Australia has been warned to prepare for the “worst-case scenario” as Cyclone Alfred heads Down Under.
The rare Category 2 storm is nearing the Australian coast and residents are being warned to act now.
People on the projected path of the rare weather event, which has been named Cyclone Alfred, have been asked to leave the area as soon as possible before the situation worsens.
Queensland premier David Crisafulli said: “There is a chance this cyclone will cross in the middle of the night with a high tide. That is not the time to be making your evacuation plan – now is the time.”
The cyclone is moving towards the south-eastern Queensland coast at a speed of around 16kph (10mph) and is expected to hit land on Thursday or Friday at the north of Brisbane.
Brisbane is shutting down train, bus and ferry services from Wednesday, with people advised to evacuate.
Alfred would be the first cyclone to hit Brisbane since Cyclone Nancy in 1990.
But what is a cyclone? And how is it different to a hurricane?
Here is what we know.
What is a cyclone?
Cyclones are rare storms characterised by a system of rotating winds, all concentrated in one area. These winds spiral around a centre of low atmospheric pressure and typically move at speeds ranging between 20mph and 30mph.
They normally bring with them very strong winds and a lot of rain and can cause devastation in their path if they hit land.
The scientific name for a cyclone is a tropical cyclone, and the Met Office describes them as “amongst the most powerful and destructive meteorological systems on earth”.
Experts state that, globally, around 80 to 100 develop over tropical oceans each year, but not all of these reach land.
Cyclones form over warm oceans, gaining energy as they move. Warm air near the ocean surface absorbs water vapor and rises, beginning the process. As this warm, moist air rises, it cools, leading to cloud formation – creating a region of high pressure. At the surface, the rising air reduces air pressure, forming a zone of low pressure.
Air from surrounding areas moves in to fill this low-pressure zone, warming and rising as well. This creates a continuous spinning motion, drawing in even more air, which sustains the cycle. As the system progresses, more clouds develop, and the cyclone grows stronger as it travels.
What is the difference between a cyclone and a hurricane?
Both of them come under the scientific term of “tropical cyclones”, but are labelled according to where, geographically, they occur.
Over the Atlantic and East Pacific, these weather events are commonly called hurricanes but, in the Indian Ocean and Australia, they are labelled cyclones.
In the West Pacific, they are most commonly referred to as typhoons.
Is a cyclone the same as a tsunami?
No, a tsunami is a series of large ocean waves capable of causing massive destruction and loss of life when they reach land.
Unlike regular waves driven by wind, tsunamis are caused by powerful underwater disturbances. These include seaquakes (earthquakes under the ocean), undersea volcanic eruptions, landslides, or even meteor impacts. These events displace vast amounts of water, generating waves that can travel across entire ocean basins.
A hurricane or a cyclone is a weather event, in essence, a severe storm which brings extreme wind speeds that begin over warm ocean water.
How do cyclones get their names?
At the start of the year, forecasters provide a list of names to be used for big weather events.
These events are named to make it easier for official bodies to communicate warnings and information about incoming weather disasters to the public.
Since the storms can often last a while, sometimes more than one storm can happen at one time, so naming each one helps to reduce confusion.
Names were first used in World War II and were subsequently adopted worldwide.
In the UK, we tend to use male and female names in alphabetical order, but it differs globally.
In the western north Pacific and north Indian oceans, for example, they use the names of flowers, animals, birds, trees or foods.
