New Marine Heat Wave Influencing South America Climate

Fig. 1-4: Marine heat waves are forming west of Chile and ongoing in the Caribbean Sea while aloft each MHW is well-correlated to an upper ridge pattern. The overall scenario will cause ongoing drying soils in Argentina to intensify.

Discussion: West of Chile a new and potent marine heatwave (MHW) has formed (Fig. 1). The northeastern South Pacific MHW is intensifying rapidly. A long-standing MHW in the Caribbean Sea remains impressive (Fig. 2). Aloft, each MHW has an influence on the upper air pattern. The new MHW off the Chilean Coast is well-correlated to an amplified high-pressure area forecast by AIFS through the next 15 days (Fig. 3). High pressure also rests over the warm Caribbean Sea. Downstream from the amplified upper ridge west of Chile a weakness in the upper air pattern forms and entrains moisture from the tropics to cause a rainy pattern, mostly in Brazil. On the back side of the upper trough, subsidence dries out Argentina. The soil moisture conditions across Argentina are trending drier (Fig. 4) and the drying is likely to continue as new drought area forms during the second half of summer.