CYCLONES

• Are centres of low Pressure surrounded by closed isobars

• Having increasing pressure outward and closed air circulation towards central L.P.

• Air blows in Anticlockwise in Northern Hemisphere and Clockwise in Southern Hemisphere.

TYPES

• TROPICAL CYCLONES

• TEMPERATE OR EXTRA TROPICAL CYCLONES

TROPICAL CYCLONES

• Developed in the regions lying between the

Tropics of Cancer and Capricorn are called

TROPICAL CYCLONES.

Characteristics

• Size : 80 – 300km diameter

• Velocity : 32 – 180kms/hr

• Moves with very high velocity in ocean and becomes weak in land.

• The centre is characterised by Low Pressure.

Types of Tropical Cyclones

• On the basis of intensity:Weak cyclones: a) Tropical Disturbances

b) Tropical Depression

Strong Cyclones a) Hurricanes

b) Tornadoes

HURRICANES

• The extensive Tropical Cyclones surrounded by several closed isobars are called Hurricanes in U.S.A

Other Names

• Typhoon – China

• Willy Willy – Australia

• Cyclones – Indian Ocean

• Baguio – Phillippines

• Taifu - Japan

Characteristic Feature

• Represented by more symmetrical and circular isobars.

• Pressure increases sharply from centre towards outer margin

• Steep pressure gradient

• Heavy down pour.

Properties

• Diameter ranges from 160 – 640km

• Size is small near equator and increases away from equator.

• Pressure range between 900 – 950mb which is lowest of all tropical cyclones.

• Pressure gradient range between 10mb – 55mb.

Eye of cyclone

The area between 6 – 48sqkm around the centre of hurricane is dry, rainless and winds are feeble.. This is called eye of the cyclone

Eye of cyclone

Effects

• Physical Damage

• Casualities and Public health: Malaria, Diarhoea, contamination of water.

• Damage to crops

• Water supplies: ground and piped water supply gets contaminated by flood.

Major Hurricane Tracks

•After 1945 hurricanes were named in Alphabetical order of their occurences each year.

Beach surge of Katrina – August 3 2005

•Hazel – 1954

•Camille – 1969

•Agnes – 1972

•Gilbert – 1988

•Hugo – 1989

•Katrina – 2005

•Wilma - 2005

Major Hurricanes

2008 NAMES• Arthur• Bertha• Cesar• Dolly• Edouard• Fran• Gustav• Horrtense• Isidore• Josephine• Kyle

• Lili• Marco• Nana• Omar• Paloma• Rene• Sally• Teddy• Vicky• Wilfred

2009 NAMES

• AnaBillClaudetteDannyErikaFredGraceHenriIdaJoaquinKate

• LarryMindyNicholasOdettePeterRoseSamTeresaVictorWanda

2010 NAMES

• AlexBonnieColinDanielleEarlFionaGastonHermineIgorJulia

• KarlLisaMatthewNicoleOttoPaulaRichardSharyTomasVirginieWalter

Mitigation Strategies

• Hazard Mapping

• Landuse Control Design

• Engineered Structures

• Coastal Shelter Belt

• Improving Vegetation Cover