Severe Tropical Cyclone Zelia is bearing down on the northwest coast of Australia and is likely to make landfall early Friday evening.
Author
- Steve Turton
Adjunct Professor of Environmental Geography, CQUniversity Australia
It's a monster storm of great concern to Western Australia. Port Hedland is the largest town in the firing line and also our busiest iron ore export port. Strong winds may extend to other areas along the coast, and inland to areas such as Marble Bar, Tom Price and Paraburdoo.
Even if Zelia doesn't hit towns directly, it's likely to cause a lot of damage. The Bureau of Meteorology predicts extremely dangerous sustained winds of around 205 kilometers an hour and wind gusts higher still, at 290km/h. That's strong enough to flatten homes, trees, power lines and other infrastructure.
This is a category five cyclone, which is the most severe possible under the current scale . But as climate change worsens, authorities may need to add another category to the scale.
Do we need a category 6?
Elsewhere in the world, tropical cyclones are called hurricanes or typhoons.
The severity of a tropical cyclone (or hurricane or typhoon) is ranked in categories from 1 (weakest) to 5 (strongest).
Category one involves maximum average wind speed of up to 88km/h, and strongest gusts up to 125 km/h. It typically causes negligible damage to homes but may damage crops, trees and caravans.
Category five, the most severe, is defined as "extremely dangerous", causing widespread destruction of buildings and vegetation. These cyclones bring maximum average wind speeds greater than 200km/h and gusts greater than 279km/h.
However, on a warming planet, cyclones are expected to become more intense . It's also making tropical cyclones and hurricanes intensify more quickly .
Some scientists have called for a category six for hurricanes, typhoons and cyclones with sustained wind speeds greater than 309km/h. They argue a new category is needed to communicate the risks associated with tropical cyclones fuelled by climate change.
Climate change is feeding storms
It's too early to say if Cyclone Zelia is directly caused, or fuelled, by climate change. However, research over the last 30 years has found a link between global warming and more intense tropical cyclones .
Globally, 2024 was Earth's warmest year on record . Ocean heat content is increasing around most tropical seas, and other places where tropical cyclones are forming. Warmer oceans, and a warmer atmosphere , both feed energy into tropical cyclones, making them more intense and fast-forming when conditions are favourable.
Zelia intensified from a category one into a five in just over 24 hours .
Australia is currently experiencing record-breaking sea surface temperatures . The area off the northwest coast has been up to 4-5°C above normal this summer .
Hurricane Milton, which struck the United States in October last year, also shows how climate change is making tropical cyclones worse . Amid very warm ocean temperatures, it intensified rapidly over the Gulf of Mexico to a category five hurricane.
We can expect more of these severe cyclones in future, if humanity keeps warming up the oceans and the atmosphere .
Slow is not good
Climate change is slowing the forward motion of tropical cyclones over the ocean and land. That means they take longer to cross the coast and pass through an area - inflicting more damage from wind and storm surge, and dumping more rain.
The Bureau of Meteorology says Cyclone Zelia's "forward speed" is quite slow, at 11km/h. So, heavy rain and the strong winds will persist for quite a few hours before and after it crosses the coast.
The strongest winds of a tropical cyclone are usually near the eye, but can extend for hundreds of kilometres. Sometimes, winds on opposite sides of the eye blow in different directions , causing destruction on the ground which damages buildings, infrastructure, farmland and the environment.
Conditions on the ground
At the moment around Port Hedland, winds are about 70-100km/h and rising. That's gale force but not too alarming. Conditions will rapidly deteriorate into this afternoon, particularly to the east of Port Hedland.
The storm has already dropped a lot of rain. This has caused local flooding and cut rail lines. But there's more to come.
The Bureau of Meteorology is also warning of a significant storm tide - when sea levels rise well above a typical high tide. This may lead to flooding and inundate coastal roads and properties.
The cyclone will continue to trek inland over the weekend, gradually weakening as it goes. People in mining and Indigenous communities hundreds of kilometres inland could experience strong winds, heavy rain and flooding.
The bureau is providing regular updates online. For those in the path of the cyclone visit www.emergency.wa.gov.au or download the Emergency WA app for the latest community alerts and warnings.
Steve Turton has received funding from the Australian government.
