The preliminary U.S. winter 2025-26 gas population weight heating degree day forecast is issued. The outlook indicates near the 30-year normal HDD for November, somewhat warmer than normal December, shifting colder than normal mid-to-late winter, and a mild March. Due to the presence of a strong marine heatwave (MHW) in the Northeast Pacific combined with a stronger than normal North Atlantic warm hole (NAWH) south of Greenland, the risk of an “Alaskan ridge bridge” and compensating downstream polar vortex over Central Canada increases for JAN/FEB 2026 if the sea surface temperature anomaly (SSTA) patterns present now persists through meteorological winter.

A short-lived La Nina is ahead and supported by vast cooling of the subsurface equatorial East Pacific during recent weeks. However, if the warming Northeast Pacific persists in early 2026, the La Nina episode ends, possibly abruptly and the warm waters of the Northeast Pacific spread south possibly causing an El Nino onset middle third of 2026 which could become intense later next year.

Vividly present is the NAWH pattern south of Greenland. Aloft, the cooler water is linked to a summer of 2025 upper trough. The 15-day forecast maintains this pattern. The upper trough forces the subtropical ridge farther south. The ridge is forcing dry air into the subtropics/northern tropics inhibiting tropical cyclone development.

The culprit to North Atlantic tropical cyclone development is too much dry air promoted by a strong subtropical high pressure stretched across the North Atlantic basin whereas the 2020-24 climatology produced low pressure in the tropical/subtropical North Atlantic due to presence of tropical cyclones.