The U.S. HDD outlook in today’s week-4 outlook is colder than normal utilizing a consensus between AI 4CastNet V2 ECM ENS, AI 4CastNet V2 GFS ENS, and AI Graph Cast ECM ENS. The CFS V2/ECM consensus is warmer. Of interest is the record strength 295 HDD forecast for the last week of January from overnight compared to week-4 forecasts made earlier this month. AI was much colder than the CFS V2/ECM consensus.

The equatorial subsurface warmed during the past few weeks although losing some intensity as mid-January approaches. Also losing intensity is remnant cool waters in the subsurface off the northwest coast of South America.

The “weeklies” skill scores from the past 30, 14, and 7 days predicting 2-meter temperature forecasts for North America is horrible. The exception is, surprisingly, GFS ENS with traditional ECM “weeklies” a distant second.

A frigid Russia air mass inspired in-part by regional stratospheric warming shifts westward into Europe during the medium range as the stratospheric warmth also shifts westward to the North Atlantic in 11-15 days. By late month, the stratospheric warming reaches eastern North America and should cause a cold ending of January/beginning of February for eastern North America.