In light of a wet summer through southern and eastern Australia that defied the El Nino phenomenon present in the Pacific Ocean, which normally leads to drier than average conditions, a climate specialist has emphasised to growers that El Nino is only one part of a complex set of factors that determine weather.
Michael Tausz, director of the Victoria Drought Resilience Adoption and Innovation Hub, said several other climate drivers were used in the Bureau of Meteorology (BOM) forecasts.
"Once the El Nino-Southern Oscillation, or ENSO, switched to the El Nino condition, many farmers were expecting - and preparing for - potentially drier conditions across much of Australia," Prof Tausz said
However, he said rather than basing any expectation of seasonal conditions just on an El Nino declaration, the Vic Drought Hub, funded by the Australian Government's Future Drought Fund, used a wider range of climate drivers, all taken into account in BOM long term forecasts.
"There are a number of climate drivers that are used in the Bureau's forecast models - and El Nino is not necessarily the decisive one."
Even with this mind, the outlooks at critical junctures in the spring still had a strong dry signal in BOM's modelling.
"In September and early November, these forecasts also reported only a 20-40 per cent chance of exceeding median rainfall in most of Victoria for the next three months," he said.
He said following editions of the long-range forecast reflected the change in climate drivers and had a far more neutral outlook, however by then agricultural business decisions had already been made.
"Perhaps not surprisingly, farmers and others in the community were scathing about the 'unreliable forecasts', and some went as far as blaming BOM for what turned out to be in hindsight poor business decisions, such as destocking."
He said a better understanding of how long term forecasts should be interpreted would be a big boost to farmers trying to factor in climate outlooks into their decision making process.
"Because of the highly complex and chaotic system that is our atmosphere, it is currently still impossible to make direct weather predictions for more than a few days ahead."
"Longer-range forecasts are therefore expressed as likelihoods of a certain condition.
"For example, the latest BOM forecast from 25 January gives a 30-60pc chance of exceeding the median rainfall in Victoria.
"As an example, a 30pc chance of exceeding median rainfall - as given for Victoria's south-western corner - should be read as follows- if we make the prediction of above-median rainfall ten times, we would get it right only three times: the 30pc chance is three out of ten predictions.
"In other words, if we predict below-median rainfall, it would be correct seven out of 10 times.
"Above-median rainfall has shorter-than-even odds, but is certainly not impossible, and should definitely not be completely discarded in any planning."
He said farmers needed to move away from evaluating forecasts over a season and instead look at long-term accuracy.
"The "correctness" of such a forecast cannot be evaluated in a single season, but only over the longer term, once such a forecast is issued multiple times."
He acknowledged the frustration with weather not going to forecast but said farmers should not be using the forecasts as the sole basis for decision making.
"This may not alleviate frustrations about management decisions being made in this particular season, which would have been different in hindsight, but using the guidance consequently and appropriately as one input for risk management over multiple seasons will be beneficial in the mid to longer term."