Coastal Flood — Knox, Maine

2022-12-23 · Knox, Maine

Event narrative

The morning of December 23rd had perfect alignment of a very high astronomical tide, peak storm surge of 2+ feet and large battering nearshore waves of 15 to 20 feet all coinciding at high tide. The astronomical tide in Portland was 11.3 feet MLLW at 10:16 am, already close to the established 12 foot MLLW minor flood level. The intense onshore winds produced a storm surge of 2.41 feet in Portland Harbor. The resulting storm tide topped out at 13.72 feet MLLW, it's fourth highest water level in modern history for the Forest City (records 1912-present). The tide remained above flood stage for 195 minutes (945 am - 100 pm). A temporary new tide gauge installed by the Gulf of Maine Research Institute (GMRI) in Belfast, reported a peak water level of 14.5 feet MLLW at high tide.

In Rockport, Kononen Park was flooded near the Andre the Seal Statue along with a complete inundation of the Rockland breakwater. The Saint George working waterfront was inundated with flooding on Factory, Cold Storage and Drift Inn Beach Roads reporting splash-over. Port Clyde Co-Op parking lot and working yard in was also inundated with multiple feet of water. Turkey Cove Road and State Route 131 in Tenants Harbor also reported splashover flooding with minor inundation. On the island of Vinalhaven numerous roads and parking lots were inundated and flooded.

Wider weather episode

Beginning on December 22nd a powerful storm was developing over the Ohio River Valley. On December 23rd the center of the storm was deepening rapidly (974mb) as it lifted through the eastern Great Lakes. While the center tracked into southern Ontario, high pressure retreated into the Canadian Maritimes creating a strong pressure gradient across the region. Strong southerly winds developed as a result, with speeds in excess of 80 knots at around 2,000 feet. Several rounds of strong to damaging wind gusts occurred, which brought widespread power outages to the region with upwards to 240,000 customers without power.

Precipitation moved into southern Maine during the late evening hours of December 22, and moved across the remainder of the state into the early morning of December 23. Snow quickly changed over to rain on the night of December 22nd, with a changeover later in the mountains towards daybreak on December 23rd. The precipitation continued through the evening hours of December 23, then gradually ended from south to north early morning, December 24. Overland flooding was prevalent for areas where rainfall exceeded 2 inches. The impacts varied from standing water in fields to complete road washouts. The runoff exceeded capacity for most feeder creeks and rivers.

The rapidly deepening area of low pressure over the Great Lakes region combined with very high astronomical tides to produce the fourth highest storm tide ever in Portland. In addition, storm to hurricane force east to southeasterly winds occurred along the coast with nearshore waves of 15 to 20 feet coinciding during peak storm surge. Significant to major coastal damage occurred during the morning high tide cycle across the beaches and Mid-Coast of Maine.

Source: NOAA Storm Events Database, event_id 1069654. Narrative written by the NWS forecast office that issued the report.