon. The lexical evolution of “pulse thunderstorm” within meteorological texts is chronicled, revealing two common, yet incompatible, present-day uses. Further, thunderstorms forming within synoptically homogeneous air masses in the absence of large-scale dynamical lift are suggested to be termed “weakly forced thunderstorms.” By corollary, pulse storms represent the subset of weakly forced thunderstorms associated with severe weather. In the interest of effective communication and reproducible research, the definition of “pulse” is proposed to be standardized according to the term’s original (i.e., severe, multicellular) meaning. The MD content analysis reveals that 1) the term “pulse” frequently appears in conjunction with severe-weather-related language and 2) that pulse-related words (e.g., brief, isolated) are equally represented in multicell-referencing MDs. The larger CO sample ( n = 997) establishes that temporal trends in “pulse” references model traditional expectations whereas the detailed MDs ( n = 458) showcase examples of pulse-related terminology. This paper reviews the history of the term “pulse,” performs a content analysis on nearly 1,500 pulse-referencing Storm Prediction Center (SPC) convective outlooks (CO) and mesoscale discussions (MD), and summarizes the deficiencies with the contemporary disorganized convection nomenclature. However, recent applications of “pulse” have evolved to also describe nonsevere, single-cell storms, and both uses can currently be observed within research, operational, and educational texts. The term “pulse thunderstorm” was originally coined to describe an anomalously strong airmass thunderstorm often associated with a larger convective complex. Further, the language used to describe the strongest, severe-weather-producing subset of these storms is applied inconsistently, posing a communication hurdle for the effective dissemination of hazardous weather risks. ![]() Isolated, short-lived thunderstorms forming in weakly forced environments are referenced through a surplus of terminology. ![]()
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