CW3E Event Summary: 21 December 2023

21 December 2023

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Low Pressure System Brings Heavy Precipitation to Southern California

  • A low pressure system that formed in the Gulf of Alaska south of the Aleutian Islands on Mon 18 Dec progressed down the US West Coast through this week, approaching California late Tue 19 Dec
  • The system brought elevated moisture levels from the southern Pacific as it propagated down the CA coast, resulting in heavy precipitation across much of Southern California on Wed 20 Dec into Thu 21 Dec
  • The third and strongest AR produced AR3/AR4 conditions (based on the Ralph et al. 2019 AR Scale) over coastal WA/OR, as well as AR2 conditions in portions of the interior Pacific Northwest.
  • There were numerous flood reports in both Santa Barbara and Ventura counties, including reports of multiple feet of water over roadways, inundated lanes, and mud/other debris covering streets.
  • As a results of the short duration, high intensity precipitation, low lying areas became inundated with water, flooding homes and businesses in Oxnard & Port Hueneme, California requiring numerous water rescues.

Click images to see loops of GFS IVT/IWV analyses

Valid: 0000 UTC 12 December – 0000 UTC 23 December 2023






Summary provided by M. Steen, S. Bartlett, and P. Iniguez; 21 Dec 2023

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