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Model output discussion - heading into 2018


Paul
Message added by Paul

Please only post model discussion in here. 
For more general chat and banter, moans and ramps, please head to the banter thread.
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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire
3 minutes ago, chris55 said:

Im just a keen amateur, though I do feel I have a relatively good grip on model understanding in general.

i was not questioning your posts eventual context, I just find your style of grammar and spelling and use of non-words quite hard to fathom. 

Im sure you have solid knowledgeable and meaningful points to make, it's just I can't decipher them.

goverend' 

 

Ok point taken.

I'll post in minimal-basic form.

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Posted
  • Location: Stroud, Gloucestershire
  • Weather Preferences: Extreme!
  • Location: Stroud, Gloucestershire
1 minute ago, tight isobar said:

Ok point taken.

I'll post in minimal-basic form.

Don't change on my behalf, I'm sure many enjoy your posts. We are all different at the end of the day. 

 

 

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Posted
  • Location: Stroud, Gloucestershire
  • Weather Preferences: Extreme!
  • Location: Stroud, Gloucestershire

We are seriously cluttering the thread lol

sorry mods, please delete when you wake up ha ;) 

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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

ECM individual ensembles: 

D8 - reasonable agreement for a weak ridge of heights to push north between low pressures close to Greenland and the UK/France - winds turning northerly for the UK as the latter low departs

And that's where the agreement ends.

After that, by D9/D10 we get a classic battle situation which is going to provide a serious forecasting headache unless a new trend supercedes the current one: Strong heights to the SW. Strong trough to the NW. Weak heights to the NE. Weak trough to the SE. The question is how they are going to interact, and the answer at the moment is - in all manner of ways! Some members have the NW trough barrelling through. Some split the NW trough and send energy to link with the SE trough, with the energy generally close to the UK (so "knife-edge" whether the UK is on the cold or mild side). A few send the whole of the NW trough under the NE ridge allowing for a full-on easterly. And finally, a few see the link up of heights between the SW and NE as the main feature, keeping the UK cold and dry. 

Perhaps slightly in the ascendancy is to "split" some energy through the UK but not enough to prevent the eventual overrunning weak heights to the E. But there's actually no way of calling it based on the ensembles tonight, or indeed this morning too. All we can say is that support is growing for some sort of signal for NE heights - but what impact it would have is a mystery right now. 

This is one of those where the trend for the UK may become clear at any time from D10 all the way down to D5. 

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

The 12z EPS control builds a surface high centred 1030mb between Iceland and Scotland as early as Saturday 6th Jan before the high relocates east to be centred over Scandinavia by early 2nd week of Jan. However, the control has the similar issue as the deterministic in dragging in mild air from southern Europe into the easterly around the low centred to the south of the UK. Ideally would want the low pressure to elongate further east across central Europe to prevent this.

However, we need to get down the route of pressure building close to northern UK then across Scandi first, the steps for this would likely be:

1. The eastern N America trough amplifying/digging south middle of next week in response to amplifying +PNA ridge upstream, this in turn amplifies a ridge over NW Atlantic

2. Further downstream response from the amplification of the flow over NW Atlantic is trough disruption close to the UK, as the jet dives SE toward Morocco.

3. A 'trigger' surface low then drops SE across UK which allows pressure to rise to the NW then N of UK

4. High to the north of the UK stays or drifts east over Scandinavia, a northesterly or easterly develops.

5. If we get as far as the above, then the question of how cold the NEly or Ely, depending on shape of high to the N and NE and shape of low over mainland Europe to the S and SE.

The 12z EC 300mb wind/jet stream loop below puts into context how the upper flow behaves to get the above evolution to happen, note the initial amplification upstream over N America, then subsequent amplification, trough disruption and jet diving south over E Atlantic / W Europe.

ec_w300.thumb.gif.bae418336d19df0a01753623a5f2ab34.gif

 

However, a lot could go wrong in the early stages mentioned above stages 2 and 3 mostly likely to go pear-shaped, the amplification over US more of a cert 

It would be ironic if an easterly does develop, it will be less cold than the NWlies we've experienced recently, given all the hype of the potential for them to develop, sometimes easterlies can be marginal or wrong side of marginal and just bring stratus and drizzle in winter unfortunately.

Edited by Nick F
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Posted
  • Location: Binfield, Berkshire
  • Location: Binfield, Berkshire

I can (just about) decipher what certain posters are saying, but please can we make it a little more simplistic for all? Riddles are never useful for all to understand here!

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Posted
  • Location: Hoyland,barnsley,south yorkshire(134m asl)
  • Weather Preferences: severe storms,snow wind and ice
  • Location: Hoyland,barnsley,south yorkshire(134m asl)

This run is looking goooooood!!!

gfsnh-0-156.png?18gfsnh-0-168.png?18

@Steve Murr

yep,running south and knocking on your doorstep by 180:)

gfs-2-174.png?18gfs-2-180.png?18

 

Edited by Allseasons-si
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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
27 minutes ago, Catacol said:

I dont have time to post more tonight - but as I watched a video of snow falling in Buxton earlier and read yet more FB posts from a friend in the Highlands who has had snow day after snow day so far it occurs to me that we are seeing a spell of weather at the moment that illustrates how effective a proper polar NW airstream can be in delivering snow. This hasnt been the case in many winters in the last 20... but quite clearly we have a sufficiently cold airmass to our NW to deliver good winter synoptics for many areas of the north and midlands. Even some areas of the south have seen snow (though not Somerset of course.... ) and perhaps I need to modify my benchmarks for success a bit. I still see high lat blocking as the pathway to a really good sustained spell of deep cold winter, but 2017/18 has so far shown that polar westerlies can deliver well for many parts of the UK even at low levels, though the cold will tend to be transient as systems pass through. Time perhaps to show a bit more respect for a NW airflow.

I recall easterlies in winters since the 90s that have disappointed more than the recent wintry NW'erlies have for cold and snow, they certainly aren't a wind direction that guarantees deep cold and snow unfortunately, some easterlies past have brought just leaden skies and drizzle in winter. The classic convective snow showers easterly off the North Sea is probably quite a rare beast these days. We have benefited from the polar northwesterly flows tapping into some very cold air over NE Canada and Greenland, though because they are inherently involved with low pressure systems moving east or southeast they tend to be transient. Certainly shades of Jan 1984 recently, though the cold and snow then was probably more entrenched rather than transient across the north.

But onto the current models and the 18z run from GFS, a more fruitful run for coldies in that a Scandi trough and high pressure to the W and NW of UK brings a NELY that taps into deeper cold than the easterly. It looks like the models are firming up on the amplification over the N Atlantic late next week, then the ridge building NE into the GIN corridor, it's whether we see the high build further east into Scandi or not looks to be less certain, but expected to be uncertain at that range.

Edited by Nick F
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Posted
  • Location: Scouthead Oldham 295mASL
  • Location: Scouthead Oldham 295mASL

18z would at least brings a few days snow cover for many with HP building in bringing very cold nights and likely cold through the day with it being early January.

I would take it now..(despite it showing a sinking high in FI imho).

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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
14 minutes ago, Allseasons-si said:

!

 

yep,running south and knocking on your doorstep by 180:)

 

 

And even Knocking on Cambourne's doorstep!!!!

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Posted
  • Location: Hoyland,barnsley,south yorkshire(134m asl)
  • Weather Preferences: severe storms,snow wind and ice
  • Location: Hoyland,barnsley,south yorkshire(134m asl)

The ext jma would have a battleground scenario at 240,a long way to go but there is some interesting chart viewing going on i would say:)

J240-21.GIF?29-12J240-7.GIF?29-12J240-594.GIF?29-12

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Posted
  • Location: Port of Ness,Isle of Lewis.
  • Location: Port of Ness,Isle of Lewis.

At present,nothing remotely cold to our East or North east...Reurmett.thumb.gif.e06391d96094f4fd1df7dcd6627dfecc.gif but as many have said earlier,the Northwesterlies have delivered us from mild zonal banality.As we look into the 10 day frame,it is worth having a look at what it takes model wise and synoptically,to get the cold in from the East.GP on January 1987.

 

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Posted
  • Location: Hoyland,barnsley,south yorkshire(134m asl)
  • Weather Preferences: severe storms,snow wind and ice
  • Location: Hoyland,barnsley,south yorkshire(134m asl)
7 minutes ago, feb1991blizzard said:

And even Knocking on Cambourne's doorstep!!!!

Shhhh!!!

don't tell sydney:rofl:

43xJFrC.gif

But he will soon come out of hibernation:nonono:

gfs-1-324.png?18

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Posted
  • Location: Windsor
  • Weather Preferences: Snow and cold
  • Location: Windsor
31 minutes ago, MildCarlilse said:

At present,nothing remotely cold to our East or North east...Reurmett.thumb.gif.e06391d96094f4fd1df7dcd6627dfecc.gif but as many have said earlier,the Northwesterlies have delivered us from mild zonal banality.As we look into the 10 day frame,it is worth having a look at what it takes model wise and synoptically,to get the cold in from the East.GP on January 1987.

 

 Great video on Jan 87. Unfortunately we were in India during the best 80s years for 7 years until June 87 after which it was a more transient wintry weather in the Pennines in the winter of 87/88 followed by a disastrous 88/89 winter ?

Edited by prolongedSnowLover
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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

Interesting that the 12z EC operational run was at the warmest end of the spread between the 6th and 8th, when that not very cold easterly is shown, the mean a few degrees lower and some much colder members in there by the looks of it, indicating a colder source is possible around then.

3D1D6067-BC7F-40CB-8164-72B2AB356456.thumb.gif.9be6f5d245aca0b3f62008529931bb34.gif

Be interesting to see if the operationals in the morning carry through this hint from the ensembles to show some colder solutions.

Edited by Nick F
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Posted
  • Location: Scouthead Oldham 295mASL
  • Location: Scouthead Oldham 295mASL
3 minutes ago, Nick F said:

Interesting that the 12z EC operational run was at the warmest end of the spread between the 6th and 8th, the mean a few degrees lower and some much colder members in there by the looks of it, indicating a colder source is possible around then.

3D1D6067-BC7F-40CB-8164-72B2AB356456.thumb.gif.9be6f5d245aca0b3f62008529931bb34.gif

Yes, they are very good ens - looks very cold in London !!

I'd say a significant cluster brings an easterly - possibly north easterly..

Edited by northwestsnow
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Posted
  • Location: st albans
  • Location: st albans
3 minutes ago, northwestsnow said:

Yes, they are very good ens - looks very cold in London !!

I'd say a significant cluster brings an easterly - possibly north easterly..

significant ?

the control cluster (which had an easterly in the extended ) has approx 16% support 

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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.

GEFS 18z   -    Whilst there is no perfectly timed undercutters where the really long fetch cold air is imported rapidly as the high orientates perfectly (1987,1991,2009), I would say that there is slightly more than a transient feel about the suite, there are a few genuine Easterlies and a lot of battlegrounds.

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Posted
  • Location: Hoyland,barnsley,south yorkshire(134m asl)
  • Weather Preferences: severe storms,snow wind and ice
  • Location: Hoyland,barnsley,south yorkshire(134m asl)

The gefs ens temps table to 192 shows it getting colder by the 6th:)

the 18z gfs shows it was a mild outlier.

table_zcs7.png

 

Edited by Allseasons-si
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Posted
  • Location: Scouthead Oldham 295mASL
  • Location: Scouthead Oldham 295mASL
13 minutes ago, bluearmy said:

significant ?

the control cluster (which had an easterly in the extended ) has approx 16% support 

A lot of those members look very cold for London Blue- there must be a high centered somewhere to the north?

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Posted
  • Location: st albans
  • Location: st albans
20 minutes ago, feb1991blizzard said:

GEFS 18z   -    Whilst there is no perfectly timed undercutters where the really long fetch cold air is imported rapidly as the high orientates perfectly (1987,1991,2009), I would say that there is slightly more than a transient feel about the suite, there are a few genuine Easterlies and a lot of battlegrounds.

I noted the number of members that amplified the n Pacific ridge well into the Arctic - at least two managed to make the full neg AO transfer to scandi block. far removed from the strat zonal onslaught we might be expecting to have manifested itself lower down by days 10 thru 16 ...............

Edited by bluearmy
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Posted
  • Location: Scouthead Oldham 295mASL
  • Location: Scouthead Oldham 295mASL
1 minute ago, bluearmy said:

I noted the number of members that amplified the n Pacific ridge well into the Arctic - at least two managed to make the full neg AO transfer to scandi block. far removed from the strat zonal onslaught we might be expecting to have manifested itself lower down by days 10 they 16 ...............

No- its all very odd when one looks at the background signals- perhaps as others have alluded to, the -QBo is really proving the wild card - the jet looks very strong...

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