The GFS 18z op digs the trough down aross the UK more than the 12z op did. The rest of the run is then like a very slow version of the ECM 12z op run, very gradually moving the Scandinavian trough away and allowing a ridge to nose in by the end of the run.
This is significant purely as a trend, as it the fact that the polar vortex is weaker and more disorganised than I recall seeing on any of the runs in November.
As for the parallel version, it has been remarkably consistent with the previous run out to day 10:
That's very close to the ECM 12z op run in terms of digging the trough south, but the jet on the GFSP run is still flatter on the previous way, which means the low heights push further east. It's the reason why the NW'rly is a little colder than ECM's version.
Trough disruption does than begin to occur, but by that time the low in the western North Atlantic has suddenly decided to stop being aligned N-S and power NE, flattening the pattern. The day 16 result is a new area of very low heights to our NE. There's also one centered over the dateline in the Pacific. In other words, the polar vortex is split in two, a theme consistent with the previous GFSP op run and also the GFS 18z op run.
This is consistent with the combined effect of a recurving Pacific tropical cyclone encouraging a deep Pacific trough and U.S./Canada ridge and an MJO progression to phase 7-8 which then promotes height rises toward Greenland.
With this in mind, the ECM run represents a variation where the low heights to our NE are actually all the way over in Siberia, with a ridge between it and the UK. You're then left waiting for the low heights over Canada to get kicked out into the Atlantic, hoping for the elusive undercut to deliver the goods.
All this analysis could be rendered seemingly irrelevant if the trend ceases or reverses tomorrow, but I don't care really because for some reason I really enjoy writing countless words as I explore the output like this. It's a luxury I probably won't be able to indulge in for too much longer, as the lull following my postgraduate study at the University of Reading draws to a close and the world of work beckons.
Nothing concrete just yet, but surely only a matter of time. I wish I could place such certainty in a significant cold spell hitting the UK this month
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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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