Managing the Physical Environment

Weather Hazards

How do storms develop?

What is a tropical storm

• Areas of extreme low pressure

• Form in the tropics over warm water and move towards land

• Energy comes from heat from the ocean

• Called different things around the world e.g. cyclones, typhoons

• Measured by Category: 1 to 5

How do hurricanes form?• Rising warm air rises fast, causing towering clouds, heavy rainfall,

and intense low pressure. The cloud brings heavy rain, thunder and lightning.

• The low pressure sucks in air, causing very strong winds which spiral - clockwise in the northern hemisphere

• In the centre is the eye of the hurricane, about 45 km across (30miles) across. Often there will be no cloud in the eye. Seen from below it will seem calmer, with a circle of blue sky above. The eye is formed because this is the only part of the hurricane where air is sinking.

• In the northern hemisphere, the prevailing easterly tropical trade winds tend to steer hurricanes toward land - although their course is unpredictable. As they move inshore their power gradually reduces, because their energy comes from sucking up moist sea air.

Click here for Hurricane Animation

Click here for an online test

Why are hurricanes a hazard?Strong winds Winds reaching 200km/h are quite common. These windscan tear up vegetation and push over electricity pylons.Buildings may be damaged, and in poorer areas wholetowns can be devastated.Heavy rainfall Heavy rainfall can rapidly increase rive levels and causeflooding. On steeper slopes there is a risk of landslides.Storm surges The low pressure means that sea-level is high. The strongwinds create huge waves, which push towards coastalareas causing extensive flooding.

Case Study: Hurricane GilbertFACTFILE

• 9th-14th September 1988• Lowest pressure ever

recorded• Winds of over 200km per

hour• Waves reached 15m in

height• 328 dead• 500,000 homeless• Billions of dollars of damage

to crops and property

Click here for HurricaneGilbert map showing its

Impacts

The Hurricane devastated St Lucia,

Puerto Rico, the Dominican Republic,

Haiti, Venezuela, Jamaica, Honduras,

El Salvador and Mexico

Case Study: Hurricane GilbertWhy is emergency relief needed after a natural disaster?