SMU

18z is woeful. No short term pub run move to the ECM tonight.

Yes modified to the ECM - GFS not even in the mix. There will be a point in the next 24 hours where the GFS operational suddenly wakes up- probs 12z tomorrow but 18z may start the ball rolling-

Just to add to my post I hadn’t seen the ECM 216 convective potential high & getting higher 168-216...

Evening All Many many pages on here today driven on at a frantic pace - FWIW here’s my analyis- The evolution from mild to cold is pretty much set now all be it with still minor resolution on whether the first batch of cold makes it to the far south at the first attempt - There’s a slight concern that the full deep cold ( sub -6c polar air ) may not make it - before its started to get mixed with the continental air- seen here It’s not to much to worry about as the continental air will be cold - just not mega cold initially- there is reasonable continuity from the models around this but post 120 they part company. Post that we have to heavily rely on historic performance in this scenario. For me that stems back of about 13 years - & there is always a couple of consistent themes. * ECM / ECM operational usually leads the mean but the mean is usually catching the OP up the day after - The mean is also less volatile. * GFS is without fail awful in ANY scenario relating to undercutting - so many people have short memories of just how bad it is - *** in particular 06z & 18z ensembles *** the GFS / GEFS will be up to 3 DAYS behind the ECMs correct solution. * GEM / JMA - are usually a lottery. * UKMO usually close to the ECM. I think personally we are on the cusp of a classic cold spell in terms of 500MB height appearance - The ECM 144 & 168 would certainly not look out of place in the archives Whats not quite as classical is the upper air temps, we don’t get the full -10c uppers from the East- so convective snow ( at the moment ) looks a bit limited to more granular flurries. Surface temps will however be very cold circa 0-2c. Based on the ECM the best opportunity for proper convective snow is day 6 into 7. Post 7 onwards - undercutting YES..... Forecast summery: GFS - will correct throughout Weds- GEFS will correct Weds- Thurs however the meeting point to the ECM may not be all the way to ECM there may be a 70/30 meeting point where the ECM / GEM blend backtracks slightly. ^^^^ This is more towards the undercutting - don’t waste your emotions or time on your the GFS... The caveat to that is the ensembles will transition towards the expected scenario but it will be jagged & slow with some suites better than others. The distribution of energy into the Northern arm is expected to gradually be modelled back south. EXPECT THE UNDECUT.... Best steve

Post update @925

ECM 144> 168 & into 192 is about as classic as you can get tonight...

THERE IS NO POINT IN POSTING MODEL PERFORMANCE STATISTICS. WE DONT LIVE ACROSS THE NH. THERE IS NO REGIONAL DATA. Which is annoying as there would be massive variation in performance...

Guys. This threads turned into total carnage. The GEFS is a total farce when it comes to Easterlies- looks at the mean posted above ^^^ then compare it with the mean from 00z at the same time with almost no Scandi High pressure. Energy will undercut, the GEM is the extreme end of the positive solution. Whilst the GEFS ( 06z) was almost the negative solution. Follow the evolving UKMO, ECM ( as long as it’s not to progressive, the ECM mean & the Aperge. s

This one

So as the GFS ignites for another run if you looking for more sustained deeper cold then the shortwave @108 going through Scandi needs to come SW not SE

Why are people worrying about the GEFS they are cannon fodder in easterlies...

GFS 216 is the first GFS run trying to get a bit of energy under the block... someone needs to map the GFS 00z 216 & run 8 hour increments back to T0 over the next 27 runs to show it backs the high west 216 00z 210 06z 204 12z 198 18z & so on...

GFS along its little merry way correcting towards the ECM again it’s all subtle shifts not apparent straight away to the naked eye but line up the run about 120-144 & you see the edge towards the ECM expected to continue on the 12z ( related to the recarving of the shortwave over scandi at 120 - 00z had 2c isotherm over the SE at 156 now it’s -4c & just because @120 it tries to recurve the s/wave SW instead of SE look how far west the deep cold moves in 1 run... This is the shortwave to watch - it needs to bend around SW not SE the one over the baltic

Hi TEITS I had earmarked the 7th pretty much all the way through December based on the strat flow alone returning to normal on the 6th / 7th so that element hasn’t been that bad

Morning all not a lot else to say - ECM @168 will have 0c maxima over the UK possibly lower- GEM is probably one of the best runs ever for sustained cold lets get The High giving that optimal flow today at 120-144 with no more flirtations with the 0c isotherm from central / SE Europe...

It could happen it’s the 18z & any great chart that’s verified has never been correct from the 18z &144-168. just remember how bad the ECM was just a couple of days ago when I called it awfully progressive - I think it’s pretty nailed ( stage 1 ) stage 2 is finely balanced — S

& then the GFS falls apart as per the same 18z last- oh well it’s all about the first bit !

18z is boom town perfect flow uppers down to -12c now for Scotland !

ECM finishes with a long fetch straight Easterly into the UK -temps around 0c...

The expectation is that 192 eastern end tilts & the western end lifts forcing cold back west again-

UK will get glazed there at least !

Simply lovely...

Updated Aperge 114

Meant to say the GEM