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Flashcards in Hazards (Storm Events) Deck (23)
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Distribution of tropical storms

Tropical maritime areas between 5-20 N/S but not on the equator.


Distribution of hurricanes

N Atlantic (11% of storms) and NE Pacific (17% of storms)


Distribution of cyclones

S Pacific/Indian (8% of storms). Off of Madagascar (11% of storms)


Distribution of typhoons

NW Pacific (33% of storms)


Distribution of willy willies

NW and NE of Australia (20% of storms)


Conditions needed to form a tropical storm

- Ocean above 27C
- Water levels at 70m below surface
- At least 5-20 N/S of Equator for Coriolis effect
- Low level convergence


Why do storms decay upon reaching land?

- Lose the source of heat and moisture
- Increased frictional drag decreases speed of storm


Four stages of tropical storm formation

- Tropical Disturbance: <23 mph
- Tropical Depression: 23-39 mph
- Tropical Storm: 39-73 mph
- Hurricane: 74 mph +


Scale used to measure tropical storm magnitude

Saffir Simpson Scale


Four factors measured by the SS scale

- Central pressure
- Wind speed
- Storm surges
- Damage potential


Frequency of tropical storms

- N Hemisphere: June-November
- S Hemisphere: November-April
- Frequent but few major hazards


Regularity of tropical storms

Irregular- Occur in some areas but no clear pattern


Predictability of tropical storms

Fairly predictable with satellite tracking of cloud formations.


Primary hazards of tropical storms

- Strong winds
- Heavy rainfall
- Storm surges


Secondary hazards

- Flooding
- Landslides


Formation process of tropical storms

- Solar radiation heats the ocean to 27C. ITCZ is usually overhead
- Warm air rises and creates an area of low pressure
- This air cools as it rises and condenses. Forms cumulonimbus clouds and heavy rainfall
- Coriolis effect causes the air to spin upwards around a central eye
- Air rushes in from high pressure areas, replacing rising air and creating strong winds
- Cold air sinks in the eye of the storm
- Carried across the ocean by prevailing winds, building with evaporated water
- When it meets land it's no longer powered by moisture and slows from friction with the land.


Storm surges

Rising air creates low barometric pressure, and therefore an area of localised sea level rise. Winds create larger onshore waves and push a surge of water inland.


Factors increasing severity of storm surges

- Low relief of coastal areas
- Funnelled coasts
- Storm track
- Intensity of storm
- High tide


Short term responses to storms

Search & Rescue. Evacuation.


Long term responses to storms

Mitigating the impacts of future storms. E.g. prevention, protection, prediction and preparedness


Methods of prediction for storms

- Geostationary satellites
- Land and Sea based monitoring (NOAA)
- Aircraft reconnaissance


Method of prevention of storms

Cloud seeding


Methods of protection for storms

- Strengthening homes e.g. barricades
- Cyclone/hurricane drills
- Land use planning to reduce access to high risk areas
- Sea walls and flood defences to reduce storm surge risk
- Emergency service drills
- Insurance