ALL THIS talk of getting a good summer because the frog-spawn is early or the dolphins are staying north makes Gerald Fleming a bit impatient.
He’s a scientist, so to him, weather forecasting is about science, not about how high up in the trees the birds are nesting.
“I don’t place any credence on the self-styled forecaster — their approach and our approach are fundamentally very different,” says the Head of the Forecasting Division at Met Éireann.
“They might go by the berries on the trees, but how do the berries on the trees affect something that’s going to happen in three months or six months? I have to understand cause and effect as a scientist before I make that connection.”
Whichever way they get it, the Irish are utterly obsessed with weather forecasts, something which has its roots, he believes, in the farming and fishing which dominated our livelihoods a generation ago.
Today that obsession remains, but our modern, unrelenting desire for barbecue summers is, sadly, more about the triumph of hope over expectation. Face facts, says Fleming, the science says barbecue weather is not an Irish phenomenon and never will be.
“Most Irish summers are unsettled, wet and not particularly warm. We’re living a long way from the equator — 54 degrees north. On top of that, we’re beside a large body of water called the Atlantic Ocean, so cool and damp will always be our predominant weather. ”
What constitutes a decent summer in Ireland would be three good weeks in June or July. We usually get one of those every third year or so, says the Wexford native.
A good hot summer on the other hand — warm settled weather lasting about six weeks — is far more rare.
“There have been exceptional summers in 1995 and 2006, but they were the last good summers we’ve had; we only get good summers of that sort once a decade.”
It all depends on how the high pressure areas move, and where they settle, he explains:
“They tend to have a life cycle of a few weeks. If the high pressure builds up over Ireland for two to three weeks it can bring good weather, but even that’s not certain, because if the high pressure is to the west it usually brings cloudy weather. To the east usually gives us some good weather.”
The hot ones, he says, in the measured tones of the scientist, come “often enough”.
And this would be?
“Once every 10 years.”
Enough, though, to leave us with powerful memories, which tease us for the rest of our lives. Hence, though summer 2010 wasn’t particularly good and summer 2011 wasn’t much use either, we’re still hoping, refusing to accept that the odds are — always — against us.
Also, even if we accept that the Irish weather is volatile, we don’t always understand the implications of this for Met Éireann.
Take an apparently simple question. Will tomorrow be cloudy?
Not simple at all, because cloud, says the father-of-three, is one of the most difficult things to forecast. To answer that question Met Éireann examines the atmosphere up to about 35,000 feet, the altitude at which a passenger jet cruises.
“Cloud can occur at almost any level there, but if you ask whether it’ll be a cloudy day tomorrow we have to examine every layer in the atmosphere from the surface right up to 35,000 feet.”
In fact, about five different levels of air need to be investigated.
“This is constantly moving and there are winds blowing through it, but we must look at the moisture content.”
If the moisture is high, clouds will form within that air and if the moisture content is low it won’t, he explains.
“There are lots of variables. So in a simple question like that there’s actually a lot of complexity involved, for example, in understanding the moisture content of each level.
“It’s important that people have an understanding that, when we give a forecast, the level of accuracy will be different depending on whether it’s a forecast for that day, for a couple of days ahead or for the week ahead. There are far more variables in a longer term forecast.”
People don’t always understand this. Occasionally, he adds, someone will phone, for example, in April to ask what the weather will be like for a wedding on June 24.
“You’d have no idea how the weather will be and they often don’t understand that.”
In some parts of the world, forecasters have developed a system of useful seasonal forecasts, he acknowledges, but then, their weather is generally more predictable than ours.
In South America and, more recently, Africa, long-range forecasting has become more common, primarily because the nature of the Pacific Ocean is very different to that of the Atlantic Ocean. Large-scale changes occur in the Pacific Ocean which affect the weather but which make it more predictable, unlike the more volatile Atlantic Ocean, where there tends to be constant small and unpredictable shifts.
“Being beside the Atlantic Ocean, we don’t have these large changes and so the big knock-on effects for the weather in our country don’t exist in the same way.”
Hence, Met Éireann doesn’t do seasonal forecasts.
A far as Fleming is concerned, summer 2012 is still an unknown and he’s not going to speculate.
“We’ve have no idea whether it will be good or bad,” he says bluntly. “The weather system which will affect us in the summer is not developed yet. A system that will affect us in July only starts to come together in late June.”
If you really want a prediction at this stage — which of course we do — he relents enough to say that statistically we have a one-in-three chance of having a decent summer this year.
The chances of a good summer, however, plummet to a one-in-10, and of course, that also depends on where you’re living, because in Ireland, the weather can change not only from day to day, but from one location to the next.
“We’re always trying to chase something which is moving. Our experience is that seven to 10 days is the furthest that we can give any forecast that we have any confidence in.
“There are all sorts of folk tales, but we’re a scientific organisation and we have to say things that we can stand over.
“What we do when making a forecast is we look at the system of the day and try to see how that is moving and developing.”
MET Éireann is happy with the accuracy of its short (two days) to medium term (two to eight days) forecasts.
It’s useful to know, however, that when a forecaster is talking about the weather being warmer than average, he or she is not referring to what the public considers the average weather experience as in the month or even the year. Met Éireann is actually comparing the weather of the moment to a 30-year reference period from 1961 to 1990. To make things even more confusing, they’re currently updating that reference to a period from 1981 to 2010.
Senior climatologist Seamus Walsh explains: “Generally speaking, it has become warmer over the last 30 years. The temperatures have risen from the late 1980s onwards, so temperatures now are a bit above average compared to the 1961-1990 period.”
Roughly speaking, says Walsh, mean temperatures have risen by half a degree between the two reference periods.
So, against the 1961-1990 period, last July’s average temperatures were about half a degree below normal.
However, in the context of the new reference period, 1981-2010, which is due to be introduced soon and whose temperatures are slightly warmer, July 2011’s weather would average as one to one-and-a-half degrees below normal.
“The period between 1981 and 2010 was warmer by about half a degree than it was in 1961-1990 so that will change how we express the current weather in relation to the average,” says Walsh.
And for those who are interested, rainfall has increased by about 5% during the two periods.
Roll on summer.
Make most of poor summer
Ken Ring, New Zealand
Although this will probably be an exceptionally hot summer in Central Europe, says Ring, here in Ireland we should expect a slow start to a mild summer.
The second half of June should be mostly dry with some warm sunshine in the last week. However, real summer temperatures won’t surface until around the last week of July, running into the first week or two of August, when we should have temperatures of between 20 and 25 degrees, though, he emphasises, don’t expect heatwaves. Generally, though, this summer’s sunshine will be a bit below normal. The month to worry about is September which may experience rainfall and some flooding in the beginning and the end of the month. There will be a full moon at the beginning and end of September and a new moon in the middle of the month, which he believes will be linked with high tides, flooding and rain.
Michael Gallagher, Postman, Donegal
As one of Ireland’s best known amateur forecasters, Michael predicts: “Overall I wouldn’t be too happy with the summer. We’ve had a very good winter. March was very warm and there was very little rain over the winter.
“I believe thunder will dominate the summer and I would advise people to make the most of any good weather we get.
“The signs are not good for a warm sunny summer. There was very late growth this year. Flowers that should have been up by the start of April were only coming out at the end of the month. The frogspawn was very plentiful in the middle of flat land, which is a sign that they’re expecting water to come.
“If good weather is coming the frogspawn tends to be located near a stream but not on flat land. I hope I’m wrong.”
* Michael Gallagher’s new book, Remedies and Cures of a Bygone Era, printed by Brown Printers in Letterkenny, is due on the bookshelves in May.
More in this section