Coastal Flood — Kenai Peninsula, Alaska

2024-11-16 · Kenai Peninsula, Alaska

Event narrative

The Gulf of Alaska low, centered south of Prince William Sound, was on a southeasterly track Saturday, November 16, 2024. With this low in place, a strong down (Cook) Inlet flow kept the morning's strongest winds focused outside of central Kachemak Bay and well south of the Homer Spit. However, when the low drifted south between 8 and 9 AM AKST, strong winds out of the Kamishak Gap were pulled north into Kachemak Bay with a weak frontal boundary. This wind shift was demonstrated as a light northwest wind shifted abruptly to southwesterly, with sustained winds around 30 mph gusting to 40 to 45 mph for a period of about 6 hours. By 2 to 3 PM AKST, these strong southwesterly winds shifted back to the northwest and diminished as the Gulf of Alaska low moved further south.

While southwest winds of this magnitude occur numerous times per year along the Homer Spit, a number of factors combined for an unusual setup on November 16, 2024:

1. The high tide in Homer that afternoon was predicted at 23.18 feet; the highest tide for the month of November.

2. While winds were nearly calm around Homer through about 8:30 AM AKST, strong

winds in the Cook Inlet built seas in the outer Kachemak Bay to 11 ft by 9 AM AKST,

peaking at 13 ft by 11 AM AKST. Seas remained elevated for the duration of the

event.

3. The strong southwesterly winds between 8 and 9 AM AKST were able to direct the

aforementioned high seas into the Homer Spit.

4. With about 5 hours of sustained strong southwest winds leading up to high tide, elevated seas would combine with the incoming high tide to create high seas and high surf along the Homer Spit.

The timing of the month's high tides and onset and duration of strong and sustained southwest winds were ideal to drive the already high seas in the outer Kachemak Bay and Cook Inlet into the Homer Spit coastline on November 16, 2024. For about a 6 hour duration, these coincident conditions led to a period of high seas and high surf along the Homer Spit, leading to noted impacts.

Damage Overview: 1. Sterling Highway (Homer Spit): A section of the highway on the Homer Spit was reduced to one lane for approximately 100 feet due to storm-related damage, requiring repairs to restore full functionality. 2. Gas Line: ENSTAR's gas line extends to the Spit. At least one client had their service shut off. Note: On November 18, the SEOC received a local declaration of disaster from the City of Homer. https://www.adn.com/alaska-news/weather/2024/11/18/erosion-from-high-surf-and-wind-leave-homer-spit-road-damaged/.

Wider weather episode

An area of strong winds developed along the CookInlet Saturday, November 16 and Sunday, November 17, 2024, wedged between a Gulf ofAlaska low pressure system centered just south of Prince William Sound, and a ridge of highpressure over the Bering Sea. In two unique regions of the Cook Inlet, local winds were enhanced by a disturbancewithin this flow aloftas it crossed the Alaska Range and moved over the Cook Inlet. Near Ninilchik, this disturbanceled to the development of a lee-side area of low pressure over the Inlet, which then enhancedcross-Inlet winds out of Tuxedni Bay, towards Ninilchik, affecting its coastline. Further south, a weak frontal boundary moving north out of the outer Kachemak Bay, resulted in several hours of strong southwesterly winds that combined with the peak high tide of the day of about 23 feet. In each case, high surf conditionsthat lasted hours to days, lead to extensive erosional damage both the Ninilchik'sandHomer Spit'scoasts.

Source: NOAA Storm Events Database, event_id 1221003. Narrative written by the NWS forecast office that issued the report.