How To Read A Hurricane Chart

By Beth A. Leonard

Understanding the tropical storm forecast charts can help keep you safe.

The minute a tropical storm might even possibly threaten the coast of the U.S., three different weather charts begin appearing across the Internet and being discussed by television weather forecasters. Each chart tells you something different about the pending storm, and taken together they provide a complete picture of the most likely movement and timing of hazardous weather. So le's take a look at them to see what they each can tell us and how to read each.

NHC Track Forecast Cone

What it tells you: The storm center's most likely track and timing, the range of probable tracks, and watch and warning areas.

What you can use it for: Assessing how likely the storm is to reach you, what kind of storm it will be if it does, and when it might happen.

What it doesn't tell you: Exactly how strong the winds are likely to get where you are.

50-knot Wind Speed Probabilities

What it tells you: The probability of 50-knot winds in your area in the 120 hours (five days) after the date and time on the forecast.

What you can use it for: Assessing how likely it is that you will get winds of 50 knots or greater in the next five days.

What it doesn't tell you: Exactly when within those five days you might get those winds.

Variations: Tropical Storm Force Wind Speed Probabilities (34-63 knots/39- 73 mph); Hurricane Force Wind Speed Probabilities (64 knots/74 mph or higher).

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Spaghetti Model

What it tells you: The forecast tracks for the storm from different weather models.

What you can use it for: Determining whether the current forecast has a high or low probability of occurring.

What it doesn't tell you: Exactly where the hurricane is going to track or how strong the winds might be if it reaches you. 


Did You Know?

Hurricane watch: Sustained winds of 64 knots/74 mph or higher are predicted within the forecast area; issued 48 hours in advance of the predicted onset of tropical storm-force winds (34-63 knots/39-73 mph).

Hurricane warning: Sustained winds of 64 knots/74 mph or higher are expected within the forecast area; issued 36 hours in advance of the predicted onset of tropical storm-force winds (34-63 knots/39-73 mph).

For more information visit the BoatUS Hurricane Resource and Tracking Center