Rare weather phenomenon occurs off coast of Western Australia

Courtney Travis
·2 min read

Multiple tropical threats will take aim at Western Australia this weekend, but AccuWeather meteorologists say they have taken a unique path before reaching land.

Activity in the Timor Sea and eastern Indian Ocean began last weekend when a system emerged and eventually developed into Tropical Cyclone Seroja.

The above satellite image shows Tropical Cyclones Seroja and Odette northwest of Australia on the morning of Friday, April 9, 2021. (AccuWeather)

Conditions were just right, with plenty of warm water and light to moderate wind shear, to the northwest of Australia for the tropical low northwest of Seroja to strengthen into Tropical Cyclone Odette on Friday morning, local time, as Seroja continued to gain wind strength.

Approximately 24 hours later though, Odette lost wind intensity and was designated a tropical low once again on Saturday morning, local time, as Seroja continued to intensify.

Both tropical systems remained close to one another, with the eye of each cyclone perhaps only 800 km (500 miles) apart at times to end last week.

With two tropical systems so close together, forecasters said a meteorological phenomenon known as the Fujiwhara effect occurred for a time on Friday. The Fujiwhara effect occurs when two tropical systems are close enough together, and strong enough, that they influence the track of the other, resulting in the two storms rotating around each other.

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"Seroja was the dominant feature, with the system formally known as Tropical Low Odette rotating in the clockwise fashion around Seroja," AccuWeather Meteorologist Mary Gilbert said. "This was the case for portions of the day on Friday and Saturday until Seroja absorbed the energy of former Odette later Saturday."

Now, Seroja is set to bring impacts to Western Australia into the early week.

Seroja was able to strengthen into a Category 3 tropical cyclone on the Australian scale for a time early Sunday, local time. The storm packed 10-minute average sustained wind speeds of 120 km/h (75 mph) at its core as it churned just off the coast. Seroja can deliver heavy, flooding rainfall and damaging winds to portions of Western Australia.

When Cyclone Seroja formed over the weekend, tropical moisture inundated portions of Indonesia, causing deadly mudslides and flooding.

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