HurricanesHurricanes

Chapter 3 Sections 2Pages 88-91

Chapter 3 Sections 2Pages 88-91

How Hurricanes Form

• Begins over warm water as a low-pressure area, or tropical disturbance

• If it grows in size and strength it becomes a Tropical Storm– Continued growth and it becomes a

Hurricane.

Hurricanes

• A tropical storm that has winds of 119km/h or higher

• Typically 600km in diameter• Usually last a week or longer

• Hurricane season lasts June 1 – Nov 30– Indian Ocean: Cyclone– Western Pacific: Typhoon.

How Hurricanes Form

• A hurricane gets energy from warm, humid air at the ocean surface

• As the air rises, and forms clouds, more air is drawn in

• Winds spiral inward towards the area of Low Pressure.

How Hurricanes Form

• Inside the storm:– Bands of heavy rain– high winds up to 320km/h– The lowest air pressure– Warmest temperature.

• The lower the pressure– The stronger the winds blowing towards the

center.

Exit Pass

What gives energy to / fuels a hurricane? What causes a

hurricane to lose strength and dissipate?

• Hurricanes travel in the direction of the global winds

– In the Atlantic Ocean are steered by the Trade Winds to the East

• Once it passes over land, the warm, moist air from the ocean is cut off

– The hurricane slows down– Loses strength– Leaves heavy rainfall behind.

How Hurricanes Move

A ring of clouds surrounding a quiet “Eye,” the hurricane’s center

Winds get stronger as the eye approaches and “reverse” when it passes by

Weather in the Eye– Calm– Clear sky.

The Eye of the Hurricane

Storm Surge

• A “dome” or wave of water that comes on shore with the hurricane

• Formed by the high winds (push the water) and the low pressure (water level rises) – Up to 6m (20ft) above

sea level.

Hurricane Damage

• Hurricanes uproot trees, smash buildings, and destroy power lines

• Heavy rains flood roads.

CategoryWind Speed

(mph)Wind Speed

(kmh)Damage at

LandfallStorm Surge

(feet)

1 74-95 119-153 Minimal 4-5

2 96-110 154-177 Moderate 6-8

3 111-130 178-209 Extensive 9-12

4 131-155 210-250 Extreme 13-18

5 Over 155 251+ Catastrophic 19+

Hurricane Safety

• Hurricane Watch means conditions are possible with in the next 36 hours– Evacuate or move away temporarily

• A hurricane warning means conditions are expected within 24 hours– Leave immediately!

Hurricane Safety

• Advances in communications and satellites have made tracking hurricanes easier, and therefore less deadly

• Stay near interior of building, away from windows

• Plan for flooding.

Exit Pass

What causes a Storm Surge to form?