While Florence made landfall Friday morning as a Category 1hurricane on the Saffir-Simpson wind scale, "it is a Category 5 heavy rain and inland flooding threat,” said Jeff Masters, meteorology director at the private forecaster Weather Underground.
That is in large part due to its tropical force winds extending 195 miles from its center. “The Saffir-Simpson wind scale is an imperfect ranking of a hurricane’s storm surge threat, since it does not take into account the size of the storm and over how large an area the storm’s strong winds are blowing,” added Masters. He calculated that the total energy of Florence’s large wind field ranked Number Five all-time after Sandy (2012), Irma (2017), Ike (2008) and Katrina (2005).
About 25 million people live in the area likely to be affected by Florence, including two million Hispanics, according to public data.
Florence slowed to a crawl as it neared the coast creating a greater flood risk. Like Harvey last year in Texas, a large portion of the storm’s circulation it likely to remain over water, allowing it to suck up more moisture which will then be dumped over land. Eight months' worth of rain is expected to fall in three days and tides are also be higher this time of year due to the phase of the moon.
The storm is forecast to dump about 18 trillion gallons of rainwater on US soil, most of it in North Carolina, meteorologist Ryan Maue tweeted.
That could break state records in North and South Carolina which is currently 24.06” from Hurricane Floyd of 1999. Thursday advisory from the National Hurricane Center warns of the potential for 40" near the coast of North Carolina and far northeast South Carolina.
It’s worth noting that North and South Carolina have a tendency to flooding. In October 2013, Hurricane Matthew killed 28 people in North Carolina and caused $1.5 billion worth of damage to more than 100,000 homes, businesses and government buildings. The town of Princeville recorded 12 feet of water when the tar River overflowed.
Flooding from historic rainfall in South Carolina’s ‘Low Country’ claimed 17 lives in South Carolina in October 2015 as rivers burst their banks and 13 state dams failed. The state capital, Columbia, had its wettest days on record when about 11 inches of rain fell, the weather service said.