Tropical Cyclones (Unit 7)(pg. 88) - Climate & Weather

is a TC high or low pressure? what pressure is found?

• low pressure

• below 990hPA

how are TC’s named?

alphabetically (using female names until recently)

when do TC’s develop? (2)

in late summer and early autumn when ocean temperatures are warm

what temperature must oceans be to be considered warm?

27°C or above

where do TC’s occur?

between 5-20° N/S

in what direction do TC’s travel?

westerly direction (E to W)

describe the wind speeds of a TC

steep pressure gradient & strong cyclonic winds

describe the size of TC’s, specifically the vortex and eye.

• massive

• -vortex is 600-800km

• eye is 30-50km

how is the air in the eye and how does it function?

• there is dry air

• dry air descends & warms adiabatically

comment on the predictability and speed and direction

• it is predictable but erratic

describe the weather experienced by TC’s

violent and damaging storms

what direction do they rotate in the SH?

clockwise

what conditions must be present for SA to be affected?

a cyclone must move through the Mozambique Channel only then SA is affected

what weather does the interior face?

dry weather with subsiding air around the outer side of the cyclone

what provinces are affected by bad weather due to TC’s (3)

Limpopo (Northern Province), Mpumalanga and KwaZulu Natal

describe the bad weather that the three provinces experience (3)

destructive winds, torrential rain with a risk of floods

what is Limpopo referred to as?

Northern Province

what five factors are necessary for formation? give reasons

• a warm ocean as the air above is unstable and sustains convection currents

• the cooling of rising, moist air and condensation as it allows for the release of latent heat which powers the cyclone

• high humidity because the storm draws energy from the evaporation of ocean water, releasing latent heat during condensation

• low amounts of wind shear so that a vortex can form

• the presence of Coriolis Force which deflects winds in the LP cell

name the steps of TC formation

1. Initial stage

2. Developing stage

3. Mature stage

4. Decaying stage

what happens during the first stage (1)

• air converges towards the LP to form a vortex

what happens during the second stage (5)

• intensity increases as the air continues to converge and rise at the LP

• divergence occurs in upper atmosphere

• the pressure continues to drops leading to wind speeds increasing

• eye begins to form with Cb clouds creating a vortex

what happens during the third stage (5)

• maximum intensity has been reached

• strong pressure gradient & winds (exceeding 120km/h)

• pressure continues drop

• eye is fully develop - clear and calm

• heavy rain, thunder and lighting

what happens during fourth decaying stage (4)

• dissipates when it reaches land and temperate ares

• cooler air enter system system, increasing pressurge

• winds are reduxed by friciton with land

• dry air enter system, reducing condensationand lamount of enegry

what is the first stage also known as?

tropical low

what is the two stage also known as?

tropical storm

what is the third stage also known as?

tropical cyclone

what weather is associated with TC? (5)

1. Very heavy rain 🌧

2. Very strong winds 💨

3. Low pressure at the centre

The “eye” of the cyclone:

• Winds are light

• Little or no rain

draw a cross section of a TC

what temperature is experienced in Vortex 1 (V1)

it is around 21⁰C and drops as Vortex 1 approaches

what pressure is experienced in Vortex 1 (V1)

drops when it approaches vortex to around 990hPa

what wind speeds are experienced in Vortex 1 (V1)

increases with maximum speeds being reached at eye wall

what weather intensity is experienced in Vortex 1 (V1)

maximum rainfall experienced at eye wall of vortex with there hail, thunder and lighting

what temperature is experienced in Eye

lowest by walls and rises in the around 14⁰C

what pressure is experienced in Eye

lowest in the eye

what wind speeds are experienced in Eye

suddenly drops and calm

what weather intensity is experienced in Eye

rain stops and weather is calm and clear

what temperature is experienced in Vortex 2 (V2)

as vortex approaches the temperature drops then slowly rises to around 22⁰C

what pressure is experienced in Vortex 2 (V2)

increases as Vortex 2 approaches around 1006hPa

what wind speed is experienced in Vortex 2 (V2)

brings extremely strong winds when it arrives

what weather intensity is experienced in Vortex 2 (V2)

torrential rain as the vortex nears which gradually ceases as the vortex moves over

what causes the destruction from TC’s (2) and what does it result in?

• wind force and storm surges

• cause a rapid rise in sea levels near the sea wall and large waves due to onshore winds

what type of damage is experienced?

• major damage and destruction as beaches and houses are washed away and damaged

how are LEDC’s affected and how do they prepare?

• worst affected

• insufficient warning systems and poorly built infrastructure

how are MEDC’s affected and how do they prepare?

• better prepared

• warning systems in place giving them time to prepare adequately

what is a storm tide

actual sea level as influenced by a weather disturbance

what is a tide

the alternate rising and falling of the surface of the ocean

how to identify TC on synoptic map?

1.) LP in circular isobars

2.) between 5°N/S

3.) steep pressure gradient

4.) summer/early autumn

5.) visible eye symbol

6.) name of cyclone on map

what are five impacts of TC’s?

1.) Loss of homes

2.) Drowning

3.) Disease outbreaks

4.) Financial strain on people

5.) Damage to infrastructure

name some preparation strategies (3)

• listen to radio, read newspapers and watch TV to stay informed

• store water and canned food

• early warning systems

name some management strategies (2)

• board up windows

• place sandbags at doors

name things emergency service should do(4)

• siren warning

• evacuation plans

• mobilise relevant emergency services\

• prepare shelters for displaced people

what are other names for a TC? (4)

• hurricane

• Willy Willies

• typhoons

• cyclones

what are TC’s steered by?

tropical easterlies