Comment on wcd-2021-35

Abstract

Shortly after midnight on 05 June 2016, in the city of Campinas with > 1.2 million inhabitants, located in the State of São Paulo, intense precipitation, including hail, a large number of electric discharges and very strong wind gusts, causing significant damage, were recorded. No fatalities were documented, probably due to the day and time (Sunday around 00:20 Local Time). The affected areas are middle and even upper-middle class neighborhoods, with solid buildings, confirming the potency of the phenomenon. The destruction pattern indicates an intense perturbation resulting in the twisting of structures and tree branches, as well as large objects having been airborne over a distance of about 50 m, and large trees ripped from the ground, all suggesting that it was a tornado of category EF2-3. Severe damage was also reported from other towns in the region. About three hours before the tornado occurred in Campinas, an even stronger event devastated part of the small town of Jarinu, 40 km southeast of Campinas, possibly an EF3 tornado, which caused one fatality and overturned two semi-trailer trucks. No alerts that a disturbance of this magnitude would impact the region were raised, demonstrating that Campinas, and probably most other Brazilian cities and towns, are not prepared for such an event. During the beginning of June 2016, the synoptic situation over Brazil was characterized by a strong anticyclone centered over the northern half of South America at the 250 hPa level and bounded by a strong zonal Subtropical Jet (STJ) in the south, resulting in moist air being advected from the Amazon and Pacific region, creating favorable conditions for strong convection in the State of São Paulo, even during the night. Images from a Doppler S-band radar, located in Bauru, recorded a supercell storm lasting 8.5 hours, which traversed the eastern half of the State of São Paulo during the night of 04/05 June 2016 and spawned a tornado in the city of Campinas during the early hours of the morning (Local Time). Despite the distance of > 200 km, these radar observations confirmed typical tornado signatures, such as a rotational damage pattern, a hook echo and a mesocyclone with a rotational velocity of 12.5 m s−1. The supercell was accompanied by intense lightning activity throughout its life cycle with a “lightning jump” from 0 to 55 ground strokes per minute within 12 min just prior to the tornado touch-down, culminating in a frequency of 238 strokes per minute of Total Lightning. Although some of the Severe Storm Parameters calculated by the TITAN (Thunderstorm Identification, Tracking, Analysis and Nowcasting) Software were slightly lower than found in previous tornado cases in the State of São Paulo, this is most likely due to the fact that this was the first occurrence of a tornado observed by radar during the dry austral winter season in this region of Brazil, as well as a nocturnal event.