Tropical Cyclone Wind Speed probability graphic
In addition to the familiar National Hurricane Center’s (NHC) hurricane track forecast with it’s iconic cone, the NHC also produces a wind speed probabilities graphic which provides probabilities (in percent) that wind speeds of at least 34 kt (39 mph, tropical storm force), 50 kt (58 mph), or 64 kt (74 mph, hurricane force) will occur during cumulative time periods at each specific point on the map. These cumulative probabilities indicate the overall chances that the indicated wind speed will occur at any specific location on the map during the period between hour 0 and the forecast hour.
These cumulative probabilities tell decision-makers the chances that the event will happen at any point on the map within the forecast time period stated. The wind speed probabilities also help users to understand forecast uncertainties, such that they are not surprised by any relatively small changes in the track. This graphic also shows why it is crucial to make proper preparations when a watch or warning is issued for your area, even if the exact track forecast does not go over your area.
Read full explanation here: https://www.nhc.noaa.gov/aboutnhcprobs3.shtml