HurricanesChapter 13.3

Objectives

• The conditions required for tropical cyclone development

• The life cycle of a tropical cyclone• The dangers of tropical cyclones

Cyclone

• Tropical cyclone– Large, rotating, LOW pressure tropical storm

A.K.A

• Tropical Cyclones have different names depending on where they form

• Pacific Ocean: Typhoon • Indian Ocean: Cyclone• Atlantic Ocean: Hurricane

Requirements for Cyclone Formation

• 1. Abundant supply of warm ocean water• 2. Mechanism to lift the warm air• 3. Minimum wind shear

1st stage of formation

• Formative stage – moving tropical disturbance– Less dense, moist air rises• Rainfall and air circulation

– As air moves to replace low pressure area, coriolis effect takes place• Produces a counter-clockwise rotation of the air• Known as tropical depression (less than 38 mph)

2nd stage of formation

• Mature stage– moving air approaches center, more condensation• more energy

– Air pressure in center continues to drop• Wind speed increases

– 39 to 73 mph• Tropical storm

Mature stage

When a tropical storm intensifies with winds greater than 73 mph it becomes a hurricane

• Eye– Center of storm– Calm and sunny

• Eyewall: surrounds the eye– Strong winds and dense clouds on the edge of the

eye

3rd stage of formation

• Dissipation stage– Moved over land – friction– Moved over cold water • No longer has warm air at the surface to feed it

Tropical cyclone movement

• Move according to wind currents which steer them– Caught up in the high pressure systems that are

present in the tropics– Move west and become caught up in the

westerlies• React with mid-latitude systems• Interaction with many systems make their path

unpredictable

Saffir-Simpson Hurricane Scale

Hurricane hazards• Damage– Mostly caused by high winds– Storm surge• Hurricane force winds carry a mound of ocean water

toward shore