Hurricanes

 

Hurricanes

  1. Why in news
    • Too many tropical storms have developed in the Caribbean in 2017 – Harvey, Irma, Jose, Katia
  2. Why is this happening?
    1. The formation of consecutive storms in this region is not an aberration, especially in Aug, Sep and Oct.
      • The ‘hurricane season’ spans 6 months – 1 June to 30 Nov. 95% of all hurricanes form during this period.
      • On an avg, 12 hurricanes develop in the Atlantic basin.
      • The NOAA of USA has among the world’s most advanced hurricane observation systems.
    2. Favourable conditions develop during the ‘hurricane season’
      • warm waters
      • lack of ‘wind shear’
  3. Role of climate change
    • Overall, with warming climate, the moisture-retention capacity of air rises + the water becomes warmer. This helps in formation of storms and produces more rain than avg.
    • As sea level rises, storm surges worsen, and thus the impact of hurricanes.
    • But, the link between climate change and hurricanes is not yet clearly understood.

 

Basics

  1. What is a ‘hurricane’
    • These are the most violent and devastating ‘tropical cyclones’.
    • Tropical cyclones are rotating low-pressure weather systems that form over the tropical and sub-tropical waters – Atlantic basin (including the Atlantic ocean, Caribbean sea and Gulf of Mexico) and Eastern & Central North Pacific ocean.
  2. Categories of Hurricanes
    1. Categories (based on the Saffir-Simpson Hurricane Wind Scale)
      • Category 1 – Wind speed – 74-95 mph
      • Category 2 – 96-110 mph
      • Category 3 – 111-129 mph
      • Category 4 – 130-156 mph
      • Category 5 – 157 mph or higher
    2. Irma’s speed (one of the most powerful hurricane ever)
      • 185mph
  3. Names of Hurricanes
    • Hurricanes are given short, distinctive and easily remembered names
      • to make them easy to identify and describe, and less prone to error while exchanging storm-related data across different locations.
    • The WMO, a specialised UN body,
      • maintains 6-yearly rotating lists of names for each of the world’s tropical cyclone basins.
      • Thus 21 names have been decided for each year form 2017-22.
      • The 2017 list will be used again in 2023.
    • If a cyclone is particularly devastating – Andrew (1992), Katrina (2005), Sandy (2012) –
      • then its name is retired and replaced by another one.
    • In case there are more than 21 storms in a year,
      • the subsequent storms are named after the Greek alphabet, beginning with Alpha, Beta, Gamma etc.

 

QUESTIONS

  1. Whar are hurricanes. How are they named and classified?