West Coast Storms

Northwestern Alaska was heavily affected by a strong storm earlier this week, bringing a sharp reminder of the severe flooding that occurred in Kotzebue last October:

https://ak-wx.blogspot.com/2024/10/kotzebue-flood.html

https://ak-wx.blogspot.com/2024/10/flood-follow-up.html

The tide gauge at Kotzebue reached well into major flood stage, and according to Rick Thoman the peak water level matched that of last October, when damage was severe.  Evacuations were carried out in Kotzebue and Kivalina this time, and the preparations seem to have prevented a repeat of last year's major impacts.

https://www.adn.com/alaska-news/rural-alaska/2025/10/09/incoming-coastal-storm-looms-as-northwest-alaska-evacuees-return-home-amid-receding-floodwaters/

The center of the storm tracked just to the west of the Bering Strait with minimum MSLP of about 970 mb, which is very low but not record-breaking.  Here's a sequence of maps showing estimated MSLP and 10m wind speed at 6-hourly intervals from early Tuesday morning through late Wednesday; the strongest winds developed in Kotzebue Sound on Wednesday after the storm center passed to the north and the wind direction went around to the southwest.

Unfortunately a second and potentially more serious threat has now emerged with a second storm that is originating from the remnants of Typhoon Halong, a tropical cyclone that passed to the south and east of Japan in the last couple of days.  Weather models show ex-Halong becoming powerfully re-energized as it gets caught up in the North Pacific jet stream tomorrow and into Sunday.  The forecasts for Sunday morning are frankly quite alarming, with minimum MSLP near 950 mb as the storm passes near the eastern end of St Lawrence Island:

If these MSLP forecasts are correct, ex-Halong may well break 1950-present records for lowest MSLP along its track in the northern Bering Sea; ERA5 data shows records of about 956 mb from St Lawrence Island to Nome.

Needless to say, impacts up and down the west coast will be severe even if the forecast details are a little off.  The latest NWS forecast shows water levels as high as Wednesday's event in Kotzebue, and higher in Nome.

The climate context for these storms will be worthy of comment in a future post.  For now, it's interesting to note that last year's storm reminded Rick Thoman of west coast storms in 1973 and 1974; and now we again have back-to-back autumns with similar severe storms.  It's likely no coincidence that the winters of 1973-74 and 1974-75 were back-to-back La Niña winters following a strong El Niño in 1972-73; and we are in the same situation today (El Niño in 2023-24, La Niña last winter, and another one on tap for this winter).