{News} 080925! SOI rises sharply to +16.5, lifting spring rain hopes

SOI rises sharply to +16.5, lifting spring rain hopes
GREGOR HEARD
25/09/2008 3:47:00 PM

The 30-day Southern Oscillation Index (SOI) has lifted sharply, back up to +16.5 – a pattern that generally suggests better than average rainfall and a move to a La Nina pattern.

Bureau of Meteorology meteorologist (BOM) Lyn Bettio, however, says that while the move is a positive for farmers hoping for spring rain, it has not yet gone on long enough to be significant.
She also warns that there are other factors required to usher in a La Nina.

Ms Bettio said that along with having an SOI above a reading of eight for a couple of months, other factors, such as sea surface temperature and trade winds, need to fall in line with a La Nina pattern, and this is not happening yet.

In parts of the northern Western Australian wheat belt and most of Queensland, chances are rising for above average rainfall, with the chance of higher than usual rainfall for October through December rising to between 65 and 70pc around Geraldton and through central Queensland.

On the flip side, farmers in far south-western Victoria and south-eastern South Australia have just 35-40pc chance of beating their average, however croppers in these areas are well set up with good subsoil moisture, so a drier finish does not spell disaster.

But for those with most at stake, through southern NSW, northern Victoria and much of South Australia, the Bureau figures do not shed much light, with an outlook firmly in neutral territory.
Many farmers through eastern Australia have been watching with cautious optimism a rising Southern Oscillation Index, which has been steadily rising since July.

Lyn Bettioe, however, warns many farmers through SA, central western NSW and northern Victoria are also equally influenced by the Indian Ocean Dipole, which is weakly positive at the moment.

This is associated with lower than average rainfall.

However, she did say that the rising SOI was a positive, because it means drier conditions, are unlikely to form across the east coast.

“At least the SOI is moving in the right direction – in June there were fears it was dropping and we could see an El Nino could develop, which is now unlikely to happen, especially with the positive SOI.”

“It’s unlikely that we’ll see the development of a late La Nina, but at least things are moving in the right direction for those needing rain.”

With crops at a reasonable stage, albeit needing rain, many farmers would be happy to take their median rainfall for October and run with it – as this would deliver average to slightly above average yields in most grain producing areas, aside from problem parts of NSW and Victoria.
One problem croppers will face is the likelihood of significant evaporation, with the likelihood of above average maximum temperatures for the coming three months as high as 80pc through most of Victoria and south-east South Australia.

Source: http://sl.farmonline.com.au/news/nationalrural/grains-and-cropping/general/soi-rises-sharply-to-165-lifting-spring-rain-prospects/1280739.aspx