storm hazards

• where - Cyclones


  Indian Ocean
• where - hurricanes


  atlantic ocean
• where - typhoons


  north west pacifc
• What is a tropical storm? - Tropical revolving storms are intense weather systems rotating around a circle of very low pressure
• Where do they develop?- hurricanes: the tropics around latitude of 8 and 20 degrees north of equator
• Why do they develop here: -converging easterly trade wind

  - plentiful supply of moisture leading to development of thunderstroms
• What are typical wind speeds

  75mph
• What distance storm hazards measure across

  200-700 km
• Distribution: occur between 5 and 20 degrees north and south of equator

  once generated they typically move westwards
• Whats the role of latent heat in hurricane formation? - name given to energy produced when a substance changes state

  - as there's a lot of condensation when clouds are formed in a tropical storm this releases heat which effectively powers the storm
• How are tropical storms measured? Saffir-Simpson Scale (1-5)

  - based solely upon speed, central pressure, storm surge, damage potential
• Speed of cat 1

  74 - 95 mph
• speed of cat 5

  > 156 mph
• Disadvantages of Saffir Simpson: - doesnt account for amount and intensity of rainfall

  - doesnt account for population density of area affected by storm

  - doesnt account how quickly storm tracks over a region

  - doesnt account for what stage strom is in when it hits land eg decaying maturing
• Northern hemisphere tropical storm season

  june - novemeber
• southern hemisphere tropical storm season

  november- april
• NOAA (National Oceanic and Atmospheric Administration): publishes prediction of hurricane activity for forthcoming season

  - uses sea surface temps

  - atmospheric conditions

  - climatic cycles eg el nino
• Storm stages: - embryo

  - developing

  - declining

  - mature
• embryo: sea surface temps of 27 degrees, warm air rises and starts to spin
• developing

  clusters of thunderstorms drift over warm ocean waters
• declining: as tropical storm moves over land it loses its source of energy and weakens
• mature: as tropical storm moves over ocean it picks up warm air wind speed increases and grows in size
• Whats clear zone in center of hurricane: eye - wind drops, eerily calm
• wheres most destructive parrt of hurricane

  eye wall
• Conditions contributing to storm development - Sea temp above 27: provides continuous source of heat to maintain rising air currents
• Conditions contributing to storm development - ocean depth of 70 m: moisture provides latent heat which powers storm as moisture condenses
• Conditions contributing to storm development - location from equator: coriolis force brings about rotation
• Conditions contributing to storm development - atmospheric instability: convergence of air in lower atmosphere
• Conditions contributing to storm development - uniform winds: allow wind speeds to build up
• Factors affecting vulnerability to storm events: - intensity

  - speed of movement

  - distance from sea

  preparations by community

  - physical geography
• Hazards associated with tropical storms: - strong winds

  - storm surges

  - coastal and river flooding

  - landslides
• Strong winds: - avg 75 mph can exceed 150 mph

  - can

  cause structural damage

  - debris can form flying missiles

  - damaged powerlines can cause fires
• Storm Surges: - high sea level results when wind driven waves pile up and the ocean heaves upwards as a result of low atmospheric pressure

  - typically 3 m in height

  -floods low lying areas

  - cause wide spread devastation and loss of life

  - inundate agricultural land

  - Hurricane Katrina 7.6m storm surge
• Coastal and river flooding: - warm humid air associated with tropical storms can cause heavy rainfall eg 200mm in a few hours

  - can trigger flash flooding particularly in urban areas

  - Hurricane Katrina caused intense river flooding due to breaking levees
• Landslides: -estimated 90% of landslides caused by heavy rainfall

  - Hurricane Mitch caused landslides killing 18000 in Central america

  - evidence for landslides causing earthquakes- Taiwan
• How can storm hazards be managed? preparation, mitigation, prevention, adaptation
• Preparedness: -evacuation drills and routes well signposted

  - authorities develop hurricane centers to estimate height and extent of storm surge

  - have emergency kit and know nearest shelter

  -communities set up search and rescue teams to tackle impacts

  - authorities install monitoring systems and can issue warning systems - Hurricane Watch in US
• National Hurricane Center in florida: SLOSH - computerised model to estimate storm surge height

  - can access data from weather satellites to give real time view of location track,size,strength of hurricane

  - info used to aid evacuation and issue of hurricane watch
• Hurricane Watch


  winds expected within 36 hours
• Hurricane Warning


  landfall expected within 24 hours