Meteorologists should add the words 'don't know' to their vocabulary

The inland of south-eastern Australia has just experienced its best late summer and early autumn break in years. With some exceptions (e.g. parts of the Broken Hill and Monaro districts) the severe drought is now all but broken, and many farms are now flush with feed. Livestock prices have soared in response. Winter crop planting is well underway, and confidence has returned to the countryside.

Apart from the usual noise and perpetual doom from activists about "climate change", the onset of the "one-in-120 year super drought" was never clearly predicted. Even worse was the complete failure by meteorologists to predict the recent turning point. In short, any farmer, who took the seasonal predictions of meteorologists and other climate "experts" seriously, would have lost a lot of money.

None of the main meteorological organisations, such as the Bureau of Meteorology (BOM), Weatherzone etc genuinely saw the severe drought coming, could adequately explain its cause, or picked the recent big break in the weather. The drought started in early 2017 in most districts (much earlier in parts of Queensland), and Victoria escaped the worst of its effects.

It is worth examining what the BOM and other forecasters were saying in the lead up and during the course of the prolonged drought.

• The BOM (25 January 2017) picked the dry Autumn and winter of 2017, but with a lot of equivocation. It forecast that "February to April (2017) rainfall is likely to be below average in much of eastern Australia". The caveat was that "Historical outlook accuracy for February to April rainfall is somewhat patchy, with moderate accuracy over most of the country, but low accuracy in inland parts of the NT extending along the WA border, as well as in small patches in Queensland, western NSW, and along the border of NSW and Victoria". A further caveat was that the "chance of exceeding median rainfall" (provided on the BOM's prediction map) was "30 to 40 per cent". In other words, its predictions were (consistently) of low statistical confidence and unreliable.
• On 31 August 2017 the prediction was "rainfall is likely to be below average in southwest Australia, above average in parts of southeast Queensland, and has a roughly equal chance of being above or below average elsewhere.....Both of Australia's major climate drivers at this time of year, the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), remain neutral. Secondary climate drivers are likely to be affecting this outlook".
• The Bureau's 11 January 2018 seasonal forecast was that "the February to April rainfall outlook shows most of eastern Queensland and WA are likely to have a wetter than average three months. February is likely to be wetter than average for much of Australia, with strongest chances in the west".
• "The May to July rainfall outlook, issued 12 April 2018, shows the far southeast of Australia is likely to have a wetter than average three months. Parts of northern Australia are also likely to be wetter than average.....The rest of the country has roughly equal chances of a wetter or drier than average three months".
• The seasonal forecast issued on 30 August 2018 noted that "much of eastern and southern mainland Australia have experienced a very dry winter and start to the year.....The spring (September to November) climate outlook shows drier than average conditions are likely for southern Australia extending up through NSW (west of the divide) and into central Australia"...."The El Niño-Southern Oscillation is currently neutral, but there is a 50per cent chance (double the normal risk) of El Niño forming in the coming months....Similarly the Indian Ocean Dipole (IOD) is also neutral. A positive IOD could develop in spring".
• The outlook issued on 17 January 2019 was that "February to April is likely to be drier than median for most of WA, western parts of the NT and SA, eastern parts of Queensland and NSW, and most of Victoria. For the remainder of the country, there are roughly equal chances of a wetter or drier three months, i.e., no strong tendency towards a wetter or drier than median season ahead"....."Tropical Pacific waters are neutral, but near El Niño levels. The atmospheric component of the El Niño–Southern Oscillation has not responded to the warmer waters, meaning an El Niño event has not become established"...."This outlook is showing little signal from any of the typical Australian climate drivers, with most in a neutral phase".
• The climate outlook issued on 29 August 2019 indicated that "a drier than average spring is likely for most of Australia, although the outlook for western Tasmania and southwest WA indicates a wetter than average September. A drier than average October to December is also likely for most of Australia, meaning the remainder of the year is expected to be drier than average for much of the country. This means little relief is in sight for those currently experiencing rainfall deficiencies after a dry start to the year for large parts of Australia. A positive Indian Ocean Dipole (IOD) remains the main driver of Australia's climate".

Overall, the seasonal outlooks issued by the BOM between 2017 and 2019 did broadly predict periods of dry weather but also some wetter or neutral periods, that often did not eventuate. The predictions in broad terms were wishy-washy and in no way anticipated the length and severity of the drought. Meteorologists (not only at the BOM) had been simply bursting to declare an El Niño event but the evidence failed to materialise. There was evidence of a positive Indian Ocean Dipole towards the end of the drought (but only then).

The BOM will never live down the climate outlook it issued on 23 January 2020.

The prediction was that "The chances of a wetter or drier than average February to April are roughly equal for most of Australia, however, scattered parts of eastern Australia have a slightly increased chance of being drier than average..February to April has roughly equal chances of being wetter or drier than average for most of Australia....This means there is no strong shift towards wetter or drier than average conditions for the coming three months for most of the country. Some parts of the east, including scattered areas across Queensland, NSW and the southern NT are slightly more likely to be drier than average.... Most climate influences are neutral.... The positive Indian Ocean Dipole (IOD), which contributed to dry conditions across much of Australia during the second half of 2019, ended in late December."

The media read the early 2020 BOM seasonal forecasts as saying that the severe drought was going to last until at least the winter of 2020. "The Land" newspaper predicted that "2020 will be a year of hardship and a long hard slog for NSW grain farmers and the industries that rely on the grain for feeding or manufacturing."

In February 2020, a paper by five climate scientists, posed the question "When will Australia's drought break"? Their answer was "This is a hard question to answer. While recent rains have been helpful, we've developed a long-term rainfall deficit in the Murray-Darling Basin and elsewhere, that will be hard to recover from without either a La Niña or negative IOD event. The most recent seasonal forecasts don't predict either a negative IOD or La Niña event forming, but accurate forecasts are difficult at this time of year. For now, we just have to hope conditions become more favourable in the coming months".

While the answer was somewhat inconclusive, it did not, however, mislead by providing unsubstantiated definitive predictions. It also attempted to explain its views using current paradigms about the causes of drought.

The paper further stated that "for large areas of the continent to experience persistent widespread heavy rainfall, it helps if the oceans near Australia to our northwest and northeast are unusually warm. For the southeast of Australia in particular, La Niña or negative IOD events provide the atmosphere with suitable conditions for persistent and widespread rainfall to occur. Neither La Niña or a negative IOD guarantee heavy rainfall, but they do increase the chances. The problem is we haven't had either a La Niña or negative IOD event since winter 2016. During the current drought we see that the rainfall deficit accumulates for several years almost identically to periods of the Millennium drought, but then the deficit increases strongly in late 2019 when we had a strongly positive IOD".

More broadly, it is interesting to hear what meteorologists in a more general context say about the accuracy of their forecasts.

The BOM says that "the chance of rainfall" forecasts continue to be reliable. "When we say it is going to be a dry day, it is dry 95 per cent of the time. Our four-day forecasts today are as good as a one-day forecast was in the 1980s".

A US Government site linked to NASA states that "A seven-day forecast can accurately predict the weather about 80 percent of the time and a five-day forecast can accurately predict the weather approximately 90 percent of the time. However, a 10-day or longer forecast is only right about half the time. Meteorologists use computer programs called weather models to make forecasts. Since we can't collect data from the future, models have to use estimates and assumptions to predict future weather. The atmosphere is changing all the time, so those estimates are less reliable the further you get into the future".

The ABC noted that "the Bureau of Meteorology provides seven-day forecasts, and even they would admit it gets a bit error-prone towards the end of the week-long outlook. The forecast for tomorrow and the day after is pretty much spot-on; up to day five it's not too bad, and by the time you reach day seven things get a little shaky". I would concur with this observation, which applies to other forecasters as well.

The Ten Day Precipitation Forecast for Australia has proved broadly indicative (though generally on the high side) for rainfall in the first five days of its forecast period. The forecast for the next five days is a lot less so and can change radically from one day to the next. I have come to broadly similar conclusion for Weatherzone's 28 day predictions, which dare to predict up to a month ahead.

The bottom line seems to be that weather forecasts for up to a week ahead are reasonably reliable, with reliability increasing as we get closer to the day being forecast. In stable weather conditions (especially those dominated by a slow moving high pressure system) accurate forecasts (usually for continued dry conditions) can sometimes be extended for a bit longer. Longer term forecasts, however, should be taken with a grain of salt. "Climate predictions" for coming decades should be treated with even greater scepticism.

As a general comment, there are few people more dangerous, if listened to, than those who claim to know when they really don't. I believe that meteorologists fall into this category in respect of their medium and long-term forecasts, or (more particularly) insofar as what the public interprets them as saying. The BOM would be more helpful if it said it could not accurately forecast more than a week or two in advance, instead of issuing long term and seasonal outlooks full of gobbledegook and veiled caveats.

Worthless seasonal outlooks have cost BOM a lot of credibility in the bush. Such loss of standing is not without precedent. The same happened with the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES). The agricultural outlook conferences of its predecessor (the BAE) were a big event 30 years ago but (following rounds of dud predictions) few in the bush bother to listen to them anymore. BOM is facing the same outcome in respect of its seasonal outlooks.

In 2018-19 the net cost of BOM services to the taxpayer was $313.7 million (made up of expenses of $406.9 million less own source revenue of $93.2 million).