Tropical Cyclone
Description
Watch Video on https://www.youtube.com/watch?v=GvumvaK9_44
Recently Cyclonic Storms Amphan and Nisraga has been formed
in the Bay of Bengal and the Arabian Sea, respectively.
Hence, hereby discussing the characteristics of Tropical
Cyclone, how they are named a disaster management strategy using a case study.
Tropical cyclones are violent storms that
originate over oceans in tropical areas and move over to the coastal areas
bringing about large scale destruction caused by violent winds, very heavy
rainfall and storm surge.
Conditions
Favorable for Tropical Cyclone Formation:
·
Large sea surface with temperature
higher than 27° C,
·
Presence of the Coriolis force
enough to create a cyclonic vortex,
·
Small variations in the vertical
wind speed,
·
A pre-existing weak low-pressure
area or low-level-cyclonic circulation, and
· Upper divergence above the sea level system.
Characteristics
· It is accompanied
by strong winds; Torrential rain; High tidal waves
and storm surge which can cause severe flooding in coastal areas, particularly
when this surge coincides with the normal high-tide.
· Wind speed in
tropical cyclones is usually directly related to atmospheric pressure. The
lower the pressure the faster the winds blow.
· The energy that
intensifies the storm comes from the condensation process in the towering
cumulonimbus clouds, surrounding the centre of the storm. With continuous
supply of moisture from the sea, the storm is further strengthened. On reaching the land the moisture supply is
cut off and the storm dissipates.
Regions
The states most exposed to cyclone-related hazards are West Bengal, Orissa, Andhra Pradesh and Tamil Nadu along the Bay of Bengal. Along the Arabian Sea on the West Coast, the Gujarat and Maharashtra coasts are more vulnerable compared to the southern part. The frequency of tropical cyclones is the greatest in the Bay of Bengal and Arabian Sea as compared to other cyclone-prone areas in the world.
|
Bay of Bengal vs Arabian Sea Tropical
cyclones Sea surface
temperatures and humidity both are directly correlated with chances of
cyclone formation, hence the Bay of Bengal is a more likely target because it
gets higher rainfall, and because the sluggish winds around it keep
temperatures relatively high: about 28 degrees around the year. Warm air currents
enhance this surface temperature and aid the formation of cyclones. In addition,
the Bay receives higher rainfall and constant inflow of fresh water from the
Ganga and Brahmaputra rivers. This means that the Bay’s surface water keeps
getting refreshed, making it impossible for the warm water to mix with
the cooler water below, making it ideal for a depression. On the other
hand, the Arabian Sea receives stronger winds that help dissipate the
heat, and the lack of constant fresh water supply helps the warm water mix
with the cool water, reducing the temperature. But not all
cyclones are formed in the Bay of Bengal. The basin is also host to cyclones
that are formed elsewhere but move towards the water body, especially those
formed in the Pacific Ocean. Cyclones usually weaken if they encounter a
large landmass. However, due to the lack of any such presence between the
Pacific and the Bay, cyclonic winds easily move into the Bay of Bengal. Once
here, the winds encounter the Western Ghats and the Himalayas, either
becoming weak or getting blocked in the Bay, but never reaching the Arabian
Sea. Further, the
Bay witnesses cyclones both pre-monsoon and post-monsoon. The
post-monsoon period sees a higher number of cyclones than the pre-monsoon
period. This is because summers and pre-monsoons see dry and hot air moving
from north-western India towards the Bay. This blocks the rise of air from
the water, and the subsequent formation of clouds, preventing
cyclone-friendly conditions. But the absence of this air movement in the
post-monsoon phase increases the chances of cyclones. |
Methodology
of Tropical Cyclone Naming
· Weather
forecasters give each tropical cyclone a name to avoid confusion.
· Adopting names for cyclones
makes it easier to remember, as opposed to numbers and technical terms. With a
name, 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.
· Each year,
tropical cyclones receive names in alphabetical order. Women and men’s names
are alternated.
· The name list is
proposed by the National Meteorological and Hydrological Services (NMHSs) of
WMO Members of a specific region, and approved by the respective tropical
cyclone regional bodies at their annual/ bi-annual sessions.
· There is a strict
procedure to determine a list of tropical cyclone names in an ocean basin by the
Tropical Cyclone Regional Body responsible for that basin at its
annual/biennial meeting.
· It is important
to note that tropical cyclones/ hurricanes/typhoons are not named after any
particular person.
· The Regional Specialized Meteorological Centre (RSMC) of Tropical Cyclones in New Delhi
is assigned the responsibility of issuing weather outlooks and tropical
cyclone advisories for the countries in the WMO/ESCAP Panel region bordering
the Bay of Bengal and the Arabian Sea. This is also the agency responsible for
naming the cyclones in this region.
Cyclone
warning and Management
· Cyclone warning and forecasting system in
India consists of six-cyclone warning centers located at Kolkata, Bhubaneswar,
Visakhapatnam, Chennai, Mumbai and Ahmedabad. These centers have their distinct
area wise responsibilities covering both the east and west coasts of India and
the oceanic areas of the Bay of Bengal and the Arabian Sea, including Andaman
& Nicobar and Lakshadweep.
· For governments to organize
disaster relief effectively, they need two things: Timely information about an
upcoming disaster, and incentives to respond to this information.
Case Study of Orissa in Disaster Management
In 1999, the Odisha government mismanaged its response to Super cyclone 05B. More than 10,000 people perished.
Since 1999, Odisha’s governments, with help from India’s federal government and the World Bank, built an impressive disaster response machinery, including a State Disaster Management Authority. Government agencies developed a system for disseminating timely information, critical for timely evacuations. They have created a large number of cyclone shelters, expanding the number from 21 in 1999 to 900 shelters in 2019 to ensure that everyone who could be threatened was within 1.5 miles of a shelter. And about 15,000 school buildings have been constructed or retrofitted to serve as temporary shelters.
In regions threatened with a cyclone, flood, or fire, governments need to decide when and where to order an evacuation. For this role of technology come into play. Meteorological satellites alerted the meteorological department when the cyclone altered its course and moved northwards.
The Odisha government ordered a targeted evacuation of the landfall areas, broadcasting the evacuation order over traditional media such as radio and television – and over cellphones, sending 2.6 million texts.
The government’s “zero casualty” policy for natural disasters and the
near accuracy of the India meteorological department’s early warning system
have helped reduce the possibility of deaths from cyclone.
