A drying trend is evident in the Bureau of Meteorology’s latest three-month national rainfall outlook, released today, reflecting the increasing emergence of climate model signals that suggest an imminent return to El Nino conditions at the end of this winter.
For about two months the Bureau of Meteorology has been quietly mentioning the dreaded “E” word, which usually equates to hot, dry weather and drought conditions in Australia. In April it reported that some long-term climate models around the world were indicating that El Nino conditions may develop during the winter or spring.
Now the language is getting stronger, with today’s monthly statement describing an increased risk of conditions approaching, or possibly exceeding, El Niño thresholds during 2012.
“Climatologists will continue to monitor conditions and outlooks closely for any further developments over the coming months,” the Bureau says.
The national outlook for July to September indicates that a drier than normal season is favoured for the southwest, southeast and eastern parts of the country and a wetter than normal season is favoured over northern Queensland.
Over the rest of the country, the chances of a drier or wetter July through to September are roughly equal.
This outlook is a result of warmer than normal waters in the eastern Indian Ocean with some influence from neutral conditions in the central Pacific Ocean.
The chances of receiving above median rainfall during the July to September period are between 30 and 40pc over southwest WA, southeastern parts of SA, the eastern half of the NSW-Queensland border, western Victoria and the northeastern half of Tasmania.
“Such odds mean that for every ten years with similar ocean patterns to those currently observed, about six to seven July to September periods would be expected to be drier than average over this area, while about three to four years would be wetter,” the Bureau said.
In contrast, the chance of receiving above normal rainfall is between 60 and 65pc over northern Queensland.
However, it should be noted that rainfall is commonly low over much of tropical northern Australia at this time of the year and contributes only a small fraction of the annual total.
The national outlook for temperatures during July to September indicates that warmer days are more likely over most of the Australian mainland with greater odds across the western half of the country, warmer than average nights are more likely across large parts of WA, and the odds favour cooler than average nights along the north east region of Australia.