Searing Heat Beneath Subtropical Ridge in Brazil/Paraguay

Highlight: Southwest Brazil heat and dryness! Western Australia tropical rains.

Fig. 1-3: ECM ENS 15-day upper air forecast (above) and the attendant 15-day temperature and precipitation anomaly projection (below) across South America.

Discussion: The convection phase of the Madden Julian oscillation (MJO) is located over the Maritime Continent and increasing intensity. The influence on South America climate when MJO is in phase_4 is dryness across Brazil. The latest ECM ENS 15-day upper air forecast indicates the subtropical ridge is parked over Southeast Brazil, strongest over the next 15 days (Fig. 1). The sensible weather favors searing heat and dryness across Southwest and South Brazil to Paraguay through much of the next 2 weeks (Fig. 2). Additionally, dry weather dominates Central and South Brazil with heavy thunderstorms just south of the high-pressure area centered on Uruguay (Fig. 3). Much of Brazil’s second corn crop is affected by the harsh dry and hot late summer climate.

Presence of MJO north of Australia enhances the North Coast monsoon rainfall and also increases the risk of a tropical cyclone. Tropical Depression 18 in the South Indian Ocean is forecast to drift toward the northwest coast of Australia this week and then turn southward into Western Australia in the 6-10-day period. This week’s rainfall is due to a tropical fetch from the ITCZ through interior western Australia (Fig. 4). The potential heavy rain on the West Coast is due to an intensifying TD 18 in the 6-10-day period (Fig. 5). In this pattern, the eastern half of Australia is hot! However, a cooler upper trough is projected for the 11-15-day period.

Fig. 4-5: ECM 10-day rainfall amount forecast across Australia.