Published: 2016-08-25 12:40:00
Updated: 2016-08-29 10:30:19
Posted August 25
Updated August 29
Twenty years ago, Hurricane Fran forced sudden, dramatic change upon the North Carolina coast and the Triangle. The next major hurricane will expose the subtle change that happens across years and decades. Gradual forces like population growth, development and sea level rise portend greater destructive potential for future hurricanes. A look at the decades ahead reveals troubling trends and uncertain outcomes.
Hurricane Fran’s devastating track from Cape Fear to the state capital wasn’t even a worst-case scenario. Some still remember a stronger storm, but for most it’s a precautionary tale or black-and-white photos from another era.
“If you’re a law of averages kind of person, you have reason to be nervous. We’re overdue,” explains Steve Pfaff, the warning coordination meteorologist at the National Weather Service Office in Wilmington. Even when the weather is peaceful, he tries to prepare a public that is growing inexperienced with the consequences of a major hurricane.
Hurricane Hazel remains the strongest storm that any North Carolinians are alive to remember. It came ashore in Brunswick County at Category 4 strength on Oct. 15, 1954, the only storm so strong in the era of modern hurricane records. 18 feet of storm surge wiped away nearly every structure on the shoreline from Calabash to Cape Fear. Like Fran, the storm ripped northward towards the Triangle and brought damage far beyond the coastline. In Raleigh, 90 mph gusts blew down thousands of trees.
Those who have only dealt with the most recent hurricanes to brush the Cape Fear region may not be prepared for what a storm as strong as Fran or Hazel could bring. “Even the people that have been through 10, 15 storms are going to be in for the shock of a lifetime,” warns Pfaff.
Hurricanes are classified by the strength of their winds on a familiar 1 through 5 scale. The Saffir-Simpson Scale doesn’t capture the complicated and deadly threat from storm surge. Pfaff often hears coastal residents draw the line at evacuating for a storm ranked Category 3 or higher. Storms that fail to whip up winds to the 111 mph Category 3 threshold are still capable of pushing a dozen feet of water onto land and into homes.
Instant news coverage of hurricanes has made it easy to picture storm surge and waves inundating barrier islands and beachfront homes. But new residents may not have a benchmark to know how far the storm surge can travel. “The tidal creeks and even the Cape Fear River and some well-inland areas can experience that,” cautions Pfaff.
The exact amount of storm surge depends on a number of factors: a hurricane’s strength, size, speed, motion, the daily tides and the shape of the coastline itself. Though a slow-moving storm can drive surge deep into estuaries and rivers, the highest surge is often found on the right side of a fast-moving storm like Hazel. A very slight change in the track of a major hurricane could shift the worst effects from one island to the next.
The 8- to 12-foot storm surge from Fran would have been even more destructive if the landfall coincided with high tide instead of low tide, according to Tim Armstrong, chief forecaster at the National Weather Service in Wilmington. “I would say a worst-case scenario is a Hugo-like storm coming ashore at high tide.”
Category 4 Hugo made a perpendicular track into Charleston, S.C., on Sept. 22, 1989. A similar hurricane shifted 100 or 120 miles to the north would drive a 16- to 20-foot storm surge into Long Bay and provide the ultimate test for the beachfront development in Brunswick County.
“It gets more complicated when you add in that human element,” warns Pfaff. A hurricane warning over Labor Day weekend, for example, would need to reach more people amid a busy tourist time. Fran struck right after Labor Day weekend when the visitor count was already in decline.
A storm like Hurricane Fran would undoubtedly cost more today, but the human impact is harder to estimate. If Hurricane Fran were repeated in 2016, it would disrupt the lives of hundreds of thousands more North Carolinians.
600,000 people currently living in the Triangle weren’t around in 1996. Population estimates generated by the North Carolina Office of Budget and State Management project an additional half million residents in Wake, Durham and Orange counties by 2035. Most of the counties along the Atlantic Ocean are growing faster than the state average. The crowding coastline and the booming Triangle are two trends expected to continue over the next 20 years.
Brunswick County – ground zero for Hurricane Hazel – has six times the population it did in 1954. The number of permanent residents has nearly doubled from 64,000 to 123,000 just in the two decades since Fran. In the two decades to come, the state estimates that number may climb by another 60,000. As the growth continues, existing vulnerabilities will be tested.
By 2035, Brunswick County is estimated to have a population with an average age of 53 – older than any other county in the state. One in three residents will be over the age of 65, a scenario that involves 60,000 people above retirement age. While some long-time residents will have had experience as young adults with Fran, many more will be retirees from other regions. Their reaction to and safety in future hurricanes will in part depend on the support of the community.
Dr. Laura Myers, a social scientist who studies how people react to disasters, finds an encouraging characteristic in the over-65 demographic. “They’re actually more weather aware and they tend to prepare more,” she said.
But the frenzied days and hours leading up to landfall can require securing a home and loading up a car, tasks that become more difficult with age. “There are a lot of limitations for them: transportation, resources, the frailty that they may face,” says Myers. “There needs to be a lot of community resources to help them to give them the support, to help them prepare.”
Steve Pfaff of the National Weather Service also considers how forecast information factors into how local agencies serve vulnerable parts of the population. “That reliance would require us to be able to provide more accurate forecasts and better lead time or even a heads up farther out so that they can make good decisions on what’s available at the time.”
State and local officials in North Carolina maintain detailed maps and statistics for which areas will flood and how long it will take to perform evacuations. Each new storm teaches lessons that shape the planning and preparation for the next storm. But when a long time passes since the last big disaster, it’s hard to know all of the human variables will come together the next time.
Pfaff and emergency managers continually spread the education message to new residents who have never experienced storm surge and strong winds. Myers cautions that the memory of a past encounter with disaster can lead to reactions ranging from fear to complacency among hurricane veterans.
The experience with Hurricane Bertha two months before Hurricane Fran was credited with teaching the public and officials how to put their hurricane plans into action. According to a study prepared for FEMA after the 1996 hurricane season, people who evacuated from Hurricane Bertha tended to also evacuate for Fran, and some even went farther inland the second time.
As the memory gets more distant, a hurricane survivor may react to a new storm based on the details and behavior of a past one. “If they do remember it, they remember it from a long time ago,” notes Myers. “The whole evacuation routing may in fact be different.”
North Carolina’s map once featured small barrier island settlements since lost to economic and natural pressure. Will small coastal towns threatened by rising seas and battered by violent storms have the resources to adapt or the room to survive to 2100?
At North Carolina State University, Dr. Gary Lackmann works with a team of meteorological researchers to simulate how today’s hurricanes will behave in a world where climate change continues to increase the temperature of the air and the oceans.
“There are some things with warming that make the storms stronger; other things make them weaker,” explains Lackmann. “You really have to do numerical experiments to sort out which processes dominate.”
Like other research teams across the country, Lackmann sees signs that the strongest hurricanes would be capable of greater intensity a century from now. A warmer world may not yield more hurricanes, however. “Decreased frequency is one of the fairly robust results reproduced by many research teams around the world,” according to Lackmann.
Sea surface temperature is not the only ingredient that affects where and how hurricanes form. Different regions and different layers of the atmosphere won’t warm uniformly and this could change the pattern of when, where and how hurricanes will develop. For instance, relatively warmer air in the upper troposphere may offset some of the potential intensity that a hotter tropical ocean could give to a storm.
Warmer sea surface temperatures may enable stronger hurricanes to maintain intensity farther and farther north. It’s also possible that a warmer climate would broaden North Atlantic hurricane season to begin earlier in the spring and last longer into the winter.
As always, hurricanes will not be just a coastal concern. Inland flooding would be worsened by a climate that favors heavier rainfall. Warmer air holds more water vapor, and hurricanes would dump larger rain totals than they previously could.
While projections of exactly how much the climate will warm and how human technology will change are uncertain, any acceleration of sea level rise will expose more land to storm surge when storms do strike.
The very shape of today’s coastline is an icon of the Tar Heel State. The outline of capes and curves is painted onto center court in the Dean Smith Center and emblazoned on T-shirts and bumper stickers. But the Carolina coast of thousands of years ago would look dramatically different. The coast of future centuries may be just as unrecognizable.
Yearly visits to the coastline reveal some slow and steady change – new developments, gradually shifting inlets, the ocean claiming rows of beach houses. Some changes are so slow as to take a lifetime to unfold, like a legacy of climate change that will affect generations to come. The effect of a few millimeters per year of relative sea level rise is barely evident on an annual trip to the beach. But over the span of decades, that small increase adds up to inches or feet, and puts more land and buildings within reach of a hurricane’s storm surge.
Like the state of the climate that drives it, sea level rise is dictated by complicated and interwoven factors. Sea level rise isn’t as simple as ice melting and inundating the beach – the ocean itself expands in volume as it gets warmer. The ground itself plays a role in how quickly the sea level rises relative to a fixed point on the land, and on parts of the North Carolina coastline that land is very slowly sinking.
Tidal gauges have measured a sea level rising at a rate of about 2 millimeters per year in Wilmington and Southport and 3 to 4 millimeters per year along the Outer Banks, which is faster than the global average. The actual trendline fluctuates from month to month and year to year due to weather patterns and ocean currents. There’s a strong consensus among climate scientists that this rise will accelerate as the 21st century goes along, particularly after 2050.
Uncertainty lies in which warming scenario will occur. If emissions continue unabated or if more ice from Greenland or Antarctica melts into the oceans, sea level rise may be as high as six feet by 2100. A conservative estimate of a two-foot rise over today’s levels seems small in comparison, but that would directly increase the potential for hurricanes to cause destruction.
Dr. Jesse McNinch, a research oceanographer at the Army Corps of Engineers Field Research Facility in Duck, emphasizes a balanced consideration of all the factors that lead to shoreline change. In addition to sea level rise, the availability of sand and sediments and the wave energy from hurricanes and nor’easters can mean the difference between little change and rapid erosion.
The effects of a hurricane can be increased by the storms that come before it. Fran eroded beaches and dunes already weakened by Hurricane Bertha two months earlier. And just as it doesn’t take a Category 3 or 4 hurricane to produce deadly storm surge, serious beach erosion can come from a weaker but slow-moving storm like Hurricane Dennis. “Their tracks are really important," McNinch said.
Each island along the Carolina coast is sculpted by a combination of factors and each spot along the coastline will react to storms in a unique way.
Barrier islands, like North Carolina’s Outer Banks, naturally migrate towards land in response to a rising ocean level. But an increasing rate of sea level rise combined with a series of catastrophic hurricanes could be too much for islands like the Outer Banks. The tipping points that could cause the islands to break apart at a faster rate are an area of ongoing research and monitoring.
McNinch points to the success of weather forecast models as a model for how the erosion caused by hurricanes and nor’easters can be predicted in the decades ahead. “I hope that we eventually can reach a point where we can provide five-day forecasts, for instance, on a lot-by-lot basis, on what we would expect in erosion and inundation and other basically damaging conditions. But we have a long ways to go before we can get there.”
Each summer, clusters of rain clouds will sweep off the African coastline and begin a long journey across the Atlantic Ocean. Most won’t organize into a violent spiral of 130 mph winds. Most won’t curve right into the coast of North Carolina. But one day, another will.
When Hurricane Hazel devastated the coast and swept inland with fierce winds, weather radar was a new breakthrough and WRAL-TV was still two years away from signing on. Computer modeling was rudimentary. Weather satellites wouldn’t scan the open ocean for another six years.
Not long before Fran hit North Carolina, the first generation weather radar was replaced by the NEXRAD Doppler radar still used today. News and weather websites were in their infancy and social media was more than a decade away.
When the next Fran or Hazel hits, scientists will have more sophisticated tools to observe the storms and the coastal changes and a better understanding of what to anticipate next. The ability of meteorologists to observe, forecast and alert people to hurricanes continues to improve each year. The stakes will get higher with more people and property in the path. For a coastline with a risky future, it will be even more important to remember the lessons of the past.