Focusing on the main trouble period...
GFS: LP coming in from NW days 5-6 slows and then just stalls near Iceland. LP over Azores positioned close enough to interact with the jet and move NE. Basically a double-slam in the gonads. The broad pattern remains favourable for recovery thanks to the U.S. pattern remaining amplified, and it comes within a whisker 10-14 so not all doors are closed there.
UKMO: that LP from the NW also slows but doesn't stall as GFS goes for. LP west of Azores is far enough away to avoid interaction with the jet for the time being at least. So the run can still erode away that Euro High but it sure is cutting things close.
GFSP: LP from NW is faster, phases with LP over Scandi so much better for getting the jet to dive towards Europe, bringing the cold air during Christmas Eve. LP to the west of the Azores even further away than UKMO has it so no chance of interaction - back to the well-supported mid-Atlantic ridge scenario.
GEM: similar to GFSP 06z out to day 6 (but doesn't evolve the same way down the line).
On the face of it GFSP and GEM seem very promising within that range, UKMO raises questions and GFS has a good go at throwing our hopes of a seasonal festive period out of the window.
Days 7-8, GFSP has changed to a flatter low over the Eastern U.S. which, instead of pumping WAA to support the mid-Atlantic ridge, allows the jet to just blast the jet right through it with catastrophic impacts on our pattern.
An ironic kick in the teeth is that the momentum then subsides just as LP has made it as far as Iceland, the amplified pattern then being set up in precisely the wrong configuration for a recovery of the situation. Had the LP stalled S. of Greenland, the amplification would have supported a high developing to our NE, much as we finally get to see right at the end of the run.
GEM hasn't got that flatter low and follows along the lines of the GFSP 00z i.e. a properly cold and snowy run of days.
GFSP is the only operational run to feature such a flat low in the U.S. but it is a real shame as I was enjoying its consistently cold output up to today's 06z.
I'm not going to hide it - this analysis took some determination to write in a level-headed manner! What's most unusual is the fact that there are different reasons for the downgraded outlook on each model output.
With so many different ideas, that could reflect some serious uncertainty and yes, confidence in these latest runs has to be rock-bottom, but I fear what the GEFS will get up to when presented with so many spanners to work with
The latest expert opinions seem to suggest that the upstream pattern on all but the GEM 12z (and this morning's ECM 00z) doesn't fit with what the background drivers should produce.
Maybe, just maybe, the models are detecting a signal for a slight adjustment and getting really carried away with it. Whatever the reality is, the dominant word is uncertainty, in fact it's probably about as high as it can possibly get for any given range starting 4 days from now.
...but beware that even if the colder solutions regain dominance soon, they may not be the same in structure or timing.
Apart from viewing the ECM, I'm hoping to take it easy this evening as that's better than trying to figure out all the reasons behind what is basically a chaotic set of output largely inconsistent with recent modelling and, up to the 00z output, trends.
If you have any problems or queries relating to TWO you can Email
[email protected] https://twitter.com/peacockreports 2023's Homeland Extremes:
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)
Keep Calm and Forecast On