The National Hurricane Center plans to shrink the “cone of uncertainty” during the upcoming season based on an improving forecast record. The Miami-based center made other changes including extending warnings and watches to 72 hours in advance of a storm, providing a full additional day to prepare. The forecast cone is calculated using the previous five-year record of forecast errors and provides a probable track about two-thirds of the time. Improved forecast tracks in recent years have allowed forecasters to narrow the cone. The center is also looking at how it issues warnings as part of a 10-year effort to improve intensity forecasts.