The 2024 North Atlantic basin tropical cyclone season ended on November 30. This year, the final tally on tropical cyclone activity was 18 tropical storms, 11 hurricanes, and 5 major hurricanes with an accumulated cyclone energy (ACE) index of 161.6. The above normal activity maintains the recent pattern (2016-24) of very active (and dangerous) tropical cyclone seasons.

Taking a look at the 11-15-day East U.S. temperature anomaly outlook reveals lingering cold when combining the GFS and ECM forecasts. However, AI models offer wildly different projections (colder or warmer). So...a look at climate diagnostics reveals what direction to rely.

The 2024-25 cold season first “bomb cyclone” either side of North America occurred Nov. 19-20 as a storm system off the Northwest U.S. Coast plummeted to 945 MB central pressure equivalent to a major hurricane. Evolution of this storm is likely in-part due to a moderate-to-strong convection phase of the Madden Julian oscillation (MJO) across the Maritime Continent coupled with intense marine heat waves across the Northwest Pacific in contrast to the rapidly cooling Northeast Pacific of the past couple weeks.

The updated month 1-4 climate outlook for the U.S. features increasing forecast confidence based on the influence on North America climate by dramatic cool phase of the Pacific decadal oscillation and warm phase of the Atlantic multi-decadal oscillation. A weak ENSO regime has limited influence.