Learning Objectives:
1) To know the cause of tropical revolving storms
(hurricanes/ typhoons/ willy willies)
2) To understand how they are formed and the
structure and characteristics of a hurricane.
Look at the satellite photo below
1) What is this?
2) Where do they happen?
3) Do they happen in the UK? Why?
Hurricane Katrina, shown in the
satellite image, began life as a
tropical depression near the
Bahamas. As it became more
intense, it was upgraded to a
tropical storm- and then a
hurricane.
Climatic hazard- is a short-term
weather event that is a threat to life
and property.
(Hurricanes, typhoons, cyclones) are particularly powerful tropical revolving storms.
They are intense, destructive, low-pressure weather systems. They have very strong
winds of over 120 km/h (75 mph) and torrential rain (250 mm can fall in one day).
They are intensely powerful storms capable of devastating large areas and causing
considerable damage to property and loss of life. The average lifespan is 7-14 days.
 In summer and autumn when sea temperatures are at their highest
 In tropical regions of severe air instability where air is converging on the surface and
rising rapidly.
Eye- of the hurricane is in the centre of the storm where cooler, denser air sinks down
towards the ground. Conditions are deceptively calm and clear.
Eyewall- on either side of the eye is a towering bank of cloud. It is here that the winds
are usually at their strongest, and where the heaviest rainfall occurs.
Once formed, the hurricane is carried across the ocean by the prevailing winds, generally
from east to west. As it moves it continues to pick up moisture from the sea, becoming
even more powerful. On reaching land the supply of water- the hurricane’s fuel- is cut off
and the storm begins to weaken.
How hurricanes are formed by the Earth’s rotation
http://www.bbc.co.uk/learningzone/clips/how-hurricanes-are-formed-by-earth-srotation/13531.html
How hurricanes are formed
http://www.bbc.co.uk/learningzone/clips/how-hurricanes-are-formed/14082.html
Broken cloud cover
Very large size
Eye wall
‘Eye’ of
the
hurricane
Circular
shape
Anticlockwise
spin
Continuous cloud cover
North west
direction of
movement
The effects of hurricanes
They cause great destruction through:
• Strong winds- with sustained wind speeds in excess of 120kph (75mph) and
gusts in excess of 200kph (125mph). Roofs are blown off houses, power lines
are torn down. Flimsy houses are totally destroyed. The damage to crops could
have long-lasting economic consequences.
• Heavy rainfall- there is potential for huge amounts of rain to fall, often in excess of
200mm. This causes widespread flooding as rivers burst their banks. Landslides may be
triggered in upland regions.
Storm surge- which are rapid rises in sea level, caused by the low pressure and driven by
onshore winds these high sea, often 3m to 5m in height, surge inland over low-lying areas
and up river valleys. A storm flattens everything in its path. It destroys crops and
inundates vast areas with salty water.
Shock- after the storm dies down, people are in a state of shock from social losses
(deaths of relatives and friends. There are also economic losses (damage to homes,
possessions and businesses, loss of crops and animals on farms).
Public utilities- are badly disrupted and life can be very difficult without access to
electricity, telephones, transport and fresh water. Disruption to fresh water supplies,
sewage treatment and waste disposal can lead to serious health problems and the spread
of diseases such as cholera and typhoid.
Political- adverse consequences if the government fails to respond well to the disaster.
Extreme Hurricanes- in rich and poor parts of
the world
Learning Objective:
1) To know two case studies of tropical revolving storms- one from a rich part of the
world and one in a poorer area.
2) To understand the specific storms social, economic and environmental effects
and short and long term responses (monitoring, prediction, protection and
preparation.
‘Oh my God. It was hell. We were screaming, hollering, lights were flashing. It was
complete chaos’ Kioka said. She had to hack through the ceiling of the shop where she
worked as floodwaters rose in New Orleans.
1) What impacts from the photo can you identify that Hurricane Katrina has had?
2) Can you identify where New Orleans in on a blank map of the USA? What do you know
about New Orleans
New Orleans, Louisiana
The National Hurricane Centre in Florida:
• Provides hurricane predictions to the US states and surrounding countries
• Aims to make people more away of the risks they face, and actions to take if the hurricane
hits. They run a Hurricane Preparedness Week every year. In 2010, it ran from 23-29 May
• Offers advice to families, and provides Family Disaster Plans.
The job of the Federal Emergency Management Agency (FEMA) in the USA is to reduce
loss of life and property. It protects people and places by making sure that areas are
prepared for disasters, as well as giving emergency help and aiding recovery.
Protecting New Orleans
The flood defences in New Orleans were left in tatters following Hurricane Katrina’ s
onslaught. However, the levees and floodwalls have been repaired and strengthened,
floodgates have been built and pumping stations improved. The rebuilding and
strengthening work was expected to continue until 2013.
Louisiana has other problems as well as its built defences. Its wetlands are rapidly
disappearing and the wetlands provide barriers which absorb the energy of the storm
surges and protect inland areas. A plan called Coast 2050 aims to recreate the mixture of
swamp, marsh and barrier islands that used to exist in Louisiana, in order to protect
places like New Orleans in the future.
Hurricane Katrina- day by day (causes and consequences- (National Geographic)
http://www.youtube.com/watch?v=HbJaMWw4-2Q
Hurricane Katrina – modelling the consequences
http://www.bbc.co.uk/learningzone/clips/hurricane-katrina-modelling-theconsequences/14075.html
New Orleans levee failures
http://www.bbc.co.uk/learningzone/clips/new-orleans-levee-failures/14081.html
Cyclone aftermath in Myanmar - 05 May 2008
http://www.youtube.com/watch?v=LXAF8AjgiWM
Nargis Cyclone CNN News
http://www.youtube.com/watch?v=H55mFbPdWeM
Track: the path or course of a hurricane.
Responses
• Meteorologists can watch tropical storms continuously thanks to weather satellites;
warnings can be given to evacuate areas.
• Police and fire services can practise emergency drills
• People can be educated in advance about emergency procedures
• Emergency shelters can be prepared with rations of food and water
The behaviour of tropical storms is notoriously unpredictable; they can suddenly become
stronger and change direction.
• Some people are always unwilling to leave their homes and property unattended.
• Others are too poor or do not have the means of transport to move inland out of the
storm’s reach. Theory and reality can be two different things.