Remembering Hurricane Florence

Florence was a long-lived tropical cyclone that made landfall as a  Category 1 hurricane  (maximum sustained winds of 90 mph) near Wrightsville Beach, North Carolina (NC), around 7:15 AM on September 14, 2018. But Florence was much more than a "typical" Category 1 landfalling hurricane, and the strength of its winds don't tell the whole story.

Florence went through multiple rapid intensification periods during its lifetime, including to a Category 4 peak, but each intensification was followed by a period of weakening, including to a Category 1 at landfall. After extensive media coverage on the storm as it crossed the Atlantic, the "weakening" of Florence's winds may have lead to a false sense of security from the public, with a possible perception that its impacts would not be as bad. However, in the case of Florence, the greater danger was from the significant slowing of the storm's forward motion. This slow motion resulted in many hours and days of torrential tropical rain, leading to historic rainfall amounts, a danger that was heavily emphasized in forecasts and briefings provided by the  National Weather Service  offices, including the  Weather Prediction Center  and  National Hurricane Center .

This is a crucial point: The wind-based tropical cyclone categories do not communicate all possible impacts. In addition to damaging wind, tropical cyclones can also produce destruction from flash flooding, river flooding, storm surge, and tornadoes. As a Category 1 storm at landfall, Florence caused disastrous freshwater flooding across much of the southeastern United States and significant storm surge flooding in portions of eastern North Carolina. Florence resulted in 22 direct deaths and was also associated with 30 indirect fatalities. ( Storm details courtesy of NHC's Tropical Cyclone Report) 

• 184: The highest wind speed, in mph, measured by a dropwindsonde released in Florence’s eyewall at the 909-mb level at 2101 UTC on September 10, 2018.
• 937: Estimated minimum central pressure, in millibars.
• 900,000+: The number of utility customers who lost power across NC.
• 22: Estimated total damage losses, in billions of dollars, in NC due to winds, freshwater flooding, and storm surge flooding. This places Florence as the all-time costliest tropical cyclone on record for NC.
• 70: Consecutive hours for which the WFO Raleigh area of responsibility (county warning area, or CWA) was under tornado watch.
• 54: Consecutive hours for which the WFO Wilmington CWA was under a tornado watch.
• 93: Consecutive hours for which some part of North Carolina was under tornado watch.
• 41: Consecutive days with a river flood warning in effect for southeast NC.
• 35.93: Inches of rain recorded at Elizabethtown in southeast NC. Other totals included 34.00 inches at Swansboro, 17.00 inches at Hope Mills, and 16.28 inches at Godwin, NC.
• 4.8: Average speed in mph of Florence as its center drifted over southeast NC and northeast SC from 5 am Friday, 9/14, to 5 am Sunday, 9/16.
• 85: Hours of constant radar surveillance by WFO Raleigh forecasters.
• 2,000+: Number of roads closed in central NC, including parts of Interstate 95 and Interstate 40.
• 39: Decision support briefings given by WFO Raleigh forecasters.
• 34 and 38: Decision support briefings, general and river-specific, given by WFO Wilmington forecasters.
• 22: Live webinars with partners given by WFO Raleigh forecasters.
• 1953: Year when "Florence" was first used as a hurricane name, making it one of the longest-lived names in NHC naming history, before the name was retired in 2019. Naming of hurricanes and tropical storms started in 1950 with phonetic alphabet names, followed by a switch to female names in 1953, then to both male and female names in 1979. 

Given the potentially significant event that was about to unfold across the Carolinas, the approach of Florence attracted the attention of the New Yorker magazine, who sent a reporter down to the North Carolina NWS forecast offices to learn about our tropical cyclone operations and how we make decisions.

This article provides a rare look 'behind the curtain' of a local Weather Forecast Office as a long lived and high impact event unfolds before their eyes.

The roughly 25-hour radar loop below, from Thursday, September 13, to Friday, September 14, uses data from multiple NWS WSR-88D Doppler radars. It shows well the open eye of Florence prior to landfall, followed by a closing-off of the eye once inland, when the wind field began to steadily weaken. Despite the weakening of the wind field prior to and just after landfall, Florence still packed a tremendous punch in terms of storm surge, damaging wind gusts, and very heavy and prolonged rainfall which led to both freshwater flooding and considerable river flooding.

Florence produced over 10 inches of rainfall across much of southeastern and southcentral NC and northeastern SC. A few totals exceeded 20 inches from the NC/SC border eastward across southeastern North Carolina. These extreme totals were due to the tropical nature of the rain (which resulted in efficient rainfall processes and very heavy rainfall rates) and to the slow forward speed of Florence prior to and after the hurricane made landfall.

This resulted in persistent bands of rain moving inland over the eastern Carolinas and training repeatedly over the same areas. A swath of 30+ inches of rain was observed from Wilmington to Elizabethtown, NC, including a peak storm total rainfall of 35.93 inches, measured about 6 miles northwest of Elizabethtown. This value set a state record for tropical cyclone rainfall (unseating the previous NC tropical rainfall record of 24.06 inches, in Southport, NC, during Hurricane Floyd in 1999). A new state tropical rainfall record for South Carolina was also set by Florence, 23.63 inches recorded at Loris, SC (exceeding the previous record of 17.45 inches from near Lake Jocassee during Tropical Storm Beryl in 1994).

The NWS had been forecasting extreme rainfall and catastrophic flooding for several days ahead of Hurricane Florence's approach toward the NC coast. The 5-day forecast created when Florence was about 200 miles off the NC coast depicted astonishing rainfall amounts, including a large area of 15 to 35 inches of rain over the southeast quarter of NC into northeast SC, and these totals verified well.

To the right is another map of the unofficial, radar-estimated storm total rainfall from Florence over NC (actual gauge-measured amounts not included). Using the average total rainfall over the state, Florence dropped about 8.04 TRILLION gallons of rain on NC!

This rainfall produced historic, catastrophic flooding of both land areas and on rivers.

The imagery below was created using a blend of color channels from the NASA MODIS spacecraft. Water clouds appear white, while ice clouds tend to be light-blue or cyan. Vegetation appears as bright green, bare ground has a pinkish tan color, burn scars appear as a reddish-brown color and water appears dark blue or black.  Blue-green areas are a mix of water and vegetation, as one might expect in a flooding situation. The flooded rivers show up very well in the post-Florence image, with labels added to help identify the mainstem rivers.

While the river flooding was devastating for many, good quality forecasts still helped many people prepare. As forecast confidence increased that the rainfall associated with Hurricane Florence would be historic and catastrophic, concerns for devastating river flood grew.  The Cape Fear River Basin was at risk to receive some of the heaviest rainfall, and even inland from the coast and the forecast 20+ inches of rain, 10-15 inches of rain around Fayetteville could cause near record flooding.  

Through multiple rounds of coordination between the Southeast River Forecast Center, the NWS in Raleigh, and emergency management in Cumberland County and Fayetteville, the official forecast (graph on right, noted by purple line/dots) called for a crest of 62.4 feet around midnight on September 18.  The river actually crested at 61.58ft around midnight on September 18, which was an incredible near-record flood forecast within 1 foot four days ahead of time! The blue line in the graph below shows the observed river stage of the Cape Fear River at Fayetteville. This compared quite well to the river stage forecast from several days prior (graph on right).

The Waccamaw River experienced catastrophic flooding in October 2016 from Hurricane Matthew and a new record high stage was observed at 17.89 feet.  Rebuilding had only recently finished as new all-time record flooding developed from Hurricane Florence.  The river exceeded Matthew's stage by over three feet.  Horry County Emergency Management reported 361 homes in Conway and 1,580 homes in the rural portion of the county were damaged or destroyed by flooding.

Florence produced 31 tornadoes over the Carolinas, including 21 rated as EF0 (winds of 65 to 85 mph) and 10 rated as EF1 (86 to 110 mph), occurring on September 15 and 16. Below is a map of tornado tracks covering both days, along with a link to the SPC Historical Severe Weather Database Browser.

To get details on individual Florence-generated tornadoes, click on the tornado tracks on the map below.

To the right is a radar loop of the storm which produced a tornado near Elm City, NC, in Wilson county, in the NWS Raleigh CWA (KRAX radar is located near Clayton, NC). The top right image shows the wind circulation associated with the tornado, with the red indicating outbound (away from the radar) velocities and green indicating inbound (toward the radar) velocities. The characteristic "hook" signature that can suggest the presence of a tornado can be seen on the top left image.

This tornado produced considerable damage in Wilson county, including this tree on a house.

 Max Wind gusts and minimum pressure spreadsheet from NHC Report 

Below is a map of peak wind gusts from Florence, in miles per hour. These gusts were strong enough to uproot numerous trees and cause widespread power outages from the Mid Atlantic through the Southeast coast, including the central and eastern Carolinas.

As of this writing, 41 fatalities have been attributed to Florence in North Carolina. Most were a result of motor vehicle accidents or drownings; medical events during cleanup; and trauma caused by wind or fallen trees.

Florence left a grim mark on this region during and immediately after its arrival, including countless downed trees, limbs, and power lines, and flooding from torrential rain, swollen rivers, and storm surge.

The town of Fair Bluff in Columbus County, NC, along the Waccamaw River, was devastated by Hurricane Matthew in 2016, then hit even harder by flooding from Florence.  With the town's population now down to half of its pre-Matthew level and poverty and joblessness widespread, the  Guardian newspaper wrote an in-depth story  on Fair Bluff and said it could become one of the U.S.'s first "climate crisis ghost towns."

The toll exacted by Hurricane Florence was not limited to just flooding, or the damage to structures and the natural world, or the physical impacts to humans and animals. The weeks after landfall also presented a mental health crisis among young people.  Runkle et al. (2020)  examined trends of those seeking mental health support via a crisis texting platform across North and South Carolina before and after Florence. They found an "immediate and sustained increase in crisis texts" for various mental health concerns, including anxiety/stress (17% increase) and suicidal thoughts (23% increase), in the six weeks after Florence's landfall. Similarly, emergency department visits by young people for any mental health condition in Florence-affected counties increased by 16% after Florence's arrival, including a 33% increase in visits prompted by suicidal ideas. These findings suggest that post-disaster assistance might also need to include increased emotional support and interventions provided by counselors, school personnel, clergy, family, and the mental health care community.

Residents along the Black River were greatly affected by flooding during and long after Hurricane Florence. Prior to Hurricane Florence, river forecasts were not available for the river gage location near Tomahawk in Sampson County.  Local residents relied on word of mouth of river conditions from friends and family upstream and in some cases did not have adequate time to prepare and evacuate the historic flood.  The graph on the right shows the Black River stage (blue line) on September 16, 2018, with no forecast despite river levels approaching major flood stage. The graph below shows the gauge readings a couple of days later, on September 18, with river levels soaring well above previous record levels.

Seeing a strong need for improved services, the National Weather Service in Raleigh worked with the local emergency management office, as well as the North Carolina Department of Health and Human Safety, to identify the need for a forecast, and the Southeast River Forecast Center in Peachtree City, GA, to develop and implement a forecast when high water is expected.  These forecasts began on Wednesday, January 18, 2023, and are an important step in providing advanced notice of flooding to the public and decision makers to help save lives and property.

Hurricane Florence was devastating in countless aspects, and living through a historic event helped us learn a great deal about tropical cyclone forecasting, public messaging of historic impacts, and much more, which resulted in improvements to forecasts, briefings, and increased resilience within our communities.

After the coastal flooding from Hurricane Florence, a need for public awareness of storm surge was identified. These colorful storm surge poles were the answer. Dare County Emergency Management Director Drew Pearson and his staff developed the poles as a way to visually represent what different storm surge levels could look like. Collaboration with the National Hurricane Center led to one of the polls being installed at the front door of NHC, and collaboration on storm surge messaging between Dare County and the National Hurricane Center has improved greatly.

These poles are colored in segments that represent the water levels above ground. Blue represents the lower end of surge, 1-3 feet; yellow represents 3-6 feet, orange means 6-9 feet, and red indicates 9+ feet of destructive storm surge. Next to each pole is a display which features additional information and a legend showing how the colors correspond with NHC's flood inundation map. These poles are an excellent and aesthetically-pleasing way to bring awareness to scale of storm surge and to prompt people to take action and protect their lives and property when a storm surge watch or warning is issued.  Click here for further details on this program via Dare County's YouTube channel.  

"North Carolina is getting hotter, wetter, and more humid. We are approaching the five-year anniversary of Hurricane Florence, a category 1 hurricane that caused unprecedented damage in eastern North Carolina. Florence was a generational storm that turned portions of Interstate 40 into a river and cut most of North Carolina off from the rest of the country.  Five years after Florence, you’ll be hard pressed to find someone in North Carolina who does not acknowledge that the state’s climate is changing. Future hurricanes will be wetter and are likely to be more intense, though it is unknown whether the number of hurricanes making landfall in North Carolina will change. Atmospheric water vapor is the fuel for hurricanes. Increased water vapor in a warmer climate will favor hurricanes that are more intense and that will produce more extreme rainfall. Increased [coastal] flooding, due largely to sea level rise, will disrupt coastal and low-lying communities. By the end of the century, these areas will experience high tide flooding nearly every day and a substantial increase in the chance of flooding from coastal storms."

Additional links:

•  Plotted track of Florence, courtesy of NOAA's Historical Hurricane Tracks 
•  Track details 
•  NHC Report on Florence 
•  Florence Summary from WFO Wilmington, NC 
•  Florence Summary from WFO Newport/Morehead City, NC 
•  Florence Summary from WFO Charleston, SC 
•  Florence Summary from WFO Raleigh, NC 
•  Florence Summary from WFO Blacksburg, VA 
•  Florence from space: Video from the International Space Station, Sept. 13, 2018