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Model Output Discussion 19th January 2014-18z onwards.


phil nw.

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Posted
  • Location: East Anglia
  • Location: East Anglia

I think matt taylor said it could get a little bit colder next week with rain at times, could this be underplaying the potential perhaps? unless mogreps has imploded, the 00z models are telling me we will be plunged into deep winter during the course of next week with those mega height rises to the north east / north spreading out and the uk having snow event after snow event.

Difficult one Karl, even here on the forum superstition has taken hold, don’t say a word about potential cold as it could jinx it. The METO as IF has alluded to over the last couple of days are not yet convinced that something cold is on the way but they do acknowledge that there are possibilities, I think that’s wise at the moment. We all know how this things look good for a couple of days and then fall apart, that’s why a slow evolution in model projections is what I want to see and not 1947 charts at 144hrs plus.

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Posted
  • Location: North East London (E4) 147ft
  • Location: North East London (E4) 147ft

Great update from Ian F.

What a difference a day makes. It must be going off over the coffees and croissants this morning down Exeter way...

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Posted
  • Location: East Anglia
  • Location: East Anglia

Indeed they were. I think certain members would be wise to remember that before they try to close down debate on a weather forum. Great to have Ian F's updates but I'm sure even Ian is happy to be challenged. That's what it is all about.

That’s not the forecast I saw, potential fog across East Anglia this morning, rain here in the west by 10 o’clock ish, rain not across the east until later in the afternoon. It’s just starting to rain here now. 

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Posted
  • Location: Evesham/ Tewkesbury
  • Weather Preferences: Enjoy the weather, you can't take it with you 😎
  • Location: Evesham/ Tewkesbury

It looks to me that the block is already much stronger than anticipated. The rain belt is not going very far east at all. The models have greatly underestimated the block to our NorthEast, Changes all ready afoot it would seemPosted Image

Edited by ANYWEATHER
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Posted
  • Location: Royston, Herts 76m asl
  • Location: Royston, Herts 76m asl

tweet from Ian:

 

Ian Fergusson â€@fergieweather 7 mins

W COUNTRY After Sunday's rain, Monday ushers-in coldest spell of winter thus-far, with snow/ice possible across parts of the region by then

 

Judging from the models, I would suggest that the West Country has the greatest chance of missing out.  Quite a few runs, at least in the more reliable stages, have LPs tracking SE over Bristol/Devon location with the likelihood of Devon and Cornwall (if not further NE than that) at least suffering yet more rain rather than snow.

 

If that happened, one would assume that areas to the north-east of this i.e. South-east, Midlands, Yorkshire, mid-north Wales being in the firing line for snow.

 

However, too early to look at the detail at this point, I suppose, seeing as plenty of time for it all to go horribly wrong!

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Posted
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.

tweet from Ian: Ian Fergusson â€@fergieweather 7 mins W COUNTRY After Sunday's rain, Monday ushers-in coldest spell of winter thus-far, with snow/ice possible across parts of the region by then

Thats convinced me.
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Posted
  • Location: Manhattan, USA
  • Location: Manhattan, USA

tweet from Ian:

 

Ian Fergusson â€@fergieweather 7 mins

W COUNTRY After Sunday's rain, Monday ushers-in coldest spell of winter thus-far, with snow/ice possible across parts of the region by then

 

Yep, appears Met coming more on board as the models showing the block being a lot stronger that before. Looks like I was right to question this yesterday when Shedhead advised I was arguing his point...

 

Posted Image

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Posted
  • Location: HILL OF TARA IRELAND
  • Weather Preferences: SNOW ICE
  • Location: HILL OF TARA IRELAND

tweet from Ian:

 

Ian Fergusson â€@fergieweather 7 mins

W COUNTRY After Sunday's rain, Monday ushers-in coldest spell of winter thus-far, with snow/ice possible across parts of the region by then

 

Posted Image

Iam going to be busy next week?

 

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Posted
  • Location: Hucknall, Nottingham 100m (328ft) ASL
  • Weather Preferences: Snow, Blizzards, Hoarfrost, Frost and Extremes
  • Location: Hucknall, Nottingham 100m (328ft) ASL

I will be very interested to see what Old Met Man's thoughts are on the evolution of this possible forthcoming cold spell. Always enjoy reading his posts, as well as many of the other more knowledgeable posters on here. Where are you OMM? Posted Image Posted Image Posted Image

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Posted
  • Location: Wellington, NZ, about 120m ASL.
  • Location: Wellington, NZ, about 120m ASL.

I stand to be corrected by those more knowledgable than me, but (counter-intuitive though this may sound) I don't think the block's "strength" is determined by how high the peak pressure is.  Although a weak HP can often be moved by stronger energy, very "strong" blocks can and do move and I don't think it's right to assume that a HP cell of, say, 1060 mb is less likely to move than one of say 1035Mb.

 

That's my understanding anyway.

 

 

 

 

Pretty much. The most robust highs on the planet are the subtropical ridges (think Azores High, North Pacific High, South Pacific High) rarely go above 1030hPa. 

 

A 1050-1060hPa high could occur from purely low level conditions (cold dense air near the surface), with little upper support. Hence, could be barrelled out of the way fairly easily. Or, it could be persistent. Hard to tell from looking purely at a surface pressure field.

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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

If you read between the lines this mornings output is another upgrade to the wintry potential that has been discussed here and I would now say the balance of probability has shifted to a more wintry outcome for the first time but still much caution needed.

 

UKMO is once again the star performer regarding consistency and it continues to nudge the pattern West this morning while maintaining good continuity through runs.

No chance of the Atlantic breaking through with that next low as some have suggested. The next chart or two would show it disrupting S/SE likely just to the W of the UK bringing snow to many. The main worry would be it was too far W to get decent ppn rates, Posted Image

 

ECM I'm certainly not as happy as some with the ECM and though it is a chilly run it is on a knife edge with plenty of mixing of the upper air.

Like the GFS it wants to phase energy 72/96 over the UK which prevents the first low clearing S/SE efficiently and allowing high pressure back West behind - it is "saved" by more amplification upstream but I would still expect it to be among the less cold members of its ensemble suit. Not a bad run but I would rather see something that more securely brings in the cold and worry about the ppn later.

 

GEM Is closest to UKMO out to the mid term and it doesn't see a return to a "westerly flow" from 120 with absolutely no real sign of the Atlantic getting in still at 240+. This is quite a turn around from this models recent output and notable as such even if the run on its own should not be overly considered.

 

GFS Easily the most progressive of the output as is usually the case and like ECM phases energy around 72/96 preventing the low the moving away efficiently while upstream it is less amplified and more progressive so basically a warning of what could go wrong with the ECM output if we tweak the energy distribution. It is really the only model this morning that leans toward the MetO very high confidence for return to Westerly type by 31st though one could argue the ECM is also zonal and Westerly to a point.

 

Summary 

 

Overall the probabilities of a cold snap/spell have continued to increase with this mornings output, probably 60/40 in favour as a rough guide but that is based on overall output of the last few days which have seen gradual improvement of prospects with the models underestimating the blocking as is often the case.

The ensembles generally continue to trend colder as well.

This is due to a Westward shift of the pattern but also some subtle changes and not so subtle changes in how the Arctic is being modelled. as mentioned previously the signal for renewed blocking in this region has strengthened and now can be seen across the output by day 9/10.

I discussed how if this signal for renewed high pressure in the Arctic region took hold and our block could hang on we would see a similar situation develop to that which we have now with the Arctic high joining forces with the Scandinavian/Russian high which would likely prove too much for what would be a waning Atlantic by that time.

If things continue to develop along these lines I expect the MetO's extremely high confidence of a return to zonal conditions experienced like much of Winter thus far by the 31st to be somewhat dented. 

They are level headed folk and don't change forecasts on a whim but I expect them to perhaps mention the increased possibility of some wintriness in their 15 day forecast update today but I can't wait to hear Ian's inside view on things and how their own data is shaping up today.

 

ECM 2 day and 10 Arctic heights.

 

Posted ImagePosted Image

Edited by Mucka
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Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

Increasing signs now for the coldest spell of winter so far to develop next week and possibly into the first full week of Feb

 

Posted Image

 

Posted Image

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Posted
  • Location: South Croydon
  • Location: South Croydon

Whilst I don't want to pee on anyones fire I would point out how quickly the models flipped to this output from a largely westerly dominated set up yesterday.  Also the fact that the Meto and models were completely wrong with Fridays forecast as recently as yesterday.  I guess what I'm saying is there are a lot posters saying "nailed on cold" which can make us all look like fools if the models flip again.  I guess that's life if you live on the margins like we do in the UK.

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Posted
  • Location: Crymych, Pembrokeshire. 150m asl
  • Weather Preferences: Extremes of all kinds...
  • Location: Crymych, Pembrokeshire. 150m asl

I am only a keen amateur but even I think I have a grasp of the potential in the models for next week.  But I am trying to understand how things might develop for the better (colder) or worse (warmer....) and looking  at this chart from the GEM it appears to me that there are two air masses both pointed towards the UK - one to the NW (A) and one to NE (B).   'B' seems to have the most potential for cold and wintry conditions but would 'A' return us to a south-westerly, warmer air-flow? Which of these two air masses is likely to reach us first?

 

post-20103-0-36948800-1390556663_thumb.j

 

If my understanding is truly wide of the mark then please feel free to have a good laugh at my expense but replies from the experienced posters will help me avoid making the same mistakes again....! I hope this is the correct thread - I tried to keep it model related?  

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Posted
  • Location: Kingsclere, Hampshire
  • Location: Kingsclere, Hampshire

I would like to see Tamara's input.

 

Of all the opinons posted on here over the past few weeks, she has been the most consistent in calling cold for end Jan / early Feb.

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Posted
  • Location: Trowbridge, Wilts
  • Weather Preferences: hot summers; frigid winters; golden fall; bright spring
  • Location: Trowbridge, Wilts

Excellent post and great to see you posting again on a regular basis TEITS, as usual it's informative for both newcomers and old hands alike. Hope your keeping well.

Echo that, good to see Dave posting with his enthusiasm. Sliding lp's are very difficult to pinpoint for position but in these circumstances they can deliver a la last January. Models will firm up in the next 48 hrs and I suspect MO will get their cold / snow vocabulary out of hibernation. ECM 12 may just show the initial lp midweek to be a little further west IMO which will make the secondary low very interesting indeed, as the saying goes...much to play for
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Posted
  • Location: Manhattan, USA
  • Location: Manhattan, USA

Whilst I don't want to pee on anyones fire I would point out how quickly the models flipped to this output from a largely westerly dominated set up yesterday.  Also the fact that the Meto and models were completely wrong with Fridays forecast as recently as yesterday.  I guess what I'm saying is there are a lot posters saying "nailed on cold" which can make us all look like fools if the models flip again.  I guess that's life if you live on the margins like we do in the UK.

 

Agree with some of this - A cold spell/snap is never nailed on in the UK - So we shouldn't get too hung up about it. The UKMO and ECM has been showing potential for cold to arrive next week for quite a few days now, and we do have quite a lot of X-Model agreement... So while nothing is nailed on, it's around 85% chance of it happening next week, and maybe even Sunday will throw up a few surprises.

 

I have been surprised today regarding the rain and how quickly / less intense it was shunted SSE, shows how strong that block is.

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Posted
  • Location: Hemel Hempstead, Hertfordshire
  • Location: Hemel Hempstead, Hertfordshire

I would like to see Tamara's input.

 

Of all the opinons posted on here over the past few weeks, she has been the most consistent in calling cold for end Jan / early Feb.

 

I wonder if Tamara is in contact with Stewart (aka GP) Posted Image

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Posted
  • Location: Carryduff, County Down 420ft ASL
  • Location: Carryduff, County Down 420ft ASL

I am only a keen amateur but even I think I have a grasp of the potential in the models for next week.  But I am trying to understand how things might develop for the better (colder) or worse (warmer....) and looking  at this chart from the GEM it appears to me that there are two air masses both pointed towards the UK - one to the NW (A) and one to NE (Posted Image.   'B' seems to have the most potential for cold and wintry conditions but would 'A' return us to a south-westerly, warmer air-flow? Which of these two air masses is likely to reach us first?

 

Posted ImageGEM 30 Jan 2014.jpg

 

If my understanding is truly wide of the mark then please feel free to have a good laugh at my expense but replies from the experienced posters will help me avoid making the same mistakes again....! I hope this is the correct thread - I tried to keep it model related?

There is nothing in the output which suggest any south westerlies of Azores origins. I think the two options you have highlighted very well, either an Easterly or a North Westerly. Of course if those two air masses combine over the UK then its a snow machine KABOOM time.
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Posted
  • Location: Lytchett Matravers - 301 ft ASL
  • Weather Preferences: Snowy Winters, Torrential Storm Summers
  • Location: Lytchett Matravers - 301 ft ASL

Pretty much. The most robust highs on the planet are the subtropical ridges (think Azores High, North Pacific High, South Pacific High) rarely go above 1030hPa. 

 

A 1050-1060hPa high could occur from purely low level conditions (cold dense air near the surface), with little upper support. Hence, could be barrelled out of the way fairly easily. Or, it could be persistent. Hard to tell from looking purely at a surface pressure field.

 

And even harder to move, as proved over the past couple of weeks, a SCANDI BLOCK, as she points her big finger ever west and says to the Atlantic, ah ah ah, you go under and around my mass, and tell your siblings to follow, I will leave when I am good and ready! Posted Image

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