2. If the storm occurs in the Atlantic Ocean
and North-east Pacific, it's called a
hurricane.
If the exact same type of storm occurs in
the North-west Pacific, this is a typhoon.
And if we find those same storms in the
South Pacific and Indian Ocean, these are
called tropical cyclones.

3. cyclone
• Cyclone is a rapidly rotating storm
system characterized by a low pressure
center, a closed low level atmospheric
circulation, strong wind and a spiral
arrangement of thunder storms and heavy
rain

4. What are cyclones?
Where do they occur?
When do they occur?
How do they form?

5. How do they occur?
Three stages:
1. Formation and initial development
2. Maturing
3. Modification and decay

6. How do they occur?
To form a cyclone, warm, moist air over the ocean
rises upward .
As this air moves up and away from the ocean
surface, it leaves is less air near the surface.
 So basically as the warm air rises, it causes an
area of lower air pressure below.
Air from surrounding areas with higher air
pressure pushes in to the low pressure area.
Then this new “cool” air becomes warm and
moist and rises, too. And the cycle continues…

8. • As the warmed, moist air rises and cools the
water in the air forms clouds
• As the cycle continues, more air rises up and
cloud becomes thick
• Condensation then releases the latent heat of
energy stored in the water vapour ( power for
cyclone)

9. • The whole system of clouds and wind spins and
grows, fed by the ocean’s heat and water evaporating
from the ocean surface
• The system spins due to the coriolis effect
The Coriolis effect makes storms swirl clockwise in the
Southern hemisphere and counter clockwise in the
Northern Hemisphere.
• As the storm system rotates faster and faster, an eye
forms in the centre.
– It is very calm and clear, with very low air pressure. Higher
pressure air from above flows down into the eye.

10. • When the winds in the rotating storm reach 39 mph
(63 kmph), the storm is called a “tropical storm”.
• And when the wind speeds reach 74 mph (119 kmph),
the storm is officially a “tropical cyclone” or
hurricane.
• Tropical cyclones usually weaken when they hit land,
because they are no longer being “fed” by the energy
from the warm ocean waters.
• However, they often move far inland, dumping many
centimeters of rain and causing lots of wind damage
before they die out completely

12. Types of cyclone
Tropical cyclone
Extra tropical cyclone ( temperate cyclone)
Polar lows or artic hurricanes
Polar cyclones
Mesocyclones

13. Tropical cyclones
• Occur over tropical ocean regions.
• Hurricanes and typhoons are types of tropical
cyclones.
• Major tropical-cyclone basins are
– North Atlantic (including the Caribbean),
– Eastern Pacific
– Western Pacific
– North Indian Ocean
– Southwest Indian Ocean
– Southern Pacific
– Australian region

14. • Tropical cyclones develop within 5 and 30
degrees of latitude.
:Because they require ocean waters of 80
degrees Fahrenheit or so to form cyclone.
( primary condition for the formation of
tropical cyclone)
How dose it occur?

16. • Classified further based on their wind speeds.
(mph- Miles per hour)

17. Midlatitude or Extratropical Cyclones
• The cyclonic storms that develop in the middle
latitudes. (between 30° and 60° latitude from
the equator)
• These cyclones develop where sharp temperature
gradients exist between adjoining air masses.
• extratropical cyclones produce rapid changes in
temperature and dew point along broad lines,
called weather fronts, about the center of the cyclone.
• Extra tropical cyclones form as waves along weather
fronts before occluding later in their cycle as cold core
cyclones

18. • The winds are generally weaker.
Formed by:
 Cyclogenisis:
development of cyclonic circulation in atmosphere.
 Extra tropical transistion:
 process by which a tropical cyclone upon encountering
with a baroclinic environment and reduced sea surface
transforms into an extra tropical cyclone

19. Polar cyclones
• Polar cyclones are 1000 to 2000 km wide in
which the air is moving in a spiral counter
clockwise in Northern hemisphere.
• Occur in Polar Regions like Greenland, Siberia
and Artic ,Antarctica and northern canada.
• Usually stronger in winter months.
• Damages are usually minimal, as they occur in
areas that aren't very populated

20. Polar Lows or Arctic Hurricanes
• Forms over Arctic and Antarctic seas.
• Sparked by frigid air moving over somewhat
warmer ocean waters.
• Their energy source – heat transfer from
water to air and latent heat released by cloud
condensation.
• Often form quickly, sometimes in less than 24
hours, and can be difficult to forecast.

21. Mesocyclone
• Is when part of a thunderstorm cloud starts to
spin, which may eventually lead to a tornado.
• Tornadoes all come from thunderstorm clouds,
but not all thunderstorm clouds make
tornadoes.
• Rotating “wall clouds” may descend from
mesocyclones and ultimately form a funnel
cloud, which, if it contacts the ground,
becomes a tornado.

23. How mesocyclone and Tornado
forms?
 Primary requirement - A wind shear, where wind blows
faster in one spot than another (A blanket of air is
flowing over another one).
 This sets up a rolling vortex, a horizontally rotating mass
of air (like the way a wave breaks when it gets to a
beach)
 This spinning vortex in the middle is called a
mesocyclone.

24. An updraft then lifts that vortex, which then
spins vertically.( Updraft happens when moist
air moves upwards)
Rotating “wall clouds” may descend and
ultimately form a funnel cloud, which, if it
contacts the ground, becomes a tornado

28. • More cyclone occur in bay of Bengal than in
Arabian sea and the ratio is 4:1
• Indian Ocean is one of six major cyclone prone
regions of the world
• There are two definite seasons of tropical
cyclones in the North Indian Ocean. One is
from May to June and the other from mid-
September to mid-December

30. Impacts of cyclone
Impact mainly depends upon:
intensity
its size
its location

31. Classified into three:
• Primary hazard : involves destructive winds,
debris and storm surge.
• Secondary hazards: include flooding and fires.
• Tertiary hazards: include spikes in prices of food
and other necessities, as well as long term hazards
like water-borne diseases.

32. Upon landfall
The most significant effects of a tropical cyclone
occur when they cross coastlines,
making landfall (destroys ships and lives)
1. Strong winds
2. Storm surge
3. Heavy rainfal
4. Tornados

33. Effects on natural resources
• Geomorphology:
– reshape the geology near the coast by eroding sand
from the beach as well as offshore, rearranging
coral, and changing dune configuration onshore
• Coastal ridges
– erode undersea sands, shell deposits, break off
corals from shore reefs, and carry all this detritus
landwards in a rolling wave of material that is
deposited onshore

34. • Limestone cave
– When tropical cyclones cross land, thin layers of calcium
carbonate of 'light' composition (i.e. unusual isotopic ratio
of Oxygen-18 and Oxygen-16) are deposited onto
limestone caves up to 300 kilometres (190 mi) from the
cyclone's path
• Landscapes