Model Output Discussion - Spring Has Sprung

[Met4Cast]

2 hours ago, keithlucky said:

Big reversal coming,winter has a sting in it's tale.Expect rapid cooling as wind swing to easterly.

No real sign of that currently & SSW’s do not always = cold weather of course. 

Given the timeframes there’s a lot of uncertainty but current modelling doesn’t indicate a quick downwelling & tropospheric response to the early March SSW & the MJO won’t be particularly favourable for blocking (it may become so later). 

I wouldn’t expect much impact until mid March at the earliest. 

[Tim Bland]

A few flurries for some on Sat perhaps ? 

[feb1991blizzard]

3 minutes ago, Met4Cast said:

I wouldn’t expect much impact until mid March at the earliest. 

Would agree but early thoughts from me is it could still pack a punch when it does, a lot of cold air could  be bottled up & ready to go.

[damianslaw]

In the near term, the models are positioning low pressure on a more southerly track, north half of UK may escape with a dry sunny if not rather cold weekend. The low may even result in dry weather for all. Slack winds and clear skies is a recipe for frost. 

As we end the month, an amplified flow continues, heights ridging to our west behind further low pressure and trough swinging NW-SE. Temps very close to late Feb average, a little below in the north. A big positive is we should see much more in the way of sunshine thanks to polar maritime air. 

[feb1991blizzard]

[Kirkcaldy Weather]

Lots going on.

As the initial deep cyclone moves in through tomorrow there will be a few developments, along the southern flank there will be spawning of additional cyclonic centres thanks to a strong Jet Stream which already broke records when it was situated over Northeastern America 

 

During the initial phase of cyclogenisis the newly developing cyclonic Centre running through central and South Southeast England will have 2 zones of convection with one being particularly prominent and linear in form... possible Line Echo Wave Pattern / Squall and additional thundery cells could develop ahead of this line.

There might be some flash flooding within this.

During tomorrow I also wouldn't be shocked seeing flash flood reports across France. 

Into Friday this develops into 3 cyclonic centres with the one from the UK undergoing rapid cyclogenisis as it moves over the North Sea and swings into Scandinavia as a deep snowstorm which links to the original main cyclonic Centre which is part of the Tropospheric Vortex. We also see another cyclonic centre developing into the Alps as a snowstorm too.

As the linear convective activities clear into the North Sea the thickness level across Ireland and UK lowers with a plethora of wintry precipitation and snow even at low levels with laying snow a distinct liklihood particularly across Scotland Thundersnow opportunities likely too.

For the next developments we need to go back to the low which brought flooding rains across Florida.

This same cyclone will deliver further snow in Newfoundland 

This same cyclone will move over the Atlantic high and become joined with the original cyclone / section of the Tropospheric Vortex North northwest of the UK this will move toward Ireland the UK and Europe by Feb 25th / 26th.

During this timeframe the Alps snowstorm will be directed Northeastwards with current guidance of a snowstorm(s) ranging from Denmark and especially Sweden to other Baltic countries such as Latvia and Finland. 

The new system moving into Ireland UK and Europe could bring new flash flood risks from Southern England, Portugal, Northwest and North Spain into France once more... track and hpa dependant possible gales too.

As the high to the east builds into a high in Scandinavia this will connect to the Atlantic High giving the cut off low by February 26th - 27th.

This connection will be brief at this stage with new trough developments close to the UK & Ireland During the last days of February into the beginning of March

During week 1 of March with further influence from phase 7 of the MJO this could see further connections between the Canadian Maritimes Blocking and the Block to our East Northeast with potential this evolves into a Greenland High a la 

[Pinhead27]

1 hour ago, feb1991blizzard said:

ANY sort of explanation/enlightenment would be helpful ...

[Saint coolio]

 feb1991blizzard this will verify as I fly to Edinburgh that day (in theory)

[feb1991blizzard]

 Pinhead27

Its the stratospheric 10mb height chart, whilst it isn't a far and wide split its the EPS mean at 360 hours so you wouldn't expect that, that does look indicative of a big westerly zonal wind drop off in a few weeks time, possibly a big & sustained reversal to Easterlies, though that is yet to be decided, if so it still has to propagate the boundary layer into the troposphere (also to be confirmed), if both of those occurred, it *COULD* lead to a prolonged spell of well below average temperatures.

[WYorksWeather]

Interesting to note the disagreement between GFS and ECM ensembles tonight even at short timescales.

ECM is very keen to keep things on the mild side from around 27th according to the mean, whereas GFS is much more undecided or possibly even on the cool side. Interestingly though, GFS has partially caved to ECM on the issue of the warmup around 27th-29th - it now shows it a little more prominently on the mean, though it still keeps things cooler going forward.

I think this uncertainty still has some way to go though, so I'd be very wary of reading much into early March at this stage until we see the tropospheric response (if any) to the SSW. 

Just for a bit of fun, it's always nice to see what the more extreme ensembles are doing. We have the ECM tonight with the winter wonderland P46 at around day 15 - BFTE repeat anyone?

At the other end of the scale, we have some early spring type stuff going on with the ECM P08 by day 10. This is just a silly setup for the time of year - an Omega block potentially setting up in early March . The cut-off low reminds me of July 2022!

Anyway, all just a bit of fun everyone. Far too early to see what March will bring, and as I hope I've shown, the models really don't have a clue at this stage.

In the meantime, colder from tomorrow, at least compared to of late, and we see whether we get a CET record break.

 

[feb1991blizzard]

 Saint coolio

Great then, you might not  need an SSW in Edinburgh, you could get battered without!, never look a gift horse in the mouth!

[WYorksWeather]

Don't have time to wait for the ensembles, but the GFS 18z is also moving towards the ECM 12z solution for the final days of the month.

The key period is from day 5 to day 8.

You can see that as the Atlantic ridge slips southwards, before colder air is introduced from the north, we see a short transitional period, which allows a brief mild sector lasting around 48 hours with temperatures back to near average or slightly above. This can be seen more clearly in the wind direction charts as well. The wind gradually backs from northerly through westerly and south-westerly, with a direct southerly later.

 

If this pattern verifies, it's the death knell for the February CET record.

Probably still time for some chopping and changing on this, as the mild slot is so small and vulnerable to tiny changes in the position of the Scandinavian and Azores highs.

Edited February 21 by WYorksWeather

[feb1991blizzard]

Blimey we have had some erratic strat modelling this year, we've got the split now with the Canadian segment stronger, the other week it was the Siberian segment stronger.

[RJBingham]

GFS goes for March mildness.

[KTtom]

 RJBingham Im afraid Im seeing little to get my hopes up of any change in the next 2 weeks either to cold or more importantly dry, PV looks as organised as it can be for start of spring...strong Azores high = westerly and unsettled conditions being the predominant pattern. 

[RJBingham]

 KTtom It's relentless, warm or cold, just need some clear dry days.

[KTtom]

 RJBingham Totally agree, as a golfer, its hard to believe in 15 weeks time the course will be parched where its currently a mass of puddles..our weather seems to be becoming more defined with less variety.. here its dry and warm April to July with vertually 0 rain, then deluge for the next 8 months!

Anyway, ECM sums it up nicely for the start of spring ..as we were, Azores and Ruski high, trough over UK with no-where to go!

[Dennis]

NOAA

scandi march ideas 

[Dennis]

 feb1991blizzard

i feel for a long time that always weather is changing 

[bluearmy]

 feb1991blizzard the 00z generally follows suit. The gefs do not.  The strat modelling suddenly looks questionable after my post yesterday saying how the continuity on this looked solid! 

Time to take a step back 

[Dennis]

today to watch....SSE UK 

[feb1991blizzard]

 bluearmy

Eps 0z consistent with 12z FI split though to e fair.

[MJB]

40 minutes ago, Dennis said:

scandi march ideas

That's what we want 

[AO-]

Good morning,

Nothing wintry or springlike in either EC or GFS. After a few days of a chillier wind direction then a number of days with Southwesterlies follow under the influence of the pv  expanding South (note the certainty). After that there is a lot of scatter in the wind direction. But there is a great possibility of a flow between north and east, albeit that the chance has decreased since last night. 

Edited February 22 by AO-

[bluearmy]

 feb1991blizzard

00z eps at day 15    Split with Asian master (just) 

pretty impressive to have a split showing at that range across 50 members 

Edited February 22 by bluearmy