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Cyclones - Get the Facts

Cyclones – formally Tropical Cyclones – are formed over the ocean in the tropics.

In order for a cyclone to form, the ocean waters need to be warm, at least 26°C. Above the warm ocean, water evaporates and form 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’s rotation 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 and increase its wind speed.

In order for it to be categorised as a cyclone, its wind speed needs to exceed 119 kilometres per hour. Once they arrive over land, their strength weakens and they begin to fade out. This is due to the lack of moisture and heat compared to the ocean over which it was formed.

How often do they occur?

Cyclone season in Australia is between November and April, but cyclones can still occur in the month of May.

The season for Hurricanes and Typhoons in the Northern Hemisphere is between June and November.

According to the Bureau of Meteorology, Australia has, on average, 13 cyclones a year. Half of these occur in the western regions.

Severity and Categories

Cyclones are categorised according to their strength. There are 5 categories: Category 1 is the weakest and Category 5 is the strongest.

Category	Wind Gusts	Ocean Swells	Damage
1	Up to 125km/hr Gales	1.2 – 1.6m	Slight damage Trees and farmland damaged.
2	126 – 169km/hr Destructive	1.7 – 2.5m	Significant Damage Minor house damage. Severe damage to signs and trees. Heavy damage to crops
3	170 – 224km/hr Very Destructive	2.6 – 3.7m	Structural damage House roofs and most likely power failures
4	225 – 279km/hr Very Destructive	3.8 – 5.4m	Significant roofing and structural damage Airborne debris, widespread power failure
5	Winds above 280km/hr Very Destructive	More than 5.5m	Almost total destruction and extremely dangerous Houses flattened, cars over turned

Every cyclone has an ‘eye’

The eye of a swirling cyclone.

The eye is in the centre of the cyclone and can vary in size, from 10 kilometres to 100 kilometres, depending on the severity of the storm.

Do not be fooled by the eye!

Due to the least amount of air pressure in the eye, it produces clear weather with light wind, no clouds, no rain and some sunshine. But, the storm is not over yet.

This is only the middle of the storm. Depending on the wind gusts, the eye may pass in a few minutes or in a few hours.

You are always advised to stay indoors during the passing of the eye of the storm, because the cyclone will continue. Always listen for the official word that the 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 the cyclone.

Did you know?

The average life of a cyclone is 1 week.
After the eye passes, and the other side of the cyclone hits, the wind blows with equal strength but in the opposite direction.
Tropical Cyclones, from the Southern Hemisphere spin clockwise, and Hurricanes and Typhoons in the Northern Hemisphere spin anti-clockwise.
Cyclone Tracy was Australia’s most destructive cyclone.
Cyclones are assigned names, which are picked from a list.

Names of cyclones

Naming of a new cyclone is done by one of the three Tropical Cyclone Warning Centres (TCWC) in Perth, Darwin or Brisbane. Cyclone names are chosen from the place where they start. So, if a cyclone starts in Queensland, then the Brisbane TCWC would choose the name for the cyclone.

Each cyclone is named from one of the names in the below table. The names start from the top of the list and take it in turns to be a male or female name.

	Perth TCWC			Darwin TCWC		Brisbane TCWC
A	Adeline	Alison	Alex	Amelia	Alistair	Alfred	Ann	Anika
B	Bertie	Billy	Bessi	Bruno	Bonnie	Blanch	Bruce	Bernie
C	Clare	Cathy	Clancy	Coral	Craig	Caleb	Cecily	Claudia
D	Daryl	Damien	Dianne	Dominic	Debbie	Denise	Dennis	Des
E	Emma	Ellie	Errol	Esther	Evan	Ernie	Edna	Erin
F	Floyd	Frederic	Fiona	Ferdinand	Farrah	Frances	Fletcher	Fritz
G	Glenda	Gabrielle	Grant	Gretel	George	Greg	Gillian	Grace
H	Hubert	Hamish	Harriet	Hector	Helen	Hilda	Harold	Harvey
I	Isobel	Ilsa	Iggy	Irma	Ira	Ivan	Ita	Ingrid
J	Jacob	Joseph	Jana	Jake	Jasmine	Joyce	Jack	Jim
K	Kara	Kirrily	Ken	Kay	Kim	Kelvin	Kitty	Kate
L	Lee	Leon	Linda	Laurence	Laura	Liz	Les	Larry
M	Melanie	Marcia	Mitchell	Marian	Matt	Marcus	May	Monica
N	Nicholas	Norman	Nicky	Neville	Narelle	Nora	Nathan	Nelson
O	Ophelia	Olga	Oscar	Olwyn	Oswald	Owen	Olinda	Odette
PQ	Pancho	Paul	Phoebe	Phil	Penny	Polly	Pete	Pierre
R	Rosie	Robyn	Raymond	Raquel	Russell	Richard	Ruby	Rebecca
S	Selwyn	Sean	Sally	Samuel	Sandra	Sadie	Stan	Sebastian
T	Tiffany	Terri	Tim	Tasha	Trevor	Theo	Tammie	Tania
UV	Victor	Vincent	Vivienne	Verdun	Valerie	Verity	Vaughan	Vernon
WXYZ	Zelia	Yvette	Willy	Winsome	Warwick	Wallace	Wylva	Whitney

Could a cyclone be named after you?

Is your name on the list?

What part of Australia would a cyclone need to start in to have your name (or your pet’s name or one of your friend’s names)?