Earth:Pulse storm
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
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
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 or a towering cumulus, 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 to develop because the Outflow boundary is a lifting mechanism for updrafts because it can force more warm humid air into the atmosphere.
See also
References
- ↑ 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.
- ↑ Jeff Haby. "What is a pulse storm?". http://www.theweatherprediction.com/habyhints2/400/. Retrieved February 20, 2020.
- ↑ 3.0 3.1 Departement of Atmospheric Sciences. "Evolution of a Single Cell Storm". University of Illinois. http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/svr/type/sngl/ev.rxml. Retrieved 2020-02-19.
- ↑ "Pulse storm". Glossary. US National Weather service. https://forecast.weather.gov/glossary.php?letter=p. Retrieved February 20, 2020.
fr:Orage#Orage ordinaire et pulsatif
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