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Paul
Message added by Paul

This is the focused model discussion - please only post about the model output. 

For a more laid back, bantery model discussion please use the Cold hunt - models and banter thread.

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Posted
  • Location: st albans
  • Location: st albans

Some jan reanalysis

B3985085-6FEF-45C6-BA5B-EC4B11EE289F.thumb.jpeg.59d1fd1462e19dfecdc8486f697de803.jpeg 3A2E69DF-A737-4485-A453-B34EE4F1F642.thumb.jpeg.c566629c3a56d23539f6ec9bcf492d0e.jpeg 2411F9B3-AA8E-49C7-A147-F2AEC0B907B7.thumb.jpeg.a22e8c6b101b6014e7732c30a5fd4352.jpeg

I suspect that during the first week when little was showing on the nwp going forward, most would have been pretty excited to be shown these as a glimpse of what was to come .... I think we’ve been unlucky 

Infact, looking at the second half of the month, one wonders why the other model thread thinks the forecasts of a cold set up were a bust 

83EB0D4C-BD4A-4C80-A7DD-E1988B92FED5.thumb.jpeg.845067d1bf3eaff3c503571032173269.jpeg

Edited by bluearmy
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Posted
  • Location: st albans
  • Location: st albans
16 minutes ago, knocker said:

Alternately

814day_03.thumb.gif.5fffad2ac522bfe89a73e4b13ce6b0a0.gifindex.thumb.png.3a629b169bab32dac8fa60bfd61bb836.png

Indeed - though it wouldn’t surprise me if week two morphed into something akin to what we saw a week or so back with W Europe height anomoly removed and the jet back onto a nw/se axis from the Canadian lobe

 

Edited by bluearmy
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Posted
  • Location: Camborne
  • Location: Camborne

To continue with the gfs. Whilst this has been going on another trough has emerged from the north east coast and by 1200 Friday is south east of Greenland but the warm front associated with is is already bringing wind and rain to the country

gfs_z500_vort_natl_23.thumb.png.b6b6fd0958df8f50fca210b4f19bfc41.png

And I think it suffice to say that over the weekend low pressure continues to dominate the Atlantic and the UK weather thus unsettled with temps varying around the average

gfs_ptype_slp_eur3_29.thumb.png.0fbd28c933d85d8fb5450be56c5eddef.pnggfs_uv250_natl_29.thumb.png.0d69b085a8cbf30fb095318c05ef9941.pnggfs_t850a_natl_29.thumb.png.e3a0912fbd5e71bf6e7692552ebe055e.png

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Posted
  • Location: Camborne
  • Location: Camborne

By t144 the ecm has the next quite deep elongated trough mid Atlantic with the associated fronts bringing some wet and windy weather to the UK by Saturday 00. Over the next 48 hours the trough moves east over the UK and becomes more neutrally aligned as the subtropical HPs amplify either side. Thus a wet and windy weekend.  From this point a familiar story unfolds as the next major trough enters stage left to do battle with the ridge which actually proves quite resilient

t144.thumb.png.ab28f88128cdd67783a5b82acdd7bb9b.pngt192.thumb.png.3dbe10ef575834ba4abf286a57012fa9.pngt240.thumb.png.1c28f0a79e5c22820f55e55b01e9664d.png

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Posted
  • Location: Camborne
  • Location: Camborne

Indications for a high amplitude Aleutian ridge seem to be strengthening  This would plunge more Arctic air down over N. America which in turn will pump up the jet stream betwixt this and the Bermuda high pressure. Which, as far as I can see, will continue to advect a lot of energy across the Atlantic making it very difficult for the Atlantic subtropical high pressure to ridge for any length of time and tending to force it east

t300.thumb.png.93dfbe8716940f86e5ae36c98fdc33c0.png

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Posted
  • Location: st albans
  • Location: st albans
12 minutes ago, knocker said:

Indications for a high amplitude Aleutian ridge seem to be strengthening  This would plunge more Arctic air down over N. America which in turn will pump up the jet stream betwixt this and the Bermuda high pressure. Which, as far as I can see, will continue to advect a lot of energy across the Atlantic making it very difficult for the Atlantic subtropical high pressure to ridge for any length of time and tending to force it east

t300.thumb.png.93dfbe8716940f86e5ae36c98fdc33c0.png

The Aleutian ridging into Alaska is about the only hemispheric anomoly that survives in a strong fashion over the next ten days - the placement of the pattern seems a bit west of recent week/10 days which I recall was the case last cycle around on the eps. Push it east somewhat and you start to get to the nw/se jet against ridging to our ne as we saw recently.  Rotate that further still and you start to get to the nirvana phase 8 analogue ........two steps too far ......

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Posted
  • Location: Emsworth, Hampshire
  • Location: Emsworth, Hampshire

EC ENS appears to be sniffing something out at 120hrs, height rises (albeit subtle) around Iceland are fully supported in all its members.

EDH1-120.thumb.gif.8a21e02e88d2c94899b55a6c4dc96339.gif

Not too far off the UKMO either, which offers some what of a blended version overall.

But as @knocker says, the cold plunge once again over N. America would promote a fired up jet across the Atlantic, with the EC showing this post 144hrs. But they appear to be slower moving lows on a Southerly tracking jet according to the outputs.

Interesting.

 

 

Edited by Dean E
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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

Although the EC46 has come in for criticism in the past month, it's worth underlining how well the ECM extended ensembles have done, in general, in pinpointing developments in the 12-15 day period. So far this year they have successfully forecast at D12-D15 all of the following:

- an above average start to January

- a below average second half of January

- a snowy period 22-24nd January

- another snowy period 30th Jan - 2nd Feb (sticking to its story even when the ECM op predicted otherwise at D7-D9)

- a milder phase after the 3rd Feb for 7-10 days after (a little wobble on this a couple of days ago but back to the same story now)

So I'm growing in confidence that the general balance of the D12-D15 will often get the general situation at D0 correct. 

This now puts us within reach of the 15th Feb - 18th Feb range. Currently, ensemble means seem to suggest any cold is out of reach, but that's probably an over-exaggeration. For the 15th Feb, we see 28 ensemble members that I would describe as on the mild side, 16 runs on the cold side and 7 runs in the balance (mainly due to high pressure so close to the SE that we may produce surface cold). For the 18th Feb, this changes to 23 members on the mild side, 19 on the cold side and 9 in the balance. Also important to note is that some runs which were cold at the 15th Feb go mild by 18th Feb, and vice versa. Looking at the clusters for this stage, you can see some of the clusters that "flip":

http://brunnur.vedur.is/kort/ec-ens/2019/02/03/00/ec-ens_nat_z500scenarios_2019020300_300.png

http://brunnur.vedur.is/kort/ec-ens/2019/02/03/00/ec-ens_nat_z500scenarios_2019020300_360.png

For instance, the control run cluster is in a cold position on the 15th, but goes milder by 18th; whilst cluster 5 (and maybe 6) seem to be transitioning colder in the same period.

To try and bring all this information together - yes, it seems milder weather will likely be the dominant weather during the middle of the month, but the closeness of the balance between colder options and milder options, added to the fact the some runs are flipping between cold and mild during the period, make me think that all out mild during this period is not the favoured scenario either. There are runs which are all-out mild - and also a fair few which are all-out cold - but not a significant number of either to think they hold the balance of power.

A more likely blend is to suggest that though more mild than cold days during the period could be expected, an endless onslaught of either mild or cold is not likely either. Probably a bit above average, then, between tomorrow and around the 18th, but with below average days in the period and some possible significantly below.

 

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Posted
  • Location: Windermere 120m asl
  • Location: Windermere 120m asl
15 hours ago, stodge said:

Evening all

It seems as of February 2nd, the inquests are already being written on winter 2018/19 which is extraordinary but inevitable especially for those who expected some snow (and were disappointed) in the past 48-72 hours.

As a reflection of my own, I suspect what we are calling a SSW was in fact a very strong Wave 1 displacement. Originating from the Eurasian side, it didn't so much split the PV as fragment it leaving a residual lobe over the Canadian side which. as often happens with Wave 1 events, became smaller but stronger and thus we had in early and mid January a 10-14 day period of mild conditions. As to the downwelling, my limited physics suggests it equates to a form of percolation. As the pressure of the downwelling increased, all it did was to increase resistance further down in the troposphere making the PV more not less resilient.

Now, if those who follow these things are correct, the downwelling should reach the troposphere next week but the models aren't interested or it's having no effect as all we see in the short and medium term is something we've not seen a lot of this winter and that's a spell of Atlantic-dominated weather.  The PV, which some had predicted would be displaced west, seems firm in its desire to remain between Greenland and Canada.

There's very little for fans of cold to hold on to in the short and medium term - a 10-14 day spell of milder Atlantic weather looks locked in and perhaps the thought that some much needed rain now may stave off problems were we to have another hot summer is perhaps a crumb of comfort. Beyond mid month is an eternity away - the 12Z GEFS had plenty of members looking to build heights through NW Europe from the south and east - the 12Z Parallel ends about as positively as it can for a cold weather fan but it's so far away it can hardly be relied on.

It's entirely possible this Atlantic spell will carry through this month and into March before we get the right ingredients for amplification but that seems to be contrary to a lot of signals so I'm far from convinced winter is "over" by any stretch and recent experience should tell us all March can be a cold and snowy month and even here in lowland London snow can fall and lay until the end of March.

There will be plenty of signals in the next 7-14 days suggesting spring is at hand but we've seen so many of these "false springs" before it's strange to see people getting sucked in again.

It may be a good time (unless you're interested in stormy conditions) to look away from the models (if you can) for a week and come back this time next week and see if the trend for a post mid-month pattern change is still being signalled. 

A good post - yes I'm going to take a break from model watching for a few days, trends from mid-month onwards will begin to surface - no doubt the models will continue to paint an atlantic dominated pattern..

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Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl

A good summary of the current outputs MWB.

Just a glance at the gefs modeled jet profile for the next 15 days does show it gradually weakening as the upstream N.American pattern changes with the the upper trough modeled further west thus the feed of deep cold into the Atlantic retracts.

Days 5/10/15

gfs-ens_uv250_nhem_21.thumb.png.891f5e9f3f8ba2935f255a56000c751c.pnggfs-ens_uv250_nhem_41.thumb.png.d4567b97c392f20944601152ee210c60.pnggfs-ens_uv250_nhem_61.thumb.png.eed9df4f989fa2e186ff6801a21af110.png

A gradual process but it would suggest a better chance of a building high towards the Uk from  sub-tropical ridging in week 2 but in the meantime this coming week does look nailed on for milder westerlies with some rain bands.

The 2m temp.ens graph pretty emphatic with this

ensemble-tt6-london.thumb.gif.c678aa963c30ec9961822d5e387c73f6.gif

As can be seen the 00z GFS op is very much on the warm side though in week 2.

Just for reference eps day 10 anomalies and flow.

ecmwf-ens_z500aNorm_nhem_11.thumb.png.1e86455f7b3090302fb6eb78fe2686cc.png

The idea of the jet easing somewhat week 2 suggests more chance of a settled spell but as ever depending on any high placement the surface could cool off somewhat with a return to some night frosts.Not sure we can expect anything better cold wise into mid-month based on these outputs.

Quite disappointing from a cold point of view as we are now looking towards the second half of February for further pattern changes in order to see Winter out on a colder note.

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Posted
  • Location: Telford, c.150m asl
  • Weather Preferences: Snow, ice, cold
  • Location: Telford, c.150m asl
16 hours ago, stodge said:

 

It may be a good time (unless you're interested in stormy conditions) to look away from the models (if you can) for a week and come back this time next week and see if the trend for a post mid-month pattern change is still being signalled. 

For some years now, I've only read the model thread in winter, trying to learn more about How Winter Happens and why it sometimes seems not to happen at all... but if there are going to be people posting in her with the same kind of clear explanations of why they hold a particular opinion, and what a chart shows, and why one model is more reliable for certain things than others.... 

...well, if you lot keep it going year-round, I'm getting more and more interested and will happily try to keep following it. Although very much from a standing start, I'm afraid... 

 

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Posted
  • Location: Reading/New York/Chicago
  • Location: Reading/New York/Chicago

Input appreciated very much from all on here. Just a note as we head into what *should* be a relatively quieter time before the next cold spell.

The extra umph from last week's frigid spell in the upper Midwest looks set to allow the Atlantic to make an appearance this week as the upstream pattern flattens and we see systems start to track towards and across the UK. It's actually much needed PPN down here, so not too many complaints.

The question is whether we become stuck in a pattern where there is high pressure to the south and east and low pressure further north and west. Some signs of this in coming days, yes, but I don't think that we will become stuck under a high drawing southerly winds from north Africa a la 1998 for a great period of time. There is a risk, of course, but the general sluggishness of systems as they approach our treacle in the NE Atlantic may spring a few surprises. 

What of northern blocking? As we were really, I feel. There are some signals conducive to blocking teleconnection-wise but we've seen difficulty overriding the stubborn Canadian PV lobe all season so until we see a chart within 48 hours showing the Canadian lobe exiting the stage we continue to look to thread the eye of the needle for easterlies or brief northerly outbreaks. In theory you'd think that the direction of the MJO would help to support some blocking, but there clearly seem to be some overriding influences.

The signal for troughing to our south seems to be receding, but much is dependent on the AO and the overall Arctic profile. The Siberian high seemed keen on heading west for a while, but with the PNA's resolute refusal to turn positive for a prolonged period it seems unlikely that Mr Siberian High will have the resources to visit our shores. We are approaching the time of year when the PV naturally recedes so chances of cold outbreaks may well increase. But, with the Canadian PV clinging on we could end up With a fudge solution where we see some continental surface cold but nothing of any real depth. 

Always the chance of some colder outbreaks of cold of course, but I cannot see how any real sustained cold arrives without the Pacific pattern changing, and at the moment there do not seem to be many signs of this happening.

 

Now I've posted this, expect the next suite of NWP forecasts to show a positive PNA and northern blocking...

 

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Posted
  • Location: Camborne
  • Location: Camborne

By 1700 the light patchy rain over the Midlands associated with the weakening occlusion draped across the country-is fizzling out but further rain from the next frontal system is into Norther Ireland , west Wales and the south west. Indications of this on the Camborne midday sounding (currently here a veil of Cs and some Ac.

PPVA89.thumb.gif.45732b769ae2a83abb310102884d499b.gifPPVE89.thumb.gif.384ddbbd9cfcd1875123aa0472e7d99b.gif2019020300.03808.skewt_parc.thumb.gif.cb39e4fc4589707616553c877378aacd.gif

The more intense rain, on this the warm front, will track north east through the evening but by 2200 the heavier belt associated with the cold front will be effecting Northern Ireland, west wales and Cornwall. The whole system will then track east resulting in a wet night in all areas before finally clearing the south east tomorrow morning and not before a touch more snow on the higher ground in Scotland. But this has swept away the colder air and virtually everywhere frost free tomorrow

p17.thumb.png.a6f06a79a3f76928e049f9205e118779.pngp22.thumb.png.062af00c4181cd4ef59d186ab37eb344.pngp02.thumb.png.cd61b78724976a5b9ad2e1a6cad857d3.pngp05.thumb.png.3d15029857fe6b6d73ed5b4a983686ff.pngp07.thumb.png.e74acc6a6babc6ad4c8284dfd7602684.pngp10.thumb.png.f66d8d369263818f63a40187130d632d.png

min.thumb.png.38107288c37aa22c2389d79628e7f951.png

 

Edited by knocker
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Posted
  • Location: Camborne
  • Location: Camborne

Strong ridging over Alaska and north west Canada next Sunday results in a very cold trough in the north east with a 150kt jet running south of it. The trough duly tracks into the Atlantic where it does battle with the re surging subtropical ridge, a recurring theme, which initiates some WAA into the UK/

gfs_t850a_noram_29.thumb.png.d7678c6bf8165aa3df9c8c09d669c699.pnggfs_z500_vort_natl_35.thumb.png.52ee14915b3f8d2f5bf2720af664a90c.png

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Posted
  • Location: Camborne
  • Location: Camborne

In many ways the theme of the ecm is similar to the gfs and it's not dissimilar to the morning run.

At T156 it has developed a trough over NE North America (nothing new there) But as it moves east into the Atlantic the subtropical high pressure amplifies both in the Atlantic and Europe. This severely inhibits further eastward movement. And in fact the ridge is so resilient the trough finally deconstructs in mid Atlantic.

t156.thumb.png.fbbec2d9e0081f982422130e6a5c7d36.pngt192.thumb.png.d48783259bf9d255fe7c1ca0ed16bd64.pngt240.thumb.png.4e6bb3c4763bfcceb3bcffd24749453b.png

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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

I see in the ECM 12z D9-D10 some reasonable signposting for the route to the next cold spell affecting the UK; height rises through and NE of the UK in response to the MJO propagating eastward again from P6 into P7 later this coming week. It's this eastward motion that's crucial - so no surprise that GEFS, which take a couple of days longer to get that going, aren't showing much sign of UK-Scandinavia height rises inside the 10 day range.

Seasonal wavelength changes naturally make easterlies an increasingly 'easy' route to cold to set up as we head through Feb, compared to northerlies via blocking across Greenland. Any chances of the latter are likely to depend upon the MJO propagating further still, across P8, during a time of +ENSO conditions... but currently there's more of an El Nino 'Modoki' pattern (biggest warm anomalies C Pac instead of E Pac) taking shape, which makes it less clear whether the Greenland or Euro height rises will extend far east enough to place the UK in a cold regime as opposed to a mild one on the eastern flank of a broad trough positioned well south of usual in the N. Atlantic. Strangely, recent GFS runs have been exploring the latter pattern in the D11-D16 range, having shown little response to the P6-P7 MJO transit. A strong GWO movement into phase 8 would be a feasible explanation, but the projections show nothing of the sort;

http://atlas.niu.edu/forecast/aam/gefsbc_gwo_fcst_current.png

In fact I find this massively upward AAM tendency through P5-P6 to be in stark contrast to the model output for the N. Atlantic-Europe sector. Traditionally it should encourage HLB across Greenland via the mid-Atlantic - yet we see very little. Just hints of some fairly tame height rises in-situ rather than via the mid-Atlantic. Possibly this is an adverse effect from the anomalies associated with the SSW, which appear to have aligned about as poorly for HLB NW of the UK as is conceivably possible following a major SSW (even allowing for displacement variants).

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Posted
  • Location: Camborne
  • Location: Camborne

The ext EPS anomaly progresses the theme of this evening's det run and a post from earlier today.

And that is the highly amplified Alaskan ridge/ North American trough complex advecting energy east across the Atlantic on the pepped up jet  This to some extent inhibits the subtropical high ridging and' blocking' the Atlantic but the latter certainly slows the eastward momentum as it is pushed east and ridges north west into eastern Greenland.

Ergo the energy flow diverges and is weakened in the eastern Atlantic portending a much quieter period of weather for the UK with temps around Average

index.thumb.png.457dee4275dd8d74e1d3c3f0ae74285a.png

And this evening's NOAA is not adverse to this evolution

814day_03.thumb.gif.07fdaf479c836befa1fba4ff4e0ddcdc.gif

 

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Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl
16 minutes ago, knocker said:

The ext EPS anomaly progresses the theme of this evening's det run and a post from earlier today.

And that is the highly amplified Alaskan ridge/ North American trough complex advecting energy east across the Atlantic on the pepped up jet  This to some extent inhibits the subtropical high ridging and' blocking' the Atlantic but the latter certainly slows the eastward momentum as it is pushed east and ridges north west into eastern Greenland.

Ergo the energy flow diverges and is weakened in the eastern Atlantic portending a much quieter period of weather for the UK with temps around Average

index.thumb.png.457dee4275dd8d74e1d3c3f0ae74285a.png

And this evening's NOAA is not adverse to this evolution

814day_03.thumb.gif.07fdaf479c836befa1fba4ff4e0ddcdc.gif

 

Backed up by the lower Strat GFS forecast for day 10 at 100 hPa

NH_HGT_100mb_240.thumb.gif.3fe1379c1e544dabad148af8c2fc8272.gif

Looking at the 500 hPa ens alongside and they suggest the same evolution in week 2 as the 00z runs ie.a UK or maybe a Sceuro high.If we do get more amplification in the pattern then we cannot rule out this developing into a Scandi.high after mid-month,but that of course is speculation at the moment. 

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