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Model Output Discussion - The Start Of Winter


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Posted
  • Location: Morecambe
  • Location: Morecambe

    I do like the trend of finally that Russian high moving well away because for me, it does nothing apart from sending mild air to Northern latitudes and it leaves you wondering where all the cold air up to the North and East. So at least Svalbard and Scandinavia may see some more significant cold soon so IF we get the right set up, it could be at least on the potent side. 

     

    At the moment though, there not an awful lot too suggest any major cold for the run up to xmas although as we know, this can change before we know it.

     

    Trend does seem to be more milder days than colder ones but its still pretty variable so it is still interesting in that respect. 

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    A few of you have asked today about rationale for the (tail-end of) UKMO latest 30-day outlook. There is, of course, a dedicated thread elsewhere for this but I'll just confirm that GloSea5 output rem

    Thanks for this Barry   You are however wrong on both counts you suggest :   1) I have explained in extended detail, as much as I am able, the progress of the patterns thus far from autumn (see firs

    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

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    Posted
  • Location: Scottish Central Belt
  • Location: Scottish Central Belt

    I do like the trend of finally that Russian high moving well away because for me, it does nothing apart from sending mild air to Northern latitudes and it leaves you wondering where all the cold air up to the North and East. So at least Svalbard and Scandinavia may see some more significant cold soon so IF we get the right set up, it could be at least on the potent side. 

     

    At the moment though, there not an awful lot too suggest any major cold for the run up to xmas although as we know, this can change before we know it.

     

    Trend does seem to be more milder days than colder ones but its still pretty variable so it is still interesting in that respect. 

     

    I think we need to be careful about how generally we talk, as it stands, the north (Scotland) see's more -5 (850) days than +5 days in the run up to xmas. So for Scotland at least, looks like average to colder than average run up to xmas. Definitely quite a north south split in the models now.

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    Posted
  • Location: Coney Hall Village 260ft asl, North West Kent
  • Location: Coney Hall Village 260ft asl, North West Kent

    Classic, have a discussion that basically says don't use the mean and voila we have a post discounting cold weather using the Mean charts.

     

    The problem with using mean charts is obvious just by looking at the ensemble charts, all those differences are basically ironed out, to be honest most mean charts will always show a predominantly westerly pattern, because on average that is the weather we get.

    Not only that they are the most boring charts (to look at). They dont float my boat, they need sprucing up a bit.

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

    One more comment on mean anomaly charts.

    They can be useful but should not be used in isolation and as has been noted they do not depict probability of a particular weather pattern, (sounds obvious but sometimes forgotten) and with that in mind it is also useful to consider that we are often looking at a snapshot of the mean which will not tell us anything on trends which are probably the most important factor.

    That is why trawling through the individual ensemble members or having access to the clusters is important as it adds this missing information. Of course there is much, much more information we should look at as well but that is the minimum really if e are trying to make judgement on the actual synoptic in 10 days+

     

    Here is ECM current and 10 day for contrast so we can see how the big picture is expected to change. It shows a window of opportunity for height rises toward Greenland as the lobe of PV in that region shifts East and a deep trough sets up to our East, something I mentioned as a possibility several days ago. (look at the difference in the Greenland region)

    What it does not tell us is how likely or strong those height rises will be, though we can discern weather it is becoming more likely or less likely by following changes within the anomaly charts.

    Currently the signal is still gaining strength and the prospect of an Atlantic ridge gaining credence. Beyond that hard to say but nice to see we have had our first Op (GFS (p)

    show a more sustained block today.

     

    EDH101-0.GIF?16-12EDH101-240.GIF?16-12

     

    Ideally in the above 10 day chart we would want to see positive anomalies removed from SW UK, stronger positive anomaly to our W/NW and the postive anomalies over Greenland area shifted SW and strengthened.

    Edited by Mucka
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    Posted
  • Location: Camborne
  • Location: Camborne

    Classic, have a discussion that basically says don't use the mean and voila we have a post discounting cold weather using the Mean charts.

     

    The problem with using mean charts is obvious just by looking at the ensemble charts, all those differences are basically ironed out, to be honest most mean charts will always show a predominantly westerly pattern, because on average that is the weather we get.

     

    I do apologise but I hadn't read your  scientific analysis detailing the reasons for completely disregarding anomaly charts. Have you informed NOAA and Nick F? The latter had just posted an excellent professional appraisal on the subject which you chose to ignore. And just so we know exactly where we stand when you you say, "don't use the mean" should we instantly comply?

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

    Not only that they are the most boring charts (to look at). They dont float my boat, they need sprucing up a bit.

     

    What do you suggest.? A small inset depicting a blizzard.

    Edited by knocker
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    Posted
  • Location: Batley, West Yorkshire
  • Weather Preferences: Heat and Snow
  • Location: Batley, West Yorkshire

    The Polar Vortex migrating to the East towards Scandinavia and Siberia in the reliable will surely benefit us down the line. All Winter we've had the Polar Vortex sending down chunks of vortex towards us bringing in wet and windy weather. This is surely the most important thing we want to see happen if we are wanting a pattern change, especially one with heights being able to move up from the Atlantic to Greenland.

     

    gfsnh-0-96.png?12gfsnh-0-120.png?12gfsnh-0-144.png?12

     

    If we do get a flow from the East we won't have to worry about not having a cold pool.

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

    Good looking UKMO at 144h which just as with this mornings run makes much more of the trough to the North than GFS which if correct would probably help amplify the pattern behind and also bring the chilly air further South for the following 48h.

     

    UN144-21.GIF?16-17

    Edited by Mucka
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    Posted
  • Location: Batley, West Yorkshire
  • Weather Preferences: Heat and Snow
  • Location: Batley, West Yorkshire

    Heights moving towards Greenland at day 8 and a cold North Westerly flow arriving for Christmas eve. Should be a cold Christmas day and wintry for some. Much better than recent mild ones!

     

    gfsnh-0-204.png?12gfsnh-1-204.png?12

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    Posted
  • Location: Batley, West Yorkshire
  • Weather Preferences: Heat and Snow
  • Location: Batley, West Yorkshire

    A cold and snowy boxing day on the GFS 12z

     

    gfs-1-240.png?12gfs-1-252.png?12gfs-1-264.png?12gfs-1-276.png?12

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    Posted
  • Location: South Croydon
  • Location: South Croydon

    To be honest can you stop using the Mean, as it is irrelevant with the data being used. Ensemble stamps are the best as you can see if different scenarios are being seen or a trend. The mean is pointless.

     

    Surely the mean gives an indication of how many std deviations a particular ensemble lies from it and as a result reliability or how much of an outlier you are looking at?

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

    GEM also starting to build a stronger Atlantic ridge.

     

    gemnh-0-180.png?12

     

    A long way to go but very good output for coldies thus far this evening with positive trends. Looking forward to see what ECM makes of it and if it backs UKMO at all.

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    Posted
  • Location: Tonbridge, Kent
  • Location: Tonbridge, Kent

    Surely the mean gives an indication of how many std deviations a particular ensemble lies from it and as a result reliability or how much of an outlier you are looking at?

    Not at all, as the mean is across all ensemble members the standard deviation is lost, now a purely standard deviation of the operational and control would be different and represented as the anomaly charts are would be a good way of seeing an outlier. The mean falls down exactly because of outliers throwing the mean out.

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    Posted
  • Location: Live Thame (Oxfordshire), Work Heathrow Airport
  • Location: Live Thame (Oxfordshire), Work Heathrow Airport

    Good run again from the GFS 12Z FI (following on from a good GFS 06Z in FI) in regards to wanting to build heights around Greenland.

    post-115-0-68135000-1418748373_thumb.png

    post-115-0-68135000-1418748373_thumb.png

    -12c 850's trying to make it into Scotland

    post-115-0-43892800-1418748448_thumb.png

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    Posted
  • Location: redcar,cleveland
  • Weather Preferences: Winter cold,snow and frost. Summer hot and thundery
  • Location: redcar,cleveland

    The GFS(p) is going for a boxing day blizzard, would be interesting to say the least.

     

    http://modeles.meteociel.fr/modeles/gfsp/runs/2014121612/gfs-0-240.png?12

     

    The fun begins now, pattern change is on the way, how it effect our small island is up for debate.

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    Posted
  • Location: Batley, West Yorkshire
  • Weather Preferences: Heat and Snow
  • Location: Batley, West Yorkshire

    The trend is growing now for a cold and wintry Christmas period, both the GFS and GFS P 06z and now 12z have shown this. UKMO also looks like it would go that way to with it being more amplified. This is why it's better to look at the operational rather than the mean charts, as they are much slower to spot a trend. ECM should be interesting tonight!

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    Posted
  • Location: Salzburger Sportwelt Lungau/ Pongau Region. Somtimes Skipton UK
  • Weather Preferences: Northeasterly Blizzard and sub zero temperatures.
  • Location: Salzburger Sportwelt Lungau/ Pongau Region. Somtimes Skipton UK

    Another encouraging run from the latest GFS. The PARA run continues to show the formation of low pressure system moving into the Southern Half of the UK around the Christmas Period and engaging the cold air to the north. Looks like snow for some at the moment.

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    Posted
  • Location: Essex, Southend-On-Sea
  • Weather Preferences: Warm, bright summers and Cold, snowy winters
  • Location: Essex, Southend-On-Sea

    Do I dare say?

     

    The possibility of channel low?

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

    I do apologise but I hadn't read your scientific analysis detailing the reasons for completely disregarding anomaly charts. Have you informed NOAA and Nick F? The latter had just posted an excellent professional appraisal on the subject which you chose to ignore. And just so we know exactly where we stand when you you say, "don't use the mean" should we instantly comply?

    Must say I'm with knocker on this one. The mean will be closer to the mark than if you just guess from a bunch of clusters. Isn't that why we have spreads too? No scientific basis for this but I find the mean kicks the butt of the op especially for ECM after T192. Well let's just look at the forthcoming Christmas Day. Means consistently say no snow in southern counties. Several op runs give hope though. Let's see which one gets closer.

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    Posted
  • Location: Bramley, Rotherham - 114M ASL
  • Weather Preferences: Snow and Cold! Winter :)
  • Location: Bramley, Rotherham - 114M ASL

    Well what a lovely set tonight from the GFS brothers!!!  :D ill not post the charts again, as I was beaten to it, but what a great Christmas they would bring. It isnt a snap either, as it lasts a few days. The P has the better uppers for longer. :cold: :cold:

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