CW3E Event Summary: 22 – 24 September 2024
27 September 2024
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Strong Atmospheric River Produced Heavy Rain in Southeast Alaska and British Columbia
- A very strong atmospheric river (AR) associated with an area of low pressure and a trans-Pacific moisture plume brought widespread precipitation to Southeast Alaska and British Columbia between September 22 and 24.
The AR:
- The AR developed within the trans-Pacific moisture plume south of the intensifying low-pressure system, eventually making landfall over Southeast Alaska and British Columbia on September 22.
- On September 22 12 UTC, GFS IVT was > 2100 kg m-1 s-1, exceeding values based on MERRA2 and GEFSv12 Reforecast between 2000–23.
- AR4–5 conditions (based on the Ralph et al. 2019 AR Scale) were observed in southern Southeast Alaska and coastal British Columbia.
Impacts:
- The heaviest precipitation occurred in the Coast and Hazelton Mountains in British Columbia and Glacier Bay National Park, AK, with more than 6 inches in some locations.
- Heavy rain falling caused minor riverine flooding in the Telkwa River, British Columbia (flow exceeded 20 year return interval).
- Rainfall in the southern region of Southeast Alaska ranged between 1–3 inches, (roughly a 1–2 year return interval).
Click image to see loop of GFS IVT analyses
Valid: 0000 UTC 20 September – 1200 UTC 25 September 2024
Morphed Integrated Microwave Imagery – Total Precipitable Water CIMSS MIMIC-TPW |
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Summary provided by D. Nash, C. Castellano, S. Bartlett, M. Steen, B Kawzenuk, J. Kalansky, and J. Rutz; 27 Sep 2024
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