WHAT DOES THE CONE MEAN

We always see the cone of uncertainty or track cone on the weathercast when a tropical cyclone is being tracked by the National Hurricane Center. This familiar product can be misinterpreted. The cone does not indicate certainty. In fact nothing is certain in meteorology which is why forecasts are expressed in probability. The cone is no different. It represents hurricane track errors average over five years for a specific forecast time. The time periods range from 12 hours to 24 hours and out to 120 hours or 5 days.

Hurricanes stay within the cone 2/3rd of the time. The Hurricane Center has to over warn due to the uncertainty that one out of three times a hurricane will track outside of the cone. Hurricane warnings average 417 miles but an average storm's length of hurricane winds are 100 miles. So the probability of hurricane force winds in a warning will be only 25% of the time.