tropical storms

• conditions needed for tropical storms to form

  • sea temp above 26 degrees
  • light wind shear
  • thunderstorm cluster
  • earth's rotation
• hazards associated with tropical storms:

  • storm surge (cause for 90% of deaths)
  • flooding
  • high wind speed
  • landslider
• tropical storms are circular in motion
• they last 7-14 days
• tropical storms spin anticlockwise in northern hemisphere and clockwise in southern hemisphere
• eye of storm is area of low pressure
• rising air spirals around eye in eyewall , causes strong winds
• near the top of the storm there is an outflow of moisture in air , cloud cover extends for long distance either side of eye
• hazards of storm hazards:

  • high winds over 300km , very strong
  • flooding form storm surges , heavy rain
  • landslides - due to soil becoming heavy when wet with high levels of rain
  • storm surges - large rise in sea level causes by low pressure , high winds , pushes water towards coast
• human factors that decrease hazard risk of tropical storms:

  • good communications and warnings
  • short and long term aid available
  • electricity supplies resume quickly
  • low population density
  • means to move inland
  • road not blocked
• physical factors that increase risk of tropical storms:

  • cliffs on coastline
  • coastal location
  • high wind speed
  • high storm surge
• physical factors that decrease risk of tropical storms:

  • higher land
  • low wind speed
  • funnel shaped bays
  • cold air joins , reducing energy
  • storm path as predicted
• short term responses:

  • evacuation
  • using sandbags , shutters
  • temporary housing
• flooding = food shortages

  • hurricane mitch : 1980 , 60% OF sugar cane gone , 3 million affected
• human factors that increase hazard risk of tropical storms:

  • sturdy building materials
  • weak economy
  • light weight building materials
  • lack of communications and warnings