Subtropical South American Hailstorm Characteristics and Environments

Abstract

Hailstorms in subtropical South America are known to be some of the most frequent anywhere in the world, causing significant damage to the local agricultural economy every year. Convection in this region tends to be orographically forced, with moisture supplied from the Amazon rain forest by the South American low-level jet. Previous climatologies of hailstorms in this region have been limited to localized and sparse observational networks. Because of the lack of sufficient ground-based radar coverage, objective radar-derived hail climatologies have also not been produced for this region. As a result, this study uses a 16-yr dataset of TRMM Precipitation Radar and Microwave Imager observations to identify possible hailstorms remotely, using 37-GHz brightness temperature as a hail proxy. By combining satellite instruments and ERA-Interim reanalysis data, this study produces the first objective study of hailstorms in this region. Hailstorms in subtropical South America have an extended diurnal cycle, often occurring in the overnight hours. In addition, they tend to be multicellular in nature, rather than discrete. High-probability hailstorms (≥50% probability of containing hail) tend to be deeper by 1–2 km and horizontally larger by greater than 15 000 km2 than storms having a low probability of containing hail (<25% probability of containing hail). Hailstorms are supported synoptically by strong upper- and lower-level jets, anomalously warm and moist low levels, and enhanced instability. The findings of this study will support the forecasting of these severe storms and mitigation of their damage within this region.

Severe Convective Storms across Europe and the United States. Part II: ERA5 Environments Associated with Lightning, Large Hail, Severe Wind, and Tornadoes

“…Brooks et al (2003) conducted a pioneering study using model data to estimate global climatology of environments leading to severe convective storms. Subsequent work has typically focused on regional studies for the U.S. (Gensini and Ashley 2011;Tippett et al 2012Tippett et al , 2014Allen et al 2015;Gensini and Brooks 2018;Tang et al 2019, Li et al 2020, Australia (Allen et al 2011; Allen and Karoly 2014; Allen and Allen 2016) Europe (Marsh et al 2009;Púčik et al 2017;Rädler et al 2018;Taszarek et al 2018Taszarek et al , 2019, China (Li et al 2018), Southern Africa (Blamey et al 2017), and South America (Bruick et al 2019). Global aspects of CAPE, convective inhibition (CIN) and hail environments were also evaluated by Riemann-Campe et al (2009), Chen et al (2020), and Prein and Holland (2018).…”

A Synoptic Evolution Comparison of the Smallest and Largest MCSs in Subtropical South America between Spring and Summer

“…Specifically, the cloud shields associated with SSA mesoscale convective systems (MCSs) are approximately 60% larger than those occurring in the continental United States (CONUS; Velasco and Fritsch 1987) and their precipitation areas are larger and longer lived (Durkee et al 2009;Durkee and Mote 2010), contributing up to ;95% of warm-season rainfall in SSA (Nesbitt et al 2006;Rasmussen et al 2016). MCSs are also responsible for the regional maximum in high impact weather such as significant hail ($2.5-cm diameter), flooding, damaging straight-line winds, and tornadoes that are detrimental to society and the economy of the La Plata basin where agriculture thrives (Rasmussen and Houze 2011;Matsudo and Salio 2011;Cecil and Blankenship 2012;Rasmussen et al 2014;Bruick et al 2019).…”

Gargantuan Hail in Argentina

“…1), making it the first well-documented case of gargantuan hail outside the U.S. Great Plains, and the first in the Southern Hemisphere. This region is known to be prone to hail (e.g., Torre et al 2011;Mezher et al 2012;Cecil and Blankenship 2012;Bruick et al 2019), though hail of giant or gargantuan size has until now not been documented there. Although the authors were 7…”