But irrespective of the generalised science behind the weather, the Jet Stream is an unusual quality and certainly one I would be interested in researching further, in an effort to isolate other instances of it being so far south.
I've gone ahead and done this, and have learned something interesting as a result. Note that there is some science behind this post, so if you don't understand any of it the
Wiki link should help.
As can be seen from
Met Office climate graphs, the amount of of precipitation the United Kingdom has been receiving - certainly since and including 2007 - has generally been higher than normal, especially during the Summer months. In particular, the BBC even quoted the Northern Polar Jet Stream (or just "Jet Stream" in their analysis; referred to as NPJS here) as being the cause of this as early as 2007, with it having been sitting at an unusually low latitude even then (
link). For no as-yet clearly identifiable reason, as published in a Geophysics journal and publicised by Komo of Seattle (
link), the NPJS - caused at least in part by circulations in atmospheric pressure known as the
Hadley,
Ferrel and
Polar Cells - has been gradually moving northwards, at an estimated rate of about 1.25mi per annum, and is also thought to be weakening, possibly due to climate change. (The eastern flowing air in the NPJS is the primary cause of most weather in this country coming from the West.)
However, over the last few years, the NPJS has been sitting at an "unusually" low latitude, typically at a range of only 50°N (roughly the English Channel). As a result, the unsettled waether associated with the NPJS - usually found at latitudes in the region of 60°N - has been spread across the lower latitudes of the United Kingdom, giving the impression that the country is suffering from unusually wet weather. (This also accounts for changes in other countries' weather of course; Poland for example has been hit for harder than we have.)
In practice however, the NPJS can be found as far south as roughly 30°N, which would otherwise be the location of the Northern Subtropical Jet Stream, so what we are experiencing isn't all that unusual. The fact that it has become prominent during the Summer is appreciative of the fact that we had an unusually "powerful"
Blocking Anticyclone, which is a fairly common trait of our weather during the Summer, earlier in the year than would often be the case.