NWS Wilmington, NC

Weather Forecast Office

Hurricane Irene Aug 27, 2011

Hurricane Irene Impacts Eastern North Carolina

WILMINGTON, NC - During the overnight hours of August 26th into August 27th, category 1 Hurricane Irene brushed the Cape Fear region on its path to landfall at Cape Lookout, NC.

Satellite Loop of Hurricane Irene approaching the southeast United States

Hurricane Irene Synopsis

Hurricane Irene formed from a tropical wave near the Cape Verde Islands west of Africa, and became a named tropical system on August 20th. Shortly thereafter as she moved west, Irene became the first hurricane of the 2011 season.

As the hurricane moved west she intensified and brushed the north coast of Hispaniola. Irene then began to turn to the northwest and became a category 3 hurricane during the time she impacted the Bahamas.

By this time, the National Hurricane Center was predicting a track that took Irene into the outer banks of North Carolina, just east of Cape Fear. Although this was several days out, this track turned out to be quite accurate and on the morning of the 27th Irene made landfall as a category 1 hurricane near Cape Lookout, NC. This spared the Cape Fear region from the worst impacts since the right front quadrant remained well east of that area.

Although the track was forecast very accurately, Irene's intensity forecast was a bit overdone. Much of the guidance several days out was predicting the potential for Irene to be a strong category 2 or even a category 3 hurricane at NC landfall. Fortunately, this did not materialize. However, with surface pressures in the eye of Irene only around 950 mb, the potential for a stronger hurricane remained possible, even as Irene continually weakened off the southeast coast.

Analysis of water vapor imagery during the day leading up to NC landfall helps explain why Irene weakened so drastically as she approached land. The two images below are water vapor satellite images at 26/1900 UTC and 26/2200 UTC respectively.

Water Vapor Imagery from 26/1900 UTC. Note the very dry air just west of Hurricane Irene

Water Vapor Imagery from 26/2200 UTC. Note the dry air (dry slot) wrapping almost entirely around Irene's core.

Irene is obvious off the southeast coast, but notice the very dry air across much of the eastern United States. This dry air was pushing east in response to a strengthening ridge of high pressure. As Irene continued up the coastline, she ingested a significant amount of dry air as evidenced by the change in structure and "dry slot" that is seen wrapping almost entirely around her core in the second image.

Fortunately, this dry air was enough to keep Irene from restrengthening over what was otherwise a favorable environment. Although the category 1 hurricane still caused considerable damage from Cape Fear to the Outer Banks, it could have been much worse across eastern North Carolina.

The following is a list maximum wind gusts reported across the Wilmington County Warning Area during the passage of Hurricane Irene

Hurricane Irene was a very large hurricane, with hurricane force winds (64 kt) extending 80 miles from the center, and tropical storm force winds (34 kt) occurring another 220 miles beyond that. This put the Cape Fear region on the fringe of the hurricane force wind radius. Fortunately, none of the area experienced hurricane force winds from Irene, but widespread tropical storm force winds brought down many limbs and trees through southeast North Carolina and northeast South Carolina.

Location	Max Gust (kt)	Source
Wrightsville Beach 27 East	62	NDBC Buoy
Johnny Mercer Pier	61	NOS Buoy
Back Island	61	RAWS
Bald Head Island	59	Mesonet
Frying Pan Shoals	58	NDBC Buoy
Wilmington	57	ASOS
Springmaid Pier	54	NOS Buoy
Sunset Harbor	54	Mesonet
Wrightsville Beach	51	Mesonet
North Topsail Beach	50	Mesonet
Turnbull Creek	50	RAWS
Wilmington	46	Mesonet
Southport	46	AWOS
North Myrtle Beach	43	ASOS
Whiteville	42	RAWS
Lumberton	40	ASOS
Socastee	39	Mesonet
Myrtle Beach	38	ASOS
Florence	37	ASOS
Georgetown	36	AWOS
Marion	34	AWOS

Map of wind swath from Hurricane Irene from the National Hurricane Center

Map of NC wind swath from Irene. Courtesy WFO RAH

The following is a list of selected rainfall reports from the Wilmington County Warning Area during the passage of Hurricane Irene

As Irene brushed the Cape Fear region, heavy rain impacted the coastal and northeast portions of the Wilmington County Warning Area. The heaviest rain fell across Brunswick County, New Hanover County, and Pender County. Although a widespread 4 to 8 inch rain occurred over this area, only minor flooding impacts were noted due to the antecedent very dry ground caused by the ongoing severe drought.

Location	Rainfall (in)	Source
Back Island	8.26	RAWS
Southport 1.0 NE	8.01	CoCoRaHS
Boiling Spring Lakes 2.3 NE	7.73	CoCoRaHS
Wilmington 4.4 SSE	7.72	CoCoRaHS
Wilmington 3.2 SSE	7.71	CoCoRaHS
Hampstead 1.9 S	7.67	CoCoRaHS
Wilmington	7.58	NWS Office
Castle Hayne 1.6 NNW	7.41	CoCoRaHS
Wilmington 7 SE	7.38	Co-Op Observer
Rocky Point 6.1 WNW	7.33	CoCoRaHS
Wilmington	7.19	ASOS
Castle Hayne 2.5 NW	7.10	CoCoRaHS
Ogden	6.97	NWS Employee
Wilmington 8.0 ENE	6.64	CoCoRaHS
Wilmington 4.1 SE	6.60	CoCoRaHS
Topsail Beach 0.9 NE	6.56	CoCoRaHS
Southport 5.8 WNW	6.50	CoCoRaHS
Bolivia 7.8 SW	5.90	CoCoRaHS
Wilmington 1.4 NNW	5.89	CoCoRaHS
Oak Island 0.7 W	5.53	CoCoRaHS
Long Beach 2.9 NE	5.41	CoCoRaHS
Rocky Point 2.3 SW	5.16	CoCoRaHS
Leland 5.7 WSW	5.08	CoCoRaHS
Winnabow 3.6 SE	5.03	CoCoRaHS
Burgaw 9.6 W	4.85	CoCoRaHS
Silver Lake 1.3 NE	4.84	CoCoRaHS
Varnamtown 1.8 ENE	4.82	CoCoRaHS
Leland 9.4 WNW	4.20	CoCoRaHS
Myrtle Beach 8.6 SW	3.62	CoCoRaHS
Murrells Inlet 1.8 NE	3.15	CoCoRaHS
Whiteville 7.0 S	3.08	CoCoRaHS
Murrells Inlet 0.3 SSW	3.04	CoCoRaHS

CoCoRaHS rainfall map of the Carolinas from 8/27

CoCoRaHS rainfall map of the Carolinas from 8/28

Map of NC rainfall from Irene. Courtesy WFO RAH

Hurricane Irene Storm Surge

Although storm surge was minor across the area, a storm tide was noted at both Wrightsville Beach, NC and Myrtle Beach, SC. The images below show the surge at both locations as the difference between the observed tide (red) and the predicted tide (green).

Wrightsville Beach Tide Gauge. Maximum surge of around 3.5 feet occurred during low tide at midnight Friday night. During this time some water over the dunes was reported along Topsail Beach just north of Wrightsville. Additionally, note the significant "blow-out" tide that occurred at low tide Saturday morning when the winds turned to the W/NW.

Springmaid Pier (Myrtle Beach) Tide Gauge. Maximum surge of 1.5 to 2 feet occurred during the approach of low tide Friday night. A lesser "blow-out" tide also occurred here near low tide Saturday morning.

Radar Loop from Hurricane Irene

Below is a KLTX 0.5 degree reflectivity loop from 26/2300 UTC through 27/1800 UTC. The images are half-hourly. Easily visible is the eye of Irene as she moves up the coast to landfall at Cape Lookout, NC. Note the several different outer bands that impact southeast North Carolina where the heaviest rain occurred.