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    • Savannah was hit hard by Helene despite being outside the hurricane’s cone
    Duluth

    Savannah was hit hard by Helene despite being outside the hurricane’s cone

    Eira Gwyneth Posted on

    For days, forecasts of the storm’s expected path remained consistent inland, while in the Caribbean Sea it gradually took shape and then strengthened as it gathered fuel from the warm Gulf of Mexico as it barreled toward Florida.

    After landing on the Gulf Coast, Helene’s Heart would pass through the western half of Georgia on its way north.

    This path was reflected in the National Hurricane Center’s signature maps, which illustrate the storm’s projected “cone of uncertainty.”

    The right edge of the strip – which represents the easternmost route that the center of Helene would potentially follow as it moves north – cuts vertically through the middle of Georgia, leaving the state’s coast well outside the path shown.

    But the Savannah area would ultimately face hurricane-force winds as the remnants of Helene, now a tropical storm, ripped through Georgia before barreling into the Carolinas.

    These conditions were expected by anyone who had been closely following forecasts from the National Weather Service, which predicted potential isolated tornadoes beginning in the afternoon of September 26 and potentially damaging wind gusts early the next morning.

    But when they emerged from their homes — most of them without power — on Sept. 27, some Savannah area residents were surprised to find fallen trees and streets littered with branches and debris.

    Some of that confusion likely came from looking at the National Hurricane Center’s maps on social media or other sources without also reading detailed explanations that put the images into context, experts say.

    “The cone of uncertainty can be problematic in my view because it shows the likely path of the center of the storm, but not the size of the storm or the extent of possible damage,” noted Professor Brian Houston and director of the Disaster and Community Crisis Center at the U of Missouri. “So when people see that they are outside the cone, they may think that they are safe and will not be affected by the storm.”

    As Helene spun counterclockwise, Savannah—highly vulnerable due to its location in the storm’s northeast quadrant—came into the path of fierce Atlantic winds that moved unhindered onto land.

    Gusts of up to 76 miles per hour were recorded at Savannah-Hilton Head International Airport.

    According to the National Hurricane Center (NHC), tropical storm-force winds extended 345 miles from the eye of Helene before reaching land.

    “Given the sheer size of this storm … it was not surprising to see these gusty winds and other threats extending all the way to the coast,” said Corey Davis, a climatologist at North Carolina State University. “Given that it was moving over Georgia as a Category 4 hurricane just hours after making landfall, one would have expected it to have some stronger winds in tow.”

    Far-reaching impact: Experts say Helene shows a growing hurricane reach well into Georgia and beyond

    “A black and white situation”

    Until 2009, the NHC added a line in the cone of uncertainty to illustrate a storm’s projected direction, but stopped doing so because it was concerned that too much attention was being paid to the line itself rather than the entire potential path of a storm.

    “But now it seems like the cone is being treated like a black-and-white situation: If you’re in it, you’re in trouble, and if you’re out, you’re safe,” Davis said. “This is also a bad misinterpretation, as the cone does not indicate the range of affected areas, but rather the historical average uncertainty in the track of the storm center a few days later.”

    For the current hurricane season, the NHC has introduced an “experimental” map that displays warnings and observations associated with a storm, as well as the cone of uncertainty.

    J. Marshall Shepherd, director of the University of Georgia’s Atmospheric Sciences Program, called the new product “a step in the right direction.”

    “I think this is more important because it shows the full width and extent of the impacts, not just the cone,” Shepherd explained. “If you look at some of Helene’s experimental maps, there are counties with warnings and watches that are well outside the cone.”

    These areas also included the coast of Georgia.

    Another experimental illustration of the NHC includes the cone of uncertainty and possible impacts of wind, rain, tornadoes, and storm surges.

    The graphic includes four maps showing the possible full extent of the storm.

    A version prepared by the NHC while Helene was still in the Gulf of Mexico predicted tropical-storm-force winds for Savannah, as well as the possibility of “many tornadoes,” “moderate flooding rain” and minor storm surges.

    Along with strong winds, Savannah eventually saw a flurry of tornado warnings and up to 5 inches of rain in areas around Helene.

    “All of this information is out there, but for some reason this type of map just hasn’t caught on,” Shepherd said. “I think there’s a societal inertia, a media inertia to show the cone, and quite frankly, an inertia for the Hurricane Center, because you have to search their website to even find these maps.”

    In the path: Savannah’s location made it more vulnerable to Helene’s hurricane-force winds

    “There was no clue”

    Monica Kast experienced firsthand the potential shortcomings of hurricane forecast maps.

    Kast, a reporter for the Lexington Herald-Leader in Kentucky, had planned to meet up with friends from college in Savannah for the weekend.

    “I checked the Weather Channel app radar all week leading up to last Friday, especially last Thursday several times throughout the day,” she said in an email. “Everything we saw looked like it was just going to rain in Savannah on Friday. We had, perhaps naively, planned a beach day for Saturday because things looked so clear.”

    Kast shared a screenshot of a Weather Channel map showing the storm’s low pressure cone over western Georgia, far from the coast.

    By the time Kast and one of her friends left Lexington on September 27, Helene had already harmed Savannah.

    “There was no indication that it would be as serious as it ended up being,” she added.

    Still looking forward to a weekend on the Georgia coast, Kast and her friend ended up driving to Asheville when flooding began to devastate the area.

    They were redirected to the nearby community of Black Mountain, where they were stranded for days because all incoming and outgoing roads were closed or impassable.

    “I’ve been a journalist for almost a decade, so I’ve covered natural disasters and floods before, but nothing like this,” Kast wrote in an account of her experiences. “I don’t have the words to describe it other than to say it’s the worst thing I’ve ever seen.”

    One of Kast’s friends flew from New York to Savannah shortly after Helene moved through.

    “The Airbnb we booked had no power and there was a power line running in the yard across the street,” Kast said in her email. “She ended up going back to the airport and catching a flight the next morning.”

    On Monday, September 30, Kast and her friends finally reached Charlotte, from where they took a flight to Louisville.

    “Don’t focus on lines and dots.”

    The cone of uncertainty for Helene has changed little from its emergence in the Caribbean to its transition to Georgia.

    That consistency reflects advances in hurricane tracking, North Carolina State’s Davis said.

    “In some ways, these predictions have become a victim of their own success, as the tracking error has gotten so much better over time that the cone has become smaller and smaller and fewer areas within it are visible,” he explained.

    As forecast storm paths shrink, storms absorb more energy and moisture as they move over warming seawater, allowing them to grow stronger and maintain their strength as they move over land.

    Some of the most catastrophic flooding in Helene occurred in Asheville, more than 450 miles inland from where the storm made landfall in Florida.

    The increasing reach of storms originating from the Atlantic and Gulf of Mexico underscores the importance of storm warnings that report possible impacts outside the cone, UGA’s Shepherd emphasized.

    “I’m talking more and more about not focusing on lines, dots and sounds on maps, but instead focusing more on the large area or the possible impacts because I think we’re in a time now where “Hurricanes are not just a problem, coastal hazards are more.”

    Savannah was reminded of that in the last two months when two Category 4 hurricanes made landfall in Florida before moving over Georgia.

    In early August, Debby dropped up to 11 inches of rain over three days in Savannah, flooding streets and some businesses. Helene was more of a coastal wind event, providing power to more than 120,000 customers in the Savannah area.

    “Look, hurricanes have always moved inland, become tropical storms, and produce wind, rain, flooding, and so on,” Shepherd noted. “But in the last few years we’ve seen several really strong storms that reached a little too far inland than our infrastructure, our pine trees and our crops are used to.”

    John Deem covers climate change and the environment on Georgia’s coast. He can be reached at 912-652-0213 or [email protected].

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    Eira Gwyneth
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