Hazards - Storm Hazards Flashcards
Where and when do tropical storms form?
1) Intense low-pressure weather systems developing in the tropics.
2) They are seasonal - Hurricane season in the northern hemisphere is August-November, and in the southern hemisphere its March-May.
3) Initially move westwards due to easterly winds in tropics e.g. trade winds in the Atlantic. 4) Lose strength as they move over land because the supply of warm moist air is cut off.
What are the three hazards that tropical storms bring?
1) Winds – wind speeds can reach more than 150 mph causing structural damage to buildings, transport and transmission lines. Also debris.
2) Heavy rainfall – bringing about coastal and river flooding. Saturation of soil on slopes creates potentially deadly landslides.
3) Storm surges – rise in sea level caused by powerful surface winds and low pressure inundating low-lying coastal land, polluting and carrying debris.
What are the conditions needed for the formation of a tropical storm?
1) Ocean – sea temperature must be above 27°C to generate rising air currents, this is reached near the equator where solar radiation is more concentrated. Depth must be over 70 meters proving moisture for latent heat.
2) Location – at least 5° north/south of equator due to Coriolis Effect (force caused by Earth’s rotation, deflecting path of winds) being weaker between 0-5° and no circular air flow developing. Wind flow in N. hemisphere is anticlockwise and in S. hemisphere it is clockwise.
3) Latent heat – evaporation in the ocean surface breaks molecular bonds to create water vapor. Air containing water vapor rises and condenses so the bonds are reformed and energy is released as (latent) heat.
4) Atmosphericpressure – when warm air expands and rises it forms a low pressure area. Cold dense air sinks downwards forming high pressure. Air moves from high pressure areas to low pressure areas making circulating winds.
What scale is used to measure tropical storm intensity?
1) Measures wind speed and potential damage. Approx. 100 tropical storms occur each year but many do not reach land and therefore not considered a major hazard. Some develop into tropical depressions, but few into cyclones/hurricanes/typhoons.
2) Category 1 would cause limited damage whereas category 5 would cause catastrophic damage.
How is prediction used in response to tropical storms?
NOAA (National Oceanographic and Atmospheric Administration) publishes annual prediction of hurricane activity. Uses indicators like: sea-surface temps, atmospheric conditions, and short term climatic cycles (e.g. El Nino). Hard to predict where the hurricane will land, only just before event.
How is mitigation/adaptation used in response to tropical storms?
1) Protect property with sandbags. Retrofitting buildings with reinforced concrete, securing roofs, constructing houses on stilts to minimize flood damage.
2) Build sea walls and levees to protect against flooding at coast and by rivers.
