Particle 101: Cyclones

Cyclones person been successful nan news a batch this season, pinch one of nan busiest seasons successful caller years. 

Severe Tropical Cyclone Sean delivered grounds rainfall and gales to nan Pilbara seashore successful January, Severe Tropical Cyclone Zelia gave bluish WA a fright successful February, Tropical Cyclone Alfred caused havoc successful Queensland and New South Wales successful March, while Ex-Tropical Cyclone Errol, a Category 4 strategy while astatine sea, crossed nan Kimberley arsenic a tropical debased successful April.

The semipermanent mean number of tropical cyclones successful Australia is 11, pinch 4 predicted to make landfall.

Cyclones mostly hap between November and April successful bluish Australia. They most often occur northbound of Exmouth connected nan WA coast, crossed nan Top End and northbound of Brisbane connected nan eastbound seashore but tin still agelong further south.

Cyclones spin successful a clockwise direction successful nan confederate hemisphere. People successful nan bluish hemisphere telephone them typhoons aliases hurricanes, wherever they rotation anti-clockwise. 

YOU SPIN ME RIGHT ROUND

Cyclones request very precise conditions to form.

The water needs to beryllium astatine a minimum somesthesia of 26.5°C, which is why cyclones mostly shape successful tropical areas.

Water evaporates to shape clouds supra nan ocean. If nan aerial unit is low, nan clouds commencement to build and spin.

To support this shape going, nan aerial must stay humid to create power and let nan cyclone to make speed. 

Caption: Cyclone Sean disconnected nan seashore of Western Australia, January 2025
Credit: MODIS Land Rapid Response Team, NASA GSFC

To beryllium classified arsenic a cyclone, upwind must recreation astatine a minimum 119km per hour. 

The eye of nan cyclone spans astir 40km pinch debased winds and nary clouds aliases rain, arsenic cool aerial sinks to nan centre of nan upwind system.

The powerfulness of a cyclone complete nan water causes swells and surges successful nan water, which tin origin harm to coastal communities and boats.

A cyclone loses power and powerfulness erstwhile it moves complete land, if it hits cooler oceans aliases erstwhile nan conditions are not favourable to create and summation energy.

The mean cyclone lasts a week.

WHAT’S IN A NAME?

The Bureau of Meteorology selects a database of names, alternating antheral and female, from which cyclones are named, progressing alphabetically done nan list.

If a cyclone is peculiarly terrible and notorious, that sanction is retired forever and a caller sanction enters nan list, truthful we won’t spot different cyclone named Tracy.

CYCLONE SCORECARD

Cyclones are graded based connected their strength. Category 1 is nan weakest, while Category 5 is nan strongest.

Caption: New South Wales flooding from Cyclone Alfred, March 2025
Credit: Alice successful nan Alice

Category 1 cyclones person upwind speeds up to 125km per hr and water swells up to 1.6 metres. They tin origin harm to trees and farmland.

Category 5 cyclones are highly dangerous, pinch upwind speeds supra 280km per hour, water swells supra 5.5 metres and nan capacity to flatten buildings.

Categories 2, 3 and 4 place upwind speeds, water swells and nan level of anticipated damage. 

If you are successful an area wherever tropical cyclones form, make judge you cognize what to do. 

So committee up nan model and necktie down loose materials, move disconnected nan utilities and return shelter aliases evacuate if told to.