🌋3.1.5.5 - Storm Hazards Flashcards
What is a tropical storm?
A violent rotating storm which occurs at mid latitudes, ie the tropics
How do tropical storms form?
Strong upward movement of air draws water vapour up from the ocean
Evaporated air cools as it rises, condenses to form thunder clouds
Condensing air releases energy which powers the storm and draws up even more water
Several small thunderstorms combine to form a giant spinning storm
Storm develops an eye where air rapidly descends.
Upon landfall, storm loses energy and it slows and weakens
Where are hurricanes found?
Over the US and Caribbean
Where are cyclones found?
South East Asia, South Pacific, India, East Africa
Where are typhoons found?
Japan, Philippines
When do tropical storms form?
After the warmest moths of the year, when sea temperatures are highest
Where are the strongest winds found?
The eyewall
What is the Coreolis force?
Deflects objects in a rotating system, due to the Earth’s rotation
Which way does the Coreolis force deflect objects in the Northern hemisphere?
To the right, so they move upwards on the globe
Which way does the Coreolis force deflect objects in the Southern hemisphere?
To the left, so they move downwards on the globe
What is a storm surge?
An abnormal rise of water, generated by a storm, over and above the predicted astronomical tide
How are storm surges formed?
When the storm blows the ocean surface and creates vertical circulation in the water, which gains height in shallower water
Which areas are at risk from storm surges?
Lowland coastal areas
What factors can affect storm surges?
Storm intensity, speed and size as well as coastal features such as bays and estuaries
How are strong winds formed by storms?
When pressure changes rapidly over a small distance, and air flows from high pressure to low pressure
Which areas are at risk from strong winds?
Coastal regions, as the storm looses energy once it reaches land
How are the strongest winds created?
By the biggest differences in pressure
What are landslides?
Involves the movement of rock, earth or debris, can be caused by heavy rain
Why can paricular areas of land slide?
When they have two separate layers, one of stable bed rock and another of loose, unconsolidated sediment
What is a common form of disaster associated with tropical storms?
Heavy rainfall and flooding
Where does the heaviest rain occur?
In the eyewall
Why do floods occur?
Because the ground becomes saturated with the heavy rain and then the water builds up and rivers burst their banks
How can storms be predicted?
Future events can be predicted using ones in the past and the frequency of storms can also show patterns
What can be used to gauge wind speeds, pressure and precipitation?
Aircraft and drones
How can meteorologists help people to prepare?
By giving a picture of the flooding or weather systems a storm may cause and the areas it may hit
How can satellites be useful?
They can track the storm and give a hemispheric view of it, as well as 3D images and sea surface temperature
What temperature must the sea surface be for a storm to form?
28 degrees
What is a Category 1 storm?
Very dangerous winds produce some damage, damage to trees and powerlines as well as some homes
What is a Category 5 storm?
Catastrophic damage will occur, high percentage of homes destroyed, total roof failure and wall collapse, power outages
What scale is used to categorise storms?
The Saffir-Simpson Scale
What do wind speeds have to reach to be a category 5 storm?
157mph
What is done by the US Air Force and National Oceanic and Atmospheric Administration?
They fly aircraft through storms to gauge wind speeds, barometric pressure, rainfall and snow as well as dropping sensors which fall through the storm and send back data
Which is the most useful satellite for monitoring storms?
The TRMM satellite - Tropical Rainforest Monitoring Mission
What has TRMM helped to discover?
Eyewall ‘hot towers’ through its CT scans of storms
What are eyewall hot towers?
Rainclouds that reach the lowest layer of the atmosphere, bringing heat to high altitudes
Tropical Storm
A violent rotating storm which occurs at the mid-latitudes
Tropical Storm Formation
. Strong upward air movement draws water vapour from ocean surface
. Air rises (convection) and cools- condensing= clouds
. Condensing- latent heat- energy, powering storm to draw up more water
. Thunderstorms combine to form a giant storm
. Eye develops- winds >120km/h on eye wall
. Storm gathers strength and energy from warm ocean
Why does a storm develop an eye?
As air rapidly descends in the centre
Where are the strongest storm winds found?
In the eye wall
What happens when a storm reaches land?
Energy cut off
Friction slows it down
4 Conditions Needed
Sea water warmer than 27°c
5° from equator to tropics
Atmospheric instability
Uniform wind direction in all levels
Why do storms need oceans?
Storms derive their moisture and energy here
Why can storms be formed at lower latitudes in the summer?
Because it’s hotter, meaning sea surface temperature increases
Why does there need to be atmospheric instability?
Warm air forced to rise
Why’s the rotation of the earth important? (Coriolis Effect)
A certain amount of ‘spin’ is needed to initiate the rotation of a storm
Not strong enough at the Equator
Why does there need to be a uniform wind direction at all levels?
As different wind directions at different altitudes prevents the storm from attaining height and intensity
4 Hazards associated with storms
High winds (300km/h)
Storm surge (>3m)
Coastal / River flooding
Landslides
Effects of high winds
Destroy buildings
Uproot trees
Carry debris + smash it into other objects- injures + disrupts transport
Damages communication networks- fires + power cuts
What causes storm surge?
Intense low atmospheric pressure and powerful surface winds- creating high waves
Effects of storm surge
Floods in low lying areas
Freshwater pollution
Destroys homes and infrastructure
Agricultural land inundated with water- useless
What causes river flooding?
Warm, humid air generating torrential rainfall
Effects of flooding
Death
Flash floods in urban areas
Damages homes and infrastructure
What causes landslides?
Intense rainfall increasing pore water pressure
Weakens cohesion, triggering slope failure
Effects of landslides
Deaths
Destroys homes and infrastructure
Factors Affecting Impact of a Storm
Intensity
Speed it travels through an area
Distance from sea
Warnings and response
Preparation
Physical geography
What’s the Saffir- Simpson Scale based on?
Wind speed and storm surge
1-5, estimates damage
Advantages of Saffir- Simpson Scale?
Straight forward
Easy comparison
Widely used
Disadvantages of Saffir- Simpson Scale?
Limited value when assessing impact
Doesn’t include rainfall
Doesn’t think about area affected i.e. pop density
Why is river flooding worsened in urban areas?
Impermeable surfaces
Drains
High building intensity
How can people prepare for a storm?
Insurance
Minor property improvements
Warnings given
Emergency services trained
Florida: evacuation routes clearly signposted
How can the effects of some storm hazards be prevented?
Can’t prevent the storm
Sea wall can reduce storm surge impact
Adaptation: Land use zoning
Coastal strips are used for recreation
Property behind
Adaptation: Adapting home functionality
Homes built on stilts
Homes have a garage at the bottom
-Means nothing valuable destroyed
Examples of Mitigation
Insurance
Structural responses
Areas at risk of storm surges
. Coastal areas
. Warmer areas
. More severe tropical storms
. Enclosed areas due to funnelling
. River mouths as the water combines to flood more severely
Example of storm surge
Hurricane Katrina
How high was the storm surge in Hurricane Katrina
25 to 28ft above normal tide levels
Winds in hurricane Katrina
125mph
Coriolanus effect
Caused by the Coriolis force which deflects objects within a rotating system
Coriolanus effect - northern hemisphere
Objects deflect to the right
Coriolanus effect - southern hemisphere
Objects deflect to the left
Tracking hurricanes by air
. A group of pilots and scientists, Hurricane Hunters, regularly soar through storms that threaten the US
. They release sensors, dropsondes, which fall through the storm and send back data in real time to improve forecasting models
Tracking hurricanes by satellites
. Create visible images and measuring weather patterns with radar and infrared sensors.
. Can track temperatures inside a storm, cloud heights, rain, snow and wind speed
. The TRMM satellite provides CT scans inside hurricanes
Supercomputers in tracking hurricanes
. Thanks to better storm models and more powerful computers the NOAA can release five-day forecasts of tropical storms and hurricanes
. The weather models improved with new understanding of global ocean and atmospheric patterns that influence budding storms
