bluearmy

the day 15 eps mean and spreads scream Greenland tpv very loudly and upper ridge into Iberia = flat zonal now the extended ens have been promising a return to a ne Canadian vortex for some time - it’s taken longer to get there than first modelled but it’s now looking v likely indeed the only caveat I have is that the trop continues to lead the dance and we know how unpredictable trop modelling is as week 2 progresses. there may be feedback issues that are consolidating a strengthening which may not verify in that fashion. Having said that, it was noted about a week ago that the modelling wanted to stretch the spv from Barents to e Canada, split it, then return the Canadian segment back to svaalbard. We know from experience that this east - west - east movement of a coupled spv/tpv will usually fire up the northern arm. It looks like the split that enables the n Atlantic height rise will also be responsible for the fired up jet as the two segments are rejoined on our side of the NH. in addition, the split Canadian segment dropping into n America doesn’t help as it increases the temp differential which leads to an even stronger jet. and the displaced nature of the spv our side means that this movement is at a southerly latitude which means the jet is aimed at us. as nick alluded earlier, there are sniffs of disruption which could force that jet into Iberia but that’s not what the nwp is showing I do have nagging doubts on this but it’s rare that the modelling for week 2 is wrong when there is so much agreement across the nwp there currently aren’t enough rogue ens members to justify any doubts (actually the 06z gefs have a few so maybe need to see what happens on the 12z eps)

There is a scientific reason for this

It’s the very best today no

Ukmo and gem are both looking southerly jet with us staying on the cold side gem diverges once out of any reliable timeframe this is the theme posted by ec yesterday 00z run

The dog is unsettled otherwise I wouldn’t be up! looks like the Arctic profile is still evolving - that could be to do with the repeated neg/pos/neg flow above 75N. Can’t be easy for the nwp to cope with that

Gfs 00z steps back a bit from the colder 18z days 4/5 Less lobe separation over Greenland Unlikely to follow the icon run too closely

It’s just a weak wave of fronts in the flow rather than a distinct system west of Ireland. As a result the flow is further south and 850’s 2c-3c lower we also see the push of slightly less cold 850’s moving west to east T108-T120 into the North Sea the lack of the distinct shortwave on this run reveals that what’s left is still very complex within the broad cold trough Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5007745

It’s just a weak wave of fronts in the flow rather than a distinct system west of Ireland. As a result the flow is further south and 850’s 2c-3c lower we also see the push of slightly less cold 850’s moving west to east T108-T120 into the North Sea the lack of the distinct shortwave on this run reveals that what’s left is still very complex within the broad cold trough

Tomorrows chart will show a mean reversal Matt but my eyes are drawn to a number of runs double dipping and the uptick to average is already looking a bit less enthusiastic the trop is leading the dance and we know how unpredictable the trop can be !

Exciting for dr Amy as she can tick 2024 off no additional consequences for what’s coming as it’s academic

The nwp is responsible for the strat forecast - the runs we see are modelling the whole atmosphere, top to bottom if you mean will the trop reflect this uptick then the answer is undoubtedly yes because the trop and strat are dancing very much in tandem at the moment with almost no lag. I assume that just as we will see reversal waves affecting the trop in the weeks to come, so will we see some uptick in zonal flow as a consequence of this brisk rise courtesy of reflective waves. however, this recovery in zonal flow could be brief as the strat could well slow down again approaching month end

Ultra consistent on the rise to average and then ????.

It looks like we will have a brief weak reversal around the 18th but it’s not going to make any difference being a tech reversal. The strat is suffering irrespective of whether it actually happens at 10 hpa 60 N

Don’t think so catcol but wrong thread to ask ! the mist is now clearing for next week (the envelope shrinking) and if the ens retain consistency over next couple runs for next weekend then we should have some confidence out to day 10/12. For now, there are too many clusters in the 10/15 day period

Would probably be shown as a trough with those arrows on it very much a snow maker but not worth pinning your hopes at this range

Depends how the low evolves from there looks like it’s deepening but disrupting a little at the same time at day six not worth over analysis

Looks like a convergence zone judging by the winds

Is that still the case now that ec46 runs every day ? obvs they don’t change the basic outlook daily but they used to pretty much only change wording Tuesday and Friday 30 dayer ec 06z ens mean is about 50 miles further north at day 6. Given the drop south on the 00z that’s of note as it doesn’t drop further south. Yesterdays 06z was a bit odd for continuity so we’ll wait for the 12z before deducing too much ref the met office potentially calling a milder period beginning end next week - that’s the cross model ens outlook. But I think the end of next week is a big call. I’d expect them to be a bit more vague than that re timing

Sadly I don’t get much of a chance to put this into practice but the ens mean 24 hour snowfall charts are a good way of judging the trends on where the snow line is once within day 5, you’d expect the ops to be more reliable as a broad brush risk indicator The geps having only 20 members are a little more crude than gefs and eps and given the operationals propensity to lay every flake and sleet drop as cover perhaps taken with a pinch of salt most recent run first eps Gefs GEPS Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006860

All three look like they run a low somewhere through the southern half of the uk - the darker the grey the more snowfall showing. You’d probably say the snowline is the base of the darker grey (or blue) because below that it’s likely to melt ec trended south on the 00z (see how n France has a darker grey on the 00z run) gefs is also trending slowly south but from n midlands approx geps is fairly static but not sure how reliable a tool that is - there is a likely a snowline within the snow map but can’t see it!

Sadly I don’t get much of a chance to put this into practice but the ens mean 24 hour snowfall charts are a good way of judging the trends on where the snow line is once within day 5, you’d expect the ops to be more reliable as a broad brush risk indicator The geps having only 20 members are a little more crude than gefs and eps and given the operationals propensity to lay every flake and sleet drop as cover perhaps taken with a pinch of salt most recent run first eps Gefs GEPS

True enough ! Just making the point I guess that whatever the worst feature that’s likely to reduce the cold for us seems to verify (or it just seems that way) We know that shortwaves pop up as the modelling gets within days 8/9 this one could just as easily have ridden the trough and come up the channel as we’ve sometimes seen in the past. Coupled with the detached ridge dropping se (suspect there is a connection),we manage to cut off the cold before its entrenched enough to guarantee snowfall from the Atlantic incursions hey ho still plenty to be watching

Except this winter we have the eps effectively giving us 50 ops. Seeing how the control often diverges from the op by day 7/8 with the same starting data, I’m not sure the ens are to be trusted any less than the op/control I always side with the further south the better because it keeps more of the country in with a chance of surprises under a cold trough to me, the alternative looks like a slush fest away from decent elevation And it looks like there is the chance that if we can get the trough further south then we can ‘adjust’ the jet that follows to drive into nw europe at a latitude that could deliver another big snowfall that bloody shortwave next week - @Mike Poole, do you remember me saying we can ignore that when ec popped it up on a day 9 or 10 run cos it won’t verify like that. And it now looks like it will!

Split tech ssw at the end of the gfs op The op model is extremely inconsistent at two weeks range

Started the day moaning about the lack of continuity on the macro and micro in the medium term A few runs later and nothing really has changed onto the 00z and hoping to get a steer on the shortwave