NAME OF THE TOPIC
TROPICAL CYCLONE
CLASSIFICATION OF TROPICAL CYCLONES
Trop. cyclones are classified into 3 main groups,based on
intensity:
1.Tropical depressions
2. tropical storms,
3. More intense storms, whose name depends on the region.
For example, a tropical storm•In the N.W. Pacific referred to as a typhoon;
•In the N.E.Pacific, or in the North Atlantic, it is called a hurricane.
•In the S. Hemisphere or the Indian Ocean,It is called cyclones
MEANING OF THE TERMS
The word typhoon, which is used today in the
Northwest Pacific, may be derived
from Arabic ţūfān (‫ )طوفان‬which in turn originates
from Greek Typhon (Τυφών), a monster
from Greek mythology .
The word hurricane, used in the North Atlantic
and Northeast Pacific, is derived from huracán,
the Spanish word for the Carib/Taino storm
god, Juracán.
The word cyclone means 'a turning wind with
one eye' and comes from an old Greek story
about a race of one-eyed giants called 'Cyclops'.
TORNADO






v/s
Tornado has diameter on the scale of
100s of meters.
It produced from a single convective
storm (i.e. thunderstorm or
cumulonimbus)
It require substantial vertical shear of
the horizontal winds to form and grow
( i.e. change of wind speed &
direction with height)
It is produced in regions of large
temperature gradient.
It is primarily an over-land phenomena
tornadoes typically last on the scale of
minutes
TROPICAL CYCLONE






Tropical cyclone has diameter on the
scale of 100s of kilometers.
It comprises of several convective
storms.
It require very low values (less than 10
m/s [ 23 mph]) of vertical shear to
form and grow.
It is generated in regions of near zero
horizontal temperature gradient.
It is purely an oceanic phenomena
tropical cyclones have a lifetime that is
measured in days
CYCLONE
V/S
ANTICYCLONE
TROPICAL CYCLONE
A tropical cyclone is a storm
system characterized by a low
pressure center surrounded by a spiral
arrangement of thunderstorms that
produce strong winds and heavy rain.
Tropical cyclones strengthen when water
evaporated from the ocean is released as
the saturated air rises, resulting
in condensation of watervapour containe
d in the moist air.
The term "tropical" refers both to the
geographical origin of these systems, which
usually form in tropical regions of the globe,
and to their formation in maritime tropical air
masses.
The term "cyclone" refers to such storms'
cyclonic nature, with counterclockwise wind
flow in the Northern Hemisphere and
clockwise wind flow in the Southern
Hemisphere. The opposite direction of the
wind flow is a result of the Coriolis force.
All tropical cyclones are areas of low atmospheric
pressure in the Earth's atmosphere. The pressures
recorded at the centers of tropical cyclones are
among the lowest that occur on Earth's surface
at sea level.
Tropical cyclones are characterized and driven by
the release of large amounts of latent heat of
condensation, which occurs when moist air is
carried upwards and its water vapor condenses.
This heat is distributed vertically around the center
of the storm. Thus, at any given altitude (except
close to the surface, where water temperature
dictates air temperature) the environment inside the
cyclone is warmer than its outer surroundings.©
EYE AND CENTRE
A strong tropical cyclone will harbor an area
of sinking air at the center of circulation. If
this area is strong enough, it can develop
into a large "eye". Weather in the eye is
normally calm and free of clouds, although
the sea may be extremely violent. The eye is
normally circular in shape, and is typically
30–65 km (19–40 miles) in diameter, though
eyes as small as 3 kilometres (1.9 mi) and as
large as 370 kilometres (230 mi) have been
observed
EYE WALL
The eyewall is a circle of strong
thunderstorms that surrounds the eye; here
is where the greatest wind speeds are
found, where clouds reach the highest, and
precipitation is the heaviest. The heaviest
wind damage occurs where a tropical
cyclone's eyewall passes over land.
Hurricane Isabel (2003) as seen from
orbit during Expedition 7 of
the International Space Station.
The eye, eyewall and
surrounding rainbands that are
characteristics of tropical cyclones
are clearly visible in this view from
space.
SIZE
One measure of the size of a tropical cyclone
is determined by measuring the distance from
its center of circulation to its outermost
closed isobar, also known as its ROCI. If the
radius is less than two degrees of latitude
or 222 kilometres (138 mi), then the cyclone is
"very small" or a "midget“. Very large"
tropical cyclones have a radius of greater than
8 degrees or 888 kilometres (552 mi).
Size descriptions of tropical cyclones
ROCI
Type
Less than 2 degrees latitude
Very small/midget
2 to 3 degrees of latitude
Small
3 to 6 degrees of latitude
Medium/Average
6 to 8 degrees of latitude
Large
Over 8 degrees of latitude
Very large
MECHANICS
A tropical cyclone's primary energy
source is the release of the heat of
condensation from water
vapour condensing, with solar heating
being the initial source for evaporation.
Therefore, a tropical cyclone can be
visualized as a giant vertical heat
engine supported by mechanics driven
by physical forces such as
the rotation and gravity of the Earth
What primarily distinguishes tropical
cyclones from Extra tropical cyclones
is deep convection as a driving
force. Because convection is strongest in
a tropical climate, it defines the initial
domain of the tropical cyclone. By
contrast, mid-latitude cyclones(Extra
tropical cyclones) draw their energy
mostly from pre-existing horizontal
temperature gradients in the
atmosphere.
To continue to drive its heat engine,
a tropical cyclone must remain over
warm water, which provides the
needed atmospheric moisture to keep
the positive feedback loop running.
When a tropical cyclone passes over
land, it is cut off from its heat source
and its strength diminishes rapidly.
Scientists estimate that a tropical
cyclone releases heat energy at the
rate of 50 to 200 exajoules (1018 J)
per day. This rate of energy release
is equivalent to 70 times the world
energy consumption of humans and
200 times the worldwide electrical
generating capacity, or to exploding
a 10-megaton nuclear bomb every
20 minutes.©
Regional Specialized Meteorological
Centers (RSMCs)
There are six Regional Specialized Meteorological
Centers (RSMCs) worldwide. These organizations
are designated by the World Meteorological
Organization and are responsible for tracking and
issuing bulletins, warnings, and advisories about
tropical cyclones in their designated areas of
responsibility. In addition, there are six Tropical
Cyclone Warning Centers (TCWCs) that provide
information to smaller regions.
Major basins and related warning
centers
Basin
Responsible RSMCs and TCWCs
North Atlantic
National Hurricane Center (United States)
North-East Pacific
National Hurricane Center United States)
North-Central Pacific
Central Pacific Hurricane Center (United States)
North-West Pacific
Japan Meteorological Agency
North Indian Ocean
India Meteorological Department
South-West Indian Ocean Météo-France
Australian region
Bureau of Meteorology (Australia)
Indonesian Meteorological and Geophysical Agency
Papua New Guinea National Weather Service†
Southern Pacific
Fiji Meteorological Service
Meteorological Service of New Zealand
FORMATION OF TROPICAL CYCLONES
Map of the cumulative tracks of all tropical cyclones during the
1985–2005 time period. ThePacific Ocean west of
the International Date Line sees more tropical cyclones than any
other basin, while there is almost no activity in the Atlantic
Ocean south of the Equator.
MOVEMENT OF CYCLONES DUE TO WINDS
RATHER THAN WAVES
Although tropical cyclones are large systems
generating enormous energy, their movements over the
Earth's surface are controlled by large-scale winds—
the streams in the Earth's atmosphere.
In the Indian Ocean and Western Pacific (both north
and south of the equator), tropical cyclogenesis is
strongly influenced by the seasonal movement of
the Intertropical Convergence Zoneand the monsoon
trough, rather than by easterly waves.
EFFECTS
On land, strong winds can damage or
destroy vehicles, buildings, bridges, and
other outside objects, turning loose
debris into deadly flying projectiles.
The storm surge, or the increase in sea
level due to the cyclone, is typically the
worst effect from landfalling tropical
cyclones, historically resulting in 90%
of tropical cyclone deaths
Over the past two centuries,
tropical cyclones have been
responsible for the deaths of
about 1.9 million people
worldwide. Large areas of
standing water caused by
flooding lead to infection, as well
as contributing to mosquitoborne illnesses. ©
OBSERVATION
In general, surface observations are
available only if the storm is passing over
an island or a coastal area, or if there is a
nearby ship. Real-time measurements are
usually taken in the periphery of the
cyclone, where conditions are less
catastrophic and its true strength cannot be
evaluated. For this reason, there are teams
of meteorologists that move into the path
of tropical cyclones to help evaluate their
strength at the point of landfall.
Tropical cyclones far from land are tracked by 1.weather satellites capturing visible and infrared
images from space, usually at half-hour to quarterhour intervals. (sample image on next slide)
2.Doppler radar- As a storm approaches land, it can
be observed by land-based Doppler radar.
3. Hurricane hunters- Measurements in real-time, can
be taken by sending specially equipped
reconnaissance flights into the cyclone. In the Atlantic
basin, these flights are regularly flown by United
States government. These aircraft fly directly into
the cyclone and take direct measurements of
temperature, humidity & pressure inside the cyclone.
infrared image of cyclone by satellite
Infrared image of a powerful southern hemisphere cyclone, Monica,
near peak intensity, showing clockwise rotation due to the Coriolis
effect ©
FORCASTING
The average wind through the depth of the troposphere,
is considered the best tool in determining track direction
and speed. If storms are significantly sheared, use of
wind speed measurements at a lower altitude, such as at
the 700 hPa pressure surface (3,000 metres above sea
level) will produce better predictions. High-speed
computers and sophisticated simulation software allow
forecasters to produce computer models that predict
tropical cyclone tracks based on the future position and
strength of high- and low-pressure systems.
However, scientists are not as skillful at
predicting the intensity of tropical cyclones
TIME
Basin
Season start
Season end
Northwest Pacific
April
January
South Indian
November
April
Northeast Pacific
May
November
North Atlantic
June
November
Australia Southwest
Pacific
November
April
North Indian
April
December
CYCLONE SEASON IN INDIA
The 2012–13 South-west Indian
Ocean cyclone season is an ongoing
event in the annual cycle of tropical
cyclone formation. It began on
November 1, 2012, and will end on
April 30, 2013, with peaks in May
and Nov.
TROPICAL CYCLONE INTENSITY SCALE
(NORTH INDIAN OCEAN)
India Meteorological Department
Tropical Cyclone Intensity Scale
Category
Sustained winds
(3-min average)
Super Cyclonic Storm
>120 kt
>222 km/h
Very Severe Cyclonic Storm
64–119 kt
118–221 km/h
Severe Cyclonic Storm
48–63 kt
88–117 km/h
Cyclonic Storm
34–47 kt
62–87 km/h
Deep Depression
28–33 kt
52–61 km/h
Depression
≤27 kt
≤51 km/h
RECENT MOST INTENSE CYCLONE IN NORTH INDIAN OCEAN
Cyclonic Storm Nilam
Formed
Dissipated
Highest winds
October 28, 2012
November 1, 2012
3-minute sustained:
85 km/h (50 mph)
1-minute sustained:
100 km/h (65 mph)
Lowest pressure
Fatalities
Damage
Areas affected
990 mbar (hPa)
75 total
At least $56.7 million (2012USD)
Sri Lanka, South India
Cyclonic Storm Nilam was worst tropical cyclone to directly affect
south India since Cyclone Jal in 2010.
NAMING MOST INTENSE CYCLONES
Reading on Beaufort Scale
17 (for most intense cyclone)
10 min. sustained winds
136 knots(252 km/h)
N E Pacific & N. Atlantic
Category 5 hurricane
N W Pacific
Super Typhoon
N. Indian Ocean
Super Cyclonic Storm
S W Indian Ocean
Very intense Tropical Cyclone
Australia & S Pacific
Cat. 5 severe tropical cyclone
MOST RECENT HURRICANE OF
CATEGORY 5
Hurricane Sandy which hit the United States
east coast in late October 2012, caused
unprecedented damage, flooded subways,
closed down all major airports, resulted in
cancellation of over 15,000 flights, and claimed
more than one-hundred lives. Ten states were
declared disaster states.
List of costliest Atlantic hurricanes
1
"Miami"
1926
$157 billion
2
"Galveston"
1900
$99.4 billion
3
Katrina
2005
$81.0 billion
4
"Galveston"
1915
$68.0 billion
5
Andrew
1992
$55.8 billion
6
"New England"
1938
$39.2 billion
7
"Cuba–Florida"
1944
$38.7 billion
8
"Okeechobee"
1928
$33.6 billion
9
Donna
1960
$26.8 billion
10
Camille
1969
$21.2 billion
RECAPITULATION






Q.1 From where the term “CYCLONE” came ?
Q.2 which of the following is over-land phenomenon :
1) Tornado 2) Tro. Cyclone
Q.3 which of the following is having low pressure at its centre1) Cyclone 2) Anti-cyclone
Q. 4 Very large" tropical cyclones have a radius of greater
than –
1) 2 degree
2) 8 degree
3) 18 degree
Q. 5 what is the full form of ‘RSMC’ ?
Q. 6 Name the recently occurred Hurricane which came in
oct. 2012 ?
THANK YOU
PRESENTATION BY-
I.D.SONI
PGT-GEOGRAPHY
K.V.TAGORE GARDEN,NEW DELHI