Characterization of Convective Precipitation Events Leading to Severe Weather—Impacts in Vulnerable Regions of South America

Satellite and ground radar have shown that tropical South America has a frequent occurrence of extreme convective storms, including robust mesoscale convective systems. These convective precipitation events occur over complex mountainous regions and sometimes produce recurrent hydrometeorological hazards for many communities that are located in near the Andes ranges. Deep, intense convective storms in some of these locations can produce significant rainfall accumulation with hail, lightning and wind gusts that favors the occurrence of flash floods and occasionally over-saturate the land surfaces to enhance soil slope movements.

This work uses radar reflectivity from a ground C-band radar in conjunction with TRMM and GPM satellites, GOES IR images, ground observations and reanalysis data from the ECMWF ERA5 to document and characterize the atmospheric factors that control the occurrence and structure of those convective extreme precipitative systems that lead to weather related emergencies over the complex mountainous terrain. These hydrometeorological related events are compiled based on actual reports of flash floods, intense hail or significant wind gust that produced natural-related emergencies over the Colombian territory.

In some cases, the results show an increased correlation of successive precipitation events that occur in relatively short periods with the occurrence of flash flood related emergencies. An important characteristic is the intensification of the rainfall as deep convective cores approach the steepest topography. However, some of the cases shown that no single precipitation event was exceptionally large to generate the flash flood, but rather the combined role of precedent rainfall, and the occurrence of an extreme short period precipitation was the cause that favored the emergency. The systematic characterization and assessment of the high impact weather that is associated with natural related emergencies in these tropical regions provides crucial information needed to mitigate the socioeconomic and public safety impacts that are produced by these types of events.