Cyclone Fani

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Cyclone Fani

Background

  • A powerful cyclonic storm named Fani (pronounced Foni) hit the Odisha coast, with its landfall near Puri.
  • Cyclone Fani, which has been classified as an extremely severe cyclone (ESC), is the 10th such cyclone to hit India in May in past 52 years.
  • The India Meteorological Department (IMD) classifies cyclones on the basis of the maximum sustained surface wind speed (MSW) they generate (One knot is equal to 1.8 kmph).
    • The cyclones are classified as –
      • severe (MSW of 48-63 knots),
      • very severe (MSW of 64-89 knots),
      • extremely severe (MSW of 90-119 knots) and
      • super cyclonic storm (MSW of 120 knots or more).
    • Data from the India Meteorological Department (IMD) show that the last time an extremely severe cyclone hit India in May was in 2004.
      • The other years when such cyclones were witnessed in May are: 1968, 1976, 1979, 1982, 1997, 1999 and 2001.
      • The last time such a powerful cyclonic storm had emerged in the Bay of Bengal at this time of the year, in 2008, it had killed more than 1.25 lakh people in Myanmar.
      • But that was mainly because of the lack of a sophisticated warning system and enough logistical preparedness to evacuate people.
    • Fani, on the other hand, has been continuously monitored ever since it developed southeast of Sri Lanka about a week ago, warnings have been issued after every few hours to fishermen and people living in coastal regions, and a massive emergency preparedness has been mounted.
    • In the last few years, India has impressively managed disasters caused by cyclones, most remarkably during Cyclone Phailin of 2013, which was even stronger than the approaching Fani.

How Cyclone Fani got its name

  • The name for this cyclone was suggested by Bangladesh.
  • The World Meteorological Organisation (WMO) has devised a mechanism where countries submit a list of names from time to time. Names of cyclones are chosen from this pool.
  • For tropical cyclones developing in the North Indian Ocean, countries like India, Sri Lanka, Bangladesh, Maldives, Myanmar, Oman, Pakistan and Thailand send their names to the regional tropical cyclone committee.
  • At present, all eight countries have submitted eight names each for naming future cyclones. The name Fani was chosen from this list containing 64 names.
  • The word Fani (pronounced as Foni) means snake.
  • In 2018 Cyclone Titli hit Andhra Pradesh and parts of Odisha. This cyclone was named by Pakistan.
  • In 2017, Cyclone Ockhi caused severe damage in Kerala and parts of Tamil Nadu. Its name was given by Bangladesh.
  • The names given by India are: Agni, Akash, Bijli, Jal, Lehar, Megh, Sagar and Vayu.

Cyclone Fani, the Outlier: What makes Cyclone Fani special

  • Timing and strength are two factors that make Cyclone Fani, pronounced as Foni, different from most other tropical cyclones in this time of the year.
  • The eastern coast of India is no stranger to cyclones. On an average, five to six significant cyclonic storms emerge in the Bay of Bengal region every year. The months of April and May just before the start of the monsoon, and then October to December immediately after the end of the monsoon, are the prime seasons for tropical cyclones.
  • Generally, extremely severe cyclones hit India’s east coast in the post-monsoon season (October-December). IMD data on cyclones that hit India between 1965 and 2017 show that the country has weathered 39 extremely severe cyclones in these 52 years. Of these, nearly 60 per cent (23) were between October and December.
  • Cyclones emerging in April-May usually are much weaker than those during October-December.
    • There have been only 14 instances of a “severe cyclone” forming in the Bay of Bengal region in April since 1891, and only one of them, which formed in 1956, touched the Indian mainland.
    • The others all swerved northeast to hit Bangladesh, Myanmar or other countries in the southeast Asian region. Since 1990, there have been only four such cyclones in April.
  • Fani is not just a severe cyclone but an “extremely severe cyclone”.
  • Fani is, thus, unusual, and that is mainly because of the place it originated, very close to the Equator, and the long route it has taken to reach the landmass.

Strengthening over seas

  • Cyclones are formed over slightly warm ocean waters. The temperature of the top layer of the sea, up to a depth of about 60 metres, need to be at least 28°C to support the formation of a cyclone.
  • Two sources Of cyclones: The Indian subcontinent experiences cyclones from two basins: the Bay of Bengal basin and the Arabian Sea basin.
    • Of the two, more cyclones are generated in the Bay of Bengal and cyclones here have also been more severe than the one generated over the Arabian Sea.
    • One of the reasons why tropical cyclones are more prone to the Bay of Bengal is that its surface temperature is more than that of the Arabian Sea.
    • Tropical cyclones generally need a temperature of around 28 degrees Celsius. The Bay of Bengal is more conducive to this than the Arabian Sea.
  • This also explains why the April-May and October-December periods are conducive for cyclones.
    • Then, the low level of air above the waters needs to have an ‘anticlockwise’ rotation (in the northern hemisphere; clockwise in the southern hemisphere).
    • During these periods, there is a zone in the Bay of Bengal region (called the inter-tropical convergence zone that shifts with seasons) whose southern boundary experiences winds from west to east, while the northern boundary has winds flowing east to west. This induces the anticlockwise rotation of air.
  • Once formed, cyclones in this area usually move northwest. As it travels over the sea, the cyclone gathers more moist air from the warm sea, and adds to its heft.
  • A thumb rule for cyclones (or hurricanes and typhoons as they are called in the US and Japan) is that the more time they spend over the seas, the stronger they become.
    • Hurricanes around the US, which originate in the vast open Pacific Ocean, are usually much more stronger than the tropical cyclones in the Bay of Bengal, a relatively narrow and enclosed region.
    • The cyclones originating here, after hitting the landmass, decay rapidly due to friction and absence of moisture.
  • A big difference between the strengths of cyclones in April-May and October-December is that the former originate in situ in the Bay of Bengal itself, barely a few hundred kilometres from the landmass.
    • On the other hand, cyclones in October-December are usually remnants of cyclonic systems that emerge in the Pacific Ocean, but manage to come to the Bay of Bengal, considerably weakened after crossing the southeast Asian landmass near the South China Sea.
    • These systems already have some energy, and gather momentum as they traverse over the Bay of Bengal.

How Cyclone Fani grew muscle

  • The in situ cyclonic systems in the Bay of Bengal usually originate around latitude 10°, in line with Chennai or Thiruvananthapuram. Fani, on the other hand, originated quite close to the Equator, around latitude 2°, well below the Sri Lankan landmass.
  • Another aspect that makes Cyclone Fani special is its trajectory. Fani started developing around the Equator and moved upwards. It thus has had a much longer journey from its starting point to the point where it made a landfall, than other cyclones that generate in the Bay of Bengal.
  • The IMD had first predicted that Cyclone Fani would make a landfall in Tamil Nadu but the forecast was updated as the cyclone altered its course.
    • Had Cyclone Fani made its landfall in Tamil Nadu, it was possible that its strength would have been lower than its present strength because a landfall in Tamil Nadu would have meant that Fani would have covered a shorter distance over the sea.
  • Most cyclones that generate exclusively in the Bay of Bengal become relatively weaker by the time they reach the Indian landmass.
  • However, the case with Cyclone Fani is different since it developed almost close to the Equator.

How cyclones cause damage

  • Cyclones are powerful storms that generate strong windspeeds and have the potential to trigger sudden and heavy rain in the affected areas.
  • There are basically three aspects related to cyclones that have the potential to cause destruction-flooding due to rising sea, destruction caused by strong winds and damage due to heavy rains.
    • When a cyclone is formed over the sea, it generates strong winds along it. These winds have the potential to generate storm surges. A storm surge is an abnormal rise in the sea level due to a storm (cyclone, hurricane etc).
      • A storm surge becomes dangerous because it has the potential to flood low-lying areas along the coast.
      • It can drown humans and animals, destroy infrastructure and damage environment by eroding beaches, flooding vegetation, among others.
    • The second dame-causing aspect of cyclones is the strong winds that are generated by the storm. These strong winds that accompany cyclones can uproot trees, electricity poles, shatter houses etc.
      • This is a common phenomenon in the United States of America which regularly weathers strong hurricanes.
    • The third aspect with cyclones is their ability to cause sudden, heavy and prolonged rain in the affected areas.
      • This causes floods in rivers, pollutes drinking water and if combined with storm surge, it becomes a double whammy.
    • Unfortunately, all the three factors occur at the same time when a cyclone makes a landfall. The IMD states that of three factors, it is storm surge that is most catastrophic and causes widespread destruction.

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