A developing storm east of Jacksonville, Fla., is riding up the Southeast coast this weekend, bringing strong gusty winds, heavy rainfall and moderate to major coastal flooding. Significant shoreline inundation has already occurred, with some communities seeing their highest water levels in years.
Last week: worst coastal flooding since 2003 for parts of the Mid-Atlantic
Coastal flood advisories and warnings span much of the Southeast coast from the Gold Coast of Florida to the Outer Banks of the Carolinas and the Virginia Tidewater, with a few instances of minor flooding likely all the way north into New England.
Flooding had occurred or was anticipated over the weekend in Jacksonville, Savannah, Charleston, Wilmington, N.C. and the Virginia Tidewater. Flooding peaked in South Florida on Friday, when ocean water engulfed streets in Miami.
Charleston saw its highest water level in nearly three years Saturday morning (since Nov. 24, 2018).
Along the North Carolina Outer Banks and in the Virginia Tidewater, the highest water levels are anticipated Sunday morning.
“Flooding will extend inland from the waterfront along tidal rivers and bays resulting in some road closures and flooding of vehicles,” wrote the National Weather Service in Wakefield, Va. “Large breaking waves of 8 to 10 feet will result in dangerous surf conditions.”
The episode comes barely a week and a half after the tidal Potomac River, Chesapeake Bay and the Delmarva Peninsula experienced their most problematic coastal flooding since 2003, with water entering businesses in places like Alexandria, Va., and Annapolis, Md.
Like the last storm, this ongoing system isn’t necessarily overly potent, but its track happens to be one that places much of the coastline under an onshore flow ripe for flooding. Tide levels should remain elevated through at least Sunday before the system moves far enough out to sea.
Flooding on Saturday morning produced a storm surge nearing two feet in Charleston and Savannah and closer to a foot around Jacksonville and Cape Canaveral.
Water levels in Charleston Harbor reached 8.44 feet Saturday morning, nearly a foot and a half above flood stage and the 11th highest level on record. Eight feet corresponds to “major coastal flooding.”
The National Weather Service warns that, at eight feet, “widespread flooding occurs in Downtown Charleston with numerous roads flooded and impassable and some impact to structures,” noting that “impacts become more extensive all along the southeast South Carolina coast including erosion at area beaches, with limited or no access to docks, piers, and some islands.”
Video from the intersection of Washington and Society streets in Charleston showed water flowing down downtown roadways as the ocean swelled to swallow residential neighborhoods.
Nine of Charleston’s 15 highest water levels have occurred since 2015 — a clear byproduct of human-induced climate change and associated sea level rise.
In Ocean Isle, just north of the South Carolina-North Carolina border, video posted to social media showed water in canals spilling into yards and properties and overtopping sea walls. In nearby Wilmington, N.C., a two foot storm surge was observed over high astronomical tides as of 10 a.m. Eastern time Saturday.
At Duck, in Dare County, N.C., tide gauges were already reporting major coastal flooding, with the expectation that the high tides on Sunday and Monday mornings will be even more prone to high-end flooding. Major coastal flooding starts when water levels hit six feet, and the Weather Service is projecting a crest around 7.3 feet on Monday morning.
The flooding is due to a trio of overlapping meteorological, astronomical and climate-derived factors whose synergy proves unfortunately impactful.
September, October and November nowadays feature routine flooding along the East Coast thanks to “king tide” season. During the autumn, tides spurred by Earth’s proximity to both the sun and the moon are more extreme, resulting in astronomically higher high tides and lower low tides. The positioning of key weather systems during the fall, like the Bermuda High, also helps to maintain an ambient onshore flow. That results in flooding.
Now tack on a half a foot of sea level rise in many spots since the 1990s. That may not sound like much, but it helps push ordinary events into disruptive territory. If every basketball player was six inches taller, odds are a lot more slam dunks would be scored each game. Miami nowadays is seeing 12 times more action-tier flooding than they did back in the mid-1990s.
In this sort of regime, it doesn’t take a major storm to bring flooding. The developing will parallel the coast and stay well offshore, but northeasterly 40 mph gusts at the beaches and offshore waves 20 to 30 feet high will help the stormy seas spell trouble.
Sea level rise is combining with other factors to regularly flood Miami
A few places on the water’s edge could also see appreciable rainfall as moisture pools along a stalled front, with up to 2 or 3 inches likely (except in coastal Georgia and north Florida, where more widespread heavy rainfall is expected). Confidence in rain totals is low, but any location that sees heavy rainfall may experience additional flood impacts as water struggles to drain into backed-up rivers near the coast.
Conditions should improve early next week as the low slips into the Atlantic.
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