Stormy Southeast

Southeast Alaska has seen a rough patch of weather recently, leading to a few notable problems.  Downed trees in Juneau caused a significant power outage on Tuesday, and last week a landslide occurred near Ketchikan, severely damaging an electrical facility.  Disaster recovery funding is being made available in connection with the Ketchikan event.

Looking at the weather data, my impression is that conditions have been stormy but not especially unusual for the time of year.  Rainfall has been heavy - the map below shows 10-day totals - but these numbers aren't off the charts.  Looking specifically at Ketchikan, 5.7 inches of rain fell last Thursday, triggering the landslide the same day, but daily rain totals this large or greater have occurred many times before, including in earlier decades in the 20th century.  The two-day total of 6.9" is not especially noteworthy either.

Strong winds accompanied last week's rain storm in southern parts of the panhandle, and Ketchikan saw gusts up to 58 mph; but that kind of wind happens nearly every year.  However, this week's wind event was more unusual, affecting the central and northern panhandle on Tuesday - peak wind gusts (mph) are shown below.  Sitka's maximum gust of 75 mph is on par with some of the strongest wind events of recent years.

Landslides in Southeast Alaska have been in the news with rather alarming regularity in recent years, and a search on this blog will bring up previous comments.  I noticed one curious similarity between last week's landslide and the one in late August 2024 (both in Ketchikan): both occurred after dry summers, and moderate drought was found in the southern panhandle at the onset of autumn in both years.  The precipitation chart below shows the rainfall deficit this year since April (green vs brown lines):

It's mere speculation, but I can't help wondering if a sudden reversal from unusually dry (in the dry season) to unusually wet (in the wet season) could destabilize the ground more than usual.  However, unlike in August 2024, last week's triggering rain event obviously wasn't the first heavy rain of the season in Ketchikan: late September was wetter than usual.