Satellite view of Tropical Cyclone Veronica (left) and Trevor (right). (CIRA/NOAA)

This weekend, two intense tropical cyclones will slam into Australia’s northeast and northwest coasts within 24 hours. The storms, named Trevor and Veronica, are expected to make landfall at hurricane-equivalent strength.

While called tropical cyclones over Australia’s waters, Trevor and Veronica are no different from the hurricanes that form in the Atlantic and the Gulf of Mexico, except they spin clockwise instead of counterclockwise. They are fueled by warm ocean waters and have the potential to unleash flooding rainfall, damaging winds and a devastating storm surge, which is a rise in ocean water above normally dry land.

It is the end of summer and start of fall in the Southern Hemisphere and, just as in the Northern Hemisphere, this is near the peak time for storms of tropical pedigree.

Even so, the presence of two storms of such ferocity at the same time is unusual. Australia’s Bureau of Meteorology tweeted that this is the first instance since 2015 that two severe cyclone have threatened Australia simultaneously.

The double cyclone threat follows Australia’s hottest summer on record. In its adjacent waters, warm sea surface temperatures — which energize tropical weather systems — have been above normal.

Trevor

Trevor is swirling through the Gulf of Carpentaria and is expected to make landfall in northeast Australia near the town of Borroloola on Saturday morning (local time). The storm packs wind speeds of 110 mph, but it is strengthening and is forecast to come ashore with winds of 115 mph, which is Category 3 hurricane intensity.

“Dangerous conditions are developing along the southern Gulf of Carpentaria as Severe Tropical Cyclone Trevor nears the coast,” Australia’s Bureau of Meteorology said.

The Bureau warned that “very destructive winds” and a “very dangerous storm tide” (or storm surge) would occur near the core of the storm as it barrels ashore. Several inches of rain could also cause localized flooding, the Bureau said.

The storm’s approach has triggered a mass evacuation from coastal areas, reports ABC Australia, the largest for the region since 1974. About 10,000 people may be affected by the storm.

When Trevor comes ashore on Saturday, it will be its second landfall. Earlier this week, it slammed into Australia’s Cape York Peninsula, where it caused damage and flooding.

Veronica

In the waters off northwest Australia, Veronica features 110 mph winds as it churns toward the zone known as the Pilbara Coast. But is forecast to weaken when it makes landfall near Port Hedland late Saturday night into Sunday morning. Its landfall intensity is projected to be around 90 mph, which is equivalent to a strong Category 1 hurricane.


Track forecast for Tropical Cyclone Veronica. (Joint Typhoon Warning Center)

Australia’s Bureau of Meteorology warned that, like Trevor, Veronica would generate destructive winds and a dangerous storm surge. In addition, because of its slow motion, its rainfall is forecast to cause major flooding near the coast and just inland.

At one point, Veronica was the equivalent of a Category 4 hurricane. “Veronica underwent a phenomenal period of rapid intensification on Wednesday, taking advantage of low wind shear and very warm sea surface temperatures (SSTs) near 30°C (86°F) — up to 1°C above average for this time of year,” said Jeff Masters at Weather Underground. “Veronica intensified from a tropical storm with 65 mph winds at 6Z March 20 into a Category 4 storm with 145 mph winds just 18 hours later — an 80 mph increase in winds.”

Since that episode of rapid strengthening, the storm has encountered hostile wind shear that caused it to weaken.