Historic Flooding Rainfall with Potential Tropical Cyclone Eight: September 15-16, 2024

Historic rainfall occurred across the Cape Fear Region of southeastern North Carolina on September 16, 2024. Gauges and automated radar estimates showed that 12 to 20 inches of rain fell in only two days, creating severe flash flooding affecting Carolina Beach, Southport, Bolivia, and Boiling Spring Lakes. Although this system never became a named tropical system, observed weather impacts including strong winds, heavy rain, and flash flooding were similar to tropical storms and hurricanes of the past.

Potential Tropical Cyclone Eight was an area of low pressure that developed off the Carolina Coast on September 13, 2024. While it initially developed along a stalled front, over several days the system began to draw energy from the warm ocean surface. As winds increased, the low was given a "Potential Tropical Cyclone" categorization late in the afternoon of September 15, indicating that conditions could support its evolution into a tropical or subtropical storm. A Tropical Storm Warning was issued for the Carolina coastline for the expectation of these weather conditions.

Infrared satellite loop from September 15-16, 2024 showing Potential Tropical Cyclone Eight moving inland

While the system displayed some tropical characteristics at times, Hurricane Hunter aircraft sent to investigate the storm found it never developed a symmetric wind circulation and it maintained horizontal temperature contrasts not consistent with the structure of tropical storms.

Regardless of the nature of the storm, Potential Tropical Cyclone Eight brought historic rainfall and flash flooding to parts of Brunswick and southern New Hanover counties. Storm total rainfall totals of 12 to 20 inches were recorded within a 25-mile wide stripe running from Carolina Beach and Southport through Bolivia, the Green Swamp, and ending south of the Delco community in eastern Columbus County. The majority of this rain fell within a 12 hour window between 5:00 am and 5:00 pm on Monday, September 16. Flash flooding quickly developed in Carolina Beach during the morning hours, then shifted northwestward following the heaviest rainfall rates as the center of Potential Tropical Cyclone Eight shifted onshore.

Radar loop from September 16, 2024 showing Potential Tropical Cyclone Eight moving onshore. Extremely heavy rain developed in a large convergence band on the northern edge of the low, dropping exceptionally heavy rainfall

Radar loop from September 16, 2024 showing Potential Tropical Cyclone Eight moving onshore. Extremely heavy rain developed in a large convergence band on the northern edge of the low, dropping exceptionally heavy rainfall which led to historic flash flooding.

Multiple roads were closed due to floodwaters and some roads were physically washed out by the immense volume of floodwater. Some major highways that were closed included:

NC Highway 133 near Daws Creek Road SE, south of Wilmington
US 421 (Carolina Beach Road) in Carolina Beach between Goldsboro Ave to Atlanta Ave
NC Highway 211 washed out in Southport near Dosher Cutoff
NC Highway 211 at St. James Dr SE
US 17 near Governor's Rd SE
US 17 near Sellers Rd NW in Supply
US 17 Business Route near Benton Rd in Bolivia
NC Highway 87 near Fertilizer Rd near Riegelwood

Rainfall Totals

MRMS rainfall estimates for September 15-16, 2024 shows an area of 12 to 20 inches of rain likely fell across the Cape Fear area.

MRMS rainfall estimates for Sept 15-16, 2024 shows 12 to 20 inches of rain likely fell across parts of the Cape Fear area.

Gauge-measured totals across southeastern North Carolina and northeastern South Carolina. These originate from a variety of networks including NWS ASOS, FAA AWOS, CoCoRaHS, NWS cooperative observers, CWOP, and Weather Underground.

Location	County	Rainfall	Location	County	Rainfall
Carolina Beach Ocean Blvd	New Hanover NC	20.81	Galivants Ferry Landing	Horry SC	5.51
Southport 6.9 W	Brunswick NC	19.13	Aynor 7.9 ENE	Horry SC	5.40
St James - Harborwalk	Brunswick NC	18.65	Mullins Coop	Marion SC	5.32
Bolivia 7.6 SW	Brunswick NC	17.85	Elizabethtown	Bladen NC	5.19
Southport - Abbington Oaks	Brunswick NC	16.97	Galivants Ferry 7.6 E	Horry SC	5.11
Long Beach	Brunswick NC	16.61	Sunset Harbor	Brunswick NC	5.09
Carolina Beach 1 S Bridge	New Hanover NC	16.51	Burgaw 0.3 NE	Pender NC	5.08
Boiling Spring Lakes	Brunswick NC	16.34	Hampstead 4.1 WNW	Pender NC	4.76
River Rd 1 N of Snows Cut	New Hanover NC	15.85	Leland	Brunswick NC	4.73
Sunny Point	Brunswick NC	15.42	Marion RAWS	Marion SC	4.61
Southport 5.7 W	Brunswick NC	14.96	Longwood	Brunswick NC	4.55
Green Swamp	Brunswick NC	14.57	Florence 6.2 NE	Florence SC	4.54
Southport - Ruark Dr SE	Brunswick NC	11.13	Darlington County Airport	Darlington SC	4.52
1 N Kure Beach Pier	New Hanover NC	10.91	Horry County RAWS	Horry SC	4.39
Green Swamp	Brunswick NC	9.80	Burgaw 5.3 WSW	Pender NC	4.26
Monkey Junction 1 W	New Hanover NC	9.12	Wilmington Airport	New Hanover NC	4.16
Near Ashley High School	New Hanover NC	9.04	Latta 0.3 NNE	Dillon SC	4.14
Wilmington 7 SE	New Hanover NC	8.78	Loris	Horry SC	3.97
1 W Holden Beach	Brunswick NC	8.70	2 WSW Wilmington	New Hanover NC	3.94
Southport	Brunswick NC	8.50	7 S Aynor	Horry SC	3.94
Myrtle Grove Sound	New Hanover NC	8.28	Florence	Florence SC	3.93
Elizabethtown 4.5 ENE	Bladen NC	7.32	St. Pauls	Robeson NC	3.81
Wilmington 1.3 W	New Hanover NC	6.82	Darlington	Darlington SC	3.81
Bolivia	Brunswick NC	6.73	Saltwater Landing	Pender NC	3.80
Turnbull Creek	Bladen NC	6.34	3 NNE Conway	Horry SC	3.79
Whiteville RAWS	Columbus NC	6.31	Wilmington 6.5 NE	New Hanover NC	3.78
Shallotte Fire Station	Brunswick NC	6.19	1 SSW Aynor	Horry SC	3.77
Shallotte	Brunswick NC	6.00	Florence 1.2 NNE	Florence SC	3.76
Wilmington 5.6 ENE	New Hanover NC	6.00	Ocean Isle Beach	Brunswick NC	3.74
West End Holden Beach	Brunswick NC	5.81	West Lakes (Florence)	Florence SC	3.71

Winds

Even though this system never became a full-fledged tropical cyclone, wind gusts over 50 mph were recorded in a number of locations. While most of these higher winds occurred near the Cape Fear coastline in association with the heavy rain squalls racing onshore, a second area of strong northerly winds gusting to 45-55 mph developed during the afternoon well inland from Lumberton to Dillon to Florence. This appears to be as cool, dry air was pulled into the western periphery of the storm's circulation, promoting mixing of stronger winds down from aloft.

Location	Time	Gust mph
Sunny Point Military Ocean Terminal	8:18 AM	77
Johnnie Mercer Pier	10:12 AM	67
Masonboro Island South	9:54 AM	64
UNCW Center for Marine Science	10:02 AM	62
Bald Head Island	1:11 PM	60
Wilmington Airport	10:08 AM	59
Buoy 5 miles SE of Wrightsville Beach	9:08 AM	58
Southport - Cape Fear River Pilots	1:08 PM	57
Frying Pan Shoals Buoy	6:20 AM	56
Buoy 29 miles SE of Wrightsville Beach	9:08 AM	55
Figure Eight Island - Surf Ct	10:30 AM	52
Lumberton Airport	1:36 PM	51
Masonboro Island North	10:00 AM	50
Florence Airport	3:12 PM	47
Buoy 2 mile S of Sunset Beach	9:08 AM	45
Wrightsville Beach Town Park	10:09 AM	44
Lockwoods Folly Inlet	10:19 AM	42

HRRR wind gusts for the morning of September 16, 2024