[quote=Brian Gaze;649556]

London snow row reaches 8 for the first time tonight:

[/quote

That and the continuous downward trend after the 19th towards the 'Big Day' are what are grabbing my attention.

Taking it easy today but feel it's worth making a serious point about GFS's handling of the pattern lately and how important that could be given what looks like something close to a repeat cycle in the 7-10 day range:

First, today's ECM +120 hour chart on the left, reflecting the general idea that all models now show for next Friday.

Then, on the right, the ECM +192 chart from 4th December i.e. for the same date.

Next, the GFS +192 chart for Friday 12th, on the left hand side. The energy transfer was straight NE instead of E then SE.

Finally, the GFS +192 chart for Monday 15th, on the right hand side. A very similar situation - could the same correction happen again?

After all, ECM's current +192 chart is incredibly similar to the +192 chart of 4th December that I posted earlier:

So perhaps both models could display similar errors yet again?

On a side note, the handling of the N. Hem pattern away from the Atlantic sector has actually been pretty good, apart from what looks to be an underestimation of those ridges of high pressure toward the Arctic by both GFS and ECM.

I can only say looks to be, as the 'verification' chart is no such thing - still at 5 days range and subject to change.

Actually James that verification analysis is very useful - always good to compare forecast with actual in the 5-7 day timeframe as it shows familiar charts rather than verification stats for 500mb which can be difficult to interpret.

18z GFS looks very interesting for NW England towards the end of the week. Surface parameters look pretty good for snow..not just to high ground either.... (Friday morning looks interesting)

We shall see. ;-)

In other news, it's currently +2C/+1C at Hulme library, already colder than forecast.

You may even get a dusting overnight if you are lucky 

http://modeles.meteociel.fr/modeles/wrfnmm/runs/2014120718/nmm_uk1-1-11-0.png?07-23

Really like the new nmm 2k 

shows up showers very well

Ah! now, my ole gut feeling for cold  around the middle of December is beginning to bear fruit

Need a few more runs... 

Still a way off!

I shall consult the cards, the damp piece of string, and tea leaves in a few days time to see if they concur with the models 

Worth keeping an eye on next week. GFS & ECM op runs both showing the chance of another colder incursion.

http://www.theweatheroutlook.com/twodata/datmdlout.aspx

PS: GFSP back today.

It's as you were yet again - quite impressive mean model consistency actually as the passage of mP and rmP in alternating waves continues for the foreseeable.
One might as well copy and paste from previous threads. Seasonal at times, windy and wild at others, frosts during ridges, wintry showers possible anywhere. All decent December stuff, but ATM no sign of a more prolonged HLB that would deliver significant cold. 

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY MONDAY DECEMBER 8TH 2014.

NEXT UPDATE TUESDAY DECEMBER 9TH 08:00

THE CURRENT GENERAL SITUATION A ridge of High pressure will cross the UK from the West today and tonight followed by a trough reaching the NW tomorrow in a strengthening SW flow.

MODELS-2 WEEK HEADLINE Rather cold and windy for most with wintry showers or longer spells of rain or sleet with snow on hills especially in the North later this week. Perhaps milder especially in the South next week. Some night frosts where skies clear.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble forecast shows the strong flow continuing just to the South of the UK this coming week before it eases North for a time but continues in an undulating fashion in conjunction between Low pressure to the North and High pressure well to the SW.

GFS OPERATIONAL The GFS operational this morning shows little change from the pattern that has been shown for some while. The model shows a sustained period of strong Westerly winds between Low pressure to the North and High to the SW of the UK. From time to time the flow turns more NW dragging colder uppers down across the UK before milder air returns East behind. This means that rain at times will be mixed in with periods of brighter and colder conditions with showers turning wintry over the hills, more especially in the North.

THE GFS PARALLEL RUN The GFS Parallel run is not available until Monday of next week.

THE GFS CONTROL The GFS control run also shows a similar pattern to the operational above but shows a more defined pull of milder tropical maritime air across the UK in conjunction with higher pressure over France through week 2 with less rainfall likely too especially over the South.

THE GEFS ENSEMBLES The GEFS Ensembles are indicative that Low pressure to the North of the UK and High to the South and SW will be the dominant pattern over the whole period. There will be alternating periods of cold and showery weather mixed with milder air at times with the trend for more of the air to be milder in the second week than week 1 as the jet flow edges North somewhat to the East of the UK.

UKMO UKMO today shows deep Low pressure to the North and later NE of the UK with a brief cold period of 24 hours or so around the start of next weekend. Very windy conditions will be dominant this week with showers or longer spells of rain at times falling as snow on Northern hills and in the South too possibly briefly at the weekend. The Day 6 chart shows milder winds encroaching over the UK from the West as winds back towards the West later with further rain at times with any snowfall becoming more and more confined to northern hills again early next week.

THE FAX CHARTS The Fax Charts show a very deep depression well to the North of Scotland with gale or severe gale West winds and rain or showers becoming increasingly wintry over the hills of the North innitially with further troughing crossing the South later this week with more prolonged rainfall here for a time.

GEM GEM this morning shows a cool and very windy period this week, often cold with snow showers over the hills especially in the North but the South too briefly near this coming weekend. As we move into next week a more pronounced shift towards milder winds from the SW will engulf the UK with some rain at times across the North and West.

NAVGEM NAVGEM this morning also shows the pattern of cold and windy conditions predominating this week with rain and showers with snow on the hills before a shift towards somewhat milder but still breezy West winds take hold at the end of the run covering the period of the beginning of next week.

ECM ECM this morning shows a very mobile Atlantic flow across the UK throughout the period of it's run this morning. The pattern will alternate between milder and windy weather with rain for all and colder and more showery periods when showers will turn to snow over the hills of the North principally but not exclusively. Temperatures overall will be close to average or somewhat below at times across the North and occasionally a little above in the South with frost restricted towards the colder and showery interludes akmost anywhere.

ECM ENSEMBLES This morning's Ensemble data remains unchanged with the overriding factor likely to be one of Low pressure situated to the North of the UK and High pressure to the SW. There will be spells ofstrong winds, rain and showers likely across all areas interspersed with colder and more showery spells with snowfall on Northern hills at times. Overall temperatures will be in the range of near or slightly below normal at times over the North and near to or slightly above average at times in the South but windchill will be a notable factor at times.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS Changes in trend to the continuing strong Westerly flow of weather across the UK are slow or non-existent with some output still showing a somewhat milder trend for next week than the week to come as High pressure edges closer to the South and SE of Britain.

MY THOUGHTS The pattern of weather over the next couple of weeks illustrated by the latest outputs indicate little change in what has been shown over recent days. In basic terms there will be a lot of days when strong winds occur with rain at times in the form of showers or brief periods of more prolonged rainfall. The main interest in this otherwise static pattern is the ingress of colder polar maritime air across the UK bringing the possibility of some snowfall in places. As is always the case this is focused most towards higher ground over the North and only briefly reaching the South for a time this coming weekend as a brief shift of winds towards the North is well documented by all output. Then next week as winds back towards the West some output shows a milder phase of weather even across the North as pressure rises to the South of the UK coupled with a change of axis to the Jet flow with rain at times for all. However, there is still some evidence that the pattern will remain mixed with further colder injections around the Southern flank of depressions North of the UK through next week too as the ECM operational illustrates well today. So in my opinion the next few weeks will remain unsettled and often windy with rain at times for all and occasional snow showers over northern hills. It looks unlikely that snow will become anything other than interest value only for the vast majority of the populous of the UK with any notable settling snow reserved to hills and mountains above 300-400mtrs in the North and many will see none at all. Nevertheless, with such a volatile pattern across the UK and Northern hmisphere in general coupled with stark temperature contrasts North and South of the Jet flow across the South of the UK there will be plenty of interest from other elements of the weather other than snow to keep us on our toes and I continue to feel that at some point in the near future a flood of cold air from the North will likely give us our first main shot of Winter weather at some point in the not too distant future.

Check out the shallow low (small green area) off the east U.S. Coast and how it's been adjusted south on today's 00z GFS op when compared with yesterday's 18z op.

The very same was observed prior to Wednesday's system being corrected from powering NE to digging down across the UK. A persistent error, though to be fair, nothing compared to the scale to which it occurs in the GEM model despite it's recent upgrade.

Really, it's no wonder the GFS run goes on to produce this (below-left):

I'm inclined to ignore the powering NE of the low off the East U.S. Coast that follows...!

ECM has very similar ideas though with the block to our east a little closer as usual which actually works against getting the cold polar maritime air mass to our shores.

That block to our east actually makes a move to split the UK and Siberian low heights as a weak ridge pushes into Greenland from Canada.

Such a feature comes and goes on the GFS 00z op run and would have made for some interesting charts had that low not powered NE beyond day 10.

So some interesting longer term developments, the consensus suggesting a repeating pattern but with slight adjustments here and there which could add a little more substance to any cold incursions from the north IF the lows track far enough east, and perhaps a low probability of a sinking UK trough scenario beyond day 10 but lacking in support at the moment.

Before all that, it remains uncertain as to just how soon the import of cold polar maritime air is cut off Friday-Saturday by LP development to the NW.  GFS and GEM are slowest, ECM is fastest and UKMO's somewhere in between.

It will be interesting to see what GFSP makes of all this when it comes back online later today 

Regarding SC's post above, these comments from Ian Ferguson have gone from confident of a westerly flow with average to slightly above temperatures back on Saturday, to low confidence in that forecast on Sunday, to today's suggestions of a -ve NAO later this month. How's that for a trend?

A -ve NAO has been as rare as hen's teeth on model output for December so I'm actually quite surprised to hear of GLOSEA 5 exploring it now.

The actual comment is borderline exciting:

"Hopefully a timely interjection, but UKMO caution (again) that medium range NWP may not be adequately reflecting ultimate broadscale outcome. First tentative signs emerging, they suggest, of *possible* pattern change (weakening of MSLP anomaly; transition to -ve NAO) second half/later December, with GloSea5 continuing to yield interesting stratospheric signals later this month. So, without wanting to sound like a stuck record, I do urge 'elasticity of thought' when assessing distant reaches of EC/GFS suites."

I've highlighted both the positive stuff and the major caveats.

It could mean that the weak Greenland ridge on the ECM run may be an acorn from which an oak tree grows, but of course it's early days yet. I also enjoy how it backs up my interpretation of GFS' post-day 10 charts 

Yep, those comments from Ian are not without interest, Matt Hugo fairly confident about a SSW also, hmm, something is brewing.

One thing is for sure, a 100% improvement on last winter and we are still in the early throws of it.

Generally looking unsettled, wet and windy with wintry showers between the rain bands.

Temps near average mostly.

Seasonal stuff for December really.

I would agree. It does "feel" like winter out there, and I am feeling it badly as my central heating is playing up!

ECM ens dont show any signs of northern blocking, just cold zonal at best. A NW flow would be a bit colder for us than De Bilt

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.php

GEM is a horror show and certainly not where we want to see the Azores high migrate

Not sure where Ian F is getting the -NAO outlook from:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.sprd2.gif

Is he known to be rather a ramper the past couple of years?

As far as I know, the Ian Fergusson that Solar Cycles mentions is a respected MetO forecaster. Whether he is a ramper of any kind, I have no idea tbh.

Ian has access to a lot of info that you or I cannot see, he is most definetely not a ramper lol

Backedge snow on Friday one to keep an eye on for sure, for example:

http://www.theweatheroutlook.com/charts/gfs/06_87_preciptype.png?cb=865

http://www.theweatheroutlook.com/charts/gfs/06_108_preciptype.png?cb=865

The Azores High looks doggedly persistent in all the model output I can see. Any variation in our weather for the foreseeable is all to do with the phasing of the lows as they scramble over the top of it.

Good for the northern hills if you like the wintry weather.

Excitement over rumours about a model we can't see is a true sign that the silly season is well under way

Potent arctic blast next week showing on the GFS6z today.

http://www.theweatheroutlook.com/twodata/datmdlout.aspx

Further comments from Ian F:

PS: MOGREPS & 00z EC ENS stamps now agree on signs of westerly waning into trend period. Circa 40% now show some form of continental block.