Some forecast models have insisted that weak La Nina redevelops by quarter 4/2025. Diagnostics confirm the La Nina potential. During recent weeks a traditional cool phase Pacific decadal oscillation has formed, and the attendant atmospheric wind is driving cool waters off the U.S. West Coast toward the tropics south and southwest of Hawaii. Upper ocean heat has suddenly cooled. If the current trend persists, weak La Nina could emerge by northern hemisphere mid-autumn.

The Operational GFS and ECM forecast models are not projecting hurricane threats through their 15-day forecast period which brings us to August 4th without a hurricane so far during the 2025 season. Since 2018, the season’s first hurricane occurred prior to August 1st and during the 2016-24 active period (seasonal activity about 30% higher than the 30-year normal) the average date of the first hurricane is July 14th.

During the past 1-2 weeks, the Nino34 SSTA has cooled by more than 0.4C to -0.28C in the latest daily analysis. The La Nina threshold is -0.5C. Running parallel (and possibly related) to the Nino34 SSTA cooling is the vivid cool SSTA off the U.S. West Coast with that cooler water riding the California Ocean Current south and southwestward toward the tropics.

On July 1st, the AIFS ENS is introduced to operational weather forecasts. The 6-10-day 2-meter temperature forecasts for regions of the U.S. indicate a skill consensus score that ranks the debut of AIFS ENS at number 1 with AIFS a close second and the routinely top dynamic model, ECM ENS, at number 3.