Tropical Storm Force Experimental Probabilities - 120 Hours

These displays show experimental probabilities of surface wind speeds equal to or exceeding 34 kt...39 mph (tropical storm force), 50 kt...58 mph, or 64 kt...74 mph (hurricane force). These wind speed probabilities are based on the official National Hurricane Center (NHC) track, intensity, and wind structure forecast, and on NHC error statistics for those forecast variables during recent years. Each graphic provides probabilities that wind speeds of at least 39, 58, or 74 mph will occur during cumulative time periods at each specific point on the map. The cumulative periods extend into the 5-day forecast period at 12-hour intervals (i.e., 0-12 h, 0-24 h, 0-36 h, ... , 0-120 h). An individual graphic is produced for each interval, and the capability to animate through the periods is provided. These experimental probabilities are intended to be provided by the NHC with each advisory package for all tropical cyclones in the Atlantic and eastern North Pacific basins. However, due to the experimental status of these products, they may not always be timely or even available. While separate graphics are centered on each individual tropical cyclone, probabilities resulting from more than one active tropical cyclone may be seen on each graphic. The existing strike probability product (in Atlantic only) is a statement about the "close" approach of the center. However, this new experimental probability product is about the weather. That is, these wind speed probabilities provide the chances of wind speeds equal to or exceeding familiar thresholds (e.g., tropical storm force, hurricane force) at individual locations. Therefore, the probabilities have more direct meaning and impact to users. These probabilities have the potential to provide users with information that enhances their ability to make preparedness decisions specific to their own situations. These new wind speed probability products could become operational in 2006 and replace the (Atlantic) strike probability text and graphics programs which would then be discontinued. It is important for users to realize that probabilities that may seem relatively small may still be quite significant, since they indicate there is a chance that a damaging or even an extreme event may occur that warrants preparation to protect lives and property.