The influence of the Pacific decadal oscillation on Southwest Canada/Northwest U.S. climate has changed due to the warming of the North Pacific Ocean. Cool phase PDO events are now much warmer and have eliminated the previous cool/wet bias to the Southwest Canada/Northwest U.S. climate in favor of warmer and drier regimes.

The upper air pattern across North America during meteorological winter 2024-25 across North America was significantly different from the 5-year and 10-year optimum climate normal and standard 30-year climatology.

A rarely observed La Nina Modoki has developed in the central equatorial Pacific Ocean. Climate Impact Company identifies Modoki using the ENSO West-East Inex (WEI) which simply compares SSTA in the Nino4 region near the Dateline and the Nino3 region in the eastern equatorial Pacific away from the moderating effects on SSTA caused by proximity to land off the northwest coast of South America (where the Nino12 SSTA region is located). The La Nina Modoki index is -0.9C for the month of February and the daily index has jumped to -1.23C.

Interestingly, the 500 MB anomaly pattern governing the Australia summer 2024-25 pattern was the polar opposite of the 2015-25 optimum climate normal. Marine heat waves once again played a large role in the Australia summer weather pattern and will continue to guide climate patterns through autumn as ENSO influence weakens with fading La Nina.