Climatology and trends of environments favorable to severe convectively-induced winds in tropical Brazil

Severe convective storms in the continental tropics are less studied than their mid-latitude counterparts, and the understanding of their environments is still poor. In tropical South America, these storms can significantly impact local communities, infrastructure, and economic activities. Despite their potential to produce damaging winds, long-term climatological assessments and historical trend analyses of environments conducive to such events remain limited in this diverse region. This study investigates the climatology and long-term trends of environments favorable to severe convectively induced winds across four broad regions in north-central Brazil, using ERA5 reanalysis data from 1980 to 2021. Favorable environments were identified by applying thresholds to convective parameters derived from ERA5 thermodynamic and kinematic profiles. The skill of the parameters in highlighting conditions prevailing during intense wind gusts was assessed using hourly measurements of 3s gusts from 2000 to 2019 from the surface network by Brazil´s National Meteorological Institute (INMET) and from 1996 to 2019 using hourly METAR reports. The set of ERA5-based parameters that best reproduced the general observed climatology of intense gusts in tropical Brazil consisted of the mixed-layer CAPE, mixed-layer lifting condensation level, and the 2-4 km environmental lapse rate, alongside a minimum precipitation criterion of 1 mm as a confirmation of convective initiation in ERA5. These thresholds were applied to hourly ERA5 data across four major Brazilian regions: Southeast, West-Central, North, and Northeast. The West-Central region emerged as the most active regarding the annual frequency of intense severe gust environments, surpassing 90 hours per year in some regions. The Southeast maxima were concentrated in the western Minas Gerais and northern São Paulo states, reaching approximately 60 hours per year. The North region showed a well-defined latitudinal gradient, with frequencies decreasing toward the equator and increasing within the rainforest-cerrado transition. The Northeast exhibited the lowest annual frequency of favorable environments, characterizing a longitudinal gradient with increased frequencies in western Bahia state surpassing 30 hours per year. The seasonal analysis revealed frequency peak from the late austral winter into the austral spring in most regions, aligned with the dry-to-wet transition season in continental tropical Brazil, with the peak shifting mainly into summer in the Northeast. The prevalence of higher frequencies during the warm-season reinforces the strong influence of thermodynamic instability in shaping the climatology of environments propitious to severe convective gusts in the Brazilian tropics. The 42-yr trends in these frequencies will also be addressed in this study.