Context: Texas, which is one of the largest hotspots for Covid-19 in the US, is now facing another threat, as Hurricane Hanna which made landfall recently.

More on the news:

  • Officials have also warned about a life-threatening storm surge and strong winds which will result in severe flash flooding and isolated minor to moderate river flooding.
  • Hurricane Hanna will produce heavy rains across portions of southern Texas and northeastern Mexico.

Probable Cause

  • The National Oceanic and Atmospheric Administration (NOAA) had announced that this year, an “above-normal” hurricane season is expected in the US.  
  • One of the reasons behind this is the warmer-than-average sea surface temperatures in the tropical Atlantic Ocean and the Caribbean Sea, along with weaker tropical Atlantic trade winds and an enhanced west African monsoon.

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. 

Importance of naming a cyclone

  • It makes it easier for people to remember, as opposed to numbers and technical terms. 
  • Apart from the general public, it also helps the scientific community, the media, disaster managers, etc.
  • Also after naming a cyclone it is easy to identify individual cyclones, create awareness of its development, rapidly disseminate warnings to increased community preparedness, and remove confusion where there are multiple cyclonic systems over a region.
  • The use of short, distinctive names in written as well as spoken communications is quicker and less subject to error than the older, more cumbersome latitude-longitude identification methods.