L2 - Weather hazards

• tropical storms are a natural hazard
• a tropical storm occurs when tropical air rises to create an area of low pressure, much lower than the depressions experienced in the UK
• as the warm, moist air reaches high altitudes, powerful winds spiral around the calm central point, creating the 'eye of the storm' and the warm air cools and condenses into heavy rainfall and thunderstorms
• from 2001 to 2010, more than 500 tropical storm disasters killed nearly 170,000 people, affected over 250 million and causes an estimated $380 billion
• tropical storms are known as hurricanes, typhoons or cyclones
• tropical storms occur in the tropics, south of the tropic of cancer and north of the tropic of capricorn
• tropical storms are usually found in areas of low latitude, between 5 degrees and 30 degrees north and south of the equator
• the sea temperature for tropical storms must be above 27 degrees to a depth of approximately 60-70 metres, to provide the heat and moisture that causes the warm air to rise rapidly in this low-pressure region
• the warmest seasons are between summer and autumn when it is most typical for tropical storms to develop
• tropical storms do not develop along the equator because the Coriolis effect is not strong enough for tropical storms to spin
• the earth spins faster at the equator than at the poles because it has further to go
• where air descends, it travels over the surface to become surface winds, these winds have descended from areas of high pressure and are cooler, as they travel over the surface, they warm up and travel to areas of low pressure, where the now warmer air will begin to rise again
• trade winds generally move to the west from the northern hemisphere and to the east in the southern hemisphere due to the coriolis effect of the earth spinning
• tropical storm formation:

  1. air is heated above the surface of warm tropical oceans, the warm air rises rapidly under the low pressure conditions
  2. the rising air draws up more wind and large volumes of moisture from the ocean, causing strong winds
  3. the Coriolis effect causes the air to spin upwards around a calm central eye of the storm
  4. as the air rises, it cools and condenses to form large, towering, cumulonimbus clouds, which generate torrential rainfall
  5. cold air sinks in the eye, therefore there is no cloud, so it is drier and much calmer
  6. the tropical storm travels across the ocean in the prevailing wind
  7. when it meets land, there is no more fuel source of moisture and heat so the storm loses power and weakens
• 1. at the start of a tropical storm, temperature and air pressure fall. air rises and clouds begin to form
  2. air pressure falls more rapidly, wind increases, cumulonimbus clouds form, heavy rainfall
  3. period of calm called the eye of the storm with no wind or rain
  4. wind and heavy rainfall increase dramatically again, the temperature drops and air pressure rises '
  5. as tropical storm ends, air pressure and temperature rises, wind and rainfall subside
• the coriolis effect bends and spins the warm rising air
• as they pass over land, they lose the heat and moisture source, friction slows them down, and as they lose energy they change direction
• coriolis effect:

  winds blow from areas of high pressure to areas of low pressure, as the world rotates, it causes the wind to bend because the earth spins faster at the equator and slower at the poles
• label diagram:

  A) winds rotate outwards

  B) clear sky and no wind

  C) heavy rain and strong wind

  D) rain bands

  E) warm moist air rises

  F) cumulonimbus clouds

  G) 27 degrees