CYCLONES
Tropical Cyclones are formed over the ocean in the area around the equator, between the Tropicof Cancer and the Tropic of Capricorn.
Cyclones are giant, spinning, whirlwind storms. They arecalled hurricanes in North America and typhoons in Asia.
In order for a cyclone to be identified as a cyclone, it mustbe travelling over 119 km per hour and it must have been
formed over the ocean in a tropical region. These greatstorms are usually dangerous and can cause damage toeverything in their path. A cyclone will often bring with it
heavy rains that can cause flooding.
In order for a cyclone to form, the ocean waters need tobe warm, at least 26°C. Above the warm ocean, water
evaporates and forms clouds. If there is low air pressure
where the clouds are formed, it pulls them in and they
begin to rotate. It is the earth rotating and spinning on its
axis that causes the cyclone’s clouds to rotate. Clouds
will continue to form and begin spinning more.
This is the stage when it can develop into a mature
cyclone, or lose its momentum. Even if it has developed
into a mature cyclone, it can still grow in size andincrease its wind speed. In order for it to be categorised
as a cyclone, its average sustained wind speed needs toexceed 63 km per hour. To be classified as severe, theaverage sustained wind speed needs to exceed 118 km
per hour.
Once a cyclone arrives over land, its strength weakens
and it begins to fade out. This is due to the lack ofmoisture and heat compared to the ocean over which it
was formed.

How often do they occur?
Cyclone season in Australia is between November andApril, however cyclones can still occur in May. The
season for hurricanes and typhoons in the Northern
Hemisphere (http://schools.aemi.edu.au/node/18#n) is
between June and November. Bureau of Meteorology(http://www.bom.gov.au), Australia has, on average,
13 cyclones a year. Half of these occur in the westernregions.

Severity and Categories
Cyclones are categorised according to their strength. There are five categories: Category 1 is the weakest andCategory 5 is the strongest.
CategoryWind gusts		

Ocean Swells 			Damage1		Upto 125kmh 		

1.2m to 1.6m			Trees and farmland damaged		Gales			Slight damage			2		126kmh to 169kmh					1.7m to 2.5m			
Significant damage		

Minor house damage. Severe damage tosigns and trees. Heavy damage to crops3		2.6m to 3.7m			

House roofs and most likely power failures170kmh to 222kmh		Destructive
4 		225kmh to 279kmh
3.8m to 5.4m			
Airborne debris, widespread power failure		Destructive		
Significant roof and													structrual damage
5		Winds above 280kmh More than 5.5m.		
Houses flattened, cars overturned				Very destructive		
Significant destruction													and extremely dangerous												conditions							Every cyclone has an eye
The eye is in the centre of the cyclone and can vary insize from 10 km to 100 km, depending on the severityof the storm. Because there is the least amount of airpressure in the eye, it produces clear weather with light
wind, no clouds, no rain and some sunshine. Do not befooled by the eye: the storm is not over yet. This is only
the middle of the storm. Depending on the wind gusts, theeye may pass in a few minutes or in a few hours.

You are always advised to stay indoors during thepassing of the eye of the storm, because the cyclone
will continue. Always listen for the official word thatthe cyclone has passed and when it is safe to leave
your shelter. When going outside, be aware of fallen
powerlines, debris and damage left behind after thecyclone.

Did you know?
The average life of a cyclone is one week.
After the eye passes and the other side of the cyclone
hits, the wind blows with equal strength but in theopposite direction.
Tropical cyclones from the Southern Hemisphere spinclockwise, while hurricanes and typhoons in the Northern
Hemisphere spin anti-clockwise.
Cyclone Tracy was Australia’s most destructive cyclone.
Cyclones are assigned names, which are chosen from alist.

Names of cyclones
Each cyclone is named from one of the names in the below table. The names start from the top of the list andalternate between male and female name. Once the end of the list is reached it begins again.

Letter		Cyclone names

A		Anika		Anthony

Alessia

B		Billy		Bianca

Bruce		Blanche

BlakeC		

Courtney

Christine

Caleb		

Clauadia

DianneDylandDebbieDamien			CharlotteD		 Dominic

Alfred		AnnE		Ellie		Errol		Edna		Ernie		EstherF		 Freddy

Fina		 Fletcher

Frances

Ferdinand

G		Gabrielle

Grant		Gillian		Greg		Gretel

H		Herman

HayleyHadi		Hilda		HaroldI		Ilsa		Iggy		Ita		Ira		Imogen		J		Jasper

Jenna		Jack		Joyce		Joshua			

K		Kirrily		Koji		Kate		Kelvine

Kimi				

L		Lincoln

Luana		Lam		Linda		Lucas				M		Megan

MitchellMarciaMarcusN		Neville

NarelleNathanNora		Noah				O		Olga		Oswald

Marian			Olwyn		Owen		Odette

P		Paul		Peta 		Penny		Paddy
Q		Quang											R		Robyn		Rusty		Raquel
S		Sean		Sandra

Riley		Ruby				Stan		Savannah

T		Tasha		Tim		Tatjana

Seth				Trevor		Riffany			

U		Uriah												V		Vince		Victoria

Vermon							

W		Wallace											Y		Yvette												Z		Zelia		Zane