The National Hurricane Center is making changes to its "cone of uncertainty" based on an improving forecast record. The cone is designed to show people where the center of a storm is likely to head. The size of the tropical cyclone track forecast error cone for the Atlantic basin will be smaller this year, but a little larger at the longer forecast times in the East Pacific, the NHC said on Monday. The Hurricane Center calculates the cone by using the previous five-year record of forecast errors and it is drawn to reflect at least two-thirds of the inaccuracies.