But the technical forecasting for the storm, he said, was better than average given the current state of the science. “The models did very well with this,” Dr. McNoldy said. As he explained, “A hundred miles is the difference between the east coast and the west coast — but a hundred miles in a three-day forecast is really good.” With such a skinny state, he said, small shifts in the storm track within the broad cone of probability meant the difference between running up the east coast or the west, with nothing in current technology capable of saying with more certainty which coast it would be.
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Many people trying to use forecasts like those provided by the National Hurricane Center, however, do not fully understand the cone of probability and focus instead on the line that runs down the middle, taking it as an accurate prediction of the storm’s path. J. Marshall Shepherd, an atmospheric scientist at the University of Georgia, explained the fallacy in a Facebook post. “Anywhere in that cone is a possibility,” Dr. Shepherd wrote, “and it has always been a challenge communicating what the cone ‘means’ versus what people ‘think’ it means.”