The Physics
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Speed of the Winds in a Hurricane

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Earth Science. Englewood Cliffs, NJ: Prentice Hall, 1987. "If the wind speed is less than 75 mph it is not a hurricane at all and the most severe hurricanes are more than 150 mph" 34–67 m/s
"Hurricanes." World Book Encyclopedia. Chicago, IL: World Book, 1998: 452-456. "Level 1, 74-95 mph
Level 2, 96-110 mph
Level 3, 111-130 mph
Level 4, 131-155 mph
Level 5, 156 mph"
33-42 m/s,
43-49 m/s,
50-58 m/s,
59-69 m/s,
> 70 m/s
Burroughs, William. Weather. Sydney: Weldon Own, 1996. "These winds can reach nearly 200 miles per hour." 89 m/s
Sigda, Robert. Earth Science. New York, 1977. "A typical hurricane has sustained winds of 100–150 mph. Winds in some stronger storms may exceed 200 mph. 44–67 m/s
> 89 m/s
Hurricane Categories. Southern Regional Climate Center. Louisiana Sate University. [see table below] 33–42 m/s
43–49 m/s
50–58 m/s
59–69 m/s
> 70 m/s

A hurricane is a powerful, swirling storm that begins over a warm sea. Hurricanes are graded according to their eye pressure, wind speeds and height. Hurricanes are usually measured according to the Saffir-Simpson scale of one to five. It is now possible to assign a specific hurricane to a category and its category will then determine the precautions needed during the hurricane. Wind speed is the determining factor in the scale.

The Saffir-Simpson Scale. Source: Hurricane Categories
Category Wind Speed Barometric
Storm Surge Damage Potential
75–95 mph
65–82 kts
33–42 m/s
> 28.94 in. Hg
> 980.0 mb
> 97.7 kPa
4.0–5.0 ft.
1.2–1.5 m
minimal damage to vegetation
96–110 mph
83–95 kts
43–49 m/s
28.50–28.93 in. Hg
965.1–979.7 mb
96.2–97.7 kPa
6.0–8.0 ft.
1.8–2.4 m
moderate damage to houses
111–130 mph
96–113 kts
50–58 m/s
27.91–28.49 in. Hg
945.1–964.8 mb
96.2–97.7 kPa
9.0–12.0 ft.
2.7–3.7 m
extensive damage to small buildings
(very strong)
131–155 mph
114–135 kts
59–69 m/s
27.17–27.90 in. Hg
920.1–944.8 mb
91.7–94.2 kPa
13.0–18.0 ft.
3.9–5.5 m
extreme structural damage
> 155 mph
> 135 kts
> 70 m/s
< 27.17 in Hg
< 920.1 mb
< 91.7 kPa
> 18.0 ft
> 5.5 m
catastrophic building failures possible

A mature hurricane consists of bands of thunderclouds spiraling around the center of the storm. The whole storm can consist of hundred of thunderstorms and measure up to 1000 kilometers in diameter. To qualify as a hurricane, a storm must produce winds of over 33 meters per second.

Hurricanes require a special set of conditions, including ample heat and moisture. For a hurricane to form, there must be a warm layer of water at the top of the sea with a surface temperature greater than 27 °C (80 °F). This is why most level five hurricanes occur over warm tropical oceans. It is very hard to predict the track of a hurricane because they are so unpredictable. They may speed up, slow down, or even stop for a while to build up strength. As it travels across the ocean, a hurricane can pick up as much as two billion tons of water a day through evaporation and sea sprays. If the heat released by an average hurricane in one day could be converted to electricity, it could supply the United States' electrical needs for about six months.

Stephanie Stern -- 1999