Learning objective: To be able to describe the distribution of hazards

Map from memory In groups of 4 Number yourselves between 1 and 4 When your number is called you may come and see the image Recreate the image on your own map Consider what information is important to your diagram.

Use p 71 Sketch on your map the distribution of tropical storms.

What are the characteristics of tropical storms?

Describing distribution Can you see patterns or do they occur randomly? Do they occur on land or in the sea? Which continents can you identify? Are they north or south of the equator? What is the latitude? – degrees north and south of the equator e.g. the tropic of cancer is 23o north

Distribution of tropical storms

Use your skills to analyse this photograph Lesson objectives: To describe the characteristics and causes of tropical storms Use your skills to analyse this photograph

Characteristics? – what do we already know? What are typhoons like?

Location Tropical storms are normally found between the tropics near the Equator. The formation of tropical storms is not fully known, but scientists do know that they draw their energy from warm seas.

High winds High Winds : In severe tropical storms the maximum sustained winds can approach 200 km/h with short period gusts closer to 300 km/h. Such violent winds can devastate natural vegetation and all but the strongest man-made structures.

Flooding Heavy rainfall is associated with tropical storms. Heavy rainfall actually causes much more damage and deaths than high winds.

Landslides Landslides are a secondary hazard. Landslides can be triggered when large amounts of rainfall saturate the ground increasing the stress on the slope.

Storm surges  Tropical storms moving in land can create storm surges and big waves. If tropical storms coincide with spring tides the impacts can be severe

Measuring tropical storms Saffir Simpson Scale Storms below 74mph (119kph) are described as only tropical storms. Anything above this speed is officially a hurricane/cyclone/typhoon.

Weather – some basics Air Pressure Simply the weight of air pressing down onto the surface of the earth. When air is warm it normally rises and creates an area of low pressure. When it is cool it sinks and creates an area of high pressure. Pressure is measured on a barometer. It is normally measured in millibars (mb).

Wind Wind is created by air moving from areas of high pressure to areas of low pressure. This can happen on a local scale or on a global scale

Condition 1 Sea surface temperatures must be over 26 degrees centigrade

Condition 2 Distance from the equator must be at least 5o north or south of the equator The Coriolis force is at a maximum at the poles and a minimum at the equator Hurricanes can not form within 5 degrees latitude of the equator. The Coriolis force generates a counterclockwise spin to low pressure in the Northern Hemisphere and a clockwise spin to low pressure in the Southern Hemisphere.

Condition 3 Low wind shear This is especially important in the upper levels of the atmosphere Wind shear is a change in wind speed with altitude Strong winds at upper altitudes destroy thunderstorms by limiting the upward movement of the air.

Formation of tropical storms http://ih-igcse-geography.wikispaces.com/3.2+Characteristics%2C+distribution+and+causes+of+tropical+storms

The Coriolis effect

Formation of tropical storms \

Questions Why do hurricanes / typhoons / cyclones form close to the equator? Why are there strong winds during a typhoon? Why is there heavy rain during a typhoon?