Simulation of a serial upstream-propagating mesoscale convective system event over Southeastern South America using composite initial conditions

Vagner Anabor, David Jonathan Stensrud, Osvaldo L.L. de Moraes

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Serial upstream-propagating mesoscale convective system (MCS) events over southeastern South America are important contributors to the local hydrologic cycle as they can provide roughly half of the total monthly summer precipitation. However, the mechanisms of upstream propagation for these events have not been explored. To remedy this situation, a numerical simulation of the composite environmental conditions from 10 observed serial MCS events is conducted. Results indicate that the 3-day simulation from the composite yields a reasonable evolution of the large-scale environment and produces a large region of organized convection in the warm sector over an extended period as seen in observations. Upstream propagation of the convective region is produced and is tied initially to the development and evolution of untrapped internal gravity waves. However, as convective downdrafts develop and begin to merge and form a surface cold pool in the simulation, the cold pool and its interaction with the environmental low-level flow also begins to play a role in convective evolution. While the internal gravity waves and cold pool interact over a several hour period to control the convective development, the cold pool eventually dominates and determines the propagation of the convective region by the end of the simulation. This upstream propagation of a South American convective region resembles the southward burst convective events described over the United States and highlights the complex interactions and feedbacks that challenge accurate forecasts of convective system evolution.

Original languageEnglish (US)
Pages (from-to)2144-2163
Number of pages20
JournalMonthly Weather Review
Volume137
Issue number7
DOIs
StatePublished - Oct 29 2009

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cold pool
convective system
internal wave
gravity wave
simulation
convection
environmental conditions
South America
summer

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

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abstract = "Serial upstream-propagating mesoscale convective system (MCS) events over southeastern South America are important contributors to the local hydrologic cycle as they can provide roughly half of the total monthly summer precipitation. However, the mechanisms of upstream propagation for these events have not been explored. To remedy this situation, a numerical simulation of the composite environmental conditions from 10 observed serial MCS events is conducted. Results indicate that the 3-day simulation from the composite yields a reasonable evolution of the large-scale environment and produces a large region of organized convection in the warm sector over an extended period as seen in observations. Upstream propagation of the convective region is produced and is tied initially to the development and evolution of untrapped internal gravity waves. However, as convective downdrafts develop and begin to merge and form a surface cold pool in the simulation, the cold pool and its interaction with the environmental low-level flow also begins to play a role in convective evolution. While the internal gravity waves and cold pool interact over a several hour period to control the convective development, the cold pool eventually dominates and determines the propagation of the convective region by the end of the simulation. This upstream propagation of a South American convective region resembles the southward burst convective events described over the United States and highlights the complex interactions and feedbacks that challenge accurate forecasts of convective system evolution.",
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Simulation of a serial upstream-propagating mesoscale convective system event over Southeastern South America using composite initial conditions. / Anabor, Vagner; Stensrud, David Jonathan; de Moraes, Osvaldo L.L.

In: Monthly Weather Review, Vol. 137, No. 7, 29.10.2009, p. 2144-2163.

Research output: Contribution to journalArticle

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