Why is Ireland's weather so random and unstable?

hatrickpatrick

I was thinking about this earlier. I'm pretty interested in weather and at the moment I'm watching the start of the Atlantic Hurricane Season with interest (First tropical storm of the year formed in the Gulf of Mexico this afternoon, pretty early in the season). It got me thinking though. If you look at a lot of other places in the world, there is a relatively predictable pattern. For example, talking of the hurricane season, around the time of year you get a persistent chain of disturbances which form over Africa and drift into the north Atlantic, known as Tropical Waves. You pretty much get a new one of these about twice a week from what I've seen. You have the Azores high, which is a more or less stationary area of high pressure south of Ireland, over the Azores islands in the Atlantic northeast. Over in the Eastern Pacific, you have a distinct pattern of storms which almost always follow the same route, forming near enough to the equator and then moving northwest (an exception was last week when an E.P disturbance went northeast, but it tends to be fairly predictable.
You look at other parts of the world and you have regular oscillations. But Ireland and the UK are completely random. I couldn't tell you with any confidence what kind of weather to expect a week from now, whereas for instance I could easily tell you to expect a persistent chain of calm weather followed by tropical waves in the Cape Verde islands for the next couple of months, at least until the end of September. In Ireland? Nothing like that. It could be an anticyclone, could be a right of high pressure, could be a trough, or could be a full on depression, and you can't say what's coming next with any confidence until you're about 4 days away from it.

Why is this? Why do weather patterns here seem less organized and less linear than in some of the other parts of the world I've mentioned? Why is there no consistent pattern here when there are patterns almost everywhere else?

mike65

My understanding

Irish weather badly sited for predicable cycles wedged between the Atlantic and Eurasia The atmosphere is controlled by two primary elements - the warm Ocean curret from Gulf of Mexico which moistens and warms air and the jet stream which propels that air, it appears the jet stream is increasingly unstable due to the warming of the Arctic and so the difference between the equator and the north Pole is narrowing this causes the stream to fluctuate in a exaggerated zig zag as it moves west to east and obviously this has a very direct impact on us being at a latitude which is right in the path of the jet stream for so much of the time.

hatrickpatrick

^ Interesting, if the jet stream is unstable due to warming does that mean that in the ancient past, we would have had a more cyclical weather pattern?
Furthermore: is there no way to predict the jet stream's oscillation over the long term, the way you can predict things like the MJO for example?

It just seems strange to me that so much of the world's weather is relatively cyclical or predictable, yet here it's like "It could be snowing next week for all we know, anything beyond about 120 hours is a pointless forecast"

Harps

For most of the year we're right on the boundary of the polar front so the weather can swing one way or another almost at random. Obviously there are factors determining what happens but as you say we have no real predictable monthly or seasonal patterns.

The simplest reason I can think of is, predictably the Atlantic, we're too far from the continental landmass for it to have any sort of regular influence on us. There's an almost constant pool of cold air over Greenland to feed the Icelandic Low and year round tropical air to feed the Azores High, we happen to be downstream of where these two clash so 90% of the time it influences our weather and we get our usual changeable, unpredictable weather. If Greenland wasn't where it was then maybe the Azores high would extend north with more regularity in late summer but that's just our luck