Right below that picture is....

The Mariners' 1-2-3 Rule, or "Danger area", is indicated by shading. The 1-2-3 Rule, commonly taught to mariners, refers to the rounded long-term NHC/TPC forecast errors of 100-200-300 nautical miles at 24-48-72 hours, respectively. The contour defining the shaded area is constructed by accounting for those errors and then broadened further to reflect the maximum 34-kt wind radii forecast at each of those times by the NHC/TPC. The NHC/TPC does not warrant that avoiding these danger areas will eliminate the risk of harm from tropical cyclones. Users operating in the vicinity of these systems are advised to continually monitor the latest Forecast/Advisories from the TPC/NHC and proceed at their own risk. This product also includes areas of possible tropical cyclone formation within the next 36 hours.

Source: National Hurricane Center