What conditions lead to tropical storms (hurricanes, typhoons or cyclones) and tornadoes and in what ways do they represent a hazard to people? Flashcards
(44 cards)
What are the features of tropical storms and hurricanes?
- Sustain wind speeds of more than 119km h-1
- Deposit massive amounts of rain in a short time
- Give rise to deadly storm surges in coastal areas
- Are highly destructive
How do hurricanes form?
- High humidity releases latent heat
- Sea temperature of more than 26-27 degrees Celsius for at least 60m depth
- More than 5 degrees north or south of equator for Coriolis effect to impact spin
- Almost constant vertical conditions
- Divergent airflow with height to draw air upwards
- Unstable air – surface winds converge
- Two moist tropical airstreams meet and denser one undercuts the other
How do hurricanes develop?
- Move westward due to earths rotation
- Continue to grow as condensation releases heart energy and picks up warmth (energy) from the sea
- Break up over land (friction and little moisture) or as they move out of tropics, as sea gets cooler
What are some characteristics of hurricanes?
- Central clear ‘eye’ of descending air
- Around eye, massive cloud walls with rapid uplift
- 12km high, 200-500km in diameter
- High volume rainfall – up to 500mm in 24 hours
- Very low air pressure – 900mn
- Eye wall dominated by intense thunderstorms
- Movement difficult to predict
What are primary impacts of hurricanes?
o Homes destroyed
o Deaths and injuries from flying debris
What are secondary impacts of hurricanes?
o Flooding o Pollution (sewage, drains etc) o Disease o Hunger o Fires (power lines down) o Transport disrupted
What are tertiary impacts of hurricanes?
o Long term economic impacts (e.g cost, destruction of infrastructure, loss of jobs etc)
What are the environmental impacts of hurricanes?
- Relief – landslides, mudflows
- Drainage – floods, waterlogging
- Vegetation – trees destroyed, habitats destroyed
- Pollution of water supplies – disease
What are the social impacts of hurricanes?
- Health – injuries and deaths, disease, depression
- Housing – destroyed, temporary shelter, forced to migrate
- Social unrest – looting, family break up, tension
What are the economic impacts of hurricanes
- Infrastructure – destroyed (e.g roads, power, schools_
- Agriculture – cash and food crops lost, pollution, tree crops hard hit
- Transport – bridges destroyed, road and rail damage, loss of aeroplanes
- Trade – loss of exports, need to import, cost of aid
What is used to measure hurricane strength?
The Saffir-Simpson scale
When did hurricane Katrina slam into the Gulf Coast of Louisiana?
29th August 2005
What category was hurricane Katrina?
went from 5 to category 4
How many people were killed in hurricane Katrina?
At least 1,500
How much damage was caused during Hurricane Katrina in the south-eastern part of USA?
At least $150 billion
How do hurricanes cause flooding?
• Hurricanes can cause the sea level around them to rise, this effect is called a storm surge. This is often the most dangerous characteristic of a hurricane, and causes the most hurricane-related deaths. It is especially dangerous in low-lying areas close to the coast
(In Katrina’s case - a lot of rainfall too)
Where did hurricane Katrina track over?
The gulf of Mexico - and hit New Orleans
Was the gulf of Mexico and New Orleans protected by hurricanes?
Yes - defence walls called levees
What happened to the levees during hurricane Katrina?
• The levees were overwhelmed by the extra water, with many collapsing completely.
How much of the city of New Orleans was flooded?
80%
How did the wind affect the damage caused by hurricane Katrina?
produce a storm surge over the ocean which led to flooding in coastal areas and was responsible for many deaths.
What were the effects after hurricane Katrina?
- Thousands of homes and businesses destroyed.
- Criminal gangs roamed the streets, looting homes and businesses and committing other crimes.
- Thousands of jobs lost and millions of dollars in lost tax incomes.
- Agricultural production was damaged by tornadoes and flooding. Cotton and sugar-cane crops were flattened.
- Three million people were left without electricity for over a week.
- Tourism centres were badly affected.
- A significant part of the USA oil refining capacity was disrupted after the storm due to flooded refineries and broken pipelines, and several oil rigs in the Gulf were damaged.
- Major highways were disrupted and some major road bridges were destroyed.
- Many people have moved to live in other parts of the USA and many may never return to their original homes.
What is a tornado?
A violently rotating column of air extending from a thunderstorm to the ground. A distinctive funnel, made visible by the dust sucked up, and by condensation of water droplets, extend towards the ground from the cloud base.
What conditions does there need to be for a tornado?
- Seasonal: June- November in northern hemisphere
* Often a remnant of a tropical storm
