Prolonged Coastal Flood/Heavy Rainfall Event, October 2-5, 2015

Prolonged Coastal Flood/Heavy Rainfall Event

October 2-6, 2015

Summary

The combination of Hurricane Joaquin passing well to the east, an upper level low pressure system off the Southeast U.S. coast and a stalled cold front led to an event that produced a wide variety of impacts across eastern North Carolina during the first week of October, 2015. Major coastal flooding, very heavy rainfall and strong winds impacted much of eastern North Carolina for several days. This is the same storm system that brought historic rainfall amounts to the Charleston and Columbia areas in South Carolina, as well as parts of southeast North Carolina.

Coastal Flooding

Water levels were already elevated across eastern North Carolina due to some of the highest astronomical tides of the year. These high tides coupled with persistent gusty east to northeast winds resulted in areas of moderate to major coastal flooding along the Outer Banks and many sound-side locations. Water level rises of 2 to 4 feet above normal, with locally higher values were observed. On the Northern Outer Banks, Highway 12 was closed at Kitty Hawk (Figure 1) due to ocean overwash and dune breaches as major flooding occurred (Figure 2). Many streets in and around downtown Columbia flooded, roads around Aurora in Beaufort County (Figure 3) became impassible, water rescues were conducted for 3 individuals near Hobucken in Pamlico County, and moderate to major coastal flooding was observed throughout Downeast Carteret County, especially around Cedar Island (Figure 4), and in the downtown areas of Beaufort (Figure 5) and Morehead City (Figure 6). Major flooding and beach erosion was also reported at North Topsail Beach.

Figure 1. Coastal Flooding at Kitty Hawk Figure 2. Duck Tide Gauge showing Major Flooding on Oct. 2, 2015

Figure 3. Flooding near Bath, Beaufort County. Figure 4. Highway 12 near Cedar Island underwater.

Figure 5. Front Street in Downtown Beaufort flooding. Figure 6. Shepherd Street in Downtown Morehead City flooding.

Heavy Rainfall

For the period from October 2 through 6, 2015, rainfall totals of 6 to 12 inches occurred across eastern North Carolina with the heaviest totals near the coast. Historic flooding was observed in South Carolina, where Charleston reported upwards of 2 feet of rainfall (Figures 7 and 8). Combined with another heavy rainfall event the previous week, eastern North Carolina recorded from 10 to upwards of 20 inches of rainfall. The Beaufort Airport recorded 21.57 inches of rain in the period from September 25 through October 6, 2015 (Figure 9).

Figure 7. Rainfall Totals from October 2 through 6, 2015

Figure 8. Rainfall Totals from September 30 through October 6, 2015 (Courtesy David Roth, Weather Prediction Center).

...RAINFALL REPORTS SEPTEMBER 25 2015 THROUGH OCTOBER 6 2015...

ASOS STATIONS (0000 EDT 9/25/15 TO 0800 EDT 10/6/15)

LOCATION                    AMOUNT    

MICHAEL J SMITH AP(KMRH)    21.57 IN
BILLY MITCHELL AP(KHSE)     17.54 IN
CHERRY POINT MCAS (KNKT)    13.01 IN
COASTAL CAROLINA AP (KEWN)   9.43 IN
NEW RIVER MCAS (KNCA)        9.37 IN

COOP STATIONS (0000 EDT 9/25/15 TO 0800 EDT 10/6/15)

ATLANTIC BEACH (ATBN7)      15.96 IN
NEWPORT WFO (MHXN7)         14.15 IN
GREENVILLE (GREN7)          11.93 IN

COCORAHS STATIONS (0000 EDT 9/25/15 TO 0800 EDT 10/6/15)

...CARTERET COUNTY...
HARKERS ISLAND 3.2 NE           21.88 IN
SMYRNA 0.3 ESE	        	21.02 IN
MOREHEAD CITY 2.4 WNW		19.63 IN
BEAUFORT 6.5 N 			19.62 IN
MOREHEAD CITY 0.6 NW            19.45 IN
PINE KNOLL SHORES 1.4 E		17.14 IN
MOREHEAD CITY 6 WNW             15.09 IN
NEWPORT 0.2 SW			14.95 IN
NEWPORT 2.5 W                   13.65 IN
INDIAN BEACH 			13.24 IN

...CRAVEN COUNTY...
HAVELOCK 7.3 E			16.66 IN
HAVELOCK 6.3 ENE		14.90 IN
NEW BERN 7.3 ESE		11.97 IN

...ONSLOW COUNTY...
HOLLY RIDGE 4.8 ENE		12.94 IN
HUBERT 4.3 SE			12.87 IN
HUBERT 4.9 SE			12.58 IN
SWANSBORO 3.3 NW		11.26 IN

...PITT COUNTY...
GREENVILLE 3.3 W		11.38 IN
GREENVILLE 4.7 WNW 		11.00 IN
GREENVILLE 5.7 NW		10.89 IN

Figure 9. Rainfall Reports from September 25 through October 6, 2015.

Strong Wind

The pressure gradient between developing surface low pressure off the Georgia/South Carolina coast, and high pressure over New England led to a prolonged period of persistent gusty northeast to east winds across eastern North Carolina and the adjacent coastal waters and sounds (Figure 10). This acted in concert with already elevated water levels due to high astronomical tides to greatly increase water levels.

Figure 10. Peak Winds Gusts across North Carolina, October 1 through 5, 2015.

...WIND REPORTS FROM THE NOREASTER LOW THAT IMPACTED OUR AREA OCTOBER 4TH
THROUGH OCTOBER 5TH 2015...

LOCATION                     SPEED     TIME/DATE       LAT/LON

...BEAUFORT COUNTY...
BUNYAN RAWS                  48 MPH    0418 PM 10/04   35.52N/76.93W
WASHINGTON (OCW AWOS)        29 MPH    0415 PM 10/04   35.57N/77.05W

...CARTERET COUNTY...
PINEY ISLAND (NBT ASOS)      52 MPH    0319 PM 10/05   35.02N/76.47W
CEDAR ISLAND RAWS            39 MPH    0225 PM 10/04   34.96N/76.28W
BEAUFORT (MRH ASOS)          39 MPH    1206 PM 10/05   34.73N/76.66W
CROATAN RAWS                 39 MPH    0105 PM 10/05   34.76N/76.90W

...CRAVEN COUNTY...
CHERRY POINT (NKT ASOS)      44 MPH    0357 PM 10/04   34.90N/76.88W
NEW BERN (EWN ASOS)          39 MPH    0221 PM 10/05   35.07N/77.04W
NEW BERN RAWS                29 MPH    0417 PM 10/04   35.10N/77.11W

...DARE COUNTY...
MANTEO (MQI AWOS)            44 MPH    1215 PM 10/04   35.92N/75.70W
DARE CO GNRY RAN (2DP AWOS)  41 MPH    0146 PM 10/04   35.67N/75.89W
DARE BOMB RANGE RAWS         41 MPH    0328 PM 10/04   35.76N/75.87W
FRISCO (HSE ASOS)            37 MPH    0459 PM 10/05   35.23N/75.62W
KILL DEVIL HILLS (FFA AWOS)  32 MPH    1255 PM 10/04   36.03N/75.67W

...DUPLIN COUNTY...
KENANSVILLE (DPL AWOS)       28 MPH    1235 PM 10/05   35.00N/77.98W

...LENOIR COUNTY...
KINSTON (ISO AWOS)           32 MPH    0355 AM 10/05   35.33N/77.62W

...MARINE REPORTING STATIONS...
30 SE NEW RIVER INLET        56 MPH    1008 AM 10/05   34.20N/77.00W
CAPE LOOKOUT                 54 MPH    1200 PM 10/05   34.62N/76.52W
FT MACON (WXFLOW)            51 MPH    1128 AM 10/05   34.70N/76.69W
ALLIGATOR BRIDGE (WXFLOW)    51 MPH    0831 AM 10/05   35.90N/76.01W
DUCK FRF RESEARCH PIER       49 MPH    0336 PM 10/04   36.18N/75.75W
JENETTES PIER (WXFLOW)       48 MPH    0910 AM 10/05   35.91N/75.59W
OCRACOKE (WXFLOW)            47 MPH    0140 PM 10/05   35.14N/76.01W
DIAMOND SHOALS BUOY          43 MPH    0350 PM 10/05   35.01N/75.40W
OREGON INLET                 42 MPH    0124 PM 10/04   35.79N/75.55W
BEAUFORT                     41 MPH    1148 AM 10/05   34.72N/76.67W

...ONSLOW COUNTY...
JACKSONVILLE (NCA ASOS)      37 MPH    0137 PM 10/05   34.72N/77.43W
RICHLANDS (OAJ AWOS)         35 MPH    0935 PM 10/04   34.83N/77.61W
HOFFMAN RAWS                 32 MPH    0110 PM 10/05   34.82N/77.32W

...PITT COUNTY...
GREENVILLE (PGV AWOS)        32 MPH    0155 PM 10/04   35.64N/77.39W

Peak Winds Observed October 4-5, 2015.

Sources

Southeast River Forecast Center

National Weather Service Offices in Raleigh, Wilmington and Charleston, SC.

Weather Prediction Center