Tuesday, August 9, 2022

Saturday’s record rainfall caused coastal flooding due to on-shore winds, full moon tide

The day's rainfall of 1.64 inches broke a previous record set in 1983 while 2018 numbers approach 100 inches. The record for total annual rainfall -- just over 83 inches set in 1877 -- was exceeded two days after Hurricane Florence made landfall.

WILMINGTON — Coastal flooding that occurred from Topsail Beach to Wilmington and Carolina Beach and as far south as Myrtle Beach was a result of record rainfall, strong onshore winds, and high astronomical tides, according to National Weather Service (NWS) Wilmington meteorologist Steven Pfaff.

“There were 30 miles-per-hour sustained winds for a period and gusts of 40 miles-per-hour, and that was all directed on shore,” Pfaff said. “If the wind came out of the northwest, from an offshore direction, we wouldn’t have had the coastal flood issues we had.”

He also said the flooding was a result of “very high astronomical tides” due to the full moon that occurred past midnight on Friday. Combined with strong northwest winds that pushed the water up to the shoreline, along with the record rainfall, conditions were ideal for coastal flooding.

Along with the rainfall, it’s hard for it to drain as it would if the tides were lower value and it didn’t have the wind pushing more water up to the coast,” Pfaff said. 

Saturday’s rainfall of 1.64 inches broke the old record, set in 1983, by almost half an inch. Meanwhile, the record for annual rainfall — 83.65 inches in 1877, which was exceeded two days after Hurricane Florence made landfall — rose to 95.27 inches.

On Saturday morning the National Weather Service in Wilmington posted on their Facebook page, "High tide has passed at the beaches, but water is still rising up the Cape Fear River where high tide will occur at downtown Wilmington around 10:15 this morning. Photos shared with us show very high water in Southport, Wilmington, and earlier at North Topsail Beach. A Coastal Flood Warning remains in effect until noon for areas along the Cape Fear River near and south of Wilmington." (Port City Daily photo/Courtesy US National Weather Service)
On Saturday morning the National Weather Service in Wilmington posted on their Facebook page photos that showed high water levels in Southport, Wilmington, and earlier in the morning at North Topsail Beach. (Port City Daily photo/Courtesy US National Weather Service)

“It actually pushed us over 95 inches of rain for the year, and that’s just under 42 inches above normal,” Pfaff said. “Normal yearly rainfall is 57.61 inches and we already have a departure from normal of 37.66 inches with a month remaining in 2018.” 

On Saturday morning, the NWS posted on Facebook that high tide had passed at the beaches but the water was still rising up the Cape Fear River, where high tide occurred at downtown Wilmington around 10:15 a.m. Photos given to the NWS showed high water levels in Southport, Wilmington, and North Topsail Beach.


Mark Darrough can be reached at Mark@Localvoicemedia.com

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