Instead, Hurricane Florence’s peak winds were around 90 mph when it made landfall near Wrightsville Beach, North Carolina September 14. But the storm’s agonizingly slow movement at two or three mph—a person could have walked inland about as fast as Florence moved—allowed it to dump unprecedented rainfall and gave it plenty of time to push a storm surge of about 11 feet up the Cape Fear River and into downtown Wilmington.

Meteorologists say the overall forecasting for Hurricane Florence was very accurate. But the inability to forecast the storm’s last-minute weakening underscores the extreme difficulty of predicting what a massive engine of wind and water is going to do at any given moment. It’s a problem that’s been a puzzlement for