The outer bands of Hurricane Florence reached North Carolina Thursday as officials continued to warn of the damaging nature of the monster Category 2 storm.

Florence remained a serious threat, packing maximum sustained winds of 105 miles-an-hour Thursday afternoon with hurricane force winds extending 80 miles from the center. And when it comes to impacts like storm surge, size matters just as much as the winds, says Rick Luettich, a coastal physical oceanographer at University of North Carolina Chapel Hill’s Institute of Marine Sciences.

“A weak Category 3 and a strong Category 2 are pretty close to each other, if you just think about category. But they may not be that much different in terms of wind speed,” said Luettich.

Luettich and colleagues at the University of Notre Dame and University of Texas spent 30 years developing ADCRIC, a computer model that gauges storm surge and other impacts of major coastal weather events.

Storm surge is caused in part by the brunt of hurricane force winds. Like a giant hair dryer, these winds push seawater into low-lying marshland and delta areas.

ADCIRC predicts Florence’s winds will cause 9 to 13 feet of storm surge in some areas along the North Carolina coast. But while the storm is predicted to pass near Wilmington, North Carolina, the majority of surge-related flooding will actually be to north near Pamlico Sound.

Those surges alone are projected to cause inland flooding of more than 9 feet in cities like New Bern, North Carolina, even without the expected 15 to 20 inches of rain. But Luettich said it is still not well understood how factors like rain accumulation and land saturation affect river and coastal flooding during major storm events. That makes it difficult to project how the region will ultimately be affected.

The National Weather Service forecasts minor to major flooding along rivers anywhere from the Carolinas to Maryland in the coming days. But it will be a few years before this river data can be integrated into models like ADCIRC, according to Ed Clark, the director of NWS’s National Water Center. His group, the Office of Water Prediction and Luettich’s team are working together to build such models now.

In the meantime, “treat the inland flooding just as seriously as you would the storm surge,” said Clark. “Remember that floods will occur in places that do not receive a hurricane or even tropical storm level winds. All across the state of North Carolina and portions of South Carolina, there will be extreme flooding or major flooding at least for a number of days to come.”

Flooding risks are also causing worries over the more than 300 wild horses living on North Carolina’s coasts.

Because most are managed as wild animals, many of the horses will be left to fend for themselves, said Paula Gillikin of the North Carolina Coastal Reserve. Her team manages 32 wild horses living in the Rachel Carson Reserve near Beaufort, North Carolina.

“The vast majority of the time the horses know what to do, and they are able to get to higher ground or protect themselves,” said Gillikin.

Still, a storm surge can overwhelm the animals, as it did in 2003 when Hurricane Isabel killed five horses and swept three others a few miles away. The latter had to be relocated back to the reserve after the storm.

“There definitely is a risk, but the horses are smart. And the vast majority of the time they are OK,” she said.

Gillikin says the North Carolina Coastal Reserve stands ready to respond with whatever resources they can to help any animal suffering after the storm.