While U.S. East Coast residents spent the weekend shoveling snow, people along Australia's north and east coasts were busy mopping up after two cyclones swept ashore on Friday. In a one-two punch, cyclones Lam and Marcia made landfall within six hours of each other—a first for Australia.
"Two storms making landfall in the same country, different locations, within 24 hours is very rare," says Chris Davis, a senior scientist with the National Center for Atmospheric Research in Boulder, Colorado, by email.
Lam rushed the coast east of Darwin (map), while the more powerful Marcia came ashore near the cities of Yeppoon (map) and Rockhampton. No deaths were reported, but the two cyclones left roughly 50,000 people without power. Marcia damaged about 1,500 homes and left a hundred families without a place to stay.
Last week's dual storms were a historical first for Australia, according to the country's Bureau of Meteorology. But double whammies have happened before in the U.S. and Mexico.
It's not unprecedented for multiple cyclones, hurricanes, or typhoons—they're all the same kind of storm—to form within a short period of time, Davis says. "[They] can occur close together in any ocean basin," he adds, or "they can form farther apart and move closer together during their lifetime."
Tropical storm Bonnie and Hurricane Charley hit Florida within a day of each other in August 2004. And Hurricanes Ingrid and Manuel clobbered Mexico on opposite coasts within a day in September 2013. Manuel came ashore as a tropical storm, killing 14 people, and strengthened into a hurricane three days later.
Hawaii dodged Hurricanes Iselle and Julio last September. Iselle weakened to a tropical storm hours before a Friday landfall, and Julio veered north over the weekend, missing the state entirely.
Hurricanes, cyclones, and typhoons—collectively known as tropical cyclones—all require storm clouds, surface ocean temperatures above 80°F (27°C), and very little wind shear. Getting all three ingredients together to generate one hurricane or cyclone is hard enough, let alone two. (Read about other things you might not know about these storms.)
Marcia was the strongest cyclone known to hit so far south, according to meteorologist Jeff Masters on his Weather Underground blog.
Scientists predict that climate change will reduce the overall number of tropical cyclones, but the most severe storms, category 3 or higher on the Saffir-Simpson scale, will become more common.
Warming oceans could also expand the area within which hurricanes form, meaning that areas closer to the Poles could get hit more often. But warming seas could be balanced by winds in the upper atmosphere, which are more intense closer to the Poles, says the National Center for Atmospheric Research's Davis. The wind shear acts like a brake on the formation of tropical cyclones.
"So while the trend might be for more storms at higher latitudes as oceans warm, there are other factors that make the outcome less clear," he explains.
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