An environmental and polarimetric study of the 19 November 2015 supercell and multiple-vortex tornado in Marechal Cândido Rondon, southern Brazil

Ferreira, Vanessa; Goede, Vitor; Nascimento, Ernani de Lima

doi:10.1007/s00703-022-00922-5

Cited by 4 publications

(3 citation statements)

References 85 publications

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“…A recent South American severe thunderstorm eld campaign (RELAMPAGO-CACTI) demonstrated that environments along the eastern edge of the Andes in CSA are not favorable for tornadoes owing to relatively weak near-ground (0-1 km) vertical wind shear (69-71), corroborating recent work using reanalysis data (56, 72). In both CNA and CSA, a dominant source of low-level vertical wind shear is the poleward LLJ over each continent (7,59,73,74,94,95,110,114). The vertical structure (e.g., peak height) differs between GPLLJ and SALLJ, as the Andes are in general taller and steeper than the Rockies such that slope effects are minimized while deeper lee cyclones develop near the Andes that help drive the SALLJ (59,63,71,74,75,77,78).…”

Section: Mainmentioning

confidence: 99%

“…Thus, the number of tornadoes is likely signi cantly underestimated, especially for some tornadoes reported over the southeastern Brazil (32,94,95). Caution should be exercised in directly comparing the frequency of tornado reports in CNA and CSA, though the stark qualitative contrast between the two regions is likely to be robust.…”

Section: Tornado and Lightning Observationsmentioning

confidence: 99%

“…We choose 25 S, as it is approximately the northern boundary of the majority of central South American tornado activity (Fig. 1a), though some tornadoes are reported at lower latitudes of South America (32,94,95). Thus, the modi ed equatorward land in smooth creates an ocean-like smooth surface upstream of the tornado hotspot of central South America, similar to North America where the smooth equatorward ocean surface (i.e., the Gulf of Mexico and the Caribbean Sea) is located upstream of the tornado hotspot of central North America.…”

Section: Real-earth Gcm Experimentsmentioning

confidence: 99%

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Upstream surface roughness and terrain drive contrast in tornado potential between North and South America

Chavas

Medeiros

et al. 2023

Preprint

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Central North America is the global hotspot for tornadoes, fueled by elevated terrain of the Rockies to the west and a source of warm, moist air from equatorward oceans. This conventional wisdom argues that central South America, with the Andes to the west and Amazon basin to the north, should have a “tornado alley” at least as active as central North America. Central South America has frequent severe thunderstorms yet relatively few tornadoes. Here we show that conventional wisdom is missing an important ingredient specific to tornadoes: a smooth, flat ocean-like upstream surface. Using global climate model experiments, we show that central South American tornado potential substantially increases if its equatorward land surface is smoothed and flattened to be ocean-like. Similarly, we show that central North American tornado potential substantially decreases if its equatorward ocean surface is roughened to values comparable to forested land. A rough upstream surface suppresses the formation of tornadic environments principally by weakening the poleward low-level winds, characterized by a weakened low-level jet east of the mountain range. Results are shown to be robust for any midlatitude landmass using idealized experiments with a simplified continent and mountain range. Our findings indicate that large-scale upstream surface roughness helps generate the strong contrast in tornado activity between North and South America.

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Section: Mainmentioning

confidence: 99%

Section: Tornado and Lightning Observationsmentioning

confidence: 99%

Section: Real-earth Gcm Experimentsmentioning

confidence: 99%

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Upstream surface roughness and terrain drive contrast in tornado potential between North and South America

Chavas

Medeiros

et al. 2023

Preprint

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Atmospheric environments associated with tornadoes in southern Brazil and neighboring areas as compared to other modes of convective hazards

Lopes,

Nascimento

2024

Clim Dyn

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Upstream surface roughness and terrain are strong drivers of contrast in tornado potential between North and South America

Li,

Chavas,

Medeiros

et al. 2024

Proc. Natl. Acad. Sci. U.S.A.

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Central North America is the global hotspot for tornadoes, fueled by elevated terrain of the Rockies to the west and a source of warm, moist air from equatorward oceans. This conventional wisdom argues that central South America, with the Andes to the west and Amazon basin to the north, should have a “tornado alley” at least as active as central North America. Central South America has frequent severe thunderstorms yet relatively few tornadoes. Here, we show that conventional wisdom is missing an important ingredient specific to tornadoes: a smooth, flat ocean-like upstream surface. Using global climate model experiments, we show that central South American tornado potential substantially increases if its equatorward land surface is smoothed and flattened to be ocean-like. Similarly, we show that central North American tornado potential substantially decreases if its equatorward ocean surface is roughened to values comparable to forested land. A rough upstream surface suppresses the formation of tornadic environments principally by weakening the poleward low-level winds, characterized by a weakened low-level jet east of the mountain range. Results are shown to be robust for any midlatitude landmass using idealized experiments with a simplified continent and mountain range. Our findings indicate that large-scale upstream surface roughness is likely a first-order driver of the strong contrast in tornado potential between North and South America.

show abstract

An environmental and polarimetric study of the 19 November 2015 supercell and multiple-vortex tornado in Marechal Cândido Rondon, southern Brazil

Cited by 4 publications

References 85 publications

Upstream surface roughness and terrain drive contrast in tornado potential between North and South America

Upstream surface roughness and terrain drive contrast in tornado potential between North and South America

Atmospheric environments associated with tornadoes in southern Brazil and neighboring areas as compared to other modes of convective hazards

Upstream surface roughness and terrain are strong drivers of contrast in tornado potential between North and South America

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