bluearmy

feb1991blizzard the dice are important because with a blocked merifional NH pattern, we still have to get lucky

still worth waiting for …..

minus10 gfs is better at picking up progressive changes to mild. IGiven that we tend to suffer these being at the eastern side of a warm ocean, it seems to do well. I’m guessing we have a better opinion of gfs here than the netweather USA would.

Mike Poole I’ve been watching the AI models and they’ve consistently been keen to trend the lows north. Given that they are based on historic patterns, it’s surprising that we’re surprised!

Frigid yes the 46 has committed to reversal today which I guess is expected since the eps did the same on its 00z run. my point was that this hasn’t just come out of the blue - the usual pattern with warmings and reversals (whether tech ssw or higher up) is that the gfs op picks it up at 2 weeks range and it either disappears as time ticks down or it slowly picks up momentum in the ens and at some point they go all in. The 46 with 100 members is having its first winter so new for us to see. So far this winter, we’ve seen the first swift decline in flow picked up well by the model but thereafter, the Jan one and now this one were spotted around two weeks out. The actual ssw in jan wasn’t picked up at more than a week out by any model.

blizzard81 it’s not sudden the model picked up on a marked slowdown about a week ago and the gfs ops began to show an appetite for a reversal ever since it was at day 16. the gefs have slowly caught up and began to show mean reversal on and off for the past couple days. The eps since this morning.

The op cluster days 8/10 is the non scandi ridge cluster (in that the Atlantic trough is too far east on that cluster). The larger two clusters (80%) have a solid scandi/scrussian ridge with easterly flow we need to find a mechanism to leave some low uppers over Eastern Europe

Too early for a response from the upcoming one (won’t have happened by 16th) could be to do with events last month - clearly we have a neg AO ongoing and getting more negative

Lukesluckybunch ec46 looks in line with weeks one and two when comparing to 7 day gefs mean. But it damn well should! It’s only a tool to use for weeks 3 and 4. And the ec op at day 10 tells you nothing re that timescale

Stephen W way too early to make that judgment because the reversal is still too far away

Geps mean not great late week 2. Could be a few clusters and the mean is a mess

feb1991blizzard no run has done that high up that op is wierd in that at 10 hpa it splits and then rejoins whereas at 30 and 50 hpa it looks like it’s headed back and then stays well split. That could be down to the trop Atlantic ridge upwelling late on. If so, given that all the ens develop that ridge, maybe we could take the risk!

The 12z gfs op has a strat split solution (as opposed to displacement). With most split runs leaving a w Atlantic segment, we see the risks again of a split ssw note the atmosphere looks pretty well coupled bottom to top, it’s hard to see where the drive is coming from although the reversal comes from the top so we’ll say it’s strat led but very quick response down through to the trop

sheikhy gfs has around 5cms lying I’d ignore all the other models unless they specifically state snow depth

Lukesluckybunch isn’t Arpege showing all the sleet etc as accumulating snowfall ??

Lukesluckybunch this is the trick in the event that we build a surface ridge to our ne

Mcconnor8 understood but because the mild air comes in quickly it’s a fairly swift snow to rain for those areas perhaps going to now get some snow to begin with. I appreciate that it helps in the middle area as it allows a longer snowfall period

The small changes early on are gone by end day 3. So it may be a slightly slower advance of the mild air pre T48 but it soon catches up

BarnetBlizzard it’s ok - the further south the better. Scandi even better because it should help keep the Atlantic ridge further west and further south means the phasing from the Atlantic jet is far enough south to keep us fully cold Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5031491

Sky Full tomorrow ? We won’t know by tomorrow re that NH pattern post day 12 ……

feb1991blizzard Weather is cool WWW.WEATHERISCOOL.COM GFS 10mb Geopotential Height -- Instant Weather Maps WWW.INSTANTWEATHERMAPS.COM

BarnetBlizzard it’s ok - the further south the better. Scandi even better because it should help keep the Atlantic ridge further west and further south means the phasing from the Atlantic jet is far enough south to keep us fully cold

feb1991blizzard I just think a full atmospheric split will lead to the same evolution as we saw in jan with the American segment heading back to the Asian side

IDO this run is an ok fit with the cross model ens suites with the NH profile (perhaps a little progressive )