Summary by: Kaylin Teneal
TROPICAL CYCLONES
CHARACTERISTICS
- Intense low-pressure systems
- Originate in late summer or autumn over warm tropical oceans.
- Need Coriolis force to from, form between 5 and 20 N and S.
- Moves east to west
- Rotate clockwise in the southern hemisphere and anti-clockwise in the northern hemisphere.
- Source of energy is the large amount of latent heat released as rising warm, moist tropical air
condenses.
- Accompanied by heavy rain, storm surges and high winds.
FACTOR OR CONDITION INFLUENCE ON FORMATION PROCESS
Sea temperature of at least 26 C Heat is needed for convection
High humidity Latent heat is released during condensation
Unstable air Atmospheric instability makes convection possible
Little surface friction Ocean surface allows unhindered movement of air
Light variable winds Strong directional winds inhibit the development
of a vortex, because they reduce both the
temperature of surface water and the production
of water vapour
Air pressure must be low with closed isobars An air pressure of less than 950 hPa at the centre
of the cyclonic system enhances convergence and
rise of air
Divergence of air at upper levels This stimulates circulation and formation of the
vortices
- In the Atlantic Ocean, North of the equator they’re called hurricanes, around Australia they’re
called “willy-willy’s”.
WHERE THEY FORM
- Tropical latitudes.
- Driven by Tropical Easterly winds.
, Summary by: Kaylin Teneal
- Form over warm oceans.
- Eastern side of continents.
FACTORS NECESSARY FOR FORMATION OF TROPICAL CYCLONES
- Warm sea surface
- Coriolis force
- Upper air divergence
STAGES OF DEVELOPMENT
- Formative stage
- Developing stage
- Mature stage
- Dissipation or degenerating stage
NAME AIR TEMPERATURE CLOUD COVER & WIND AREA UNDER
PRESSURE PRECIPITATION INFLUENCE
Formation stage LP system High sea/air Cirrus and cumulus Winds Small area is
develops temperatures clouds and light circulate influenced.
over the and humidity. rain occurs. Tall the LP -
sea. Strong Condensation vertical clouds clockwise
convection. and release of develop. Eye of the in the SH.
Rising air latent heat storm now starts High wind
causes LP. feed system. to take shape. speeds.
There is The LP starts
convergence to deepen.
of air and a
vortex
develops.
Developing/immature Air pressure The vortex Spiral bands of Divergence Storm is still
is contracts and clouds form and of air takes small in size,
stage
decreasing. the storm light rain occurs. place in but a larger
Converging intensifies as Cumulonimbus the upper area is
warm, moist heat continues clouds surround air. High influenced.
air to feed the the eye. wind
continues to system. Wind speeds.
rise. This speeds
leads to a increase with
decrease in more
air pressure evaporation
in the and
TROPICAL CYCLONES
CHARACTERISTICS
- Intense low-pressure systems
- Originate in late summer or autumn over warm tropical oceans.
- Need Coriolis force to from, form between 5 and 20 N and S.
- Moves east to west
- Rotate clockwise in the southern hemisphere and anti-clockwise in the northern hemisphere.
- Source of energy is the large amount of latent heat released as rising warm, moist tropical air
condenses.
- Accompanied by heavy rain, storm surges and high winds.
FACTOR OR CONDITION INFLUENCE ON FORMATION PROCESS
Sea temperature of at least 26 C Heat is needed for convection
High humidity Latent heat is released during condensation
Unstable air Atmospheric instability makes convection possible
Little surface friction Ocean surface allows unhindered movement of air
Light variable winds Strong directional winds inhibit the development
of a vortex, because they reduce both the
temperature of surface water and the production
of water vapour
Air pressure must be low with closed isobars An air pressure of less than 950 hPa at the centre
of the cyclonic system enhances convergence and
rise of air
Divergence of air at upper levels This stimulates circulation and formation of the
vortices
- In the Atlantic Ocean, North of the equator they’re called hurricanes, around Australia they’re
called “willy-willy’s”.
WHERE THEY FORM
- Tropical latitudes.
- Driven by Tropical Easterly winds.
, Summary by: Kaylin Teneal
- Form over warm oceans.
- Eastern side of continents.
FACTORS NECESSARY FOR FORMATION OF TROPICAL CYCLONES
- Warm sea surface
- Coriolis force
- Upper air divergence
STAGES OF DEVELOPMENT
- Formative stage
- Developing stage
- Mature stage
- Dissipation or degenerating stage
NAME AIR TEMPERATURE CLOUD COVER & WIND AREA UNDER
PRESSURE PRECIPITATION INFLUENCE
Formation stage LP system High sea/air Cirrus and cumulus Winds Small area is
develops temperatures clouds and light circulate influenced.
over the and humidity. rain occurs. Tall the LP -
sea. Strong Condensation vertical clouds clockwise
convection. and release of develop. Eye of the in the SH.
Rising air latent heat storm now starts High wind
causes LP. feed system. to take shape. speeds.
There is The LP starts
convergence to deepen.
of air and a
vortex
develops.
Developing/immature Air pressure The vortex Spiral bands of Divergence Storm is still
is contracts and clouds form and of air takes small in size,
stage
decreasing. the storm light rain occurs. place in but a larger
Converging intensifies as Cumulonimbus the upper area is
warm, moist heat continues clouds surround air. High influenced.
air to feed the the eye. wind
continues to system. Wind speeds.
rise. This speeds
leads to a increase with
decrease in more
air pressure evaporation
in the and
