Model Output Discussion - 23rd Jan - 12z onwards

[carinthian]

With thicknesses for 500-1000hPa at c. 523dam in a few places it may be cold enough for snow.

 

With thicknesses for 500-1000hPa at c. 523dam in a few places it may be cold enough for snow.

Will getter a better profile on the thickness profile when the fax charts get updated and the duty forecaster has put his thoughts in to the proceedings. The latest Met Office forecast  refers to snow in its wider forecast for Friday and possibly into the week end.

[Chris K]

Looking at the polar NH profile I'd suggest this is a 14 to 21 day cold spell with heavy snow showers cold and ice days galore....A very cold Feb is in the offing!

Potential for heavy snow showers and ice days for some yes...

14 to 21 day cold spell though....?

Sorry I am a bit unsure on that...Is there a chance you could explain how the NH polar profile is showing this?

Edited January 24, 2015 by Chris K

[Mucka]

Just a follow up on actually how the models have firmed up on and lengthened potential cold. Here are GFS 12z Op runs for Feb 1st.

They are also useful to see how the models develop a synoptic

 

Jan 21st

 

 

Jan 22nd

 

 

Jan 23rd

 

 

Today

 

Edited January 24, 2015 by Mucka

[knocker]

Good chart from 00z run

http://www.atmos.albany.edu/student/abentley/realtime/atlantic.php

Edited January 24, 2015 by knocker

[Banbury]

Potential for heavy snow showers and ice days for some yes...

14 to 21 day cold spell though....?

Sorry I am a bit unsure on that...Is there a chance you could explain how the NH polar profile is showing this?

Me too, very optimistic , hope the longevity is correct, slim chance I feel though

[knocker]

Regarding thickness the 1000-850mb is probably a better guide for snow but anyway if anyone is unsure of thicknesses this should help.

 

http://weatherfaqs.org.uk/node/152

[492]

Met O TV forecaster seemed highly confident at around 5.00 pm of bitter north winds setting in later Wednesday and kept emphasising how cold it will be.

[Jason M]

GEFS are a further downgrade IMHO. Others will no doubt see thing differently (which is perfectly fine)

By 252 hours the Atlantic has broken things down on all but a couple of ptrbs. In terms of the depth of cold a few are better than the opp, but overall the opp is representative of the 12Z suite.

so then, over the last 24 hours the cold spell has increased in duration from 2 to 3 days to 4 to 5 days, but the depth of cold has downgraded considerably. Based on where we are NOW this leaves us with 4-5 days of rather cold temperatures with some snow which will be confined largely to the north and high ground. Wintry mix elsewhere (can't rule out snow anywhere). The problem as always is that the source of the airmass is PM not Arctic. This is compounded by the lack of any cold pool to our East / Northeast.

Very disappointing for us down south, but still time for things to change (how often has that been said this winter?).

EDIT: I'm ignoring the GFS snow predictions as they are utter rubbish and always overplay things.

Edited January 24, 2015 by Jason M

[Jason M]

Met O TV forecaster seemed highly confident at around 5.00 pm of bitter north winds setting in later Wednesday and kept emphasising how cold it will be.

Presumably wind chill will be fairly high. Actual 2m temps won't be anything dramatic though based on what we can see tonight. Maybe 3c to 6c range.

[Banbury]

GEFS are a further downgrade IMHO. Others will no doubt see thing differently (which is perfectly fine)

By 252 hours the Atlantic has broken things down on all but a couple of ptrbs. In terms of the depth of cold a few are better than the opp, but overall the opp is representative of the 12Z suite.

so then, over the last 24 hours the cold spell has increased in duration from 2 to 3 days to 4 to 5 days, but the depth of cold has downgraded considerably. Based on where we are NOW this leaves us with 4-5 days of rather cold temperatures with some snow which will be confined largely to the north and high ground. Wintry mix elsewhere (can't rule out snow anywhere). The problem as always is that the source of the airmass is PM not Arctic. This is compounded by the lack of any cold pool to our East / Northeast.

Very disappointing for us down south, but still time for things to change (how often has that been said this winter?).

EDIT: I'm ignoring the GFS snow predictions as they are utter rubbish and always overplay things.

Of course you are assuming GFS is the correct forecasting model??

[doggy123]

Looking at the polar NH profile I'd suggest this is a 14 to 21 day cold spell with heavy snow showers cold and ice days galore....A very cold Feb is in the offing!

dream on lad

[PolarWarsaw]

Evening, 

 

Just a quick post. But until 3 or 4 days ago this cold wasn't showing up on the models as anything 'but' a cool down of sorts, nothing snowy - perhaps a few frosts. Since then we have trended towards a cold spell and there has been a couple of runs where snow may look plausible. What don't people understand about charts after T72? They are just a set of computer generated charts that nobody, including professionals take seriously, or should do. These are fake, they don't exist, they are nothingness drawn by a set of computer numbers, they will rarely if ever come off UNLESS they are vociferous, consistent and backed up by Ops/means/ens/forecasters... non of which has happened so far. 

 

Remember - there is a cool down progged as a general theme. If the 12z shows no snow - it's not a downgrade, because nobody has consistently forecasted anything of such sort. It's just another set of computer data producing what that set of data suggests COULD, physically, possibly happen. Some of you will end up with bipolar.

[Backtrack]

Evening, 

 

Just a quick post. But until 3 or 4 days ago this cold wasn't showing up on the models as anything 'but' a cool down of sorts, nothing snowy - perhaps a few frosts. Since then we have trended towards a cold spell and there has been a couple of runs where snow may look plausible. What don't people understand about charts after T72? They are just a set of computer generated charts that nobody, including professionals take seriously, or should do. These are fake, they don't exist, they are nothingness drawn by a set of computer numbers, they will rarely if ever come off UNLESS they are vociferous, consistent and backed up by Ops/means/ens/forecasters... non of which has happened so far. 

 

Remember - there is a cool down progged as a general theme. If the 12z shows no snow - it's not a downgrade, because nobody has consistently forecasted anything of such sort. It's just another set of computer data producing what that set of data suggests COULD, physically, possibly happen. Some of you will end up with bipolar.

 

I'm sorry, but you're wrong. Charts that are in the high resolution time frame should ALL be taken VERY seriously. Of course the professionals take them into account, how do you think the Met Office come up with the medium and long term outlooks? Granted they will use more than one model.  It's called a FIVE day forecast for a reason, and they can be made with reasonable confidence.

Now when talking about precipitation amounts or sunshine amounts, charts past the 72hr mark are useless yes, but when examining the upper air profiles for trends or to get a jist of the outlook over the next 5-7 days, each and every run counts.

 

Suggesting people calm down over a set of charts that are realistically WELL into the reliable time frame is just plain stupid.

 

Rant over. 

Edited January 24, 2015 by Backtrack

[Jason M]

Of course you are assuming GFS is the correct forecasting model??

Yep, entirely fair point. We don't have access to much else at 10 days out though, so I'm basing my views on the sum of what I've seen today including three GFS ensemble suites and GEM ensemble suite from this morning. Even ECM is of limited value as we don't see the ensembles.

MET Office will have more info than us, so if Fergie contradicts my view this evening I'm happy to defer to him (maybe MOGREPS is better).

[bobbydog]

I'm sorry, but you're wrong. Charts that are in the high resolution time frame should ALL be taken VERY seriously. Of course the professionals take them into account, how do you think the Met Office come up with the medium and long term outlooks? Granted they will use more than one model.  It's called a FIVE day forecast for a reason, and they can be made with reasonable confidence.

Now when talking about precipitation amounts or sunshine amounts, charts past the 72hr mark are useless yes, but when examining the upper air profiles for trends or to get a jist of the outlook over the next 5-7 days, each and every run counts.

 

Suggesting people calm down over a set of charts that are realistically WELL into the reliable time frame is just plain stupid.

 

Rant over.

to be fair mate, suggesting people calm down is never stupid...

[Ali1977]

If ECM shows anything like this morning then I'm not sure the surface temps will be 3-6c, I think people are wrong with thoughs...more like 1-4c seen as though we are still in Jan.

[Mucka]

Well yes PolarWarsaw, I think it is a case of perception V reality. No point in getting hung up on detail, worry about the general synoptic.

Also worth pointing out that whereas earlier runs barely had a cold snap now any breakdown is being modelled in FI.

If we look at the Northern hemisphere view at the end of Hi Res things look pretty decent and it is hardly a surprise GFS ensembles overrun the pattern in FI.

 

I understand the frustration of those who have not seen snow, I haven't and I'm in the"snowy" North LOL, but we are on the verge of another cold spell quicker than we could have hoped a few days ago, it seems a little churlish to write it off before it even arrives even if the South doesn't look best placed to benefit currently - things change.

[chris55]

Well looking at GFS i thought it was a pretty bloody good run to be honest,

 

From Wednesday onwards we stay in a cold pattern, no -20 uppers lol, but just cold enough for lots of interest IMO and no Atlantic breakthrough as we move into the weekend, 192 highlights the fact we are still in the cold northerly flow!!

 

  

 

Also if you take the Dewpoints through from Wednesday, they stay on the right side of marginal (just) throughout for the bulk of England and Wales, 

 

 

http://www.wetterzentrale.de/topkarten/fsgfsmeur.html

 

 

Id say this weeks earlier "possible" snow is perhaps subduing peoples expectation a little, and caution is needed, however with a sustained north/north easterly flow i wouldnt discount anything, polar low comes to mind!!!

[Cheese Rice]

I've learnt alot over the last pm disaster and this cold spell is -currently- not conductive for low lying snow over southern England. The spell favours high ground in Northern England/ Northern Ireland and Scotland. Eventually the uppers get mixed out further with a stationary low, of course this can all change but we need a blast of sub -7 uppers to move away from the wintry theme in the south to a snowy outlook.

[Long haul to mild]

 

The overall trend today is to keep that damn Azores high waiting in the wings to ruin everything , IMO a short lived cold spell that will not be remembered this time next year as being any significant. 

This is the time when you start looking at trends to see if a decent cold spell is coming or if another 3 day cold snap is coming and the balance for me has shifted very much toward a cold snap of maybe 4 or 5 days at best before a return to westerly driven weather, to be honest the UK weather has become very predictable in the past 12 months, it's getting a bit boring now

 

I agree that this has an equal potential to be as disappointing as it could be exciting but I would be very wary of taking charts from FI (i.e. the ones that show the return of Westerlies) at face value. We haven't even got the depth of the cold snap/spell sorted yet (that's still 5 days away), so what happens in week 2 is anyone's guess really.

[Mucka]

Yesterdays ECM 12z in comparison with today.

 

 

Edited January 24, 2015 by Mucka

[Daniel*]

I've learnt alot over the last pm disaster and this cold spell is -currently- not conductive for low lying snow over southern England. The spell favours high ground in Northern England/ Northern Ireland and Scotland. Eventually the uppers get mixed out further with a stationary low, of course this can all change but we need a blast of sub -7 uppers to move away from the wintry theme in the south to a snowy outlook.

PM sourced air is not what we're looking at air sourced from the heart of Arctic Circle it is a totally different matter, compared to NW'lies which have to travel many km over moderating N Atlantic. Scotland, Northern England looks like a pretty great place to be at this time, with elevation not crucial.

[Cloud 10]

An amazing 120 hrs chart from the ECM this evening,with everything but the kitchen sink on 

offer if it verified!

 

[Iceberg]

Yep ECM pretty much a carbon copy of METO to T144, with Thicknesses of around 522 in the south and a nice sub -6 cold pool in the south as well.

will be interesting to see where the EC goes after T144, given its upstream similarities to UKM.

Anybody in the south thinking this isnt for them...will need to consider imho.

[Mucka]

JMA 12z comparison. Yesterday/today.

 

 

 

Vive la downgrades.

Edited January 24, 2015 by Mucka