Model Output Discussion - The Start Of Winter

[Duane S.]

Not surprised by Ian's update. I struggle to see where significant amplification is going to come from to lead to a cold spell / pattern change in the next 10-14 days. It certainly looks like a pretty unsettled spell is on the way in one form or another, could at least be PM sourced unsettled weather and the Scottish mountains could at least get hammered in time for Xmas! Interesting to see that for the 2nd run in a row the GFS (p) handles that tropical depression differently to most of the other output, not phasing it with the vortex but running it zonally underneath and straight into the North of the UK, one to watch.

 

I have just read through the MET winter forecast paper. All a bit jumbled and messy and there was nothing in there most people on here didn't know but after 50 odd pages though, this summed it up...

 

"positive NAO for DJF 2014/15, not clear which driver may be responsible for this response in models; most drivers which are in an active phase would typically favour the opposite"

 

So it is a simple case of a computer model going against the collective primary driver states/forecasts?

 

Interesting that even the OPI team were scratching their heads a bit that one of their models went completely against the low OPI/ high SAI forecast. Cohen himself has indicated recently hinted feedback response not as expected possibly due to anomalous low pressure system in NW Asia. December will be interesting in that respect at least.

 

To my mind the holy grail of medium-long term forecats is knowing the primary drivers, forecasting how active (their atmospheric coupling, downstream response) and most importantly their interaction with each other. i.e.why does i.e. the MJO override the ENSO signal in one instance whilst not in another. In fact, that would be pretty straghtforward in itself but throw in a dozen+ drivers and I can't see how a 96M supercomputer can come close to resolving that little puzzle!

[IDO]

Although the ECM NH pattern continues with the theme of the PV being less organized and more mobile, at D10 it has returned to Greenland vicinity. In fact much like the GEFS have been suggesting for many days. ECM have seemingly ditched its medium term travels to Siberia. GFS has proved very solid in the 8-12 day range re synoptic changes (compared to the ECM op):

 

 

With that sort of starting point for the middle of December it is no surprise the ECM 32 day update suggests a more zonal pattern till the New Year. It does tie in with many long range models for the UK's Winter (GloSea and UKMO just a couple). So the SSW is possibly going to be a make or break for this Winter and I know the Pros are very confident of this sometime in January, hopefully not too late in the month.

 

Even GEM, who have arguably led us up the garden path more than ECM have a zonal onslaught at D10: 

 

Both have been playing catch up with GFS. The GEFS are maintaining the mobile PV in FI, a time sequence of the mean:

 

D10:  D13:  D16: 

 

This does not really promote any HLB in that period due to the mobility of the pattern and I am assuming that it will then transfer its energy elsewhere afterwards. There is also a flow of the mean cold uppers from D10 towards Siberia and this is not ideal for the UK to grab any trop cold:

 

D10:   D16: 

 

So in reality just run of the mill December weather coming. Absolutely no sign of any cold snap (meaning snow) let alone spell (through blocking) and with the synoptics not conducive to cold then it remains a waiting game.

Edited December 2, 2014 by i'm dreaming of...

[Polar Maritime]

This mornings GFSP continues to show bouts of cool Pm air from the N/W, With Snow over Northern hills. A possible stormy period for the North around the 8th.. As ido says a pretty standard affair for December, It will certainly feel Wintry  

 

Edited December 2, 2014 by Polar Maritime

[johnholmes]

Worth a look in detail at where we sit with previous syntheses and very latest (Nov) seasonal analysis: http://medcof.aemet.es/Medcof/events/medcof3/docMedcof3/presentaciones/MedCOF3_Brookshaw.pdf

 

Worth reading everyone to find out what Met use, throws a spanner in the ideas of some who suggest various things mentioned ie SAI they do not use. Also worth noting some of the results of scientific research rather than hope. Not nice for cold lovers but interesting results. Again a number will not like their assessment of no clear signal, that is what it shows so that is what has to be said. Interesting that they suggest an SSW late on.

yes do read it-not what most coldies want with their cornflakes this morning but do read it.

 

also worth a read is that from S4Lancia a bit back on this page=post 101

Edited December 2, 2014 by johnholmes

[bluearmy]

not sure i see the mean ec32 in quite the same way as ian painted it. of course he has sight of the postage stamps and clusters but as a mean, it seems to present a picture of much the same with a mid atlantic ridge waxing and waning with troughs dropping over us/to our east into central europe. no upper anomoly to speak of, warm or cold.

[BlueHedgehog074]

Next few days are likely to be generally quite calm with a mixture of sunny spells and cloudier periods with some drizzle or rain in the South-East today. Thursday could be the cloudiest day of the week (this was also admittedly according to the TV forecast I heard this morning). Certainly some good support now also for a cold blast from the North-West on Friday with a cold front sweeping South-East through the UK followed by an army of snow showers for hilly areas to the North-West (maybe cold enough for some of these to fall to lower levels at times).

Additionally, there is some reasonable agreement for the UK to become under invasion by another cold blast from the North-West during the Sunday/Monday period with further wintry showers likely...

(Examples from other models like the ECMWF and GEM)

The UKMO at 144 hours, though, also shows some kind of chilly flow from the West-North-West around then.

Just a reminder that we have the Netweather chart viewer to view various maps/charts and data (like the examples above, and also the Netweather Extra Subscription to view additional charts and data). http://www.netweather.tv/index.cgi?action=charts-and-data;sess=

[Hocus Pocus]

Disagree on first sentence (I recall well the persistent zonal & routinely deeply cyclonic signature it accurately offered almost every run!) but largely subscribe to your second point!

Yes I was confusing last year with the year previously Ian, last year was about as rock solid as it could get.

Edited December 2, 2014 by Hocus Pocus

[Penrith Snow]

Oh dear, not a good morning is it and yet again the reputation of ECM hits the dust as it drops amplification in the medium term and joins GFS.

On the positive the flow does look like having a cool, north westerly element so some snow likely over high ground in the north and it will feel cold.

In the long term we just have to wait and see but we need the PV to move out of Greenland to get any chance of real cold and in the current set up this could take weeks.

But don't despair some of our best winters of the past had zonal Decembers so all is not lost.

BTW good analysis by the MetO and I admire their honesty, it's a puzzle that the models are going against the background signals but how strange that the creators of the models do not know why! Maybe they have joined forces and become self aware.......Skynet lol

Andy

[Frosty.]

 

So in reality just run of the mill December weather coming. Absolutely no sign of any cold snap 

 

It's not run of the mill at all, run of the mill would be a sw / ne aligned jet with endless mild mush. What we have is frequent incursions of colder air from polar regions mixed with somewhat milder atlantic airmass, in that overall mix we will have wintry showers, night frosts and yes..some milder wet and windy spells but after such a ridiculously warm autumn..I would not call this run of the mill!

[fergieweather]

not sure i see the mean ec32 in quite the same way as ian painted it. of course he has sight of the postage stamps and clusters but as a mean, it seems to present a picture of much the same with a mid atlantic ridge waxing and waning with troughs dropping over us/to our east into central europe. no upper anomoly to speak of, warm or cold.

Agreed on your summary. I was referring to 2m temp anomaly, not uppers.

[IDO]

It's not run of the mill at all, run of the mill would be a sw / ne aligned jet with endless mild mush. What we have is frequent incursions of colder air from polar regions mixed with somewhat milder atlantic airmass, in that overall mix we will have wintry showers, night frosts and yes..some milder wet and windy spells but after such a ridiculously warm autumn..I would not call this run of the mill!

Yes compared to last year a lot cooler, and compared to the last two months we lose the mildness, but looking at 30 year averages, it is relatively speaking within "normal" December expectations. As I.F. suggests the EC32 for later in the month (FWIW to some on here) suggests maybe slightly milder than average temps, and this will balance out the next few cooler than average days.

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY TUESDAY DECEMBER 2ND 2014.

NEXT UPDATE WEDNESDAY DECEMBER 3RD 08:00

THE CURRENT GENERAL SITUATION. A cold front will edge very slowly SE across the SE of Britain followed by a ridge of High pressure across Central Britain later.

MODELS-2 WEEK HEADLINE  Mostly dry and benign conditions will slowly give way to more unsettled and changeable weather with rain or perhaps wintry showers at times.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble forecast shows a brief dip South in the flow across NW Europe before returning North quite quickly and then blowing across the UK while slowly sinking to the South of the UK later in the run.

GFS OPERATIONAL The GFS operational this morning shows a gradual change to more unsettled and very changeable conditions taking over with spells of windy and rainy weather alternating with colder and clearer air with showers, some wintry in places as Low pressure digs further South down across the UK displacing the High to the South and SW further away for a time. Late in the run the High returns close to the South over France and a mild Westerly flow re-establishes across the UK with wind and rain most likely to continue towards the North and West.

THE GFS PARALLEL RUN The GFS Parallel run shows a similar synoptic setup as the operational though individual times and positioning of the driving pressure systems affect the weather differently over the UK day to day but the overall mess age is the same in that High pressure to the South and Low to the North remain dominant throughout.

THE GFS CONTROL.  The GFS control run also shows a more volatile and potentially stormy period a week from now as deep and vigorous Low pressure is allowed to make much larger inroads across the UK with gales and heavy rain followed by chilly aor with wintry showers at times. The trend later is for pressure systems to be less pronounced and with High pressure never far to the South the rain looks like it could become more biased towards the North and West later in a milder westerly flow

THE GEFS ENSEMBLES.  The GEFS Ensembles maintain a period of westerly winds over the next two weeks circulating around Low pressure to the North and High to the South. As the Jet Stream sinks further South later the winds will become chillier at times especially in the North with wintry showers at times between the passing rain bands.

UKMO UKMO today shows a rather cold Northerly flow at the start of the weekend with outbreaks of rain being replaced by wintry showers for a time with a rinse and repeat pattern of rain followed by colder and showery conditions looking likely again early next week.

THE FAX CHARTS  The Fax Charts show a slow movong trough close to SE England at the weekend before a cold front moving down from the NW bring cold and bright weather with some coastal and hill showers falling as snow in places. Then at the end of the period a warm front brings milder Westerly winds back to Scotland by Monday.

GEM  GEM shows a pattern which deteriorates conditions across the UK from the North later this weekend as Low pressure makes it's way South deeper into the UK with spells of rain and gales for all interspersed by brighter and colder but still windy conditions with squally showers, wintry on hills especially in the North. This pattern then persists out to the end of the run.

NAVGEM NAVGEM too winds up to a more unsettled spell next week powered by a developing deep depression close to Northern Scotland at the end of the run with Westerly gales and rather cold conditions following a band of rain with frequent squally and wintry showers especially across the North and West.

ECM  ECM this morning shows a pattern also is similar to the rest of the output with strong support for a more coherent attack from Low pressure to the North and NW next week with the quiet and rather chilly benign conditions between now and then giving way to wet and windy conditions followed by cold and showery conditions in a WNW flow. The end of the run signifies the unsettled and changeable period is expected to continue with Westerly winds carrying bands of milder rainy weather followed by colder and showery spells.

ECM ENSEMBLES  This morning's Ensemble data illustrate a typical Winter pattern for the UK with Low pressure to the North of the UK and High pressure near the Azores giving rise to a strong Westerly flow across the UK with rain at times and average temperatures overall.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The theme has now become strong in support for the quiet and benign spell of late giving way to much more unsettled and windy spells of weather with rain bands and gales alternating with colder and still windy weather with showers, wintry on hills.

 MY THOUGHTS   The models have firmed up on the trend towards much more changeable weather with strong winds developing for all areas as we move through next week. The High pressure to the SW looks like losing a lot of it's influence as deep Low pressure areas tilt towards a slightly South of East track to the North of Scotland. This powers up strong Westerly winds with spells of rain followed by successive periods of colder and showery conditions with some snow likely on high ground mostly in the North at times before the next surge of Low pressure brings the next band of rain and milder air through. This type of structure and sequence is supported by all output with the longer term trend beyond the end of the 1st week maintaining basically Westerly winds and rain at times for all with no clear indication of any major shift towards anything other than a continuation of the zonal train at the end of week 2 this morning. With support for this theory from both the GFS and ECM Ensemble data this morning one has to believe that this evolution maintains a strong chance of verifying from todays output.

[Nick B]

Worth reading everyone to find out what Met use, throws a spanner in the ideas of some who suggest various things mentioned ie SAI they do not use. Also worth noting some of the results of scientific research rather than hope. Not nice for cold lovers but interesting results. Again a number will not like their assessment of no clear signal, that is what it shows so that is what has to be said. Interesting that they suggest an SSW late on.

yes do read it-not what most coldies want with their cornflakes this morning but do read it.

 

also worth a read is that from S4Lancia a bit back on this page=post 101

Hi John and good morning,

I noticed on p. 27, dealing with North Atlantic sea-surface temperature, the following... 'NAO prediction based on this factor alone: +0.5'.

That seems an interesting statement to make; it seems they take the NAO state which they are expecting for the next three months based entirely from one factor (and that with a seemingly not very strong signal too): current North Atlantic sea-surface temperatures.  Am I interpreting this correctly? (- I was!!)  If so, what is it about this particular signal that means it gets to be the only one worth considering? (- now irrelevant, they don't). Also, p. 31 seems to paint a different picture using a hindcast method? (still interested in what the charts there show...).  Slightly (less) confused by this one (now!)...

Edited December 2, 2014 by Nick B

[TEITS]

Lets hope this 945mb Low pressure over Scotland does not occur from the GEFS control run!

 

http://modeles.meteociel.fr/modeles/gens/run/gens-0-1-180.png?0

 

Overall though im disappointed with the output. A cool/cold NW,ly is looking likely around the 10th Dec but at this stage it looks as though only higher ground will experience snowfall.

[nick sussex]

Morning all , not much change this morning, generally wet after a drier start

 

In the earlier timeframe whats going on with the UKMO which is still different from the rest, it looks like the UKMO have modified their fax charts again but its a bit bizarre how for some reason this output is still not backing down.

 

As for the rest of the outputs the ECM now takes that low in the Atlantic and phases it with the PV which is different from yesterday evenings, after that its low after low with the ECM eventually building in  higher pressure to the east which looks like causing  a bit more trough disruption over the UK.

 

The GFS P has the good grace to develop a small window of opportunity around the T224 hrs mark as the Azores high briefly amplifies, whether that survives till tonight only time will tell.

 

Overall a pretty typical December pattern, not quite the horror mildfest of last December at this stage but thats just an effort in "self-soothing".

 

It might not be spam but its really not much better than  a bit of chewy cheap steak.

 

Coming soon my new Slush Warning System which will need to be in operation unless the NWP starts delivering something for us coldies!

Edited December 2, 2014 by nick sussex

[johnholmes]

Hi John and good morning,

I noticed on p. 27, dealing with North Atlantic sea-surface temperature, the following... 'NAO prediction based on this factor alone: +0.5'.

That seems an interesting statement to make; it seems they take the NAO state which they are expecting for the next three months based entirely from one factor (and that with a seemingly not very strong signal too): current North Atlantic sea-surface temperatures.  Am I interpreting this correctly?  If so, what is it about this particular signal that means it gets to be the only one worth considering?  Also, p. 31 seems to paint a different picture using a hindcast method?  Slightly confused by this one...

 

hi Nick

I read it to mean IF you took that alone. From that I assume they do not do that?

Anyone else who has read the whole paper got views on this?

 

mod/admin I suspect this along with another post from me might be best put in the winter 2014-15 thread?

[knocker]

Not much to choose between the ECM and GEFS anomaly. A difference on the orientation of the weak trough and Azores HP. So not much change and not a flake in site ( obviously that depends on your definition of flake) unless your trekking in the Highlands. The ecm has the temps below average towards the end of the run.

Charts courtesy weathebell

Edited December 2, 2014 by knocker

[IDO]

Its between D6-10 that the north may see some wintry weather and its about a 20-25% chance at the moment: NW 

 

Further south its 5-10% so an outsider: 

 

As it is coming from the NW and that flow tends to get downgraded as the uppers are modified then all rather uncertain. However it is also to do with how the Atlantic storm interacts with the jet and this changes run to run and amongst the ensembles. 

[BLAST FROM THE PAST]

Its between D6-10 that the north may see some wintry weather and its about a 20-25% chance at the moment: NW graphe3_1000_232_0___.gif

 

Further south its 5-10% so an outsider: graphe6_1000_306_141___Londres-27.gif

 

As it is coming from the NW and that flow tends to get downgraded as the uppers are modified then all rather uncertain. However it is also to do with how the Atlantic storm interacts with the jet and this changes run to run and amongst the ensembles. 

Its forecast by Friday for the north IDO not 6-10 days....according to BBC/metO.  As regards to despondency it was only the 18th when IF posted EC and Mogreps were forecasting return to mobility and some deep depressions......still waiting for them.

 

Very interesting re UKMO model as Nick S says, a flat pattern isn't in the bag at all

 

BFTP

Edited December 2, 2014 by BLAST FROM THE PAST

[Iceaxecrampon]

On for this weekend - the 5th to the 7th Dec was trending as early as the 27th November so all credit - still time to go all **** up though.

 

 

 

Keswick on Sunday ppn of sorts down to 600ft  - tops should see their first realish falls although Scafell has had a dusting already.

 

Ian

 

 

[joggs]

Well all i see is cool zonal on pretty much all models after the next 5 days or so.The biggest bugbear is the limpet vortex near greenland.And with the pattern change(hopecasting)not showing,and tbh never was,we can only hope wave/warming will happen sooner rather than mo later!

Frustarting times ahead for us coldies and i must say the ecm is testing at times with the over amplyfication shown on numerous times.On mobile so cant post charts.

[blizzard81]

not sure i see the mean ec32 in quite the same way as ian painted it. of course he has sight of the postage stamps and clusters but as a mean, it seems to present a picture of much the same with a mid atlantic ridge waxing and waning with troughs dropping over us/to our east into central europe. no upper anomoly to speak of, warm or cold.

Thank you BA, I for one really do value your analysis on these updates and also your views on ensemble means etc.

[IDO]

Its forecast by Friday for the north IDO not 6-10 days....according to BBC/metO.  As regards to despondency it was only the 18th when IF posted EC and Mogreps were forecasting return to mobility and some deep depressions......still waiting for them.

 

Very interesting re UKMO model as Nick S says, a flat pattern isn't in the bag at all

 

BFTP

Only a 15% chance according to the GEFS for Friday in the NW. I don't include the mountains. UKMO really has little support for the half day northerly on Friday and the FAX is not really supporting it, so I am not hanging my hat on that.

[garbagebags]

Well all i see is cool zonal on pretty much all models after the next 5 days or so.The biggest bugbear is the limpet vortex near greenland.And with the pattern change(hopecasting)not showing,and tbh never was,we can only hope wave/warming will happen sooner rather than mo later!

Frustarting times ahead for us coldies and i must say the ecm is testing at times with the over amplyfication shown on numerous times.On mobile so cant post charts.

 

Really? Looks like a fairly good snow event here for Sunday, at ground level

 

Edited December 2, 2014 by garbagebags

[shaky]

Well well gfs 06z has got the northerly further west again! ! Ukmo might be onto something you know! !