Hurricane Florence

Hurricane Florence was a slow-moving rainfall disaster that demonstrated, like Harvey a year earlier, that a hurricane's category often says little about its deadliest hazard. Though it weakened to a Category 1 before reaching the North Carolina coast in September 2018, Florence stalled and unloaded record-breaking rain, producing catastrophic freshwater flooding across the Carolinas.

Meteorological History

Florence reached Category 4 intensity over the open Atlantic, with peak sustained winds of 150 mph (240 km/h), before encountering wind shear and weakening as it neared the coast.¹ It made landfall near Wrightsville Beach, North Carolina, on September 14, 2018, as a Category 1 hurricane.¹ Florence then slowed to a crawl, allowing its rainbands to train over the same areas for days. Ahead of landfall, more than a million people were ordered to evacuate across the Carolinas and Virginia; and even as the winds eased, the storm grew larger, spreading its heavy rain over a wider area.¹

Record Rainfall and Flooding

Florence's slow movement made it a rainfall multiplier. It set a new North Carolina record for rainfall from a tropical cyclone, with localized totals around 36 inches (914 mm), and produced major and record river crests across the Carolinas.¹ Flooding cut off communities, breached animal-waste lagoons and coal-ash containments, and persisted for days after the winds had subsided.

The totals set new records for rainfall from a tropical cyclone in both North Carolina, about 35.9 inches (912 mm) near Elizabethtown, and South Carolina, around 23.6 inches (600 mm) near Loris.¹ Rivers kept rising for days after landfall: the Cape Fear River crested above 61 feet (18.6 m) near Fayetteville, and the city of Wilmington was entirely cut off when every road into it flooded.¹

Toll

Florence was responsible for 22 direct deaths, most from freshwater flooding and drowning, and roughly 54 deaths in all once indirect fatalities are counted, while causing about $24 billion in damage.² As with most modern U.S. hurricanes, inland flooding, not wind, was the leading cause of death.¹

Legacy

Florence reinforced that forward speed and rainfall, not category alone, often determine a hurricane's lethality, strengthening the case for communicating rainfall and inland-flood risk separately from the Saffir–Simpson wind category.

We have long thought the headline category is the wrong number to anchor an evacuation decision to: it describes wind, and in most recent U.S. hurricanes the water has done the killing. Florence, a Category 1 whose worst damage came from freshwater flooding, is about as clean a demonstration of that as the record offers, and it is part of why forecasters have moved toward separate, explicit messaging for rainfall and flood risk. It also spotlighted the environmental hazards, from hog-waste lagoons to coal-ash ponds, that hurricane flooding can unleash.¹ More than 130 hog-waste lagoons in North Carolina were breached or overtopped and an estimated 2,000 cubic yards of coal ash washed into the Cape Fear River, a reminder of how floodwaters can turn farms and industrial sites into pollution sources.¹

Sources

1. National Hurricane Center. (2019). Tropical Cyclone Report: Hurricane Florence (AL062018). NOAA. https://www.nhc.noaa.gov/data/tcr/AL062018_Florence.pdf ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹

2. NOAA National Centers for Environmental Information. U.S. Billion-Dollar Weather and Climate Disasters. https://www.ncei.noaa.gov/access/billions/ ↩