Tropical Cyclones Flashcards
(24 cards)
Other names for tropical cyclones
Hurricanes (US)
Typhoon (SEA)
Cyclones
Willy-Willie’s (Australia)
What are tropical cyclones?
Intense low pressures.
Destructive storms.
Cause considerable loss of life.
Cause damage to property and vegetation.
How are names given to tropical cyclones?
First letter indicates how many cyclones in the area.
Alphabetical order.
Alternating male and female names.
E.g. Eline would be 5th cyclone in the region for the season.
Which season do they occur?
Late summer or autumn.
Warm tropical ocean temperatures at least 26.5 C
Factors necessary for formation of tropical cyclones.
Sea temp at least 26.5 - heat needed for convection
High humidity - latent heat released during condensation
Unstable air - makes condensation possible
Little surface friction - ocean surface unhindered air movement.
Light variable winds - important for development of vortex
Air pressure below 950hPa - enhances convergence and rise of air.
Air divergence in upper levels - stimulates circulation.
Where do they form?
Tropical regions
Over tropical oceans
Further than 5 of Equator
(Need coriolis force for spinning winds- no Corliolus at equator)
Movement
Westward - East to west
Towards high latitudes - Away from equator.
Curve back eastwards at 20 - 30 degrees (unpredictable direction and speed)
Description
Intense low pressure systems, accompanied by heavy rain, storm surfers and high winds, which are extremely destructive.
Stages (4)
Formative
Immature
Mature
Dissipating
Formative stage
Low pressure forms over sea with strong convections/rising air. (High temp and humidity)
Pressure drops rapidly (less than 1000 hPa)
Convergence of air - vortex forms.
Covers small area.
Vortex force winds.
Immature stage
Converging air continues to rise, divergence in upper air.
Pressure in centre drops below 1000 hPa and continues to drop.
Still small, covers larger area.
Hurricane force winds develop.
Mature stage
Pressure reaches lowest point and stops dropping (900-940 hPa).
Size of storm had increased.
Air sinks in centre-known as eye cumulonimbus clouds, with heavy rain, thunder and lightning.
Worst weather in dangerous semi-circle (ie active/front left quadrant in SH)
Dissipating stage
Pressure rises when cyclone reaches land.
Friction weakens coriolis force slowing down rotation and supply of moisture cuts off.
Moves into higher latitudes/cooler waters: cold air enters system (no warm, rising air)
As storm approaches
Hurricane force winds from south in southern hemisphere.
Air pressure decreases.
Very heavy rainfall.
In eye
No wind
No clouds
No rain
Temperature increases
Lowest air pressure
As storm moves away
Wind changes to north in SH
Storm to hurricane force winds
Air pressure increases
Heavy rainfall.
Environmental consequences
Erosion due to heavy rain and flooding.
Flooding of islands, low lying areas and coastal areas.
Accelerated coastal erosion, forests damaged, water polluted.
Dangerous conditions on sea due to large waves and strong winds.
Economic consequences
High energy storm waves cause damage to shipping.
Loss of livestock and crops on farms - food shortages.
Buildings and infrastructure damage
Business close, prices increase, loss of income, cost of repairs, insurance claims.
Social consequences
Human injury, disease and death.
Property and cars damaged - people displaced and homeless.
Isolation due to communication structures that are destroyed.
Shortage of fresh water, water courses contaminated, diseases.
Food shortages.
How to prepare for tropical cyclone?
Secure your home - close shutters, brings items indoors.
Listen to radio or TV for information.
Avoid using phone except for emergencies as it clogs the networks.
Fill car with petrol - ready to evacuate if needed.
Ensure supply of water for sanitary purposes - fill bathtub or large containers.
Stockpile non-perishable foods as there won’t be power.
Conditions to evacuate?
Mobile home or temporary structure.
High rise buildings - hurricane winds stronger at higher elevations.
If you live on the coast, floodplain, near a river or on island waterway.
Move to higher ground.
If unable to evacuate?
Stay indoors away from windows and glass doors.
Close interior doors, secure and brace external doors.
Keep curtains and blinds closed.
Avoid elevators.
Strategies to prepare and manage effects of tropical cyclones
Good weather forecasts
Early warning systems
Medical and rescue services on the alert
Build houses of strong materials
Evacuation procedures must be known
Stay indoors
How to recognise tropical cyclones on synoptic weather maps
TC symbol in the middle
Low pressure cell
Circular isobar patterns
East coast
Name of cyclone
Clockwise rotation
Date - late summer/ autumn
Weather stations: overcast clouds, rain/thunderstorms, strong winds
