Recent research regarding “Sensitivity of Easterly QBO’s Boreal Winter Teleconnections and Surface Impacts to SSWs” by Dillon Elsbury, Amy Butler, Yannick Peings, and Gudrun Magnusdottir was reviewed to assess the claim that wintertime SSWs are more common during the easterly phase of QBO. The question is important due to the direct connection of sudden stratospheric warming (SSW) events causing a split in the polar vortex with southward migration to Eurasia and North America causing arctic air generation and outbreaks for high population middle latitude locations.

The performance of lead operational models forecasting rainfall across South America continues wetter than observed across northwest continent, west/southwest Brazil, and southeastward toward Uruguay. The ECM wet bias is stronger than GFS across Brazil. The GFS indicates a moderate dry bias across Northern Brazil.

The updated U.S. gas population weight HDD forecast for winter 2025-26 reveals a warm start to the season as NOV and DEC fall beneath the (warm-biased) 10-year normal. The coldest risk is (clearly) evident in JAN when the HDD projection is equidistant between the 30-year and 10-year normal. FEB and MAR ease back to near the 10-year normal.

Upper shear is inhibiting development. However, once an organized inner core has formed, given the 86F/30C SST which is 1-2C warmer than normal and 3rd warmest upper ocean heat on record for the Caribbean Sea, there is potential for rapid intensification (RI) as early as Thursday (HWRF) or later this week (HMON) to a strong category-2 hurricane or category-3 major hurricane.