Model output discussion 25th Jan onwards

[Nick F]

Gfs 06z is again looking wintry for next week!!hopefully ecm backs it up later with a bit more disruption!!yesterdays ecm 12z looked good but this morning there is not as much disruption!!ukmo looks closer to the gfs which can only be a good thing!!

 

Yes, 06z GFS suggests snow potential across Wales, SW Moors, central and northern England, even to lower levels, Tuesday and Wednesday. 850-1000mb thicknesses and dew points falling sufficiently for snow by then. Surprised by the comments of the charts looking uninspiring for cold. Looks cold to me next week. 00z EC only turns it milder later next week, which may change.

Edited February 5, 2014 by Nick F

[TEITS]

Predicted max temps next Mon/Tues.

 

http://www.wetterzentrale.de/pics/Rmgfs1324.gif

 

http://www.wetterzentrale.de/pics/Rmgfs1564.gif

 

Nothing mild on those charts. Fair enough the models do not suggest bitterly cold, powder snow, but when you haven't seen a snowflake all winter I will take wet snowfall.

[Frosty.]

 but when you haven't seen a snowflake all winter I will take wet snowfall.

I would take a wet sleet flake, at least it's white.

Edited February 5, 2014 by Frosty.

[Mucka]

Some well observed posts this morning but others missing the big picture IMO.

I stated last week that the PV residing over Canada or thereabouts would be on the move East as we head through the second week of Feb and the models now seem to be firming up on this being the case. My "hopecast" was for a trough to set up over Scandinavia around mid month with a more amplified pattern upstream resulting in the formation of an Atlantic ridge around mid month. I say hopecast because there is actually no way to forecast something so far ahead. Really we can only go off previous experience and what is being hinted at in FI within GFS ensembles and extrapolate from there.

 

This method has served me quite well this Winter but as always the Devil is in the detail and the detail is everything when it comes to our weather. So it is all very well predicting a MLB to our NE forming in two weeks time as I have done correctly in the past for example but there is no way of knowing how much influence that can bring to bear over the UK and that can be the difference between cold and snow and rain, rain, rain. That is one of the reasons I have a lot of difficulty with some of the more detailed Winter forecasts for the UK unless there is a very, very strong signal for a mobile pattern. I'm still reflecting on how much weight to give current and forecast strat conditions and for what period of time but it seems there is reasonable evidence that in a strongly biased Winter such as this where the strat is very cold and no warming is forecast by those on the cutting edge in the strat thread, that the state of the PV and its feedback to the troposphere should be given a lot of credence. However, I will be particularly interested in LRF methods developed where signals are weaker or more mixed regarding interaction and feedback between trop and  strat.

It seems to me one can still make a skilled judgement on what pressure patterns may look like up to around two weeks in advance regardless of strat conditions or even anomaly charts at that range - thereafter I would say predicted strat conditions would be a better tool but there will always be cross over in the time period and there will always be a fair margin of error. Still, as far as the MO thread goes I think there is room for speculation about what we may see things modelled at these more uncertain time-frames and people can take or leave them what they are, speculative.

 

Anyway I digress.

Back to current MO and the big picture.

Once that PV gets on the moves then we have our window of opportunity for more amplification upstream. there are clear signs that this will indeed happen though as yet there is no way to know how amplified or how strong any Atlantic ridge will be. As previously stated signals that far out tend to wax and wane so it is very hard to say the signal is getting stronger or weaker day to day while the potential remains in low res - we will begin to know more this evening and more especially from tomorrow onward as it comes into range of ECM. Still, don't be surprised if ECM throws up a strong Atlantic ridge or even a Greenland high at day 10 over the next few days even though that might appear very unlikely looking at current output and anomaly charts.

Often the models overplay these signals when they first pick up them and a lot will depend on how much residual energy from the Canadian PV is left behind and how that gathers itself from around day 7+. If it quietens then the Southerly jet should do its job and we will see more and more amplification, it could be jackpot first attempt or it may be we need a couple of attempts or perhaps things will go the way of all things this Winter. Either way we we are still looking at the period toward mid month for developments and likely the second half of Feb for any cold spell to set up and bring that elusive snow.

 

Back to the future and a more predictable regime has set up with low pressure over the UK and associated wind and rain. As the trough associated with the PV moves East there will the chance of some wintriness even to low levels, more particularly in the North and West, and those with some decent elevation may see a fair bit of snow fall next week. A lot will depend on how far South the pattern is forced with UKMO digging quite far South while ECM this morning was very shallow in comparison and GFS somewhere in-between. I imagine we would struggle for any wintriness to low levels if ECM is correct but UKMO and GFS offer that potential.

 

So with certainty we have more wind and rain out toward mid month, particularly over the coming days, with perhaps some wintriness thrown in here and there next week.

Thereafter a window of opportunity for a pattern change.

Edited February 5, 2014 by Mucka

[mulzy]

I think the mild/cold debate gets very subjective at times.

 

Think we need to refresh the facts:

 

CET to date for February = 5.4C (which is above average).

 

http://hadobs.metoffice.com/hadcet/cet_info_mean.html

 

5-day BBC forecast for London suggests mild - yes I know this stuff is computer generated.

 

http://www.bbc.co.uk/weather/2643743?day=2

 

Not saying there will not be any average/cooler than average days in the mix, but mild in the medium term (at least for the south) is a prety good call.  Even though it's about 9C now, it does FEEL cold (due to the wind).

Edited February 5, 2014 by mulzy

[Frosty.]

It depends on how much faith you can have in the Gfs 06z against the less cold Ecm..It would be nice to have cross model agreement on a colder spell but we never seem to get it..not this winter anyway, and not once this winter has any proper wintry weather verified despite several promising model runs before it disappeared in a puff of smoke.

[Purga]

To be honest, worrying about seeing a few wet sleet flakes next week is pretty trivial when faced with the potential disruption over the next days!

 

METO have now upped the SWW over large areas of SW / S England from Yellow to Amber alerts predicting gale force winds and heavy and persistant rain from now right through the weekend!.

 

http://www.metoffice.gov.uk/weather/uk/uk_forecast_warnings.html

 

It affects my own area but fortunately we seem to have excaped the worst so far. I feel really concerned for the poor folk in the already stricken areas (i.e. Somerset etc).

 

I really adore proper snowy weather but tbh there are far more anomolously extreme weather events unfolding right now before our very eyes.

[nick sussex]

I'm somewhat disappointed by the trend in todays outputs, the jet is modelled further north and we seem to have lost those slacker areas of low pressure over the UK, if you're not dealing with deep cold you need less development of those and by and large its a case of chasing some wet snow around which after the winter so far is hardly going to make up for the previous two months of general dire winter fare for cold and snow lovers.

 

We also have to factor in some model bias with 850's shown at later timeframes which end up being generally moderated nearer the time.The PV over Canada whilst relenting a little still looks too close for comfort and the ECM ensembles are uninspiring:

 

Overall I find very little to get excited about unless you're on a mountain, and there looks to be a lot more snow for the Scottish ski resorts, apart from that theres no sign of anything more than the odd colder blip.

 

Although some areas of the UK could be colder than De Bilt given the set up these are still poor and show absolutely no sign of anything decent in terms of cold over western Europe:

 

 

Unless we get some blocking in a favoured location and a way of finding some decent cold to advect into the UK then I think its another 10 days of frustration and the clock is ticking rapidly to the end of what is turning into a winter of dire proportions both on the wind, rain and flooding front aswell as the complete lack of anything remotely wintry.

 

 

 

[bluearmy]

Strongly disagree with Gibby, Purga posts this morning.

 

For starters the ensembles do not suggest mild.

 

http://cdn.nwstatic.co.uk/ensimages/ens.20140205/00/t850Cambridgeshire.png

 

Upper temps around -3C, low heights centred across the UK, disturbances within the circulation is a recipe for surprise snowfall even at lower levels. This is especially true if these disturbances occur overnight and under heavy precip. Also it is reasonable to assume that max temps could be just a few degrees above freezing. I personally consider temps of 10C to be mild at this time of year.

 

I do wish some members looked at the models in more detail rather than just assuming low pressure, W,lys equals mild & wet!

 

 

the ecm op looks out of kilter with its euro height rise. maybe a slight over reaction and we will see a shallower ridge moving west to east to our south.

 

our trough really looks like it isnt going anywhere for the next two weeks (as the extended ens have shown).

 

the reforming canadian vortex through week 2 doesnt look quite as angry as we've seen so with a gentle high height anomoly around greenland, we may well see the jet continue to be set on a nw/se axis into iberia.

[Mucka]

I think the mild/cold debate gets very subjective at times.

 

Think we need to refresh the facts:

 

CET to date for February = 5.4C (which is above average).

 

http://hadobs.metoffice.com/hadcet/cet_info_mean.html

 

5-day BBC forecast for London suggests mild - yes I know this stuff is computer generated.

 

http://www.bbc.co.uk/weather/2643743?day=2

 

Not saying there will not be any average/cooler than average days in the mix, but mild in the medium term (at least for the south) is a prety good call.  Even though it's about 9C now, it does FEEL cold (due to the wind).

 

Well the CET isn't any use for predicting future temperatures and I don't see an argument stating that it has been cold, only that it will not be mild, especially next week where it will generally be cool to average though feeling cold at times.

When comparing the average monthly CET to the temperatures forecast you have to bear in mind that the average CET will include a variety of conditions including night time frosts which bring the CET down even though daytime temperatures may well be average or a little above - therefore in dissimilar conditions where we are looking at daytime temperatures you will get a skewed perspective of relative mild/cold using that as your yardstick. You really need to compare the average daytime CET for the same period to make an argument based on CET alone as obviously the start of the month also has a lower average CET than the end of the month.

 

All said and done it is pretty much semantics but I doubt anyone outside would describe the weather as feeling mild for much of next week but that's more semantics and we need to differentiate between actual air temperature and "real feel", with wind chill etc factored in. 

 

My view is that we could see snow fall to low levels occasionally next week, particularly the first half of the week and it is difficult to describe that as mild and there is no mention of mild in the MetO forecasts with terms such as "feeling cold" over the weekend and this summary of there 15 day forecast, "Temperatures mostly near normal, but rather cold at times in the north with a risk of frost and ice."

Edited February 5, 2014 by Mucka

[johnholmes]

It takes all sorts and we all make our own summation of other posters posts but quite why this summary has required comment that there is no sign of mild early next week is a bit odd in my view?

 

In Summary today the weather remains in a very unsettled state with further spells of rain and wind for all, especially over the next week. there are modest signs of something a little quieter in Week 2 but rain will still never be far away with flooding issues still a problem for many. Temperatures remain no problem given the time of year with little frost and ice though the incidence of snowfall could increase somewhat over the hills with time.

 

Where does it suggest mild? Rain and flooding will remain a problem into the start of next week! No it does not mention the probability of snow to lower levels but few on here attempt to give such a full run down on the models as he does. I would agree that wet snow is a fair probability at times early next week as the coldest air, surface and at levels higher up, crosses the country out of the main Canadian vortex, as to how low then this far ahead is impossible to say. Worth keeping an eye on in my view for Midlands north perhaps?

Edited February 5, 2014 by johnholmes

[Troubleatmill]

Looking at the ensmbles on the 06z, i believe our best chance for any 'proper cold' is from the slight height rises to our north retrogressing westwards and linking to an azores high ridge in the mid atlantic creating a block to our west and North. The PV is shown to be relinquishing its grip into next week, but still strong enough to spawn DPs and send them our way. Hopefully they stay on a southerly track and we manage to get a full cut off as some ensembles are starting to show 

 

Next week looks promising for areas inland to see snow falling to quite low levels at times, Monday through to Thursday, all in all quite an interesting set of models runs so far today

Edited February 5, 2014 by Nicholas B

[Iceaxecrampon]

Vicious.

 

 

 

Hope this does not materialize TBH - centre approx 950milli - what was the 1987 low?

 

Ian

 

 

[MR EXTREMES]

953 mb

the 87 storm heres the link omg it could be serious.

http://www.metoffice.gov.uk/education/teens/case-studies/great-storm

[Troubleatmill]

Vicious.

 

h500slp.png

 

ukwind.png

 

Hope this does not materialize TBH - centre approx 950milli - what was the 1987 low?

 

Ian

 

953mb!! hold on to your hats 

[Bobby]

953mb!! hold on to your hats 

 

ECM and GFS both have it bottoming at around 944-945mb, similar to the current storm. Not the absolute depth that's so important though but the gradient and also things like a sting jet which the 1987 storm had but this storm likely won't. So won't be as bad as back then but it's a nasty little storm nonetheless.

 

[MR EXTREMES]

ECM and GFS both have it bottoming at around 944-945mb, similar to the current storm. Not the absolute depth that's so important though but the gradient and also things like a sting jet which the 1987 storm had but this storm likely won't. So won't be as bad as back then but it's a nasty little storm nonetheless.

 

what is the record for lowest ever pressure ?

[Canalboy]

what is the record for lowest ever pressure ?

Acccording to Christopher C Burt (who he?) the most commonly accepted figure as the world record is that observed during the peak intensity of Super Typhoon Tip when a reading of 870 mb (25.69â€) on October 12, 1979 when the storm churned in open waters near the island of Guam.

[MR EXTREMES]

Acccording to Christopher C Burt (who he?) the most commonly accepted figure as the world record is that observed during the peak intensity of Super Typhoon Tip when a reading of 870 mb (25.69â€) on October 12, 1979 when the storm churned in open waters near the island of Guam.

thank you for that and uk record was it 87 storm do you u think.

[Summer Sun]

what is the record for lowest ever pressure ?

 

UK record is 925.6mb recorded on 26th Jan 1884 - in Perthshire

 

Scotland also holds the record for the highest pressure ever recorded which was 1054.7mb on 31st Jan 1902 in Aberdeen

Edited February 5, 2014 by Summer Sun

[Bobby]

what is the record for lowest ever pressure ?

 

925.6 mbar at Ochertyre, near Crieff, Tayside on 26 January 1884.

 

Just been reading this funnily enough, source: http://onlinelibrary.wiley.com/doi/10.1256/wea.53.05/pdf

[Troubleatmill]

what is the record for lowest ever pressure ?

 

ECM and GFS both have it bottoming at around 944-945mb, similar to the current storm. Not the absolute depth that's so important though but the gradient and also things like a sting jet which the 1987 storm had but this storm likely won't. So won't be as bad as back then but it's a nasty little storm nonetheless.

 

 

Indeed and thankfully so, you can see this from the fax for the time, but hold on to your hats all the same, saturdays looks like it maybe even stronger than todays! and cycling into work i thought i saw a witch and a cow float by this morning!!

 

Its amzing for such a tiny island how divesre our weather is from place to place, i remember 1987 well and wondered what all the fuss was about, until i turned on the news. Thankfully very rare, not good when exciting becomes deadly 

Edited February 5, 2014 by Nicholas B

[MR EXTREMES]

925.6 mbar at Ochertyre, near Crieff, Tayside on 26 January 1884.

 

Just been reading this funnily enough, source: http://onlinelibrary.wiley.com/doi/10.1256/wea.53.05/pdf

thats very intresting bobby thanks for that. 

sorry mods its my fault its looking rather nasty.

[phil nw.]

I'm somewhat disappointed by the trend in todays outputs, the jet is modelled further north and we seem to have lost those slacker areas of low pressure over the UK, if you're not dealing with deep cold you need less development of those and by and large its a case of chasing some wet snow around which after the winter so far is hardly going to make up for the previous two months of general dire winter fare for cold and snow lovers.

 

We also have to factor in some model bias with 850's shown at later timeframes which end up being generally moderated nearer the time.The PV over Canada whilst relenting a little still looks too close for comfort and the ECM ensembles are uninspiring:

 

Overall I find very little to get excited about unless you're on a mountain, and there looks to be a lot more snow for the Scottish ski resorts, apart from that theres no sign of anything more than the odd colder blip.

 

Although some areas of the UK could be colder than De Bilt given the set up these are still poor and show absolutely no sign of anything decent in terms of cold over western Europe:

 

050200.png

 

Unless we get some blocking in a favoured location and a way of finding some decent cold to advect into the UK then I think its another 10 days of frustration and the clock is ticking rapidly to the end of what is turning into a winter of dire proportions both on the wind, rain and flooding front aswell as the complete lack of anything remotely wintry.

I think that is a realistic summary of the situation Nick.

Indeed some quite cold westerlies are modeled with some -4C uppers for a time next week but really to get  widespread snow at lower levels in an Atlantic pattern with higher dew points is difficult.

http://modeles.meteociel.fr/modeles/gfs/runs/2014020506/gfs-1-126.png?6

Plenty of further snow likely for higher elevations certainly and with some low thicknesses the wet bulb freezing level may drop in any heavy precipitation but this is not easily forecasted until nearer the time.

Overall though with this Atlantic pattern for most of us it's the wind and rain that continue to make the headlines.

[DR(S)NO]

925.6 mbar at Ochertyre, near Crieff, Tayside on 26 January 1884. Just been reading this funnily enough, source: http://onlinelibrary.wiley.com/doi/10.1256/wea.53.05/pdf

According to the met office website 936 was recorded on Christmas Eve at Stornoway in the Western Isles.Goes to show what a ridiculously stormy spell we've had since the beginning of December really