1

Tropical Cyclonesin the

South-WestPacific

Tropical Cyclones are a natural phenomena that sometimes

threaten people.

2

3

Tropical Cyclones.Tropical Cyclones are known by many

names:

• Typhoons in South-East Asia

• Hurricanes in the Caribbean.

• Tropical Cyclones in the South West Pacific

• These weather patterns are extremely dangerous to humans because in general we live on or near the coast.

• In the South-West Pacific tropical cyclones regularly devastate the social and economic basis of many countries. ie Queensland after Cyclone Yasi

• Most of the smaller Polynesian countries are at risk from Cyclones. Fiji Tonga or Vanuatu.

4

• Category One: Winds 74-95 mph (119-153 kph). Storm surge generally 1-2m above normal. Little damage to buildings.

• Category Two: Winds 96-110 mph (154-177 kph). Storm surge generally 2-2.5m above normal. Some roofing, door, and window damage of buildings.

• Category Three: Winds 111-130 mph (178-209 kph). Storm surge generally 3-4m above normal. Some structural damage to small residences and outside buildings

• Category Four: Winds 131-155 mph (210-249 kph). Storm surge generally 4-6m above normal. External walls fail with some complete roof failures on small houses.

• Category Five: Winds greater than 155 mph (249 kph). Storm surge generally greater than 6m above normal. Complete roof failure on many residences and industrial buildings. Serious flooding.

Category 1 to 5 Cyclones

5

How things work Dept of Interior: Anatomy of a Hurricane

The Processes On the Earth: Simple

Southern Summer:Cyclone Season is December to May

The ITCZ, the wide strip of Calm weather created by rising warm air moves with the sun as far as 15° South (The South Pole is 90° South).Why were they called the ‘Horse Latitudes’.

8

• The warm settled conditions create large amounts of evaporation which rise to become clouds.

• As the warm moist air rises it creates an area of low air pressure beneath it

• This why it is called a Low. (pressure area)• As the warm wet air rises into the atmosphere

cooler air moves in to replace it - it creates wind.• As this wind moves toward the centre of the

Low, the Earth's rotation causes it to spiral (SPIN) in towards the Centre.

• This spiral effect is called the Coriolis Affect.• The closer the wind gets to the Low the faster it

moves.• As the moist air reaches the centre and rises it

condenses (cools) releasing large amounts of (LATENT) heat energy which helps to strengthen the Cyclone.

Processes above the Earth

9Seawater warms to 26°C

Low Pressure

Wind

The Processes On and Above the Earth

EVAPORATION

The difficulty with the Coriolis Effect:even experts struggle…

10

11

Cyclone Zoe

12

The Storm Surge and its effects on a Low Island

Low

The surge can raise the sea level by several metres. Most Low islands are only a few metres above high tide. Even if the surge is not as high as the island, high waves – often over 5 metres can still cover the island. As well as the flood and wind damage the sea can also poison valued fresh ground water supplies.

The Low Pressure allows the sea to rise and appears as a large hump many kilometres across.

A Category 5 Cyclone can raise

the sea level by 6m

13

South Pacific Cyclone

14

Tropical Cyclone Prezi• Construct a Prezi describing the processes which

produce a Tropical Cyclone /Hurricane.

Describe the processes which produce your chosen Hazard.

Time of the YearDec- May Zoe and Ami

Sea Temperature26.0° CCreates evaporation

ITCZMoves South followingThe Sun (Season)Creates warm calm conditions

Low pressureWind Coriolis Effect

Wind Further EvaporationLatent heat Low to Cyclone

1

5

3

2

4

15

Damage caused by Tropical Cyclones.

• The high winds generated within a cyclone can create havoc, causing large amounts of damage to structures such as buildings as well as crops.

• The heavy rainfall associated with a cyclone can cause problems through flooding damaging buildings, roads, bridges, drainage systems and crops.

• The high winds and the heavy rainfall can endanger peoples lives, mainly through drowning, or through injury.

• Storm Surges can destroy structures and drown people.

• Extensive damage can be caused to peoples property and to Public utilities and services.

16

17

The End.

Henry Hollis

Geography Department

Wellington High School

2004