Post-Tropical Cyclone BERTHA
50 Knot Wind Speed Probabilities
- 48 Hours
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About this product:
Note: The time of the tropical cyclone's center location at the bottom of the graphic will
be 3 hours earlier than the time of the current advisory. The forecast cycle for each advisory
begins 3 hours prior to the issuance of the advisory products.
These graphics show probabilities of sustained (1-minute average) surface
wind speeds equal to or exceeding 50 kt...58 mph. These wind speed probability
graphics are based on the official National Hurricane Center (NHC) track,
intensity, and wind radii forecasts, and on NHC forecast error statistics for
those forecast variables during recent years. Each graphic provides cumulative
probabilities that wind speeds of at least 58 mph will occur during
cumulative time periods at each specific point on the map. The cumulative
periods begin at the start of the forecast period and extend through the entire
5-day forecast period at cumulative 12-hour intervals (i.e., 0-12 h, 0-24 h,
0-36 h, ... , 0-120 h). An individual graphic is produced for each cumulative
interval, and the capability to zoom and animate through the periods is provided.
To assess the overall risk of experiencing winds of at least 58 mph at any
location, the 120-h graphics are recommended.
These probabilities will be updated by the NHC with each advisory package for all
active tropical cyclones in the Atlantic and eastern North Pacific basins. While
separate graphics are focused on each individual tropical cyclone, probabilities resulting
from more than one active tropical cyclone may be seen on each graphic.
Additionally, these probability products are available on the National Weather Service's
National Digital Forecast Database (NDFD)
graphical tropical webpage.
The previously provided strike probability product (discontinued after 2005) conveyed the
chances of a "close" approach of the center of the cyclone. However, these new probability
products are about the weather. That is, these cumulative wind speed probabilities provide
the chances that wind speeds of at least 58 mph will occur at individual locations.
The cumulative probabilities can answer the question, "What are the chances that sustained
winds of tropical storm or hurricane force will occur at any specific location?" This can
also help one answer the question, "Do I need to take certain actions to prepare?" A companion
product, the wind speed probability text product, will also be issued and updated with each
advisory package. That product is recommended to more easily assess when winds of each threshold
are most likely to start at any specific location, helping to answer the question, "How long do
I have to prepare?" Overall, these probabilities provide users with information that can enhance
their ability to make preparedness decisions specific to their own situations.
It is important for users to realize that wind speed probabilities that might seem relatively
small at their location might still be quite significant, since they indicate that there is a
chance that a damaging or even extreme event could occur that warrants preparations to protect
lives and property.