Hurricane Helene causes significant destruction and loss of life in south-eastern US
Hurricane Helene has caused widespread devastation across the south-eastern United States after making landfall in Florida’s Big Bend region as a powerful Category 4 storm (NASA, 2024a). The hurricane brought severe flooding, storm surges, and wind damage to Florida, Georgia, Tennessee, and the Carolinas, affecting over 2 million people. With over 120 confirmed fatalities and many communities still isolated due to infrastructure damage and power outages (FEMA, 2024), rescue efforts are ongoing as authorities work to reach the hardest-hit areas.
Overview and Timeline
On 17 September 2024, the National Hurricane Center (NHC, 2024) highlighted the potential for tropical cyclone development in the western Caribbean Sea, driven by a broad monsoon low-pressure system. By 22 September, a low-pressure area had intensified, leading to the gradual formation of showers and thunderstorms. With the system posing an increasing threat to land, it was classified as Potential Tropical Cyclone Nine on 23 September (NHC, 2024). The following day, Hurricane Hunter aircraft recorded winds of 52 mph (84 km/h), prompting the NHC to upgrade the system to Tropical Storm Helene. By 25 September, Helene had intensified into a hurricane with winds reaching 80 mph (130 km/h) as it moved northward into the Gulf of Mexico, influenced by an upper-level trough and a high-pressure ridge. Helene was noted for its size, being in the 90th percentile for hurricanes at comparable latitudes (NHC, 2024).
Figure 1: Timeline and path of Hurricane Helene from 17 September to 30 September 2024 (NHC, 2024).
Helene made landfall in Florida’s Big Bend region at 11:25 PM on 26 September (NOAA, 2024a), resulting in widespread flooding and significant damage. The storm remained classified as a hurricane for six hours after landfall before downgraded to a Tropical Storm. States of emergency were declared across Florida, Georgia, and the Carolinas, with major flooding and storm surges reported (NASA, 2024a; FEMA, 2024). By the early hours of 27 September, flash flooding impacted Georgia, and Tennessee experienced river flooding later that morning. The Great Smoky Mountains saw unprecedented flooding, leading to road closures and widespread power outages. By the evening of 27 September, eight fatalities were confirmed in Florida, with two additional deaths reported in Georgia due to flash flooding (Reuters, 2024). The storm weakened over the Carolinas on 28 September, though it continued to cause significant flooding in cities such as Charlotte and Wilmington before dissipating.
Impacts
The storm caused widespread devastation, particularly in Florida’s Big Bend region, and led to severe flooding across Georgia, the Carolinas and beyond. More than 120 deaths across multiple states have been reported. Fatalities (as of 1 October from CNN) have been reported from North Carolina (56), South Carolina (30), Georgia (25), Florida (11), Tennessee (6) and Virginia (2). Furthermore, scores of people have been reported missing from the impacted regions. Millions of people across the impacted states have been left without power and clean water. Damage to road infrastructure has hampered the delivery of essential supplies to the affected area. The extent and the nature of the damage incurred has led the federal government to declare a public health emergency in North Carolina. The damage caused by the storm is estimated to run into billions of dollars, with rebuilding efforts predicted to take several months, if not years.
Florida
Hurricane Helene made landfall in Florida’s Big Bend region as a powerful Category 4 storm, bringing catastrophic storm surges between 2-4.5m (6 and 15 feet) along coastal areas (Politico, 2024). Significant flooding was reported in cities like Tampa, where the storm surge reached as high as people’s attics, and widespread power outages affected over 4 million homes and businesses across the state (Reuters, 2024). Search and rescue operations were hampered by the extent of the damage, with boats and trees blocking streets throughout the region.
Georgia
After Florida, Helene moved quickly into Georgia, where heavy rain and strong winds caused severe damage. Atlanta experienced record-breaking rainfall, with over 280mm (11 inches) falling in just 48 hours, the most the city had ever seen (Politico, 2024). In rural areas, fallen trees caused multiple fatalities and flooding led to widespread outages and infrastructural damage.
North Carolina
Helene brought heavy rain to the Blue Ridge mountains causing significant flooding and mudslides in the Asheville area, cutting off communication and making roads unusable (Politico, 2024). Government officials and aid organizations coordinated efforts to deliver essential supplies to the severely impacted tourism hub of Asheville and nearby mountain towns. At least 40 people have been confirmed dead in Buncombe County as a result of the disaster (AP News, 2024a).
South Carolina
Helene’s destruction has resulted in at least 30 fatalities in South Carolina, it is the deadliest storm to impact the state since Hurricane Hugo killed 35 people in 1989 (AP News, 2024b).
Tennessee
Helene’s remnants stalled over Tennessee, where intense rainfall led to river flooding, particularly in the east, along the Nolichucky River (Politico, 2024). Unicoi County Hospital in Erwin, near the Nolichucky River, had to evacuate patients by helicopter due to floodwaters overtaking the building (AP News, 2024c).
Why did Hurricane Helene cause so much destruction
Hurricane Helene’s rapid intensification was driven by favourable conditions in the Gulf of Mexico, including elevated sea surface temperatures and low wind shear. The hurricane reached Category 4 strength, with maximum sustained winds of 140 mph (220 km/h) at landfall in Florida on 26 September 2024. It exhibited a well-developed eye and maintained strength due to the warm waters of the Gulf of Mexico’s Loop Current. The storm's development can be attributed to the influence of the Central American gyre and the Madden-Julian Oscillation (MJO). The Central American gyre is a broad monsoon-like low-pressure system that forms seasonally over Central America, where westerly winds in the eastern Pacific interact with the easterly trade winds of the western Caribbean, generating a large cyclonic flow. The MJO, behaving similarly to a smaller-scale ENSO, moves eastward from the Indian Ocean to the eastern Pacific, enhancing westerly winds and further supporting the gyre’s cyclonic flow. Persistent thunderstorms within this system ultimately led to the formation of Helene. Although the storm weakened after landfall, it continued to deliver heavy rainfall and flooding as it moved inland across Georgia and the Carolinas.
Figure 2: Satellite-observed rainfall for south-east USA between 25 and 29 September 2024. Rainfall data source: NASA GPM 3-hour rainfall accumulation (2024b). Animation produced by JBA Risk Management (2024).
Despite predictions of an active 2024 hurricane season (NOAA, 2024b), driven by warmer sea surface temperatures, the Caribbean has seen fewer storms than expected. Heavy rainfall across the Sahara Desert created atmospheric conditions that suppressed storm formation in the Atlantic (The Conversation, 2024). The rain affected the development of "tropical waves" that typically travel westward, reducing the number of potential hurricanes in the Caribbean during the season's peak. While the overall storm count has been lower, the intensity of storms like Hurricane Helene underscores the increasing severity of those that do form.
How does Hurricane Helene compare to previous storms
Hurricane Helene, with significant impacts across Florida, Georgia, and North Carolina, joins the ranks of major historical hurricanes such as Agnes, Ivan, Irma, and Michael. Analyses by ClimaMeter (2024) suggests that cyclones like Hurricane Helene are up to 17 mm/day (20%) wetter over the south-eastern US and locally up to 5 km/h (7%) windier in Florida’s Gulf compared to the past. While Helene was an unusually powerful event, both natural climate variability and human-induced climate change contributed to the increased precipitation and wind speeds observed. These factors combined to create the storm’s unprecedented intensity, underscoring the evolving nature of severe weather in a warming climate.
JBA conducted an Extreme Value Analysis on historical river and rainfall data from Florida, Georgia, and North Carolina to estimate the return period of Hurricane Helene (Figure 3). Using NOAA (2024c) and NWIS (2024) data, a Generalised Pareto Distribution (GPD) was applied to produce exceedance probability curves. Tampa, FL, experienced a 5.76m (18.95 ft) storm surge, equivalent to a 120-year event. In Atlanta, GA, 170mm (6.69 in) of rain fell, a 1-in-150-year event. The French Broad River in Asheville, NC, peaked at 5.63m (18.47 ft), corresponding to a 185-year event.
Figure 3: Estimated extreme surge height, rainfall and river level return periods for Tampa, Fl, Atlanta, GA, and Asheville, NC. The curve is shown by the solid orange line in with the 95th percentiles given by the dashed lines and observed values by the blue lines. Data for rainfall provided by NOAA (2024c). Data for surge height and stream level from NWIS (2024).
JBA provides a probabilistic catastrophe model for the United States, offering flood risk insight for both current-day and future scenarios.
A flood footprint for this event detailing extents and depths of the flooding in areas affected will be released in due course. Email eventresponse@jbarisk.com for more details.
References
AP News, 2024a. Supplies arrive by plane and by mule in North Carolina as Helene’s death toll tops 130. [Online]. Available at: https://apnews.com/article/hurricane-helene-north-carolina-asheville-f02869c7d01e68f2d7f0553abb82252f [Accessed 1 October 2024]
AP News, 2024b. Death toll rises from Helene while supplies are rushed to North Carolina and Florida digs out. [Online]. Available at: https://apnews.com/article/hurricane-helene-tropical-weather-destruction-16b41006d3cb6fedad78d19ca3f389a9 [Accessed 1 October 2024]
AP News, 2024c. Rescue missions after Helene’s flooding include dozens stranded on Tennessee hospital roof. [Online]. Available at: https://apnews.com/article/hurricane-helene-florida-georgia-north-carolina-2277be0d4b8648113508f39bfff56193 [Accessed 1 October 2024]
ClimaMeter, 2024. 2024/09/26-27 Hurricane Helene. [Online]. Available at: https://www.climameter.org/20240926-27-hurricane-helene [Accessed 3 October 2024]
FEMA, 2024. Hurricane Helene Disasters & Assistance. [Online]. Available at: https://www.fema.gov/disaster/current/hurricane-helene [Accessed 30 September 2024]
NASA, 2024a. Powerful Hurricane Helene Makes Landfall in Florida’s Big Bend. [Online]. Available at: https://gpm.nasa.gov/applications/weather/news/powerful-hurricane-helene-makes-landfall-floridas-big-bend [Accessed 30 September 2024]
NASA Global Precipitation Measurement (GPM), 2024b. Precipitation Data Directory. [Online]. Available at: https://gpm.nasa.gov/data/directory [Accessed 30 September 2024]
National Hurricane Center (NHC), 2024. Hurricane HELENE Advisory Archive. [Online]. Available at: https://www.nhc.noaa.gov/archive/2024/HELENE.shtml? [Accessed 1 October 2024]
NOAA, 2024a. Hurricane Helene Makes Landfall in Florida. [Online]. Available at: https://www.nesdis.noaa.gov/news/hurricane-helene-makes-landfall-florida [Accessed 30 September 2024]
NOAA, 2024b. NOAA predicts above-normal 2024 Atlantic hurricane season. [Online]. Available at: https://www.noaa.gov/news-release/noaa-predicts-above-normal-2024-atlantic-hurricane-season [Accessed 3 October 2024]
NOAA, 2024c. CPC Global Unified Gauge-Based Analysis of Daily Precipitation. [Online]. Available at: https://psl.noaa.gov/data/gridded/data.cpc.globalprecip.html [Accessed 02 October 2024]
National Water Information System (NWIS), 2023. USGS NWIS: Web Interface. [Online]. Available at: https://waterdata.usgs.gov/nwis [Accessed 02 October 2024]
Politico, 2024. How Helene became the near-perfect storm to bring widespread destruction across the South. [Online]. Available at: https://www.politico.com/news/2024/09/29/hurricane-helene-widespread-destruction-south-00181569 [Accessed 1 October 2024]
Reuters, 2024. Hurricane Helene floods Florida and moves north. [Online]. Available at: https://www.reuters.com/graphics/STORM-HELENE/xmpjbglrnpr/ [Accessed 1 October 2024]
The Conversation, 2024. Experts predicted more hurricanes in the Caribbean this summer – where are the ‘missing’ storms? [Online]. Available at: https://theconversation.com/experts-predicted-more-hurricanes-in-the-caribbean-this-summer-where-are-the-missing-storms-238824 [Accessed 3 October 2024]
