1. Tropical Cyclones TROPICAL CYCLONES HURRICANES TYPHOONS
Katrina aiming for New Orleans 27 August 2005
Tropical Cyclones

2. Tropical Cyclones
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms
Tropical Cyclones: Grounds of rotating, low-pressure storms.
cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure

3. Cyclones, Hurricanes, Typhoons
Named according to region where they develops
Cyclones – Develop over the Indian Ocean on warm waters
Hurricanes - Develop over Atlantic and eastern Pacific Oceans
Typhoons – Develop over western Pacific Oceans
All produce similar effects
Eye
Typhoon Odessa, Philippines

4. Developmental Stages Progression: depression storm cyclone
Classified according to wind speeds
Tropical Depression - sustained winds less than 39 m/h
Tropical Storm - between 39 m/h and 73 m/h
Tropical Cyclone - at least 74 m/h

5. Tropical Cyclones Introduction
Tropical cyclones are intense, rotating, low- pressure storms
Develop over warm, tropical oceans
Produce strong winds and heavy rainfall
Can lead to immense flooding
Destructive Winds

6. Formation of tropical cyclones
Tropical Cyclones require to basic conditions to form: an abundant supply of very warm ocean water and some sort of disturbance to lift warm air and keep it rising.

7. Formation of Tropical Cyclones
Warm water generates formation of tropical cyclones
Ocean temperatures must be at least 26.5°C which is warm
Over warm oceans moist, humid air (water vapour)
Warm air moves along the surface
This air converges and rises rapidly
Intense rising of air forms low pressure systems

8. Formation of Tropical Cyclones
As air rises, it cools, becomes saturated and condenses
Water vapour condenses into liquid droplets
Formation of thunderclouds
Condensation releases heat stored in water vapour
This latent heat warms the atmosphere
Air becomes lighter causing strong updrafts

9. Formation of Tropical Cyclones
Air expands and diverges at higher levels
Occurs only where wind speed/direction remain constant (no wind shear)
Air moves in at surface taking the place of rising air
This intensifies convergence
Creates wind and increases rising movement
Builds and progresses into a mature cyclone

10. Coriolis Effect
Spinning of earth on its axis produces wind deflections (Coriolis Effect)
Causes rising air to spiral around center (core)
Spirals with great force
Winds are now rotating, rising and moving in to fill spaces
Wind speeds increase and cyclone grows

11. Coriolis Effect
Northern hemisphere winds are blowing counter- clockwise around center core
Southern hemisphere winds are blowing clockwise around center core

12. The Eye, Eyewall, Rainbands
The Eye - the clear, calm center of storm
Cool air descends into this center (downdrafts)
Eyewall – ring of thunderstorms close to eye
Eyewall produces the most devastating winds
Rainbands – curved groups of clouds and thunderstorms
Rainbands travel away from eye in a spiral motion

13. Storm Surges Occur when tropical cyclones reach land
Storm surge – raised swell of water
60 to 80 km across
Around 2 to 5 meters higher than normal tides
Created by heavy winds and cause flooding

15. WIND PENETRATING BUILDING ENVELOPE
CAUSES OF DAMAGE
WIND PENETRATING BUILDING ENVELOPE
UPLIFT OF ROOF SYSTEM
FLYING DEBRIS
SEVERE WINDSTORMS
STORM SURGE
IRREGULARITIES IN ELEVATION AND PLAN
DESIGN PROBLEMS
FLOODING AND LANDSLIDES

16. AUSTRALIA’S COMMUNITIES
HAZARDS
INVENTORY AT RISK
VULNERABILITY
LOCATION
CYCLONE RISK
ACCEPTABLE RISK
UNACCEPTABLE RISK
RISK
CYCLONE DISASTER RESILIENCE
DATA BASES AND INFORMATION
AUSTRALIA’S COMMUNITIES
PREPAREDNESS
PROTECTION
EARLY WARNING
EMERGENCY RESPONSE
RECOVERY and
RECONSTRUCTION
POLICY OPTIONS
HAZARDS: GROUND SHAKING GROUND FAILURE SURFACE FAULTING TECTONIC DEFORMATION TSUNAMI RUN UP AFTERSHOCKS