Yeah, quit it GFSP... that storm would be devastating if it verified with near 90mph gusts across the central swathe of the UK following 100mph gusts across Ireland.
It happens to coincide with the final moments of the very strong jet that we look to have firing at us for much of the next 9 days
The jet then weakens dramatically and a mid-Atlantic ridge builds. This is the key opportunity for a colder spell to establish, with plenty of scope for the ridge to build up towards the higher latitudes as the polar vortex is in a very disorganised state.
However... enough amplification is needed across the U.S. to achieve this, so that the seemingly inevitable low pressure development along the cold/mild boundary (where the subtropical jet is) is forced to behave in favour of sustaining or building the ridge rather than flattening it.
GFSP is not far away days 9-10 but it's not quite enough... the jet is then boosted again and we see a strong trough push from NW of the UK to NE.
Massive high latitude blocking then springs up from the Pacific, probably due to the MJO hanging around in a favourable location (phase 6/7) combined with the strat. vortex wandering away from Greenland toward Scandinavia, but that's a whole other kettle of fish.
Speaking of the MJO, the EC-32 (see below left) has that decaying in phase 7 (favours increased high latitude blocking but happens too fast for much of a pattern response to occur), then redeveloping just a few days later in phase 6 (good for strong pole-ward ridges of high pressure), back on route to phase 7. That would lead to a lot of amplification of the pattern by the end of this month if it verified, which explains the news from Ferguson.
As for the bias-corrected GEFS (above right), they show a stronger MJO in the next 5-6 days followed by something briefly closer to ECM, after which they really diverge as there is no decay on the GEFS(BC) output.
While the Met Office consider GEFS to be overdoing it, these bias corrected runs actually make the MJO even stronger, though with less progression east toward phase 8.
There are some highly technical reasons to believe that the MJO will make it further east without decay than has been the case for a long time, which I am still trying to get my head around, but seems to boil down to the decline at the turn of the year of an atmospheric setup that had for a long time been 'enticing' the MJO to keep returning to the Indian Ocean/Maritime Continent rather than set up shop in the Pacific, rooting it in locations unfavourable for driving amplification of the hemispheric pattern.
The Indian Ocean in particular is now looking hostile to the MJO so it looks like travelling to the Pacific during the coming week, after which warm SST anomalies associated with the on going El Nino pattern (though weak) may help to keep it there rather than letting it travel on towards the western hemisphere and Africa.
ECM decayed the MJO a bit too quickly back in December (period of 7th-14th, visible as red line on each chart - ECM at about a week's range had it totally decayed before even reaching phase 7) so I believe some adjustment toward GEFS(BC) may occur. Equally, the GEFS(BC) may tone it down a bit... a typical coming together of the output.
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T-Max: 30.2°C 9th Sep (...!) | T-Min: -7.1°C 22nd & 23rd Jan | Wettest Day: 25.9mm 2nd Nov | Ice Days: 1 (2nd Dec -1.3°C in freezing fog)
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