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No responsibility is assumed by the National Oceanic and Atmospheric Administration or WeatherOnline Ltd. in the use of these data.
It is important to realize that a tropical cyclone is 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 areas shown enclosing the most likely track area of the center.

Potential Day 1-3 Track:

Track (large Points):

The points represent the official NHC forecast locations of the center of a tropical cyclone. Forecast center positions are given for projections valid 12, 24, 36, 48, 72, 96, and 120 h after the forecast's nominal initial time, provided that a closed surface wind circulation is expected to exist at the forecast projection time.

The letter inside the dot indicates the NHC's forecast intensity for that time:

D: Tropical Depression – wind speed less than 39 MPH
S: Tropical Storm – wind speed between 39 MPH and 73 MPH
H: Hurricane – wind speed between 74 MPH and 110 MPH
M: Major Hurricane – wind speed greater than 110 MPH

It is important to remember that tropical cyclone track forecasts are subject to error, and that the effects of a tropical cyclone can span many hundreds of miles from the center.

Track (Lines):

This product will aid in the visualization of an NHC official track forecast, the forecast points are connected by red line segments. The track line(s) are not a forecast product, however, and because there are an infinite number of ways to connect a set of forecast points, the lines should not be interpreted as representing a specific forecast for the location of a tropical cyclone in between official forecast points. It is also important to remember that tropical cyclone track forecasts are subject to error, and that the effects of a tropical cyclone can span many hundreds of miles from the center.

Cone:

The cone represents the probable track of the center of a tropical cyclone, and is formed by enclosing the area swept out by a set of circles along the forecast track (at 12, 24, 36 hours, etc). The size of each circle is set so that two-thirds of historical official forecast errors over a 5-year sample fall within the circle. Based on forecasts over the previous 5 years, the entire track of a tropical cyclone can be expected to remain within the cone roughly 60-70% of the time. It is important to note that the area affected by a tropical cyclone can extend well beyond the confines of the cone enclosing the most likely track area of the center.

Best Track:

Small Points:

The NHC working best track is an experimental product that the National Hurricane Center is testing during the 2009 hurricane season.

The working best track is a subjectively-smoothed representation of the tropical cyclone's location and intensity (maximum 1-minute sustained surface wind speed and minimum sea-level pressure) at 6 hour intervals over its lifetime. The working best track may not exactly match the information contained in the real-time storm advisories because the data in a working best track are subject to modification during the life cycle of the cyclone.

(Note: The "working best track" represents the forecasters' best estimates of the location, intensity, and size of a tropical cyclone while the cyclone is ongoing. After the life cycle is complete, forecasters prepare a "final best track", using data that might not have been available operationally, and it is the final best track that represents NHC's official historical record for the cyclone.)

d: Disturbance
L: Low
D: Tropical Depression – wind speed less than 39 MPH
S: Tropical Storm – wind speed between 39 MPH and 73 MPH
H: Hurricane – wind speed between 74 MPH and 110 MPH
M: Major Hurricane – wind speed greater than 110 MPH