Model Output Discussion - 23rd Jan - 12z onwards

[Captain Shortwave]

Day 6 charts

ECM

Low pressure centred over Scotland with a strong and chilly north west wind

 

UKMO

Low pressure over Scandinavia, a bitter northerly wind setting up already.

 

GFS

Between the Euros with low pressure in the northern north sea, a cold north westerly wind, though some significant modification of the 850s is observed.

 

GEM

Low pressure over Scandinavia, similar to the UKMO but the trough is not as deep, the cold northerly does arrive though.

 

The GFS and ECM show the risk of the trough being too rounded and close to the UK, resulting in a cool rather than cold pattern. Looks quite unsettled across the board with showers or longer spells of rain spinning round the low. These could turn to snow if the conditions are right though. The UKMO is by far the best output this morning in terms of setting up an Arctic plunge in the semi-reliable time-frame.

Edited January 24, 2015 by Captain shortwave

[EML Network]

The UKMO screams Wishbone effect, indeed looking across the board these charts are very cold, BUT they're not really at all good for snow inland or across the South. 

 

 

With this chart you would get snow running down the East and West coasts and they would fizzle out as they made their way inland it would be a frustrating day to say the least for many as they see their resident snow shields up and heaven for a few lucky others who saw lengthy spells of snow feeding in off the coast

Edited January 24, 2015 by EML Network

[bluearmy]

His close is the trough going to be? Some of the output this morning has us very close to the main surface trough complex. over the past few days, this low centre has appeared to contain the highest uppers (as us usually the case, not being a polar sourced feature).

I wouldn't assume too much about the make up of this system for another couple days. how the system of lows actually evolve prior to heading towards n Europe could change somewhat under a very mobile set up. The uppers indicated could well be -3/-4. However, come the time, they could be -5 and depending whether we end up with a quite slack flow under the lows or a fast flow to the west of them will make big differences. I note the DP's on the ECM run to be largely favourable but that's one run and too far out to draw conclusions.

As far as the polar profile is concerned, there is no evidence that the vortex will come back together again whilst high res runs are ongoing. and if this episode continues to be strat influenced, this is no toppler with the strat vortex pointing itself firmly at Europe.

[Frosty.]

Upgrades all round, Ecm 0z has cranked up the cold wintry synoptics in terms of longevity too, could be a prolonged arctic spell. As for wishbone effect, I would expect to see organised troughs swinging south with bands of snow showers and maybe even a polar low or two, this is no lame toppler..later next week onwards looks increasingly wintry for all and the snow when it does come will drift due to the strengthening arctic winds. :-)

Edited January 24, 2015 by Frosty.

[carinthian]

Just a quick look at the models at breakfast. Excellent UKMO, seems the coldest sourced run. Snowy week to start February looks very likely. Lets hope this theme continues throughout the weekend. Should have a update on Monday from the portal service regarding the extent of a February cold spell and the change to -A0.

Have a good weekend,

 C

[Duane S.]

Guessing a lot of late risers out there because when I noticed we were still on page 8 here before viewing the model output, I assumed they were going to be a poor set! I think it's safe to say I was pleasantly surprised.

This is looking increasing less and less like a toppler and more like a very interesting cold spell on the horizon. More runs needed as always but looking good.

[jellybaby1969]

Lots of ramping this morning...but caution ! Lots of blues and purples shown however not a particularly cold source. No big freeze as yet.

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY SATURDAY JANUARY 24TH 2015.

NEXT UPDATE SUNDAY JANUARY 25TH 2015 08:00

THE CURRENT GENERAL SITUATION A chilly NW flow covers the UK before a weak ridge of High pressure and then a warm front moves East over the North and West of the UK later tonight and tomorrow

MODELS-2 WEEK HEADLINE Changeable with rain at times but some drier spells too. Less cold. Turning more generally unsettled and very cold again later with snow in places, especially over the North and East.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Forecast shows the flow driving sharply South over Europe later next week and ridging North across mid Atlantic keeping the UK on the cold side of a Southeast moving flow to the SW of the UK by next weekend.

GFS OPERATIONAL The GFS operational today shows a very changeable couple of weeks to come for all areas. Firstly a continuation of the see-saw pattern of one day mild and one day cold continues as successive fronts cross East bringing occasional rain and milder temperatures then colder and brighter days with showers in the NW. Then from midweek a more coherent spell of cold weather lasting some time slips down over all areas with cold windy conditions with NW or North winds and sleet and snow at times especially across the North and East. This then gives way to spells of cold zonality with further Low pressure moving SE for seveal days then East later  with further wintry precipitation at times before the very end of the period sees less cold Westerly winds with rain at times.

THE GFS CONTROL The GFS control run follows a similar pattern to the operational today and maintains a rather cold and unsettled pattern with a more generally milder but still unstable Westerly flow by the end of the period

THE GFS CLUSTERS The GFS Clusters today show the Azores High and a polar vortex to the North of the UK continuing to dominate the UK in both 10 and 14 days time. Many of the clusters at Day 14 show less cold and Westerly winds replacing the spell of cold weather under a more direct NW flow in 10 days time.

UKMO UKMO this morning shows a belt of Low pressure to the North midweek mivng SE to develop a very deep trough over Europe and bathing the UK in ever colder NW and later North winds. Rain and strong winds would be swept away East and SE to bring in cold and wintry weather to many with sleet or snow showers for several days late in the week under a strong NW or North flow.

THE FAX CHARTS The Fax Charts continue to show an alternating pattern of rather cold and milder conditions as troughs pass over from the west before towards midweek more complex frontal systems cross the Uk from the West with colder air over the North Atlantic encroaching towards the UK.

GEM GEM today also continues to show the deepening of a strong and cold WNW flow later next week and weekend as Low pressure slips SE across the North Sea and NW Europe with strong and cold NW or North winds and sleet or snow at times for many later in the period.

NAVGEM NAVGEM today only differs in the positioning of the deep and cold pool of air late next week as it holds the cold and deep European trough further West and indeed over the UK itself later. While this could lessen the impacts of the cold North flow the others show the weather would still likely be cold with wintry showers or longer spells of rain, sleet and snow at times broght in on more variable winds from the West or North.

ECM ECM this morning looks very wintry later next week as the deep Low complex having moved over Northern Europe becomes fairly slow moving and keeps the strong and very cold NNW flow over the UK with widepread spells of sleet and snow showers driven South in the flow making for some severe conditions at times especially over exposed Northern locations.

ECM 10 DAY MEAN(12z) Using yesterdays 12z run the Northerly flow at Day 9 is shown to back more towards the NW on Day 10 as some members obviously indicate a toppling ridge scenario as we approach that time. The new 10 day mean was not avialable to me at time of publish.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trend remains for much colder and windy weather later next week and through next weekend. The longevity of the spell is still unclear with various options both for a longer spells and not are shown this morning.

MY THOUGHTS One day on from the wintry charts of yesterday and the trend remains locked in place throughout this morning's output for all areas to experence a spell of very cold weather on a very strong Northerly flow next week as a deep trough resides over Europe. In the interim period fairly benign weather looks likely with High pressure to the SW continuing to steer relatively weak troughs East over the UK with alternating periods of mild and slightly cold weather with a litte rain and wintry showers at times to the NW. It's soon after midweek that Low pressure to the North makes it's move SE into Europe deepening markedly as it goes and driving the cold weather South to all areas by next weekend. Pressure looks like staying very low across the UK and although Southern England will likely see a lot of dry if very cold and windy weather all exposed locations facing North will see a lot of wintry showers of sleet and snow with some significant falls of snow in places givng rise to disruption in places. Also there would be evry chance of disturbances running South in the flow giving some more organised and potent areas of snow at times. Frosts would also likely be severe at night due to windchill. Then before I get carried away with all this talk of wintry weather we have to look further ahead and try and determine how long this show lasts. Well we have mixed messages this morning as GFS gradually slackens the trough over Europe and with the Atlantic High slipping back nearer to the Azores all their output puts the UK back in milder Westerlies by 14 days time. However, we have GEM, NAVGEM and particularly ECM who all look at least interested in maintaining cold and unstable air over the UK rather longer as High pressure over the Atlantic looks like holding firm at least for a time. I would though think that it would only be a matter of time before a ridge collapses across the UK and ends the spell unless we can pull the Atlantic ridge further North towards Greenland but I must add that some of the output goes some way towards addressing this today and wouldn't take much more of a shift to keep the UK in the freezer. Nevertheless, a very interesting spell of weather coming up with plenty of interest for coldies especially with no doubt some snowfall for many late next week. There is a while to go yet though before it can be classed as a definite to happen though with such good cross model support I think we can at least say a cold snap is on the way for sure. Details beyond that fact must be taken with a pinch of salt until nearer the time.

[Mother Goose]

Thank you very much Gibby, a brilliantly well informed forecast.

[Frosty.]

Here comes the increasingly cold and disturbed spell the met office have already discussed, by midweek it's turning cold and windy across Scotland with snow showers and that cold and very unsettled weather pushes south to the rest of the UK, the Ecm 00z op shows a prolonged wintry spell becoming established which would last well into February with plenty of snow, frosts and ice.

[Gibby]

I notice some folks looking a bit down with regard to insufficiently cold uppers shown at the moment. I suggest don't worry about that at this range. I can guarantee that with synoptics like those shown it will feel and be cold enough for snow for many. As I hinted at the end of my report above get the cold here first then worry about specifics nearer the time. I firmly believe that if all this fails then so be it but as it stands currently it does offer our best chance of a cold spell of note on a Northerly for several years.

[bluearmy]

Just to add that the gefs become progressively pants for cold as they head through week 2.

whilst I don't have huge faith in them to pick up a change into cold, they do seem rather good at picking up the change back to not cold, once they have recognised the cold will indeed come.

[IDO]

It is nice to see this far out the Atlantic amplification looking nailed by models and all GEFS. In fact this was picked out a while back (dropped for a few runs) so impressive. I know Bluearmy picked out this synoptic last weekend from the ECM ENS. The D6 GEFS mean:

 

 

 

Still variations on the rotundness of the low digging the Euro trough with the most southern showing a satellite low at the base. The spread highlights this and also the possible spoiler low coming in from the west. These lows have been a pain to model this season and again it is carried on the jet so by D7 the ensembles begin to show varying solutions. Before its arrival we get a few days of cold uppers UK wide but it's introduction around D8 brings in warm sectors and washes out the uppers. Even more spread from there with some flattening the pattern due to the blown up "spoiler" low. Again by D10 the majority have flattened the pattern. There remains a small cluster that keeps the more meridional Atlantic (22%).

 

So again FI at around D6-7 with many possibilities within the upcoming synoptic pattern change. No point guessing the likely outcome though the GEFS as a guide suggests the most likely solution is a flattening of the pattern as lows fire off the US trough as it recycles the daughter PV over the western US:

 

 

This has been episodic during the current winter, the PV bursting back into life after a short period of calm. So we usually end up with 4-6 days of colder output. The D8 and D13 charts highlight the GEFS current signal for this to be repeated again:

 

 

 

Normally a reboot of the PV may still allow cold but with any longer term HLBs on the other side of the NH the UK is directly inconvenienced by the restlessness of the PV's journeys. Warnings re the ECM D10 charts and the UKMO D6 charts when both have notoriously led us up the garden path during pattern changes this year, though thats not to say they are wrong this time.

[chris55]

Corking ECM this morning with a nice ridge and persistent northerly!! As BA has said details, 850s - dew points etc will need to be watched as we get further runs but a v nice overall pattern. If we can hold the pattern into the more reliable timeframe then corrections West would be very unusual with this kind of set up, so pushing the trough further east is likely, this may allow a colder flow for the uk, and with disturbances running south we may be looking at better snow chances the closer we get!

[Stuie]

GEFS anomaly. Wish it was a bit darker......

[BLAST FROM THE PAST]

Terms I've been using and drum beating....PV KO'd and in pieces come Feb, severe weather warning/alerts, Very cold air from NNW/N and at times NE quadrant, deep troughing over UK, to our East in Scandi and NW Europe around turn of month into Feb, AZH ridging in Atlantic/linking with Greenland at times, very cold volatile situation with potential polar lows popping up.

Very good support from models re troughing and ridging which seems to be increasing within the timescale [so good starting point].  However, This winter again thus far has taught us that models latch onto something and then nearer time water it down somewhat.  Its only 24th so plenty of watering down time left but also plenty of concentrating time too.  The models are also showing that with trough positioning itself where it is it can deliver longer cold than just a two day shot.

FWIW, I think we are in for a longer than a two to three day shot, I think the models this time are very much on the money because we aren't relying on holygrail GHP or Massive Russian HP Backing west to Scandi.  However, as its morning and I have sensible head on....we have been let down somewhat this winter and we must be prepared for potential watering down....but we must also be prepared [especially our friends t'up north, NI and Scotland, N Wales] for potential impactual winter weather. 

Although I'm sure our Canadian and N Scandinavian friends will say UK is turning autumnal.

All in all, a good wintry continuation....lets see where we are come Tuesday/Wednesday

No charts posted as our friends above have amply posted what is on show...long may it continue if you are a coldie.

 

BFTP

Edited January 24, 2015 by BLAST FROM THE PAST

[Day 10]

Guessing a lot of late risers out there because when I noticed we were still on page 8 here before viewing the model output, I assumed they were going to be a poor set! I think it's safe to say I was pleasantly surprised.

This is looking increasing less and less like a toppler and more like a very interesting cold spell on the horizon. More runs needed as always but looking good.

Totally agree, could be our best cold spell of the winter, hopefully worth the wait!

[Ali1977]

Looks like Thurs is when the fun starts up North, when is classed as reliable time frame for this set up? Are Northerlies harder to forecast that other set ups?

[Captain Shortwave]

ECM ens happy with conditions turning colder from Thursday with a strong north westerly wind developing behind a cold front.

Winds remain north to north westerly out to day 10

Spreads

Decent support for the operational. Especially with the Euro/Scandi trough, uncertainty more to do with the level of upstream amplification but I would certainly say a 5 day+ spell of colder weather is likely, starting from Thursday.

 

850s turn much colder in week 2 as we finally see a pure Arctic flow develop, unsure about how the preceding days will pan out (850s around the -4C mark). Low heights at the surface and 850 level with a prolonged spell of winds from the north should hopefully mean we can develop bands of showers or even longer periods of precipitation, which could potentially deliver snow to many areas (if it is cold enough). In this set up, whilst the wishbone effect will be present in the showery interludes, I would be surprised if a 5-7 day northerly didn't produce some sort of frontal event and hence something widespread across the UK.

Edited January 24, 2015 by Captain shortwave

[gottolovethisweather]

Corking ECM this morning with a nice ridge and persistent northerly!! As BA has said details, 850s - dew points etc will need to be watched as we get further runs but a v nice overall pattern. If we can hold the pattern into the more reliable timeframe then corrections West would be very unusual with this kind of set up, so pushing the trough further east is likely, this may allow a colder flow for the uk, and with disturbances running south we may be looking at better snow chances the closer we get!image.jpg

 

Ah I would suggest that chart is showing the elusive Omega Block out in mid Atlantic, oooer OMEGA, OMEGA, OMEGA I say.  If these cold charts remain and start venturing into the reliable by next Monday's and Tuesday's outputs, I will then start getting on board with the rest of you, for now I remain cautious however. More appropriately I remain cautious, in part due to my location and the fact that my region has been effected by that pesky Azores High ridging for more weeks than I care to remember and will that feature do as currently progged. All of that said, I would love the weather gods and goddesses to bring on the cold snowy synoptics, slowly slowly catchy monkey. 

Edited January 24, 2015 by gottolovethisweather

[bluearmy]

Mean Thicknesses in London 528 by day 6 and then dropping quickly to low 520's through to the end of the run. Those are means and the spread on uppers is not high. Whilst no promise of snowmageddon, I do feel some are very laid back about the possibilities that will likely appear within the overall setup.

Can the dam hold ?

[Ice Day]

Guessing a lot of late risers out there because when I noticed we were still on page 8 here before viewing the model output, I assumed they were going to be a poor set! I think it's safe to say I was pleasantly surprised.

 

 

Glad I'm not the only one who page counts!

 

ECM at 240 is one of my favorite charts of the winter.  There's so much to like, air sourced straight from the arctic, heights shooting up towards greenland, PV in tatters etc.  *IF* this happened to verify, I think there would be a lot of fun and games in the days after!  Anyway, too far out to take too seriously but the charts have my full attention at the moment!

 

[mushymanrob]

apologies if this has been mentioned, not read all the pages.

it appears to me that the key to how severe the possible cold spell might be is whether the azores high ridges north to join with the greenland high. the gfs 00z doesnt make much of it, so atlantic systems break through and keeps us changable, whilst the ukmo and ecm make more of this feature thus locking us in arctic air.

[Fozfoster]

Mean Thicknesses in London 528 by day 6 and then dropping quickly to low 520's through to the end of the run. Those are means and the spread on uppers is not high. Whilst no promise of snowmageddon, I do feel some are very laid back about the possibilities that will likely appear within the overall setup.

Can the dam hold ?

image.jpg

BA , I think the term once bitten five times shy !!!! Lol.

[Cloud 10]

Interesting feature over Scotland at 144 hrs on the 00z ECM with a 963mb LP wrapped up in cold uppers and super-low thicknesses.

 

 

Not much chance of verifying like that,but would certainly provide some interest if it did!

 

 

ECM ensemble mean at day 10 is pretty impressive all round.