Seroja Slams Australia

Seroja Slams Australia

On April 11, 2021, a category three storm made a rare landfall in Western Australia, causing significant damage to coastal towns that are mostly ill-equipped for cyclones. Tropical Cyclone Seroja tore through 1,000 kilometers (600 miles) of land, knocking down trees and damaging buildings along its southward path. At least 15,000 homes lost power. Seroja has since weakened and moved offshore, but government agencies are now dealing with the damage.

The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this image on April 11, hours before the storm made landfall.

Kalbarri, a resort town of around 1,500 people, received the brunt of the storm’s force. Seroja made landfall just south of Kalbarri on the evening of the 11th and damaged about 70 percent of the town’s structures, according to news reports. Wind gusts clocked in at 170 kilometers (100 miles) per hour—likely the strongest winds in the area in more than 50 years. Overnight, Kalbarri received around 167 millimeters (6.6 inches) of rain.

Seroja continued southeast and caused damage in the city of Geraldton, too. Downgraded to a category two storm at the time, Seroja was the first storm of that intensity to hit Geraldton in more than 50 years. The storm was further downgraded on April 12th as it moved across the Wheat Belt, located in the southwest corner of Australia.

Seroja’s southward trajectory is unusual; scientists estimate that cyclones of this intensity have only traveled this far south 26 times in the past 5,000 years. However, Seroja curved south when it interacted with a different tropical system earlier in the week. This clash—a rare phenomenon known as the Fujiwhara Effect—caused the systems to rotate around one another and launched Seroja towards the west. Seroja intensified due to warmer-than-normal sea surface temperatures influenced by La Niña conditions. Winds kept Seroja away from the coast and the weakened effects of land, allowing the cyclone to sustain relatively high intensity.

Before entering Australian waters, Seroja had already caused significant damage to Indonesia and was the strongest tropical cyclone to hit Indonesian land since 2008. Seroja, which hit eastern Indonesia on April 5, caused flash flooding and landslides. It damaged hospitals, homes, roads, and bridges, cutting off access to many villages. More than 180 people were killed and at least 10,000 people have been displaced.

NASA Earth Observatory image by Joshua Stevens, using VIIRS data from NASA EOSDIS LANCE, GIBS/Worldview, and the Suomi National Polar-orbiting Partnership. Story by Kasha Patel.

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