PREDICTION, as any meteorologist will tell you, is an inexact science. But at least weather forecasters have some actual facts to start with: the conditions as they are outside the office window. When you predict what will happen in a rugby season, on the other hand, you are doing so before a match has been played, and thus have little to go on, other than the strength on paper of the various teams.

At least, that’s my excuse for making some predictions for the PRO12 season that already, four rounds of matches into the tournament, look well out of date. Not all of them, of course: I’ll stand by the commonsense suggestion that Treviso, Dragons and Zebre will make up the bottom three, for example.

But how likely does it now look that Leinster, Glasgow, Cardiff and Ospreys will make up the top four, in that order? Or that Connacht and Edinburgh will take up the other two places in the upper half of the table? Or that Ulster will end up down in seventh, ahead of Scarlets and Munster?

My confident assessment of Ulster back at the start of the month was that their squad “is growing into one of the best in the league, but this may be a year too soon” for them. Less than a month later, they have won all four of their games - the only team to do so other than Cardiff - and look like genuine title contenders.

Naturally, it is always legitimate to wonder how long it will take a new team to gel, but in the case of the Irish province, the key arrivals appear to have slotted in seamlessly. While the Ulster team as a whole had the upper hand in their 22-17 victory over the Warriors at Scotstoun last Friday night, prop Rodney Ah You and winger Charles Piutau, in particular, were devastatingly effective.

It is a cliche to say that certain sides bring physicality to a rugby match, because after all it is one of the most brutally physical of sports, but Ulster did take physical power to a new level against Glasgow. Gregor Townsend’s team did well to get a losing bonus point at the end, because for much of the game they could not come close to finding an answer to the awesome power of Piutau and his team-mates.

Ulster finished fourth last season, and lost the semi-final to Leinster. There’s a long way to go, of course, and any number of chance events can come along and derail a team that’s going well. But on current form, they must be favourites to make the play-offs again.

And after that? Well, so much depends on which teams make it into the top two and thus get home semi-finals.In the PRO12, teams that finish fourth simply do not win the title. They have to travel for the semi-final, and they lose it.

At least that is what has happened so far. Ulster came as close as anyone to bucking that trend in 2015, when they led at Scotstoun with five minutes to go before DTH van der Merwe and Finn Russell combined to snatch a win from the jaws of defeat. But last year Ulster went behind early on in Dublin before losing 30-18, while Glasgow lost 16-11 to a Connacht side who always looked that little bit too strong on the day.

The Warriors’ early-season wins over both Connacht and Leinster were impressive, and they have the depth of squad needed to challenge towards the summit. But the way in which Ulster are flourishing suggests that the fight to finish in the top four will be tougher than ever.

As for Connacht finishing fifth? John Muldoon, the champions’ veteran captain, said at the PRO12 launch in Dublin that ending up in the top six would be a good result for his team, and at the time many of us thought that the forward was either deliberately downplaying expectations or trying to lull some of his opponents into a feeling of complacency.

After three defeats, however, Muldoon’s assessment now appears to have been an honest and realistic one. True, Connacht have played a game less than all their rivals bar Zebre - their match with the Italians was abandoned because of poor weather - and a home game against Edinburgh this week may be just what they need to kickstart their season. But they have lost several key players, and perhaps put so much into their historic triumph last time round that this will be a time of recuperation for them.

In short, predictions may provide good talking points before a ball has been kicked, but they are all too soon superseded by events. This was never brought home to me more forcefully than when, in a previous existence, I had to predict the outcome of the 2006-07 SPL campaign.

Rangers, I suggested, would win the title, thanks largely to “Paul Le Guen’s tactical acumen”. The Frenchman, who had only taken over at Ibrox in the summer, was gone days into the New Year and Celtic won the league by a dozen points. If I had a middle name, it wouldn’t be Nostradamus.