From the beginning of the water year (Oct 1, 2022) through Christmas, the Bay Area had received generally 5” to 7” of rain. This mainly came from weak fronts moving across the region. December 26, 2022, saw a change to the pattern as it ushered in the first in a series of storms that tapped into the high moisture content of the sub-tropics. This storm series engulfed the Bay Area and Monterey Bay regions, and much of the state, from late December through mid-January. While “breaks” in the main storms did occur, there remained lingering showers, which dotted the area. This left many residents feeling exhausted from near constant rainfall.

From late December through mid-January there were approximately six storm systems that brought a wide variety of hazardous weather to the Bay Area and Central Coast. These systems varied in dynamic set-up from narrow cold-frontal rain bands (NCFR), atmospheric rivers and even included a low-pressure center that underwent "bomb cyclogenesis". The result of these storms produced hazardous weather over a three-week period which included: large surf over 30 feet, wind gusts over 100 mph, widespread flooding which included river flooding, gusty thunderstorm outflow winds, small hail, two waterspouts and several reported shallow landslides, just to name a few. Unfortunately, there was loss of life experienced from these storms, while other people's lives forever will forever be changed. 

Drier conditions returned after January 19th, but not without a lasting impact throughout the State of California. Between December 26th, 2022, and January 17th, 2023, Downtown San Francisco received 17.64" of rain. SFO Airport set a 23-day rainfall record at 15.28", while the city of Oakland set their own 23-day rainfall record with 18.33" of rain. The State maximum total rain was in Honeydew, California (Humboldt County) which received 47.74" since December 26th. Many of the area coastal peaks as well as the Sierra Nevada received between 20" to 35" of rain! All of this rain saw a modest improvement in drought monitoring as well as much greener satellite imagery.

Numerous weather alerts were issued during the three period including a few tornado warnings in the Central Valley.	Numerous hydrological related alerts were issued during the three period.

CW3E has a few event summaries available here

https://cw3e.ucsd.edu/cw3e-event-summary-29-december-2022-1-january-2023/

https://cw3e.ucsd.edu/cw3e-event-summary-26-27-december-2022/

https://cw3e.ucsd.edu/cw3e-event-summary-29-december-2022-1-january-2023/

Composed by: MMehle / DKing

Satellite loop showing the evolution of the Atmospheric

River impacting the Bay Area and Central Coast. Additional

Satellite loops available via RAMMB-CIRA

 

Satellite loop showing evolution of a Bomb Cyclone off

the West Coast.

Map showing the total precipitation that fell during from

late December '22 to January '23.