Storm Hazards Flashcards
What is air pressure?
The amount of pressure the air puts on the earth or sea’s surface
What type of pressure does warm air have and why?
Warm air rises and therefore creates low pressure.
What type of pressure does cold air have and why?
Cold air sinks and therefore creates high pressure.
How are winds created?
They are created as air moves from areas of high pressure to areas of low pressure
What directly informs the weather and climate patterns that exist?
Heat from the equator is redistributed by the atmospheric and oceanic circulation systems
What causes the global energy balance?
There is a surplus of energy at the tropics and a deficit in polar areas.
How is the global energy balance maintained?
Atmospheric and oceanic circulation move energy from areas of surplus to areas of deficit.
Where are the areas of surplus located?
Between 38 degrees North and South
Where are areas of deficit located?
Above 38 degrees North and below 38 degrees South
What does the three cell model show?
Atmospheric circulation
What are tropical revolving storms?
Low-pressure weather systems that develop in the tropics
How wide do these storms tend to be?
2200-700km in diameter
Where do tropical revolving storms begin?
In areas of low pressure resulting from surface heating and warm air being drawn in in a spiral
How do tropical storms develop?
They start off as small-scale disturbances before evolving into tropical depressions with their own rotating wind systems.
What sea temperature is required for a tropical revolving storm to form?
27 degrees C
Why do oceanic temperatures need to be warm?
To provide a continuous heat source so that rising air currents can be maintained.
How deep does the ocean need to be?
A least 70m
Why does the ocean need to be deep?
Moisture is released by the storm in the form of condensation and so the ocean provides a source of moisture to drive the storm
Why does a tropical revolving storm have to form in a specific location?
So that the Coriolis force can bring about rotation
Where is the Coriolis force strong enough to bring about rotation?
At least 5 degrees north or south of the equator
Why don’t tropical revolving storms occur near the equator?
The Coriolis force is not strong enough to bring about rotation
Why is a low level of convergence in the lower atmospheric circulation system needed?
Winds have to come together near the centre of the low pressure zone
Why is a rapid outflow of air in the upper atmospheric circulation required?
To push away the warm air that has risen close to the centre of the storm
What happens once the tropical revolving storm reaches maturity?
A central eye develops
How wide is the central eye?
10-15km in diameter
What are the conditions like in the eye?
They are calm with clear skies, higher temperatures and descending air
What wind speeds have been observed around the eye?
Wind speeds of more than 300km/hour
What happens once the tropical revolving system reaches land or colder waters polewards?
The storm declines as the source of heat and moisture is removed
Where do these storms occur?
Between 5 and 20 degrees north and south of the Equator
In which 6 places do tropical storms often occur?
In the Caribbean/ Gulf of Mexico
Western side of Central America (eastern Pacific)
Arabian Sea/ Bay of Bengal
Off southeast Asia
Off Madagascar
Off north-western and north-eastern Australia
Where are tropical storms known as hurricanes?
Around the Americas
Where are tropical storms known as cyclones?
In the Arabian Sea and Bay of Bengal
Where are tropical storms known as typhoons?
Off southeast Asia
Where are tropical storms known as willy-willies?
North-western Australia
What percentage of tropical storms occur in the Caribbean Sea and Gulf of Mexico?
11%
What percentage of tropical storms occur on the western side of Central America?
17%
What percentage of tropical storms occur in the Arabian Sea and Bay of Bengal?
8%
What percentage of tropical storms occur off Madagascar?
11%
What percentage of tropical storms occur near Australia?
20%
Which area experiences the most tropical storms?
Southeast Asia
One-third of all storms occur here every year
On what scale are tropical revolving storms measured?
The Saffir-Simpson scale
How many points does the Saffir-Simpson scale have?
5
What is the Saffir-Simpson scale based on?
Central pressure, wind speed, storm surge and damage potential
What pressure does a scale 5 event have?
Central pressure at 920mb or below
What wind speed does a scale 5 event have?
250km/hour or greater
How big is the storm surge of a category 5 event?
At least 5.5m
What does scale 5 damage potential refer to?
Complete roof failure of many buildings
Lower floors damaged on all structures less than 3m above sea level
Evacuation of all residential buildings within 16-24km of the coast is likely
What is the average lifespan of a tropical storm?
7-14 days
How many tropical storms develop each year?
80-100
How many tropical storms each year develop into tropical revolving storms?
Approximately 80%
What 6 factors does the vulnerability of people to a storm depend on?
Intensity Speed of movement Distance from the sea Physical geography of the coastal area Preparations made by a community Warnings and community response
What are the impacts of wind on an area?
Can cause structural damage and bring down electricity transmission lines as well as devastate agricultural areas.
Debris that are thrown about are harmful to people.
What are the impacts of heavy rainfall?
Severe flooding, landslides and mudslides
How much rainfall can fall during a storm event?
200mm-300mm
How much rainfall can fall in coastal areas with high relief during a tropical revolving storm?
Over 500mm a day
What do storm surges result from?
High sea levels when wind driven waves pile up and the ocean heaves upwards as a result of the lower atmospheric pressure
What are the impacts of storm surges?
Flooding
Storm surges are the main reason for death
Agricultural areas can suffer as a result of soil being contaminated by sea water.
What is the weather bureau in Florida called?
The National Hurricane Centre
What can the National Hurricane Centre access?
Data from geostationary satellites and from both land- and sea- based recording centres.
How does the USA maintain round-the-clock surveillance of tropical storms that have the potential to become hurricanes?
It uses weather aircraft
How does the USA decide when to evacuate an area?
It compares the data it collects to models
Why is it essential that evacuation warnings are correct?
It is costly to evacuate people
People may be less likely to evacuate next time if they weren’t affected.
How much does it cost to evacuate coastal areas in the USA?
$1million per km of coastline
Why does it cost the USA so much to evacuate its coastal populations?
There are losses in business and tourism
Provision of protection
Why is it not always possible to give more than 12-18 hours warning?
Cyclones tend to follow an erratic path
Why is there insufficient evacuation in poorer areas?
Communications are poor
Give two locations with established warning systems
Central America and the Bay of Bengal
Where was the 1997 tropical cyclone warning?
Cox’s Bazaar area of Bangladesh
How many people were evacuated thanks to the 1997 tropical cyclone warning?
300,000
How many people died in the tropical cyclone at Cox’s Bazaar?
Less than 100
What is cloud seeding?
The process of creating more precipitation over oceans so that more water is released into the sea, weakening the system as it approaches land.
Why is research into cloud seeding no longer continued?
Concerns over the effects of cloud seeding on the global energy system
What is the name of the protection unit in the USA?
The National Guard
What do protection units do?
Prevent homes and commercial properties from being looted
What is ‘Project Safeside’?
A hurricane awareness programme in Florida
What does ‘Project Safeside’ do?
It has precautionary hurricane drills for schools and operates the Emergency Operations centre of the state.
What can be done to minimise the threat of storm surges?
Land-use planning can be used to identify the areas at the greatest risk and limit certain types of development in some areas.
Build sea walls, breakwaters and flood barriers
Put houses on stilts
How many people were killed in the 1900s Texas storm surge?
Over 6000
What was built after the 1900s Texas storm surge?
A sea wall
Why is a sea wall like the one in Texas unlikely to be built again?
It was so expensive
Whereabouts in Texas is the sea wall?
Galveston
How do local authorities in the USA address the problem of storm surges?
They limit expenditure on developments in high-risk areas and direct the population away from them
Sound evacuation plans to reduce the evacuation times
Plans for post-disaster redevelopment
Why does expenditure on developments in high-risk areas take place in poorer areas?
The need for land often outweighs these other considerations
What can be done to structures to ensure greater safety during an event?
They can be retrofitted
What happened in 1994 in Dominica?
Some homes were retrofitted
Who retrofitted homes in 1994?
A joint project between the Organization of American States and the government of Dominica
How successful was the retrofitting of buildings in Dominica?
The following year, all retrofitted buildings withstood the impact of Hurricane Marilyn
Where are the Outer Banks located?
North Carolina
What are the Outer Banks?
Barrier islands
What are the aims of the Outer Banks Mitigation Plan?
To save lives and money Protect property and natural resources Reduce future vulnerability Speedy recovery Post-disaster funding
What else is in the Outer Banks Mitigation Plan?
An emphasis on making as much information as possible available to the people of the Outer Banks area
What are people in HICs encouraged to do?
Take out insurance
What is needed to help people in LICs?
Both long and short term aid
Why do poorer areas suffer more?
Land-use planning, warning systems, defences, infrastructure and emergency services are inadequate
Which area did a cyclone hit in 1991?
Bangladesh
How many people died in the 1991 Bangladesh cyclone?
131,000
What was the monetary loss as a result of the 1991 Bangladesh cyclone?
$1.7 billion
Where was Hurricane Andrew?
Florida
When did Hurricane Andrew strike?
1992
How many people died as a result of Hurricane Andrew?
60
What was the monetary loss as a result of Hurricane Andrew?
$20 billion
Which cyclone was Hurricane Andrew similar in strength to?
The Bangladesh cyclone in 1991
