Another Catastrophic Brazil Flooding Event

Latest major flooding event in Brazil: Another major rainfall/flooding/landslide event has taken place in Brazil this time in Petropolis located in the hills above Rio de Janeiro and following historical rainfall/flooding events in Sao Paolo in late January and Minas Gerais in mid-January. The excessive rainfall events in Brazil have been common during summer 2021-22 extending westward from the Brazil Coast to Central/Southwest Brazil (Fig. 1). The cause of this persistent heavy rain has been the presence of a semi-permanent upper-level low-pressure trough located just-off the Southeast Brazil Coast (Fig. 2). The wet climate extreme is adjacent to another climate extreme…dryness and drought in Paraguay/northern Argentina to far Southeast Brazil. A high-pressure ridge off the Argentina Coast has extended its influence toward Paraguay to induce the dry summer climate. The convective rains over Brazil are compensated for by the atmosphere by producing subsidence and drying over central/east-central South America.

Fig. 1-2: The meteorological summer 2021-22 (so far) rainfall anomalies across South America and the prevailing upper air pattern.

In the 2-week outlook, ECM ENS indicates more heavy rain for Rio de Janeiro and introduces patchy shower/thunderstorm activity for Argentina while southern Argentina is quite wet (Fig. 3). Central Brazil turns drier in the week-2 ahead forecast (Fig. 4).

Fig. 3-4: ECM ENS percent of normal rainfall for South America for the next 2 weeks.