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Pulse storm

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A pulse storm is a single cell thunderstorm of substantial intensity which only produces severe weather for short periods of time. Such a storm weakens and then generates another short burst – hence "pulse". The term was coined by researchers at the National Severe Storms Laboratory in 1979 to describe a single storm cell briefly becoming severe within a cluster of multi-cellular thunderstorms, but has since been used to describe a variety of isolated and brief thunderstorms with both severe and non-severe characteristics.[1]

Description

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Single cell thunderstorms ordinarily form in environments with low wind shear and moderate instability, with the low wind shear contributing to a short average lifespan of less than an hour.[2] When the instability, calculated by convective available potential energy (CAPE), is strong, the updraft will bring a larger amount of humid air very high above ground and generate a cumulonimbus cloud with high water and ice content.[3] When the rain content, and even hail, falls from it, they can generate damaging winds brought about by downbursts. Rarely, a weak tornado develops in association with a pulse storm as the environment is only weakly sheared, or not at all.[4]

Life cycle

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Life cycle of a pulse storm.

One can distinguish three stages in the evolution of a pulse storm:[3]

  • Formation: the upward current of the cell intensifies and allows the condensation of water vapor from the rising air parcel. This forms a cumulus congestus, then a cumulonimbus when ice crystals form at its apex which spreads horizontally in contact with the tropopause.
  • Maturity: downdrafts are emerging. This stage is accompanied by characteristic phenomena such as lightning and thunder, showers, and gust front.
  • Dissipation: the cold pool descending from the cloud extends to the Earth's surface and helps to block the feed by pushing the updraft downstream. The outflow can then serve as a trigger for other single cell or even multi-cell thunderstorms.

See also

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References

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  1. ^ Miller, Paul W.; Mote, Thomas L. (May 2017). "Standardizing the Definition of a "Pulse" Thunderstorm". Bulletin of the American Meteorological Society. 98 (5): 905–913. doi:10.1175/BAMS-D-16-0064.1.
  2. ^ Jeff Haby. "What is a pulse storm?". www.theweatherprediction.com. Retrieved February 20, 2020.
  3. ^ a b Departement of Atmospheric Sciences. "Evolution of a Single Cell Storm". ww2010.atmos.uiuc.edu. University of Illinois. Retrieved 2020-02-19.
  4. ^ "Pulse storm". Glossary. US National Weather service. Retrieved February 20, 2020.