Context: Typhoon Rolly or Goni, as it is called internationally, made landfall in the eastern Philippines recently.

More on the news: 

  • This is the 18th typhoon to hit the Philippines this year.
  • The catastrophic violent winds and intense to torrential rainfall associated with the region of the eyewall and inner rainbands of the typhoon is prevailing or expected within the next 12 hours .

About Tropical cyclones or hurricanes

  • Location: They use warm, moist air as fuel and therefore form over warm ocean waters near the equator.
  • Mechanism :
    • When the warm, moist air rises upward from the surface of the ocean, it creates an area of low air pressure below. 
    • After this, the air from the surrounding areas, which has higher pressure, enters this space, eventually rising when it becomes warm and moist too.
    • As the warm and moist air continues to rise, the surrounding air will keep entering the area of low air pressure. 
    • Ultimately, when the warm air rises and cools off, the water in the air forms clouds.
    • And this corresponding system of clouds and winds continues to grow and spin, fuelled by the ocean’s heat and the water that evaporates from its surface.
    • As such storm systems rotate faster and faster, an eye forms in the center.
  • Direction:  
    • Storms that form towards the north of the equator rotate counter-clockwise. 
    • On the other hand, those that form south of the equator spin clockwise because of the rotation of the Earth on its axis.
  • No difference between a hurricane and a tropical storm
    • Depending on where they occur, hurricanes may be called typhoons or cyclones. 
    • As per NASA, the scientific name for all these kinds of storms is tropical cyclones. 
    • The tropical cyclones that form over the Atlantic Ocean or the eastern Pacific Ocean are called hurricanes.
    • On the other hand, tropical cyclones that form in the Northwest Pacific are called typhoons.

Naming of the tropical cyclones

  • Atlantic tropical storms have been named according to lists by the National Hurricane Center (NHC)
    • The National Hurricane Center (NHC) is the division of the United States' NOAA/National Weather Service.
  • Earlier it was also decided that the NHC will use alternating men and women’s names, on the lines of the practice earlier adopted by Australia’s Bureau of meteorology.
  • Role of WTO:
    • These names are also maintained and updated by an international committee of the World Meteorological Organisation (WTO)
    • The WTO represents over 120 countries and uses predetermined lists of names for each ocean basin of the world. 
  • Guidelines for naming
    • The names should be short and should be readily understood when broadcast.
    • There are six such lists of names with 21 names each.
    • Each name starts with one alphabet except Q, U, X, Y, and Z (because names beginning with these letters are in short supply).
    • These names are used in rotation, which is to say that the list of names attributed to Atlantic tropical storms in 2019 will also be used in 2025.
    • However, names of storms that caused particular damage and deaths are retired and in case there are more storms than names in the list, NHC names them using the Greek alphabet.
    • Further, the only time that a storm may be renamed is when it dissipates to a tropical disturbance and reforms.

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