Hope for summer rainfall remains

Hope for summer rainfall remains


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There is unlikely to be a climate driver in place creating strong odds for below average rainfall over summer.

There is unlikely to be a climate driver in place creating strong odds for below average rainfall over summer.

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The BOM outlook for spring made for horror reading, but the silver lining is that the event keeping it dry will break down before summer.

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The Bureau of Meteorology (BOM) spring outlook was not pleasant reading for farmers anxious for rain, with virtually the entire Australian mainland likely to see lower than average September to November rainfall.

However, there was a small consolation in the forecast in that the major driver of the dry spell, a positive Indian Ocean Dipole (IOD) breaks down much faster than an El Nio, the other major weather event influencing Australia's climate.

Unlike an El Nino weather event, which can impact climate until March or April the following year, an IOD phenomenon is virtually certain to break down in December.

Dr Watkins said this was due to the south-east Asian monsoon, which acts as a giant sea breeze.

"The world would virtually have to spin the other way for the IOD positive event not to break down at some stage in December."

This means that summer dominant rainfall will enter the period with neutral conditions and no climatic constraint on achieving average rainfall.

But the IOD positive event was not necessary the cause of the dry autumn for eastern Australia.

Dr Watkins said conditions had hovered at close to El Nino levels early in the season before fading back to neutral.

"Sometimes when you get conditions approaching El Nino thresholds you can get dry periods and we saw them in that autumn period.

In terms of the areas that have received rain this year, Dr Watkins said a series of strong Southern Annular Mode (SAM) negative events had been responsible for bringing up weather from the Antarctic and delivering rain over parts of southern Australia.

The rain is set to continue in Tasmania, with western Tassie one of the few areas in the nation Dr Watkins said could expect a wetter than average spring.

Parts of southern Victoria, also constantly swept by cold fronts from the south, are closer to neutral than the majority of inland regions.

Temperature wise Dr Watkins said the spring was also likely to be hotter than average, following on from the warm winter, which is likely to see places such as north-east NSW record their hottest winter on record.

Dr Watkins warned the ongoing dry and potential for hot weather meant the summer was likely to have a high risk of bush fires.

The story Hope for summer rainfall remains first appeared on Farm Online.

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