Geography climatology:
Tropical cyclones
Tropical cyclone: A low pressure cell that develops over warm oceans between
the tropics.
Names of tropical cyclones: The first letter of the name tells us how many
cyclones have occurred that year.
Areas where tropical cyclones form:
Tropical cyclones occur between 30 degrees South and 30 degrees North
Latitude.
They do not occur between the equator and 5 degrees n and s because they
depend on Coriolis force for formation. Coriolis force is 0 at the equator.
Tropical cyclones usually occur on the Eastern side of continents. These seas on
the East are warmed by warm ocean currents.
Factors necessary for formation:
1. Hot moist air: Tropical cyclones develop at the ICTZ where there is hot moist air
from the tropical easterlies. ITCZ: intertropical convergence zone, region where
two sets of tropical easterlies meet.
2. Intense low-pressure cell: Hot air starts rising and forms an intense low-pressure
cell on the surface.
3. Coriolis force: Deflection of winds, causes wind to spiral towards low pressure.
This causes the eye to form. Eye: The calm area at the centre of a tropical
cyclone.
4. Season- late summer early autumn.
5. Latent heat- Evaporation - condensation
6. Steep pressure gradient
Stages of development:
1. Formative/initial stage: No clear eye, winds start spiralling, gale force winds,
pressure above 1000 hPa.
2. Immature stage: pressure is below 1000 hPa, hurricane strength winds, in area
30-50km from the eye.
3. Mature stage: Pressure gradient is very strong, hurricane strength winds, as far
as 300km from the eye, calm clear well-developed eye, pressure gradient is well
below 1000 hPa, moves SW direction.
4. Degenerating/dissipation stage: winds slow down- friction with the land, drier
air system-less condensation-less energy, cyclone moves into sub-tropical area
where pressure increases. Pressure rises. Eye is visible.
Tropical cyclone characteristics:
Move from east to west
Turn east at 30 degrees.
Tropical cyclones
Tropical cyclone: A low pressure cell that develops over warm oceans between
the tropics.
Names of tropical cyclones: The first letter of the name tells us how many
cyclones have occurred that year.
Areas where tropical cyclones form:
Tropical cyclones occur between 30 degrees South and 30 degrees North
Latitude.
They do not occur between the equator and 5 degrees n and s because they
depend on Coriolis force for formation. Coriolis force is 0 at the equator.
Tropical cyclones usually occur on the Eastern side of continents. These seas on
the East are warmed by warm ocean currents.
Factors necessary for formation:
1. Hot moist air: Tropical cyclones develop at the ICTZ where there is hot moist air
from the tropical easterlies. ITCZ: intertropical convergence zone, region where
two sets of tropical easterlies meet.
2. Intense low-pressure cell: Hot air starts rising and forms an intense low-pressure
cell on the surface.
3. Coriolis force: Deflection of winds, causes wind to spiral towards low pressure.
This causes the eye to form. Eye: The calm area at the centre of a tropical
cyclone.
4. Season- late summer early autumn.
5. Latent heat- Evaporation - condensation
6. Steep pressure gradient
Stages of development:
1. Formative/initial stage: No clear eye, winds start spiralling, gale force winds,
pressure above 1000 hPa.
2. Immature stage: pressure is below 1000 hPa, hurricane strength winds, in area
30-50km from the eye.
3. Mature stage: Pressure gradient is very strong, hurricane strength winds, as far
as 300km from the eye, calm clear well-developed eye, pressure gradient is well
below 1000 hPa, moves SW direction.
4. Degenerating/dissipation stage: winds slow down- friction with the land, drier
air system-less condensation-less energy, cyclone moves into sub-tropical area
where pressure increases. Pressure rises. Eye is visible.
Tropical cyclone characteristics:
Move from east to west
Turn east at 30 degrees.
