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Coastal Watches and Warnings

[Image of storm location, predicted track, and coastal areas under a warning or a watch]
3-Day Forecast Track
(closeup)
[Image of storm location, predicted track, and coastal areas under a warning or a watch]
5-Day Forecast Track

Viewing Tip: Make sure that you've turned off the option in your browser to shrink oversize images to fit in the page as this tends to render the graphics rather poorly.

This display shows an approximate representation of coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow). The orange circle indicates the current position of the center of the tropical cyclone. The black line and dots show the National Hurricane Center (NHC) forecast track of the center at the times indicated. The letter inside the dot indicates the NHC's forecast intensity for that time.

NHC forecast tracks of the center can be in error; the average track forecast errors in recent years were used to construct the areas of uncertainty for the first 3 days (solid white area) and for days 4 and 5 (white stippled area). The historical data indicate the entire 5-day path of the center of the tropical cyclone will remain within the outer uncertainty area about 60-70% of the time. There is also uncertainty in the NHC intensity forecasts. The intensity forecast chart and table below provide intensity forecast and intensity forecast uncertainty information.

It is also important to realize tropical cyclones are not a point. Their effects can span many hundreds of miles from the center. The area experiencing hurricane force (one-minute average wind speeds of at least 74 mph) and tropical storm force (one-minute average wind speeds of 39-73 mph) winds can extend well beyond the white areas shown enclosing the most likely track area of the center. The distribution of hurricane and tropical storm force winds in this tropical cyclone can be seen in the Cumulative Wind Distribution graphic displayed below.



Strike Probabilities

[Image of probability of storm center approaching within 75 statute miles]

This is an experimental product. This display shows the probability, in percent, that the center of the tropical cyclone will pass within 75 statute miles of a location during the 72 hours beginning at the time indicated in the caption. The caption also provides the name of the tropical cyclone and the advisory number from which the probabilities were generated. Contour levels shown are 10%, 20%, 50% and 100%.



Cumulative wind distribution.

[Image of areas affected by tropical storm and hurricane force winds]

This display shows how the size of the storm has changed, and the areas potentially affected so far by sustained winds of tropical storm force (in orange) and hurricane force (in red). The display is based on the wind radii contained in the set of Forecast/Advisories indicated at the top of the figure. Users are reminded that the Forecast/Advisory wind radii represent the maximum possible extent of a given wind speed within particular quadrants around the tropical cyclone. As a result, not all locations falling within the orange or red swaths will have experienced sustained tropical storm or hurricane force winds, respectively.



Wind speed forecast and probability chart.

[Chart of forecast and probable wind speeds]

This is an experimental product. It shows the National Hurricane Center (NHC) maximum 1-minute wind speed forecast as a broad blue line on a chart of wind speed versus forecast period. The narrower lines, labeled 10% and 20% (or 30%), indicate the probability that the maximum wind speed will be some other magnitude than what the NHC has forecast. For example, the cyclone could become stronger than the NHC has forecast, with there being a 10% chance that the wind speed will attain the level indicated by the 10% line plotted above the NHC forecast. The probabilities are based on NHC forecasts from 1988-1997. The data base excludes unnamed tropical depressions. Current advisory information is shown near the bottom of the chart. When applicable, the Saffir/Simpson Hurricane Scale is shown at right. "Inland" is indicated for periods when the cyclone center is forecast to be over land. "Ext" indicates that the NHC forecasts the cyclone to be extratropical at that time.



Wind speed probability table.

[Table of probable wind speed intensity range]

This is an experimental product. The table shows the probability that the maximum 1-minute wind speed of the tropical cyclone will be within any of eight intensity ranges during the next 72 hours. It is based on the outcomes of similar NHC wind speed forecasts during the period 1988-1997. The data base excludes unnamed tropical depressions. NA indicates data not available. TF indicates too few (<10) similar forecasts during 1988-1997 to yield reliable results.


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Page last modified: Tuesday, 14-Sep-2004 21:18:05 MDT