Niño atípico trae lluvias a Australia

CANBERRA (Dow Jones)--A developing El Nino climate episode is showing
peculiar signs, including what is a temporarily strongly positive Southern
Oscillation Index, and good signs for rainfall, Grant Beard, a climatologist at
the government's Bureau of Meteorology, said Thursday.
"A lot of warmer-than-average water around Northern Australian such as we
have at the moment is a good sign for rainfall," Beard said by telephone.
El Nino is also usually associated with sustained strong negative values for
the Bureau's Southern Oscillation Index, but the SOI has risen in recent weeks.
The SOI stood at +8.9 in the 30 days ended July 14, rising strongly from the
lowest 30-day value in June of -12, the bureau's figures show.
El Nino refers to the extensive warming of the central and eastern Pacific
and cooling in the western Pacific. It generally leads to a major shift in
weather patterns across the Pacific and in Australia and usually - but not
always - is associated with below average rainfall in eastern and southern
Australia, potentially withering winter crops such as wheat and barley.
Climatologist Beard said the rise in the SOI is peculiar, but he still
expects it to fall sometime soon given what the bureau's prediction models are
saying with the warming of the equatorial Pacific.
"It's a temporary fluctuation," Beard said.
Some previous El Nino events have also seen SOI values rise but not to the
current level, and seen reasonable rainfall over southern Australia, such as in
1991, he said.
"All these events are different and this one in terms of that sort of thing
is behaving strangely" and different from El Nino events in 2002 and 2006, he
said.
"It may be one of those ones that deliver a mixed bag of rainfall outcomes,"
he said. "Every El Nino is different and some do see reasonable rainfall
outcomes."
The Indian Ocean Dipole, or IOD, also has remained in a negative mode for two
weeks, he said.
A negative IOD period is characterized by warmer-than-normal water in the
tropical eastern Indian Ocean. A positive mode for the IOD was previously
identified as a key influence for a drought in 2007 that wrecked winter crops,
including wheat, in southeast Australia, as it can hinder the formation of the
northwest cloudbands that are an important source of winter/spring rainfall in
southeast Australia.
But that isn't the case now.
"It's quite warmer than average right across the equatorial Pacific and even
across the waters north of Australia," Beard said. "There's a very wide band of
warmer-than-average water."
The high SOI is probably linked to these warmer-than-average waters, he said.
"This could be just a temporary blip, a month ago it was fairly solidly
negative," he said.
Most official and private forecasts for Australian wheat production this year
ending March 31, 2010, are in a range of 22 million to 23 million metric tons.
Australia produced 21.4 million tons of wheat last crop year ended March 31.
After annual domestic demand of almost 7 million tons is met, the balance is
available for export, making Australia a major supplier to the global trade.
An El Nino in 2006 cut the nation's wheat output to 10 million tons.