CW3E Event Summary: 01-04 December 2020

December 4, 2020

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Southeast Alaska Pounded by Atmospheric River while California’s Fire Season Persists into December

  • A persistent high pressure and ridge has set up in the eastern Pacific and has directed all AR activity poleward towards Alaska and British Columbia
  • AR landfall over the Alaska Panhandle has resulted in AR 4 conditions, heavy precipitation, flooding, and debris flows
  • Several locations in southeastern Alaska broke daily and 48-hour precipitation records
  • The heavy precipitation triggered a landslide in Haines, AK leaving dozens of homes uninhabitable and prompting search and rescue efforts
  • On the opposite end of the spectrum, the offshore flow around the southeastern portion of the high pressure created a strong Santa Ana wind event over Southern California where wind gusts >80 mph were recorded and several fires were sparked during the dry and gusty conditions

MIMIC-TPW2 Total Precipitable Water

Valid 0000 UTC 30 November – 1600 UTC 04 December

Images from CIMSS/Univ. of Wisconsin

Click images to see loops of GFS IVT/IWV analyses

Valid 0000 UTC 30 November – 1200 UTC 04 December 2020

Summary provided by C. Hecht, C. Castellano, B. Kawzenuk, J. Kalansky, J. Cordeira, and F. M. Ralph; 04 December 2020