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.