Model output discussion pm 13/01/2016

[Methuselah]

2 minutes ago, feb1991blizzard said:

I agree but I suspect more like the 2nd week towards mid feb before this displacement Strat warming (shown on the 12z very nicely) effects will be felt, Potent Northerly Mid feb is my bet.

 

Anyones guess after that though.

I'm so pleased that I never suggested that an easterly would happen, merely that such things have occurred before. Phew!!

[Banbury]

49 minutes ago, booferking said:

ARPEGE run is great for us who love to prolong this cold spell..

That is a stunning set of charts

[Jason M]

1 minute ago, PerfectStorm said:

Not true, it's more likely in these scenarios for snow to fall across the east and rain in the west. This is because the warm front has pushed through the west, raising the temperatures, but it's still cold in the east as the block has more influence. Your right though that the extreme east never does well, as mostly the precipitation dissipates or doesn't push any further across. 

I think your missing my point. Of course its colder in the east. My point is simply that in these scenarios if the precipitation gets east of London its because the block isn't strong enough and the whole frontal system tends to move through quickly = lots of sad faces on this forum. If the block holds the front often doesn't reach the SE (as you have also said). Either way, its not great here!

Anyway, there are always exceptions as prev stated. Sweet spot in these scenarios is often midlands and central southern england. IMBY we generally just freeze under the cloud shield  

[nick sussex]

1 minute ago, Banbury said:

That is a stunning set of charts

Interestingly that's a combo upstream between the flat GFS and the UKMO more amplified. Perhaps the ECM could split the difference and back the GEM/ARPEGE!

[Cheshire Freeze]

8 minutes ago, feb1991blizzard said:

I agree but I suspect more like the 2nd week towards mid feb before this displacement Strat warming (shown on the 12z very nicely) effects will be felt, Potent Northerly Mid feb is my bet.

 

Anyones guess after that though.

The troposheric vortex will, IMO, destroy itself before then. We've seen the GFS and ECM over the past couple of days (possibly) over react to a modelled antagonistic reformation of the trop vortex with Siberian heights seemingly perpetually underplayed. It's akin to a wounded animal having a last fight back at its attacker. However, the writing is on the wall. As it happens I don't think a technical SSW will be needed this year as at the troposheric level the vortex is its own worst enemy in the long run.

Edited January 15, 2016 by CreweCold

[chrisbell-nottheweatherman]

18 minutes ago, feb1991blizzard said:

I agree but I suspect more like the 2nd week towards mid feb before this displacement Strat warming (shown on the 12z very nicely) effects will be felt, Potent Northerly Mid feb is my bet.

 

Anyones guess after that though.

As I understand it, GP's prediction of an Atlantic block into Greenland and Scandinavian trough is not predicated on strat warming, but rather on AAM towards polar regions disrupting the troposheric vortex.

Edited January 15, 2016 by chrisbell-nottheweatherman
Correcting typo.

[Blake]

4 minutes ago, *Sub*Zero* said:

The chart Perfect Storm posted are accumulations from 0h onwwards not a 24hr accumulation. 

The ppn charts Monday & Tuesday showing fairly light ppn. 

I didn't say it was a 24hr accumulation chart, but the accumulations for "about" 24 hour's worth,... well especially SE. As you hover over timeframes, 1-2mm per hour from around T+60 to T+94 (34 hours in fact), IF, and only if it falls as just snow, and the 1mm precip = 1cm snow... more likely to be half that amount, but still a nice dumping. Precip comes in from West, stalls and sinks S/SE almost a day and a half after it begins. No doubt it'll change by then, hopefully for the better!

[feb1991blizzard]

7 minutes ago, Ed Stone said:

I'm so pleased that I never suggested that an easterly would happen, merely that such things have occurred before. Phew!!

I still think an Easterly wouldn't be out of the question but probably later in Feb, I don't really understand Dr Cohen being downbeat, the GFS runs have still been shifting the upper strat vortex towards Siberia, as long as that warming at 1hpa is still showing good strength at the end of the run then there is a chance of enough of a downwelling for a frigid feb, I wouldn't like to call exact synoptics beyond mid feb but I would put a lot of money on fairly long spell of blocking happening before March is out.

Edited January 15, 2016 by feb1991blizzard

[danm]

23 minutes ago, Jason M said:

In these set ups the extreme east rarely does well. If the front reaches east of London it is usually a mostly rain event. Its not unheard of for a front to stall out over the SE and EA but its unusual (there was an example about 3/4 years ago). Come the day, the set up will probably either correct west keeping the SE dry or the milder air will quickly turn any snow to rain. Its mostly conjecture at this point but its one thing where past performance is a good indicator of the future! I'm sure TEITS would say much the same. 

Be great to be proved wrong though 

 

February 2012 was a great example of a stalling front approaching from the west that delivered a lot of snow for this neck of the woods (London/SE). 

[Mucka]

Euro4 still showing a weakening band of sleet/snow moving down from the NW sat night/sun morning, could give some a dusting but looks marginal the further West you are and the further South you are the lighter the ppn will get. Could be good for West Yorkshire for example

Edited January 15, 2016 by Mucka

[perry011110]

28 minutes ago, perry011110 said:

Well the bbc forecasting is certainly in a bit of a pickle..i remember yesterday seeing a euro4 chart on this forum of varying rain/sleet/snow predictions for Ireland/nw england pushing se..according to there latest forecast there is some uncertainty as to how much rain/snow these places will get..so to me it seems that fi begins at t36 if that..

minutes ago, fergieweathersaid:

Key issues into (the nearer-term) medium range are compounded by mismatches between 00z/06z model solutions and imagery. The latter is already looking more amplified in the Atlantic versus output, favouring the slower solutions. This slower progression was always suspected and remains the main caveat set against ongoing deterministic modelling, which continues to show marked swings including run-to-run within the same suites (and even lately between UKMO-GM Operational and Parallel suites). No detailed analysis of current output is really trustworthy into the start of next week... 

Many thanks Ian for your unexpected reply, i wasn't criticising the professionals in any way but i just wish everyone would take on board your last sentence..

[swilliam]

1 minute ago, Mucka said:

Euro4 still showing a weakening band of sleet/snow moving down from the NW sat night/sun morning, could give some a dusting but looks marginal the further West you are and the further South you are the lighter the ppn will get. Could be good for West Yorkshire for example

Looked much better on the Aperge - gave 4/5 cms even down to the S coast

 

[feb1991blizzard]

21 minutes ago, CreweCold said:

The troposheric vortex will, IMO, destroy itself before then. We've seen the GFS and ECM over the past couple of days (possibly) over react to a modelled antagonistic reformation of the trop vortex with Siberian heights seemingly perpetually underplayed. It's akin to a wounded animal having a last fight back at its attacker. However, the writing is on the wall. As it happens I don't think a technical SSW will be needed this year as at the troposheric level the vortex is its own worst enemy in the long run.

I agree with that, I don't think a technical SSW is ever needed though, its a notional descriptive method TBH, a very near mean reversal at 10hpa, 60N as opposed to one just over the threashold will offer little difference, although obviously the bigger the reduction in zonal winds the better. I do have fears that that displacement could only be temporary and vortex over the pole could resume quickly, i suppose if we could keep getting these wedges of high heights in the trop slicing Northwards then we could get away without the strat doing anything spectacular but it but i think we would be lucky to go right through to the end like that tbh.

1994 feb was a great example of a non SSW induced bitter spell, much underrated that one.

Edited January 15, 2016 by feb1991blizzard

[Ben Sainsbury]

Just now, swilliam said:

Looked much better on the Aperge - gave 4/5 cms even down to the S coast

 

It's because there two different days! Ones 16th ones 17th.

[swilliam]

8 minutes ago, Ben Sainsbury said:

It's because there two different days! Ones 16th ones 17th.

Err - yes - this is the accumulation after it has snowed.

[feb1991blizzard]

Is it my imagination or does the ECM look very decent compared to the last run?

[I remember Atlantic 252]

better undercut from ECM on monday, uppers -2, good enough off fronts moving into continental air

[nick sussex]

Whats going on with the ECM? T72hrs looks most interesting!

Clean shortwave ejection at T96hrs then its game on.

Edited January 15, 2016 by nick sussex

[swilliam]

3 minutes ago, Banbury said:

The Beeb show nothing like that , it fizzles away to nothing

Yes - this is the only model showing this much - Euro4 last night showed something similar. As IF just said FI is T36

[booferking]

1 minute ago, nick sussex said:

Whats going on with the ECM? T72hrs looks most interesting!

All energy under at 72hr nick would you say..

[Methuselah]

Hey peeps, look what I've found - a thread dedicated to Hurricane Alex: 

[chris55]

2 minutes ago, I remember Atlantic 252 said:

better undercut from ECM on monday, uppers -2, good enough off fronts moving into continental air

Excellent chart! Snow incoming for those inland and away from the coasts.

[Roger J Smith]

Bigger picture ... current cold spell relents slowly with perhaps some back and forth along stalled frontal boundaries, some may cash in with snow, then a volatile period end of next week into last week of month, one or two much milder days seem inevitable but strong signals for a colder turn at end of January again with the more desirable easterly source. Baltic and North Sea have not cooled that much yet, a bitter easterly over those waters will become moisture laden very quickly and if it is cold enough phase problems should sort themselves out within five miles of coastlines.

[shaky]

Crazy ecm!!!what an undercut!!and to think parts of wales midlands and north west england could see snowfall tomorrow night!!think of that as a taster!!

[nick sussex]

3 minutes ago, booferking said:

All energy under at 72hr nick would you say..

Looks like the UKMO is going to be dumped this evening. Its a cruel world in terms of models, one minute the hero then one run and your last weeks news and nobody wants to be your friend! lol

The ECM still needs to disrupt another shortwave at T120hrs under the high otherwise it might sink, so perhaps the UKMO might get a reprieve!

Edited January 15, 2016 by nick sussex