August 2, 2013
Wave energy, not wind, caused most of the destruction in Isabel
.......WITH SLIDE SHOW
By IRENE NOLAN
Hurricane Isabel churned in the Atlantic on its journey to the Outer
Banks, the conversation in the villages was totally predictable.
Everywhere you went, the question was, "Are you staying or are you going?"
the storm was a formidable Category 4 or 5 on the Saffir-Simpson scale,
the answer was a no-brainer. Almost all were leaving — or at
least seriously considering it.
However, as the days went by and
Isabel was downgraded to a Category 3 and then a Category 2, many
started rethinking their decisions.
A Category 2 storm with
winds of 105 mph didn’t seem all that threatening. Islanders had
been through worse, and even a good nor’easter can bring those
conditions. Even a predicted storm surge of 8 to 10 feet didn’t
seem all that bad.
However, what we didn’t focus on — and what
we should focus on in future storms — is something called wave energy
or wave action.
Wave energy is what caused most of the
devastation in Hatteras village. It is what flattened the dunes
in the village and up towards Frisco, destroyed homes and buildings on
the village’s eastern end, and opened a new inlet between the two
Hatteras village’s fate was sealed when Isabel
spent a week as an unusually persistent Category 4 or 5 hurricane
in the Atlantic on its journey toward North Carolina. In front of
it were huge waves being pushed toward the coast.
Isabel began as a strong tropical wave off the coast of Africa in early
September. It became a tropical depression and then was
christened Tropical Storm Isabel on Sept. 6. By the next day, it
was a minimal hurricane, but it rapidly progressed up the
Saffir-Simpson scale. A day later, on Sept. 8, Isabel was a
Category 4 with winds of 135 mph. The winds kept going up and on
Sept. 11, it became a Category 5 with winds measuring 160 mph.
The 160-mph winds persisted for the better part of three days.
After that the storm went briefly back to a Category 4, back up to a
Category 5, and then back down to a 4 before becoming a Category 3 on
Isabel was downgraded to a Category 2 on Sept.
16 and stayed there until it made landfall between Ocracoke Inlet and
Cape Lookout at about 1:30 p.m. on Sept. 18 with sustained winds of 100
mph, according the National Weather Service at Newport.
Newport NWS office posted a report on its website
(www.erh.noaa.gov/mhx) on the hurricane’s effects on the region.
According to that report, the peak gust at Ocracoke was 105 mph at
11:45 a.m. on Sept. 18. At the Cape Hatteras Fishing Pier in
Frisco, it was 96 at 11:46 p.m. Residents with instruments in
their homes also reported peak gusts up to 105 from Rodanthe to
Ocracoke. The official NWS reporting station on Hatteras Island
is an automated surface observation system at Billy Mitchell airport in
Frisco. Unfortunately, it stopped working when the power went
out, so the peak gust measured there was 68 mph.
official wind reports were hampered by the power outages, weather
experts agree that wind did not cause the most devastating damage on
the Outer Banks, especially in Hatteras village. Neither, they
say, did the storm surge, estimated at 6 to 8 feet.
was wave energy — those huge waves being pushed out in front of Isabel
during its long reign as a Category 4 and 5 hurricane.
was a Category 5, it generated very high surf," said Dr. Steve Lyons,
who in 2003 was the Weather Channel’s tropical weather expert in an
interview the week after the storm. "The high surf continued to
move on shore and made the wave action on landfall much larger than
would have been expected in a Category 2 storm."
others note that Hatteras village was in the right front quadrant of
the storm as it came ashore to the south. That’s the area that
can expect the worst weather — the highest winds, waves, and storm
surge. Hatteras, Lyons said, had "the highest waves of any on the
He added that Isabel was a Category 2 storm in
terms of its winds and storm surge, but he said it was a Category 5 for
Gene "Iceman" Chiellini, who in 2003 was a
hydrometerological technician at the Newport weather office, is even
more emphatic that wave energy was the most destructive force in Isabel.
the Category 2 storm, didn’t do that damage that you see," he
said. "The winds didn’t do this. They did some of the
damage. But most of the damage you see was done by wave action."
forecasts just before the storms predicted wave heights of 30 to 35
feet, but Chiellini, an avid surfer with 27 years experience with NWS,
felt that estimate was conservative. He said the model that NOAA
uses to predict wave height was showing seas of 45 to 50 feet in front
of Isabel. That was a height so phenomenal that few NWS officials
could believe the models.
forecasting was further complicated by the fact that during Hurricane
Fabian, which hit Bermuda in August, the wave models were also
predicting huge seas in the same range as they were with Isabel.
Those predictions never panned out, so maybe these wouldn’t either.
Chiellini noted that Isabel was heading toward the North Carolina coast
at a lower latitude than Fabian, it was moving more slowly, and it had
been a Category 4 or 5 hurricane for "days and days, stirring the ocean
up to astronomical heights."
On the afternoon and evening of
Sept. 17, the day before Isabel hit the coast, Chiellini said the NOAA
buoy at Diamond Shoals, about 15 miles off Cape Hatteras, was
registering waves of 16 to 18 feet. By 9 p.m., the wave height
was up to 21 feet. At 2 a.m. it was 27 feet, and then an hour
later, at 3 a.m., the buoy registered a 44.6-foot wave and stopped
reporting. He presumes the buoy has been blown to parts unknown.
says the Weather Service estimates that the storm surge was 6 to 8 feet
with 15- to 20-foot waves breaking onshore in Hatteras village.
That would have put the wall of water with tremendous energy hitting
the shoreline in the range of 21 to 28 feet. Lyons at the
Weather Channel put the height at 20 to 26 feet.
power of the storm surge plus the wave energy was apparent in Hatteras
village. Motels along the beach were destroyed, with buildings
moved into or across Highway 12. Buildings, such as the Hatteras
Cabanas, were moved across the highway and into the marsh. Other
buildings were washed off their pilings. Houses sat in sink holes
with only a few feet of the top floor and the roofs above water.
One house was washed out into the Pamlico Sound. Buildings stood
with only side cinder-block walls, the front and back walls blown out
by the wave energy and the building swept clean of furnishings.
Cars and trucks were flipped and crushed, and many feet of sand filled
the lower floors of many buildings.
Although most of Hatteras
Island did not have soundside flooding, as it does in most hurricanes,
even homes in Hatteras village that were not on the oceanfront were not
immune from damage. The surge with the waves on top washed over
the eastern end of the village and into the sound near Sandy Bay.
The east wind blew the water around the back of the village and in
through the creeks that run through it. Homes were flooded, and
debris from the oceanfront — refrigerators, air conditioners, beds,
dressers, motel room doors with the numbers still on them — lined the
back creeks into the village.
Chiellini calls Isabel a
"legendary and historical" storm because of the wave energy — not the
wind or storm surge. He’s in close touch with many of his surfing
buddies on Hatteras Island and says many of them he talked to evacuated
during Isabel for the first time ever in a storm.
Keith Andre of
Buxton was one of them. He had planned to leave the weekend after
the storm anyway to go to parents’ weekend at his daughter’s
college. At first, he thought he might pass on the weekend event
and stay at his Cape Pines Motel. However, he changed his mind.
"I didn’t like the way the storm looked, with the seas so high," he said, so he left the island with the rest of his family.
needs to be more emphasis in future storms on Category 4 and 5
hurricanes that last this long," says Chiellini. "There should be
emphasis placed on wave energy. Isabel could have come ashore as
a tropical depression and it still would have wiped out Hatteras."
CLICK HERE TO VIEW SLIDE SHOW
(This article was written for an October 2003 Special Report on Hurricane Isabel in The Island Breeze.)