El Nino Tames Australian Cyclones as 46-Year-Old Mark to Fallby
Only three storms formed in season that ends April 30
El Nino is given credit for keeping storm numbers down
El Nino is getting some of the credit as Australia nears a record for the fewest tropical cyclones since 1970.
“With the end of the season approaching and only three cyclones so far, the 2015-16 Australian region tropical cyclone season is on track to be the least active since reliable records began,” said Blair Trewin, a climatologist with the Australian Bureau of Meteorology in Melbourne.
In an average season, which runs from Nov. 1 to April 30, about 11 storms form in the seas around Australia. The systems are called cyclones there and referred to as hurricanes and typhoons in other parts of the world. The current record low is five, in 1987-88 and 2006-07.
Australian cyclone records go back to 1906, and since then there have been years with three or fewer storms. However, it’s likely some were missed, Trewin said.
Before satellites looked down from space, storms that didn’t hit land were known only if a ship was unfortunate enough to run into one, so forecasters in Australia use 1970 as a reliable starting point. The gaps in the record aren’t limited to that nation -- many basins, including the Atlantic, have almost certainly been under-reported, according to researchers.
El Nino, a warming of the Pacific’s surface near the equator, causes weather patterns around the world to shift. In Australia, as in the North Atlantic, this means fewer storms. The three previous years in the satellite era with the fewest storms have all occurred during El Ninos, Trewin said.
During an El Nino, storm activity in the South Pacific is displaced eastward, which is why there is less activity near Australia, he said. This year, Fiji and Tonga were raked by Tropical Winston, a Category 5 storm on the Australian storm scale. At least three people died on Fiji as its winds flattened villages on the island east of Australia.
In the Indian Ocean, storm activity shifts to the western part of the basin. Cyclone Fantala, now churning in the seas north of Madagascar, is evidence of that.
Australia’s luck may turn next year, as both the Bureau of Meteorology and the U.S. Climate Prediction Center say the chances are good a La Nina could replace El Nino by next November. A La Nina is a cooling of the Pacific, and it also disrupts weather patterns around the world.
La Nina storms tend to shift toward Australia, but this isn’t always the case. In some La Nina years, there haven’t been as many cyclones in Australian waters, according to research by Hamish Ramsay at Monash University in Melbourne.
During the La Ninas of 2010-11 and 2011-12, the phenomenon went away and then came back. There was a below-average number of storms around Australia, Ramsay said in a presentation Monday at the American Meteorological Society’s Hurricanes and Tropical Meteorology conference in San Juan, Puerto Rico.
He theorizes there may be a change in the way weather patterns interact between the Pacific and Indian oceans that might be keeping the number of storms lower during La Ninas.
Trewin said that while some La Nina years don’t produce a large number of cyclones, they do feature a lot of overland monsoonal low-pressure systems. These “never reach cyclone intensity, but still produce large amounts of rain,” he said. The La Nina of 2010-11 was such an event.