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.

NOAA’s multivariate ENSO index (MEI) changed its data input from the Japanese Meteorological Agency’s JRA-55 reanalysis dataset to JRA-3Q as of January 2024. However, the data has not been attainable since May although NOAA claims the data is available (although hard to decipher with the government shutdown). MEI is a handy climate diagnostic identifying the atmospheric reaction to the SSTA/SLPA pattern across the Pacific tropics/subtropics.

The latest marine heatwave report identifies many large episodes in the northern hemisphere, common during early autumn in the current decadal pattern. Strongest marine heatwaves are off the East Asia Coast, Central Pacific, and off the Northwest Eurasia Coast. The "warm blob" in the Northeast Pacific during late summer has rapidly weakened during the past several weeks. Southern hemisphere marine heatwaves will strengthen as summertime arrives.