A summary of tropical storms for AQA Geography A-level

1. HayleyPower12I
Tropical StormsResearch
TheNatureof TropicalStorms andTheirCauses
What are they?
 A very intense lowpressure weather system that can last for weeksin the tropical regions
of the planet
 Spinsdue to the Coriolis of the earth’sspin (the earth is widest (40,000 km)atthe equator
andtravels 1,700km/h, however, at60° NorthandSouth ofthe equatorit's only half thesize
so travels halfasfast. This meanswind is deflected rightinthenorthernhemisphere andleft
in the southernhemisphere. This deflection causesthe tropical stormsto rotate).
 They rotate clockwise towardsthe south west inthesouthernhemisphereand anticlockwise
towardsthe northwest inthenorthernhemisphere
 Also knownas Hurricanes (northAmerica), Cyclones (India)andTyphoons (JapanandEast
Asia)
Facts
 In a normalyear over a dozen hurricanesfromoverthe Atlantic ocean
 They head westward towardtheCaribbean, theeast coast of Central America and Southern
USA (especially Florida)
 They can last upto a month
 Travel quite slowly (15mph)
 Wind speedscan reach 75mph
 Mostcommonbetween May andDecember inthenorthernhemisphere
 Mostcommonbetween November andApril inthesouthern hemisphere
Where do they happen?
 A bandthatlies between the tropics of Cancer andCapricorn
 Sea temperature 27°C andabove
 Sea over 60m deep
 Mosteffected area is South East Asia, whichhasaround 26 stormsayear
 Least effected area is India, withonly 2 stormsayear
Naming
 They havebeen named since the early 1950s toavoidconfusionand streamline
communications
 1953: femalenames
 1978: maleandfemale names(Northern pacific)
 1979: aboveadoptedby Atlantic
 Alternate between male and female names
 Go throughthe alphabetrestarting with A at the startof each year (excluding Q, U, X, Y and
Z)

2. HayleyPower12I
Tropical StormsResearch
Why do they happen?
1. Warm, wet air rises andcondensesto from clouds (and heavy rainfall) aswell as a low
pressure zoneon the surface of the water
2. The warm rising air causes the pressureto decrease at higher altitudes. The warm air I under
a higher pressure thanthe cold air somovestowards the space occupiedby the colder air.
The low pressure“sucksin” air from the surroundingswhich also rises, creating more clouds
andrain
3. Air surrounding thelow pressure zone flows in a spiral at highspeeds
4. Air is ejected at the top of the storm(can be 15kmhigh)andfalls to the outsideof the storm,
away from the eye. This reduces the massof the air over the eye, further increasing wind
speeds. Somealso cools, dries andsinks(adding to the low pressure).
5. The faster the wind blows, the lower the pressurein the centre (so the hurricane gets
stronger)
6. Fromabove, hurricanes can be seen as huge circular bodiesof thick clouds about 450km
wide. These clouds bring heavy rain, thunderand lightning
7. In the centre is the eye. Itis about45kmacross. Thereare no clouds, weak winds andlittle to
no wind as cold air is descending
8. As hurricanes moveinshore they lose energy as they can nolonger draw it from the sea and
eventually die
Structure
Eye Eye wall Edge of storm Surrounding area
Calm weather Warm moistair spirals
upwards
Lighter rain and winds Air suckedin
Stormsurge at highest
point
Heavy rain
Strongwinds
Effects
 Primary
 Electricity cables damaged
 Livestock killed
 Coastalhabitatsdamaged
 Flooding
 Buildings, bridges, homesetc. damaged
 Injuries/lossof life
 Secondary
 Shortageof food
 Rise in unemployment
 Diseases spreaddue to shortagesof clean water

3. HayleyPower12I
Tropical StormsResearch
 Emergency services can't get throughdue to blockedroads
 People left homeless
 Psychologicalproblems
Responses
 Before
 Build a sea wall (prevent flooding from stormsurge)
 Evacuate people
 Educate people
 Build onsafe zones
 During
 Emergency services
 Shelters
 Aid
 After
 Rebuildingdamaged buildings
 Makinghomes/buildingsstronger
Case study
 Hurricane Katrina (morelikehurricanetortilla) –see flashcards
Sources
 http://www.coolgeography.co.uk/A-
level/AQA/Year%2013/Weather%20and%20climate/Hurricanes/Tropical%20Storms.htm
 https://www.bbc.com/bitesize/guides/z37wrdm/revision/1