Chapter 2 Flashcards
Tropical cyclones
Alternate names
o Hurricanes
o Willy Willies
o Typhoons
o Cyclones
General Characteristics
o Shown by circular isobars enclosing intense low pressure
o Moves westwards
o Steered by tropical easterlies
o Diameter: 300-500 km
o Follows erratic paths; unpredictable
Conditions for formation
o Temperature above 27C (For high evaporation)
o Warm air rising; unstable atmospheric conditions (For convection)
o Latitude between 5-25 N/S (Coriolis force is strong)
o Calm conditions (Wind will not allow vortex to form
o Upper air divergence (To maintain LP centre)
Stages in formation
o Initial
* Centre pressure above 1000 mb
* Isobars far apart
* Gale force winds
* Cirrus and cumulous clouds
o Immature
* Pressure drops below 1000 mb
* Eye forms
* Wind reaches hurricane strength
* Diameter 100 km
* Cumulonimbus clouds around the eye
o Mature
* Centre pressure well below 1000 mb
* Isobars very close together
* Diameter between 300-500 km
* Dangerous semicircle: effects of intense winds combine with force of cyclone moving
forward (bottom left).
o Dissipating
* Centre pressure rises above 1000 mb
* Occurs when cyclone: Encounters land
Moves over cold oceans
Weather associated with tropical cyclones
o As storm approaches:
* Cumulous clouds
* rain
* windy
* cumulonimbus clouds
* dangerous semicircle: torrential rain and hurricane winds
o Eye:
* Calm
* Cool
* Clear
Impact of tropical cyclones:
o Flooding
o Storm surges
o Crop losses
o Transport disrupted
o Silt in dams
o Ecosystems disrupted
Precautionary and management strategies:
o Stock up water and canned food
o Keep first aid kit
o Keep livestock on higher ground
o Sandbags on river banks
o Evacuation plans
o Early warning systems
Tropical cyclone
A low pressure cell that develops over warm oceans between the tropics.
ITZC
The Inter Tropical Convergence Zone; a region in the tropics where the two sets of tropical easterlies meet.
eye
The calm area at the center of a tropical cyclone
latent heat
‘Hidden’ heat energy that is given out when water vapour condenses.
Storm surge
Bulge of seawater caused by strong winds blowing during a tropical cyclone.
Adiabatic
Temperature change due to change of height and pressure.
Why do tropical cyclones die out rapidly when they reach the land?
- the winds are slowed down by friction with a land surface rather than a sea surface.
- drier air enters the system, which reduces the amount of condensation and therefore the amount of energy
- the cyclones also move into cooler subtropical areas and the air pressure increases, rainfall continues for a few days and then the weather clears up.
