Model Output Discussion 17th Dec.2013-12z onwards.

[TonyH]

Indeed BA mine informing Gibby that he may have got his Christmas Calender mixed up was moved but I have PM'd him now, but I thought it was relevant to inform as Gibby's outlook is in the MO and it may mislead as it currently is.

 

He omitted Monday when there is set to be a potential storm as consistently modelled, I think he may have mistaken Monday for Christmas Eve?

Edited December 20, 2013 by TonyH

[carinthian]

Indeed lots to have positivity aligned to.  Yep we may not have or get GHP or Russian HP advancing but we have a Jetstream shifting south and I indeed think that we're in for a very wintry treat as we enter 2014.  Before that though trouble with wind and rain....and lots of it. 

 

BFTP

Thats the plan.

 C

[Newberryone]

Only a couple of days ago some models were hinting at the possibility of the pattern easing somewhat by Dec 28th owing to a rise in pressure to the southwest. Ecm op run showing that rise at the time with little or no support however from its ensemble member.

Judging by the latest Ecm output it would appear the op is now more in line with the ensemble for this particular time frame.

Who knows, perhaps to equal the almost unprecedented weather happenings of Dec '09 and Nov/Dec '10 for cold we are now about to experience a new historic weather event courtesy of an extremely active vortex. I think it's fair to say, judging by the last 3 frames of the Ecm 00z, this has the potential to run and run.

[nick sussex]

http://images.meteociel.fr/im/2858/gfs-2-120_wna2.pngThe queue at the bookies will be long based on such a model output from the ever reliable 06z!! Great, that's christmas paid for!!

Apparently COBRA are going to meet as there maybe significant slush! It's like going to the buffet and finding out all the good bits have been eaten already, we're left with stale potato salad and some dry turkey! In terms of a possible shallow feature producing a  two hour slush event the ECM does have something similar in terms of De Bilt, any feature crossing there will have to run through the south of the UK:

 

The ECM operational shows that quick wind change around to the ese and then nw as the feature clears through,it looks marginal even for Holland but perhaps with some evaporative cooling there maybe a few hours of excitement!

 

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

[Alexis]

Tomorrow night shows a real scorpion tail stormy episode coming through on the parent low, one to watch as that would produce quite extensive damage i would of thought, only short lived but severe!

I wouldn't be surprised if it shunted north, just like every low on rails between NW Scotland and Iceland at the moment.  For a supposed stormy spell, there seems like nothing much of interest happening for anyone away from the far NW. 

[nick sussex]

We were discussing marginal snow events the other evening, they can happen, indeed January 1994 is one of the biggest surprises, who would think that this chart produced some significant snow in the south:

 

 

Especially if you look at the 850's:

 

 

That produced as much as 6 inches of snow towards Epsom, in these marginal events you generally need light winds to aid evaporative cooling.

 

 

 

 

[Mucka]

I'm still not seeing the doom and gloom for January, sorry.

 

We already knew w e were locked in zonal for December, all that has changed is that the more favourable conditions for blocking as we end the month are manifesting themselves in the output - mainly in the ensembles but not exclusively so.

Now this doesn't mean HLB and a strong cold signal should appear in the same timeframe and I wouldn't expect ECM ensembles to show anything other than Ian F describes because within the 15 day timeframe any blocking is very unlikely to establish itself to the extent of bringing a cold spell and even decent blocking that is forming within those ensembles may well show a Westerly flow and moderate or even mild temperatures. Forget ECM32, or at least take its long range output with a pinch of salt, it is just going with the favourite instead of looking at the form guide.

 

The fact is there will be a window of opportunity for blocking to grab a foothold as the jet moves South with low pressure moving into Central Europe out to the mid term and what is considered reasonable reliable timeframe of the output (around 144) at the same time we have pressure rising on the other side of the pole - I will use the latest GFS 06z output to illustrate.

 

Mid term, Southerly jet, low pressure (trough) pushes South into Europe

 

 

From here a lot will depend on how much energy is forced NE over the ridge to our East and how fast and flat the next low pressure system is to our West. Too fast and flat and then the PV and mobile theme will likely override any blocking signal but  a slower pattern behind with the next low not quite so deep will likely keep the pattern amplified - see yesterdays GFS 12z (before it updates today) against the flatter faster ECM this morning.

 

 

Now Nik Sussex has already called fail on yesterdays 12z but it isn't a done deal yet IMO because there is still a signal for a slower pattern behind within GFS ensembles and GEM is still showing this today.

 

 

Even if we take a blended solution the pattern will still be more favourable for blocking going into January proper.

 

We can look at GEM at day 10 and on face value it would show an unsettled Westerly regime but look how much more favourable the pattern is for possible future developments with an almost split vortex. Now this maybe on the optimistic side of the output but ECM is on the pessimistic side IMO and even then it looks like a more amplified pattern would develop again from day 10.

 

 

 

 

 

We already knew we were playing the long game so I'm not sure how the output is so disappointing for January prospects, I just don't see it. I see increased blocking opportunities toward the end of December and through the first week of January (these will unlikely show up as cold runs even where blocking is gaining a foothold) and I do think we have a reasonable shot of a cold spell developing for the second week of Jan with prospects increasing for further blocking from there no matter what EC32 output is.

 

If we end up with a flat zonal pattern at the end of December/ start of January, I will feel very differently but I just don't see that as written in stone at the moment.

I'm not saying it will be cold and snowy second week of January (no hopecasting)- even if we got a decent block set up there is no guarantee we will be on the right side of it. All I am saying is let's not go writing January off on the basis of the current output and the EC32.Even when things look bad we can only realistically write off cold prospects for 14 days max and the output really isn't that bad and the improvements in the output over the last few days seem to have been largely overlooked because the broad theme will remain the same.

 

Granted a lot will depend from developments around the 26th Dec (I pick the 26th arbitrarily because that is when low pressure pushes South into Europe and we are on the edge of reliable output) and it may well turn out we are staring down the barrel again come the end of December but I'm just trying to give an opposite (optimistic) view of how the output may turn more favourable in January.

Edited December 20, 2013 by Mucka

[Frosty.]

The GEFS 06z mean shows the polar front jet digging way south into spain at times during the next few weeks and with the jet further south than usual, this opens up all sorts of wintry options as we go through christmas into the new year. There are plenty of 6z perturbations plus 6z control run which are cold enough for snow on christmas day, especially the further north you are, although the xmas day weather is still out of focus, we now have a good idea that it will be rather cold, very unsettled and windy, not only is there an ongoing risk of flooding for prone areas, there also appears to be a chance of significant snow on the big day, currently the north of the uk is most favoured, especially higher ground, then it continues very disturbed into the new year with the PFJ remaining to the south of the uk and further cold incursions for the BI.

Edited December 20, 2013 by Frosty.

[nick sussex]

In terms of Muckas post, of course nothing is set in stone but the fail is to do with a key part of the output, the better GFS runs had a weaker feature moving out of Newfoundland, indeed the best output had hardly any phasing, keeping the low a separate entity until very late, by which time the low over the UK had a chance to move east and not just ne.

 

The natural outcome of phasing generally throws the first low north, you can see across the big 3 what happens as the Newfoundland low phases with the UK one, the energy goes north. Its frustrating to see that lobe of high pressure in the Arctic not able to influence things  because more amplification upstream could have led to something a lot more interesting.

 

In terms of anything much more wintry within T240hrs we do need a very big turnaround from the models, of course I'm not saying things couldn't develop more favourably into January, we just have to wait and see.

 

And of course there is the marginal snow event, who knows maybe somewhere will get lucky.

[nick sussex]

Heres another of those marginal surprise snow events, that shallow low moved east producing some snow for Wales and the  Midlands, on the face of it the chart looked very average from a cold perspective:

 

 

A great read for those interested in how this happened:

 

http://www.weatheronline.co.uk/reports/philip-eden/Absorbing-latent-heat.htm

 

Generally the crucial factor with marginal snow events is lack of wind to stop too much mixing.

 

[Mucka]

In terms of Muckas post, of course nothing is set in stone but the fail is to do with a key part of the output, the better GFS runs had a weaker feature moving out of Newfoundland, indeed the best output had hardly any phasing, keeping the low a separate entity until very late, by which time the low over the UK had a chance to move east and not just ne.

 

The natural outcome of phasing generally throws the first low north, you can see across the big 3 what happens as the Newfoundland low phases with the UK one, the energy goes north. Its frustrating to see that lobe of high pressure in the Arctic not able to influence things  because more amplification upstream could have led to something a lot more interesting.

 

In terms of anything much more wintry within T240hrs we do need a very big turnaround from the models, of course I'm not saying things couldn't develop more favourably into January, we just have to wait and see.

 

And of course there is the marginal snow event, who knows maybe somewhere will get lucky.

 

Hi Nick, I agree with you over the T240 output whether or not we get flatter or more amplified pattern post Xmas.

Actually my post wasn't aimed at you or any one person, I just was mentioning the "GFS fail" because it is important regarding prospects going forward.

 

I understand what you are saying about the weaker low being slower and not phasing with our trough and of course I agree with your interpretation but I took you to mean that the fail was that it was wrong and we were now guaranteed a faster flatter pattern which is what I am not so sure about. 

 

Of course there are a myriad of blended solutions and I believe many of these will still offer better conditions for potential blocking to form in January than the ECM 00z for example - although I don't even feel that is a completely lost cause despite so much energy travelling NE as the jet looks to be digging South again behind and I would expect some reasonable ridging going forward 48hours - still pure conjecture on a chart unlikely to verify and my point is that I think we have an opportunity for something much more favourable for future cold chances to verify at day 10 than the current ECM output.

 

There is no right or wrong in discussing possible scenarios, I don't know what January will bring but I think I am more hopeful than most that conditions will be much more favourable for blocking to develop at that time. 

It just seemed to me that the general mood was quite despondent today so I thought I would view the output with some optimism for balance. 

Again, as far as the 10 day period is concerned you will need to get very lucky in the South to see anything wintry, the North and high ground may see some significant transient falls of snow - flooding and high winds will be making the headlines rather than snow for the foreseeable.

Edited December 20, 2013 by Mucka

[damianslaw]

We remain locked in a classic zonal pattern - very text book, with one low pressure quickly followed by another, deep marked cold and warm sectors and consequently plenty of windy weather - but this isn't a mild zonal outlook, indeed its a very seasonal one, with pronounced polar maritime sectors digging into the country behind what look like increasingly shorter lived milder tropical maritime sectors particularly in the north, thanks to a shifting the PFJ on a more southerly course.

 

For the northern half of the country temperatures at best in the next week or so look very average bordering on slightly below at times, with plenty of snow for the hills and on lower ground on occasion with frost. For the south chance of wintry showers at times in the polar flow.

 

Christmas day and Boxing Day could throw a few wintry surprises, I've seen many similiar forecasted synoptics deliver snow to quite low levels - all will depend on the intensity of any precipitation which in the heavier stuff will aid evaporative cooling.

 

This is often a very stormy unsettled period of the year - it does however, feel pay back for the relatively very benign second half of November and early December which is traditionally the most westerly period of the year.

 

For those who think oh dear will we ever see an end to the zonal weather- yes, we will eventually, when who knows at this stage. But history shows on many occasion such spells often do come to abrupt endings, often thanks to pressure rises over the mid atlantic or to our NE, there is no reason why this spell can't come to a sudden end as we hit the new year.

 

So in overview - its a very traditional outlook for the time of year, indeed very similiar charts to this time last year and in 2011, but colder than the last two christmas's - there are similiarities to the charts of late Dec 94, 97, 98, 99, 03, 04. Indeed its rare for the latter part of December to be settled or cold and snowy. I would much prefer a chilly blustery christmas day than a dry mild sunny one - sunshine on christmas day never feels right unless accompanied by deep cold - a la Dec 09 and 10. Hopefully we will see some brightness to reveal white coated fells. I just hope the weather remains settled enough for at least one day of fell walking over the christmas period when you don't get battered by gale force winds, driving sleet snow and hail and low cloudy gunk... please give us at least one short window of calmness Mr Vortex!

 

 

[syed2878]

@blast from the past. What makes u think that we r about to enta a cold faze come 2014? Looking at today's 00h runs none of the models shows anything wintery. Infact 25th and 26th looks to have a bit of a break from the deep lows. Going by ian f's update from the ec32 it doesn't sound too inspiring. Lets hope strat gives us coldies something to chear about come 2014.

[itsnowjoke]

Does the eye in the sky not post anymore ?

[Summer Sun]

Does the eye in the sky not post anymore ?

 

He does, but sadly he had a family bereavement

 

November 16th he posted this status update 

Going to be a while before I participate on the forum. Just spent 3 weeks visiting my dad in the Critical care unit and sadly he passed away. My dad means the world to me and I use to see and speak to him every day. Im devasted as his death was unexpected to us all. Now its just me and my mum and my cat. Damn GP, diagnosed indigestion and yet 12hrs later he needed 25 units of blood as an undiagnosed ulcer ruptured an artery. My poor mum witnessed this blood loss at home!!

[Summer Sun]

Today's NAO update shows it heading towards natural as we get closer to January

 

 

And today's AO update looks to be going in a similar direction

 

[Cheshire Freeze]

Today's NAO update shows it heading towards natural as we get closer to January

 

 

And today's AO update looks to be going in a similar direction

 

 

The AO will tank as we hit January IMO. Signs of that on those ensembles now. Whether we see a swift shift to a -NAO is a different matter altogether.

[gottolovethisweather]

Whilst the GFS 12z is in it's very early stages there is a quite a strong signal for plenty of snow over Scotland and higher routes in the North and also Ireland during the latter part of the weekend.

[snowmadchrisuk]

The AO will tank as we hit January IMO. Signs of that on those ensembles now. Whether we see a swift shift to a -NAO is a different matter altogether.

 

Interesting to see a few members on there do go negative though 

 

[Cheshire Freeze]

UK being sieged by low pressure. Is that 932 millibar I see there??

 

Edited December 20, 2013 by CreweCold

[gottolovethisweather]

To add to that Monday 23rd December then becomes very wet and potentially stormy across the South of the UK in particular.

[Cheshire Freeze]

Parts of NI and Scotland would be facing Christmas without electricity if this happens

 

[Summer Sun]

Just about as bad as it can get in the run up to Christmas

 

[mountain shadow]

UK being sieged by low pressure. Is that 932 millibar I see there??

 

927 by my reckoning!!

[gottolovethisweather]

Parts of NI and Scotland would be facing Christmas without electricity if this happens

 

 

Indeed, scary synoptics and with it comes the potential for blizzards in the regions affected by the Christmas Eve storm as the day wears on.

Edited December 20, 2013 by gottolovethisweather