✅HAZARDS 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 months of the year (Jul/Aug), when sea temperatures are highest (27.5 C)
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
Clockwise
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
Distribution of tropical storms
usually 5°-20° North and South
Typically East to West, due to prevailing winds like trade winds
Curved trajectories, towards the poles due to coriolis effect
Need over 27°C to form
Trends of tropical storms
no evidence they are increasing in frequency or intensity yet
although should do as sea levels rise
predicted 2-11% by 2100 rise in avg. intensity
But rising heat could increase wind shear, meaning overall fewer storms, predicted, to decrease 6-34% in frequency
Why are tropical storms more predictable
Their conditions are known
Seasonality known (July to Oct typically, although winter hurricanes sometimes happen, but rarely)
Their paths aren’t known until days prior
Conditions for tropical storms
over 27°C
Over 70m deep
Low wind shear (difference in wind speeds at different heights, too much will split the storm apart)
Adaptation for tropical storms
Houses on stilts, avoid storm surge damage (big waves caused by storms)
e.g., in the Philippines
Can tropical storms be prevented
No
example: Project Stormfury in the 1960s, used cloud seeding with chemicals to alter prescription
Failed + was expensive
Prediction and Preparation
Evacuation can cost $1m per km^2 evacuated, $2-3m in some parts of US
Development= preparedness usually
Even areas that rarely receive them, only due to stuff like El Nino, like in California where only 1 death, manage well
