Storm hazards Flashcards
Storm hazards
A tropical storm is a low pressure, spinning storm with high winds and torrential rain.
Conditions for a tropical storm to form and develop :
- Temperature: Ocean temperatures must be around 26 - 27°C and at least 50 metres deep. Warm water provides the storm with energy.
- Air pressure: Must be in areas of unstable air pressure - usually where areas of high pressure and low pressure meet (convergence) - so that warm air rises more readily and clouds can form (this air must also be humid for cloud formation). - Warm air rises because it is less dense than cold air.
- Wind shear: Winds must be present for the swirling motion to form, but not too strong or the storm system will be ripped apart in the early stages.
- Rotation: Tropical storms only form around the equator, but no less than 5° on either side. The Coriolis Effect is the effect of the Earth’s rotation on weather events. The storm spins because the Earth is spinning; but there is no Coriolis Effect at the equator, hence why these storms will only form a certain distance away from it.
- A trigger: a pre-existing thunderstorm, a spot of very high sea surface temperature, an area of low pressure and many other factors can act as a trigger for a storm to develop, which will only further develop when the other conditions are present.
Formation
- Warm, moist air rises, leaving an area of low pressure below. This causes warm air from surrounding areas of higher pressure to move into this low pressure area and rise too. Overall, warm air is constantly rising and accumulating in the atmosphere.
- When the warm air rises, it cools, condensing into thunderstorm clouds.
- The whole system is spinning due to the Coriolis effect. In the southern hemisphere, the storms spin clockwise; in the northern, anticlockwise
. 4. The constant additions of energy from the warm air causes the storm to spin faster and generate higher wind speeds. At 39 mph the storm can be classed as a tropical storm.
- The eye of the storm is in the centre. This is an area spanning around 30 miles wide that is of extremely low pressure (can be 15% lower pressure than areas outside of the storm). Cool, dry air (cool from the higher altitudes and the moisture has been transferred into the system) descends in the eye, causing the weather to be relatively calm and cloud free. The more intense the storm, the clearer the eye.
- Surrounding the eye is the eyewall, the most intense and powerful area of the storm. Warm, moist air rapidly rises here, with extremely high winds and torrential rain. When winds reach 74 mph, it becomes a hurricane/cyclone/typhoon
. 7. When the tropical storm reaches a coast, the low pressure and high winds will cause a large amount of sea water to be taken into the system and then released as a high wave called a storm surge
. 8. When the storm reaches land, it no longer has a supply of energy (warm, moist air from the sea) and the eye eventually collapses. Heavy rain can persist for days.
Magnitude
Measured on the Saffir-Simpson Scale (A scale of 1-5) based on wind speed and thus power of the storm.
Frequency
- Tropical storms form in the Northern Hemisphere from June-November, and the Southern Hemisphere from November-April.
- The majority of tropical storms do not develop into strong storms and do not reach land. Tropical storms that are higher magnitude and reaching land are thought to be increasing in frequency.
Regularity
- Tropical storms are irregular because although they occur in the same areas, their path does not follow a set route
- the route taken is dependent on the storm and the climatic conditions.
Predictability
- Tropical storms form away from land meaning satellite tracking of cloud formations and movement can be tracked and the general route can be predicted
- The closer the hurricane gets, the easier it is to predict. Storm surges can also be predicted based on the pressure and intensity of the storm.
- From past storms and climatic trends, the probability of a storm hitting an area can also be predicted. Scientists have predicted how many years it will take for a tropical storm to hit certain areas.
Hazards caused by tropical storms : High winds
over 300km/h and therefore very strong.
Hurricane winds are strong and also blow heavy debris at high speeds, which can obviously cause damage and injure anyone who comes into contact.
Hazards caused by tropical storms : Flooding
- coastal/river flooding from storm surges and heavy rain.
- River flooding also sends more floodwater to other places, which can cause areas outside of the tropical storm’s path to flood also
Hazards caused by tropical storms : landslides
due to soil becoming heavy when wet with high levels of rain
Hazards caused by tropical storms : Storm surges
Large rise in sea levels caused by low pressure and high winds, pushing water towards the coast
Primary effects
- Beaches eroded
- Sand displaced
- Coastal habitats such as coral reefs are destroyed
- Businesses destroyed
- Agricultural land damaged
- Drowning
- Debris carried by high winds can injure or kill
- Buildings destroyed
- Government buildings destroyed
Secondary effects
- River flooding/ salt water contamination
- Animals displaced from flooding e.g. alligators
- Water sources changing course from blockages
- Rebuilding and insurance payout
- Sources of income lost
- Economic decline from sources of income destroyed
- Homelessness
- Polluted water supplies spread disease
- Food shortages from damaged land
- Issues paying back international aid
- Pressure for government to do more about global warming
Prevention to Storm hazards
- In current climates and weather conditions, tropical storms cannot be avoided
- Strategies to mitigate climate change could prevent higher category storms
Preparedness to storm hazards
- Awareness through education of what to do during a tropical storm
- Evacuation plans and training
- Satellite image tracking to manage the areas that are at risk
- Storm warning systems and television broadcast tracking the storm
