In the afternoon of 18 January, a severe thunderstorm caused wind damage in São José dos Campos-SP. Several trees and power lines were downed by the storm (https://g1.globo.com/sp/vale-do-paraiba-regiao/noticia/chuva-e-vento-derrubam-arvores-nas-zonas-norte-e-sudeste-de-sao-jose.ghtml). High winds were also observed in Botucatu-SP (https://g1.globo.com/sp/bauru-marilia/noticia/temporal-derruba-arvores-e-prejudica-fornecimento-de-energia-em-botucatu.ghtml).
The São Paulo-SP 12Z sounding shows an unstable lower troposphere, with CAPE over 800 J/kg in the morning and 20°C of dewpoint temperature, quite high for São Paulo. After radiative heating, the CAPE would increase to more than 2000 J/kg. Also, the winds in the 1000-500-hPa layer are relatively strong for mid summer, which helped to organize the storms in the region.
Fig. 1: 12Z 18 January 2018 São Paulo sounding.
Storm initiation took place over São José dos Campos at nearly 18Z along a north-south line. The storm attained high reflectivity (Fig. 2) over the city and remained stationary for about 1 hour.
Fig. 2: São Roque radar reflectivity at 18:50Z 18 January 2018.
The analysis of VIL and Echo Top (Fig. 3) at 18:50Z evidence that the storm presented severe characteristics. The VIL values are higher than 35 mm at the center of the storm, which possibly indicates large amounts of hail. 35-dBZ echoes were observed at altitudes higher than 10 km, and supports the fact that the storm contained high amounts of hail in its core.
Fig. 3: São Roque radar (a) VIL and (b) 35-dBZ Echo top at 18:50Z 18 January 2018.
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