Meteorologists regularly state in no uncertain terms that they’re unable or unwilling to predict weather with much accuracy any further than ten days in the future. Even a ten-day forecast is considerably less dependable than the next day one, and despite ever-improving technologies, some international meteorological organisations won’t predict past a week.

The mainstream consensus is distant forecasts lead to ever diminishing returns - there are simply too many unpredictable variables determining the weather.

Met Eireann forecaster Evelyn Cusack told Newstalk back in May that “anyone who [invests in long-term forecasts] is either delusional or disingenuous. People should never buy forecasts beyond a week because it’s just not possible to predict. They are a waste of money.” This is particularly true in Ireland, since our latitude and geography ensure our weather is constantly variable, especially in the summer time.

Nonetheless, many people and ‘alternative’ meteorologists do make an effort to predict the weather of the future. Sometimes, whether it’s through genuinely accurate forecasting or simple good luck, they get it right.

Accurate predictions?

New Zealand forecaster Ken Ring attracted a lot of attention in his home country after “predicting” the Christchurch earthquake of February 2011, and his annual almanacs have become bestsellers in New Zealand, Ireland and Australia.

He gave a prediction for a stellar Irish summer way back in January, elaborating in March that “with the arrival of July also comes a heatwave lasting about 10 days and with maximums expected to reach around 30 degrees Celsius. Hot maximums come again from Jul 19 to Jul 25 and Jul 28 to Jul 30.” As anyone who was outside over the last two weeks can attest to, the first part of that forecast has been right on the money.  

Users of Irish forum boards.ie will likely be familiar with M.T. Cranium aka Peter O’Donnell - a Canadian hobbyist known for his detailed and oftentimes accurate forecasts, both short and long-term.

His prediction for the summer back in May was less date-specific than Ring’s, but did state “I believe there will be considerable improvement of the weather pattern ahead, and some chance of prolonged warm, dry spells. At the very least, I think this will be one of the better summer seasons in recent years, and there's some chance of it being an exceptional summer... Drought is also possible given the strength of the warm signal at the foundation of this forecast."

Methodology

Such long-term forecasting is based on a variety of factors - common monitoring tools, pattern analysis and, in some cases, less traditional methods of analysis (groundhogs excluded).

Peter O’Donnell explains that his process is “basically conventional meteorology”, but combines this with long-term research that “seeks to identify processes in the atmosphere that result from interactions with the Moon and (independently) with variations in the solar system magnetic field.”

Ken Ring’s process is heavily based on lunar patterns, with his website explaining “the science is based around the concept of rising and ebbing in the daily tide of the air. By such daily vertical motion, well documented by weather balloon behaviour, changes in air-height result in changes in temperature and thereby a daily variation in water vapour amounts and densities. This manifests in more or less sunshine heat and amount, rain, wind and snow being able to form and reach ground.”

Critics & sceptics

Of course, like your typical horoscope, long-term weather forecasters can use clever language to ensure their predictions will almost always contain some degree of accuracy. Keep the predictions general and non-specific, and odds are they could be interpreted as generally solid. Predicting there is a high chance of “warm, dry” periods during the summer months is of course a relatively logical conclusion, even in unreliable Ireland.

One Washington Post article discusses how two different Farmers’ Almanacs in the US are invaluable and reliable weather predictors for many readers. As the article points out, however, “it’s impossible to fully assess the books’ accuracy, because many of their predictions read like a meteorological fortune cookie: vague enough to accommodate a wide range of weather. Both publications, for example, tend to make such predictions as ‘sunny, cool’ in four- or five-day chunks. In any given workweek, there are usually periods of sun and some temperature variation. Does that make the prediction correct? When the almanacs risk testable predictions, they often fail”.

Sceptics have typically been vocal in their criticisms of long-term forecasters, arguing that the ‘science’ behind the predictions is vague and imprecise, even “reckless and irresponsible”.

On the subject of Ring’s earthquake prediction, Waikato University lecturer Alison Campbell commented “he's also hedging his bets – the phrasing here is so vague that just about any untoward event would count as an accurate prediction. Just what would qualify as a ‘severe weather event’? The problem is... that such vaguely worded 'predictions', with their lack of precision, are so wide open that they lend themselves to confirmation bias”.

Incorrect predictions

There’s also the argument that for every accurate long-term weather prediction, there are likely to be dozens of incorrect ones. Ring particularly came under fire for saying New Zealand’s South Island would be subject to another major Earthquake - “it could be one for the history books” - on March 20 2011. The prediction caused many Christchurch residents to leave the city temporarily.

Although there was a 5.1 magnitude aftershock in Christchurch on the 20th, there was nothing on the scale suggested by Ring, with most pointing out it was in-line with existing aftershock patterns.

Forecasters like Ring have also been accused of revising or distancing themselves from inaccurate predictions after the fact. But then again, this is hardly unique to long-term forecasts: how many times has the nightly weather report got the next day completely wrong?

The theories behind long-term weather forecasting are mostly rejected by mainstream scientists and meteorologists. However, the long-term forecasts have their fair share of believers too: believers often willing to pay for access to detailed future forecasts, especially those whose livelihoods are heavily dependent on the weather. And, although it’s easy to be sceptical, sometimes, for whatever reasons, the forecasts are right on the money.