An evolving longwave upper trough extending from Western Russia to Southwest Europe causes deepening and expansion of Western Eurasia snow cover and steady intensification of an attendant winter chill. Supported by strong negative phase of both the arctic oscillation and North Atlantic oscillation this feature locks-in for the last third of December into early January.

The Australia Bureau of Meteorology identifies the developing heat wave across Northern Australia as rare for this early in the season! The aerial coverage and risk BOTH peak during the 3-day period of Dec. 16-18. During that time maximum temperatures are well over 100F with very warm nights offering limited recovery.

A rare super-outbreak of violent tornadoes occurred December 10, 2021. There were two primary tornado "lines". One stretched from eastern Missouri to east-central Illinois while a second began in northeast Arkansas and reached southwest Kentucky. The second line featured (potentially) the longest path of one tornado on record. The violent weather was caused by interaction with the East Pacific tropics, Gulf of Mexico and cold snow-covered areas to the north and enhanced by a vigorous jet stream and low-level jet out of the western Gulf.

La Nina 2021-22 peaks in January and fades to neutral phase during Q2/2022. El Nino risk is indicated for late 2022. The PDO regime which tends to run parallel to ENSO stays in the cool phase but is weaker for much of 2022. The North Atlantic warmth is likely to continue and be stronger than indicated by the analog forecast.

The November 2021 snow cover analysis by the Rutgers Snow Laboratory is complete. The data indicate the North America snow cover is lagging behind normal ranking 11th least snowy in the 56-year climatology. Meanwhile Eurasia is just-the-opposite ranking 9th snowiest since 1966.

Meteorological autumn (SEP/OCT/NOV) 2021 ranked 3rd warmest on record. Almost the entire nation ranked in the MUCH ABOVE normal category including California, the West-central and Southwest U.S., all of the Great Plains and into the Northeast States. Only Alabama, Georgia and South Carolina ranked near normal.

More heavy precipitation in the 5-day forecast for Southwest Canada and into Washington is indicated by GFS. The 6-10-day forecast has shown heavy precipitation into California this week but an upgrade to excessive amount is indicated today. New to the forecast is more excessive precipitation into California days 11-15. There is no direct connection to the tropics ALTHOUGH the Madden Julian oscillation (MJO) shift toward the Dateline is definitely helping.

The Hawaiian Islands brace for a rare “Kona Storm” this week. An intense storm has become quasi-stationary west-northwest of the islands and caused surface wind across Hawaii to turn into the southwest. A southwest wind in Hawaii is rare and known as a leeward or “Kona” wind. Coupled with the unstable atmosphere associated with the upper trough, the moist southwest wind leads to frequent wind squalls, life-threatening flooding rainfall and even heavy snow in the highest mountains.