Nor’easter ranks just behind Irma for coastal flooding

Yes, the floods have been more frequent lately

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All beach gates in St. Augustine are temporarily closed to vehicular access due to tidal flooding. Below are pictures of our beach this morning during this rainy weather. (Pictures taken by Cmdr. Travis Harrell with the St. Augustine Beach Police Department)

The November 2021 nor’easter will be remembered as a classic low-pressure storm that packed more punch than typical local nor’easters.

The low pressure that spawned tropical storm-force winds was a true nor’easter originating from the clash of cold air diving into north Florida with the warm Gulf Stream current flowing north along the east coast this weekend. The resulting low pressure allowed for higher winds in contrast to more typical northeast wind events generated from strong high pressure or anticyclonic ridges.

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The strong winds reached 63 mph at Marineland, along with several 40-50 mph gusts around Duval County. The wind direction caused moderate to major coastal flooding as waves reached 16 feet Saturday morning. Sand washed down the beach and inundated shorelines and with some of their highest water levels since Irma.

Several river gauges in the St. Johns reported water backing up over a foot above normal predicted levels with some of the higher locations around the Buckman Bridge and up into Julington Creek.

The unfortunate timing of the Moon’s extra gravitational pull in the King Tide cycle boosted flooding along the beaches and rivers, but it was not the only catalyst.

The combination of the weather overlapping with astronomical and climate-derived factors, including sea-level rise, unfortunately, proved impactful yet again in our area.

St. Simons Island’s water gauge reached its fifth-highest historical water level Sunday morning, topping out at 2.79 feet just short of Hurricane Irma’s flooding in 2017.

November 7 Moderate flooding at St. Simons Island occurred when water reached 2.79 feet

Sixteen of St. Simons’ 20 highest water levels have occurred since 2015 — a clear byproduct of human-induced climate change and associated sea-level rise.

This graph shows just how much more flooding has come from this rise, plus the floods that would have taken place anyway.

Tack on almost a foot of sea-level rise at Mayport since 1928. That extra 11 inches of water helps push ordinary events into disruptive territory like we just witnessed.

Tide gauge at Mayport shows sea level has trended .9 feet higher per century or 2.76 mm per year since data has been collected.

About the Author
Mark Collins headshot

After covering the weather from every corner of Florida and doing marine research in the Gulf, Mark Collins settled in Jacksonville to forecast weather for The First Coast.

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