The October-2024 Pacific decadal oscillation (PDO) was -3.81, the strongest negative (cool) phase in the 1950-2024 record. Previously, the strongest monthly value was -3.55 observed in July 1955. The current record-strength -PDO is part of a 5-year cool phase beginning in January 2020. Additionally, the ongoing -PDO regime sustains the cool long-term cycle of PDO which began in the late 1990’s.

In 2025, the ENSO forecast WAS neutral ENSO and possibly a second attempt at La Nina later next year. That possibility remains but is considerably weaker. Added to the potential scenarios of ENSO phase during the second half of 2024 is an El Nino analog and shift by ECMWF favoring Nino34 SSTA shifting into an El Nino.

A developing marine heatwave off the East Coast of South America is expected to continue strengthening while shifting southward toward and off the Argentina Coast. MHW's in this position during summertime are well-correlated to an upper low-pressure area near the southeast coast of Brazil. Subsidence on the back side of the low leads to a dry climate and increased drought risk in Argentina and possibly Western Brazil.

Tropical Storm Rafael reaches peak intensity in the northwest Caribbean Sea where upper ocean heat is plentiful and the upper shear pattern is light. Rafael maintains intensity across the warm waters of the Southeast Gulf tomorrow night. However, continued northwest tracking beyond the LOOP Current brings Rafael into cooler waters causing some weakening. On the weekend, Rafael encounters a vigorous shear pattern considerably lowering Rafael’s intensity.