On Sunday evening, Beaufort County was in the forecasted track of Hurricane Florence.
By Monday morning, it was just outside of the Category 3 storm’s predicted path, known as the “cone of uncertainty.”
That cone is a graphical representation of a storm’s probable track, according to the National Hurricane Center. It uses average forecast errors of the last five years to predict a storm’s path, said Dennis Feltgen of the center.
“Two times out of three it’ll be in that cone,” said Feltgen. “The flip side is one time out of three it won’t be in the cone. We say don’t pay attention to the skinny black line. The storm could hit anywhere within the cone or outside of it.”
The black line and dots forecast the track of the center of the storm at a particular point in time, according to the National Hurricane Center.
The solid white area indicates the storm’s forecast for days 1-3.
The spotted area indicates the forecast for days 4-5, according to the center.
The cone is smaller this year because of continued improvements in forecasting, according to a news release from center earlier this year.
“It’s been shrinking every year,” said Feltgen. “This has been improving each year for the last 20 years as computer models and forecasting have improved.”
Neil Dixon, a meteorologist at the National Weather Service in Charleston, said there is a 67 percent chance that a storm will hit within the cone.
Five days before landfall, there could be a 175-nautical mile difference between the storm’s actual track and the forecast. Four days before, that difference is 150 nautical miles, he said. The potential for error shrinks as the storm inches closer to shore.
At 11 a.m. Monday, Florence was 580 miles southeast of Bermuda, moving west at 13 mph, according to the National Hurricane Center.
The storm may stall and “make some kind of loop,” the National Weather Service told The Island Packet and The Beaufort Gazette previously.
“The storm has a long way to travel,” Dixon said. “It’s going to be undergoing some major changes between now and the next two days. The forecast will become an upper-end Category 4 storm. As these storms intensify, it’s not uncommon for them to change speed and track direction.”
Feltgen said it’s important that people don’t get “hung up on the cone,” and prepare for the possibility of impacts in areas outside of it.
“People think that’s the area where the impacts are going to take place, and that’s not right,” he said. “Impacts are going to occur well outside the cone.”
Those impacts could be felt in Beaufort County, and local and state officials have urged residents to prepare.
On Saturday, S.C. Governor Henry McMaster declared a state of emergency, which allows emergency services and government to prepare for the storm.
No evacuations have been ordered as of Monday morning.