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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.

Watch/Warnings:

The NHC official watch/warning data is an experimental products that the National Hurricane Center is testing during the 2008 hurricane season. Coastal areas placed under tropical cyclone watches or warnings are delimited by specific geographical locations known as "breakpoints" (e.g., a hurricane warning is in effect from breakpoint "A" to breakpoint "B"). This file consists of one or more lines connecting the breakpoints delimiting any current watches or warnings.

Tropical Storm Watch

Tropical Storm Warning

Tropical Hurricane Watch

Tropical Hurricane Warning

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