Basics of Tropical Storms

• Tropical storms have different names depending on where they happen:

  1. Typhoons in the South China Sea and west Pacific Ocean
  2. Hurricanes in the Gulf of Mexico, Caribbean Sea and west coast of Mexico
  3. Cyclones in the Bay of Bengal, Indian Ocean and northern Australia
• Define Tropical Storms:

  Tropical storms are rotating spiralling; they are intense low-pressure weather systems that develop in the tropics but can at times extend beyond.
• Characteristics of Tropical Storms

  • Heavy rainfall
  • High wind speeds (over 120 km/h)
  • They can be 200 - 700 km in diameter (size)
  • High waves and storm surges
• Necessary conditions for tropical storms to form include:

  1. Sea temperature must be above 27 °C
  2. the ocean must be at least 70 meters deep
  3. Location has to be at least 5° north or south of the equator. Essential for the Coriolis force to cause it to spin.
  4. Low wind shear: if the wind shear is too high, it can disrupt the organisation of the storm and prevent it from strengthening
  5. Atmospheric instability: in tropical regions, warm, moist air near the surface rises, creating instability and leading to the formation of clouds and precipitation
• • In low-pressure zones, air rises because it is hotter, increasing precipitation. (England) (more cloudy = colder temps) (0 degrees to 60 degrees North & South)
• • In high-pressure zones, air falls because it is colder, decreasing precipitation (deserts). (less cloudy = hotter temps) (30 degrees North & South)
• • High and low pressure zones are due to Global Circulation cells; these cells are formed due to changing temperatures in the air. (eg Hotter temps at equator)
• Name the different cells that are apart of the global circulation:

  • Polar Cells, at 60 degrees (N&S) to the poles
  • Farrel Cells, between 30 degrees and 60 degrees (N&S)
  • Hadley Cells, 0 degrees and 30 degrees (N&S)
• The Coriolis effect is the apparent deflection of moving objects (such as air and water) due to the Earth's rotation. It is caused by the fact that different parts of the Earth rotate at different speeds; e.g., the equator rotates faster than the poles.
• Define deflection:

  To cause something to change direction.
• How the Coriolis Effect Works

  When air moves from one latitude to another, it carries the speed of the location it came from. Differences in speed cause the air to spin.
• How does the coriolis effect cause storms to rotate?

  1. Deflection by the Coriolis Effect: The incoming air is deflected (changes direction).

  • Northern Hemisphere: Air curves to the right, causing anticlockwise rotation.
  • Southern Hemisphere: Air curves to the left, causing clockwise rotation.

  1. Cyclone Rotation: This deflection (change in direction and therefor speeds of air) leads to a spinning motion of tropical storms
• Coriolis effect basics:

  • The Coriolis effect is strongest at the poles and weakest at the equator (which is why hurricanes don’t form near the equator).
  • It affects large-scale weather patterns, including trade winds, jet streams, and ocean currents.
  • It explains why hurricanes rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
• More tropical storms are formed in the northern tropics. Particularly in east asia (30% of storms(Typhoons)).
• Formation of tropical storms:

  1. Warm, moist air rises → Creates low pressure.
  2. High pressure air rushes in to take place of rising lown press air. → Strong winds form.
  3. Continuous rising air → causing storm growth.
  4. Air cools & condenses → Forms cumulonimbus clouds.
  5. Eye wall develops → Brings heavy rain & strong winds.
  6. Latent heat released due to energy from condensation of clouds → Powers the storm.
  7. Air moves outward at the top.
  8. Coriolis effect → Spins air and therefore the storm.
  9. Cold air sinks in the eye → Creates a calm center.
  10. Storm weakens over land/cool water → Loses energy.
• The area that experiences the most tropical storms is the western Pacific Ocean, which generates the highest number of tropical typhoons, impacting countries like Japan, China, Taiwan, and the Philippines, making this region the most active basin for tropical storms globally. 
• There have been at least 127 typhoons that have made landfall in China since 1970.
• Distribution

  • Tropical storms typically form between 5 ° and 30 ° latitude.
  • Storms can extend beyond the Tropics into places like Japan, China, and the eastern seaboard of the US.
  • More tropical storms are formed in the northern tropics.
  • 30% of tropical storms form in East Asia