Hurricane

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With winds reaching as high as 200mph, hurricanes are strong, cyclonic, convective storm systems that form over the ocean in the troposphere and can cause devastating damage once they reach land. Hurricanes may also be referred to as tropical cyclones or typhoons dependent on their location.

Structure of a hurricane

Structure of a hurricane
  • A hurricane has an eye at its center where there is very little or no precipitation. The eye is surrounded by deep cloud wall with heavy precipitation and the strongest of winds. This is referred to as the eyewall. [1]
  • Just outside of the eyewall, there are often narrow rainbands, called inner spiral rainbands with more strong winds. [1]
  • Further outside are more rainbands with relatively strong convective forces. These rain- bands are referred to as outer spiral rainbands. [1]
    Satellite view of hurricane Katrina
  • In the lower troposphere, just above the Earth's surface are strong inflows of warm air. [1]
  • The inflow then converges and turns upward in the eyewall to begin convection. [1]


  • A large part of the air from the eyewall updraft turns radially outward, spinning and forming a cool outflow layer. The pressure and temperature difference between the inflow and outflow air in the system causes these powerful, convective swirling winds. [1]

Measuring a hurricane

Category The Saffir-Simpson Hurricane Wind Scale uses a categorical system to measure the intensity of a hurricane based on sustained winds speeds. [2]

  • Category One 74-95 mph
  • Category Two 96-110 mph
  • Category Three 111-130 mph
  • Category Four 131-155 mph
  • Category Five 156+ mph

Millibars [3] The average sea level atmospheric pressure is 1013.25 millibars (mb) measured with a barometer. A drop in atmospheric pressure usually indicates the approach of a storm, such as a hurricane. Hurricane atmospheric pressure typically ranges between 930-980mb.

Normal and storm surge conditions

Storm surge [3] The storm surge is the increase in sea level due to hurricane pressure and winds. As the sea level rises, tides reach further inland potentially causing major flooding. This can be particularly dangerous for coastal areas as sea levels can rise above 20ft flooding miles inland the coast. The storm surge has the potential to cause more damage than the winds of a hurricane.

Damage cost Hurricanes typically cause costly damages. The damages depend on the size, strength, duration, and location of the storm. Because of these various factors, damage cost may be used to measure a hurricane.

Effects of climate change on hurricanes

Hurricanes are continuously growing in prevalence, size, and strength in a linear pattern. Studies suggest that these changes are directly related to the increase in average global temperature. An article published by the American Geophysical Union in 2006 states “results indicate that anthropogenic factors are likely responsible for long-term trends in tropical Atlantic warmth and tropical cyclone activity.” [4] This research suggests humans may have a direct impact on the prevalence and strength of hurricanes due to our continuously growing CO2 emissions. Because warm, moist air is the perfect breeding ground for a hurricane, as the average global temperature increases, so does hurricane incidence. [4]
Hurricane approaching land

Historic hurricanes by category

Category 1

  • Hurricane Agnes (1972) 977mb $2.1 Billion [5] [6]

Category 2

  • Hurricane Juan (2003) 969mb $200 Million [6]

Category 3

  • Hurricane Sandy (2012) 940mb, $50 Billion [6]
  • Hurricane Irene (2011) 942mb, $16.5 Billion [6]

Category 4

  • Hurricane Gustav (2008) 941mb, $6 Billion [6]
  • Hurricane Floyd (1999) 921mb, $6 Billion [5] [6]
  • Hurricane Dennis (2005) 956mb, $2.5 Billion [5]
  • Hurricane Wilma (2005) 882mb, $16.8 Billion [5]

Category 5

  • Hurricane Mitch(1998) 905mb, $5+ Billion [5] [7]
  • Hurricane Katrina (2005) 902mb, $75 Billion [5]

Hurricane preparedness

Although hurricane season begins on June 1st and ends on November 30th each year, storms can be very unpredictable; therefore it is crucial to be prepared for any kind of weather at any time. Hurricane preparedness should be practiced during hurricane season especially for those most at risk of flooding. The National Hurricane Center, under NOAA, provides details on Hurricane Preparedness steps you can take to prepare yourself for hurricanes and how to recover after the storm. [8]


See also

Other closely related articles in this wiki include:


References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Wang, Y. (2015). TROPICAL CYCLONES AND HURRICANES | Hurricane Dynamics A2 - Zhang, Gerald R. NorthJohn PyleFuqing. In Encyclopedia of Atmospheric Sciences (Second Edition) (pp. 8–29). Oxford: Academic Press. Retrieved from http://www.sciencedirect.com/science/article/pii/B9780123822253004886
  2. Saffir-Simpson Hurricane Wind Scale. (n.d.). Retrieved April 8, 2016, from http://www.nhc.noaa.gov/aboutsshws.php
  3. 3.0 3.1 Hurricane Glossary | SECOORA. (n.d.). Retrieved March 23, 2016, from http://secoora.org/classroom/virtual_hurricane/hurricane_glossary
  4. 4.0 4.1 Mann, M. E., & Emanuel, K. A. (2006). Atlantic hurricane trends linked to climate change. Eos, Transactions American Geophysical Union, 87(24), 233–241. http://doi.org/10.1029/2006EO240001
  5. 5.0 5.1 5.2 5.3 5.4 5.5 Hurricanes in History. (n.d.). Retrieved April 8, 2016, from http://www.nhc.noaa.gov/outreach/history/
  6. 6.0 6.1 6.2 6.3 6.4 6.5 Hurricanes. (n.d.). Retrieved April 8, 2016, from https://coast.noaa.gov/hurricanes/
  7. NCDC: Hurricane Mitch. (n.d.). Retrieved April 8, 2016, from https://www.ncdc.noaa.gov/oa/reports/mitch/mitch.html
  8. Hurricane Preparedness - Be Ready. (2016). Retrieved February 24, 2016, from http://www.nhc.noaa.gov/prepare/ready.php


External links

Relevant online sources to this wiki article include: