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phil nw.

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

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WeatherBell snow accumulation out to +240 from the 0z ECMWF Det.

 

Posted Imageecmwf_snowdepth_europe_41.png

 

Bear in mind not to take the actual depths shown too seriously as this is based upon a 10:1 snow to liquid equivalent ratio - something that is unlikely to be true under marginal conditions, nevertheless it shows that the 0z ECMWF det. was indeed a snowy run and suggesting otherwise is a little misleading.

 

Of course that is taking this at true face value, this does not mean this is what will necessarily occur.

 

SK

 

 

For me the models today have the most potential we have seen all winter. Hoping the 12z's continue that theme

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Currently the met office update only sounds wintry in terms of the risk of accumulating snow across the far north / ne of uk unless I'm reading it wrong, I must say, the models I've seen so far today paint a much more wintry picture eventually for much of the uk by the middle of next week with Easterly gales and snow across the far north east of scotland and n.isles.

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Which is proabbly why they will be more cautious in their forcasts over the few hours/days

I suspect they have probably been a 'little less cautious' with organisations that pay for their forecast data. Those on the need to know lists will have least been advised, if not warned, but that still doen't make this any more of a done deal yet imo.

Edited by shedhead

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For me the models today have the most potential we have seen all winter. Hoping the 12z's continue that theme

10p in the 'p' box for you  ST...Posted Image

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But we are not looking at streamers.

 

The lows crossing NW - SE will bring the precipitation.

 

You will not get a Thames streamer etc initially from this set up as -5c uppers will not generate strong convection.

 

I am confused by this statement. In order for a Thames Streamer or Kent Streamer to deliver snow, on a broad brush basis, uppers need to be -5 or below.

 

Are you implying from your statement that colder upper temperatures will deliver greater convection, or have you twisted yourself into a knot by implying temperatures would need to be warmer than -5, in which case precipitation would not be snow, and a Thames or Kent Streamer could not exist...?

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Just tweeted @liamdutton and he tells me the rain will win out later today

 

Eh? The batch of rain coming later, which is pretty much drenching the whole country, is of course not going to miss. What did I miss here?

 

Anyway, things are looking up, but we have seen "promising" things on at least two occasions the past three weeks only to have it snatched away. Although Gibby is on board to an extent, I don't think anyone should get too carried away until tomorrow evening or so. I wouldn't want to see some very insightful posters become some disheartened again. Can't really argue with the Metoffice take at the moment. A few good runs so far out is not something to invest too much into.

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I haven't time to post anything in detail, but to answer CH - I think that the strat is far more conducive now to allowing the forecast trop outlook to occur. Critically, we have lost the period of Vortex Intensification (VI) that has plagued the winter so far, and that leaves us with a vortex that is being bruised and battered by the forecast wave activity. We may not get a SSW or strong Greenland heights, however the disrupted vortex should be just enough to allow  the Scandi block to persist. Will hopefully be able to post more thoughts later in the strat thread - but the promise is good and not unexpected and could improve further still by mid Feb.

 

I'll come out of forced hibernation - I didnt want to upset people by continuing to talk down the chances of snow - but I have huge respect for your views so if you believe we can have heights supported under the current vortex profile then that is great news. I'll await your strat update with great interest because my reading of it just cant see a scandy high with enough grunt to push westwards under a SE storm track within the context of the strat as forecasted... so it looks as though I might get a bit of education handed my way later! Always up for a bit of that...

Edited by Catacol_Highlander

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I am confused by this statement. In order for a Thames Streamer or Kent Streamer to deliver snow, on a broad brush basis, uppers need to be -5 or below.

 

Are you implying from your statement that colder upper temperatures will deliver greater convection, or have you twisted yourself into a knot by implying temperatures would need to be warmer than -5, in which case precipitation would not be snow, and a Thames or Kent Streamer could not exist...?

 

What?

 

You need deeper cold (i.e. -10 850s) for streamer formation as the difference between sea and air temperature needs to be greater than 15c on average.

 

I think my statement is fairly easy to understand :)

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Well, the met office didn't sit on the fence in nov / dec 2010 did they, that was a very strong wintry signal..I thought this was too judging by the models, including their own ukmo model which has looked very wintry for the last 3 days in a row..so why is it only significantly wintry for the far north of scotland?

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Well, the met office didn't sit on the fence in nov / dec 2010 did they, that was a very strong wintry signal..I thought this was too judging by the models, including their own ukmo model which has looked very wintry for the last 3 days in a row..so why is it only significantly wintry for the far north of scotland?

I think Frosty they're just not saying too much because its still quite a few days away and there is still uncertainty with how the low sinks, you can also see the issue of shortwave energy to the north of the UK which is a complicating factor, you'll note from the GEFS that the coldest solutions are generally those that make less of that shortwave activity.

 

I would say its imperative that the block is further west because the Pacific ridge is breaking down and theres a strong signal now to move the PV out of Quebec and towards Greenland, if the block is sufficiently west then I would expect good trough disruption and energy heading se to the west of the UK as per the ECM ensemble mean.

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Well, the met office didn't sit on the fence in nov / dec 2010 did they, that was a very strong wintry signal..I thought this was too judging by the models, including their own ukmo model which has looked very wintry for the last 3 days in a row..so why is it only significantly wintry for the far north of scotland?

 

I think if the Models still show the theme continuing on the 12z, with ensemble backup, we don't have anything to worry about until the next run. The data we have available to us, if consistent across the big three models, can't be far off the mark. Today's 12z is going to be an important output this afternoon, if the MOGREPS says different, not much point worrying about something we don't get to see.

 

As far as I'm concerned, nothing has changed since this mornings runs, so we are still in the same position as we were at 11am, apart from maybe a bit of anxiety setting in, understandably. 

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Well, the met office didn't sit on the fence in nov / dec 2010 did they, that was a very strong wintry signal..I thought this was too judging by the models, including their own ukmo model which has looked very wintry for the last 3 days in a row..so why is it only significantly wintry for the far north of scotland?

Hi Karl ,I think because there was a lot of noise in the background back then , we had the a completely under developed vortex as it was only November , the Atlantic was very quiet also , and all the long range computer models were painting the same story . Now we have a raging vortex , although not as bad as December , and a strong jet, also it's only been the last 2 days that the models have developed this (apart from the ukmo model) , so with the fact it's still 4/5 days away and beyond , you can understand them holding off from shouting at the roof tops . Let's hope their morgreps model isn't showing something we don't want !? If we can get cross model agreement this evening I'm sure they will come on board.

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I think Frosty they're just not saying too much because its still quite a few days away and there is still uncertainty with how the low sinks, you can also see the issue of shortwave energy to the north of the UK which is a complicating factor, you'll note from the GEFS that the coldest solutions are generally those that make less of that shortwave activity. I would say its imperative that the block is further west because the Pacific ridge is breaking down and theres a strong signal now to move the PV out of Quebec and towards Greenland, if the block is sufficiently west then I would expect good trough disruption and energy heading se to the west of the UK as per the ECM ensemble mean.

So do you see the dreaded shortwave drams been the spoil again nick? As models only pick up on them closer to the time so that would only now be coming into range , that will be yet another kick in the teeth !??

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The Met Office / BBC are not expecting anything too cold next week highs in the north of 4c and 6c in the south, the wind will make it feel colder in the north with a chance of some snow in eastern Scotland and North east England the coldest air out east isn't likely to make it over here hence why the temperatures are not expected to drop much lower than 4c

 

Its probably going to be a cold snap is how Darren Bett describes it "a few days early next week" signs are milder air will come back in from the Atlantic bringing more rain and the threat of more flooding

 

Its " a tricky situation" early next week according to Darren I get the feeling they are still not 100% certain on how things will pan out during the first part of the week minor changes to the models could make big differences to what we may or may not get

I am a regular visitor to this forum and enjoy reading  the various opinions that are expressed. Clearly the majority favour cold solutions but the reality is that this is the UK and extreme cold spells are rare. Particularly in this part of the country - North East Somerset (I've known Gibby for 30+ years) we miss nearly every snow event - either 100 miles to our east - Kent on many occasions, 100 miles to the south - rare, but Channel Islands March 2013 an example or 100 miles to the north - late March 2013 in North Wales for example. One of these days we may get a repeat of the Feb 1978 West Country blizzard - but that of course was also a "local event" I still have more faith (generally) in what the BBC forecasts state but one thing I would wish to correct in the above post is that minor changes to the models will not make any difference at all to the weather we actually get - it may change the forecasts but Mother Nature/laws of physics/meteorology will make the final decison (as we all know) on the weather. Apologies for not being model related - I'll continue to make my own conclusions as to what may be around the corner whilst assessing all the options on offer.

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So do you see the dreaded shortwave drams been the spoil again nick? As models only pick up on them closer to the time so that would only now be coming into range , that will be yet another kick in the teeth !??

Its likely there will be some phasing of energy spilling east off the PV and some residual left to the north, unless that is the block is further west. Its not a disaster if there is some phasing but it depends on where that takes place to the north, if its going to happen you want it to be as far west as possible because as the energy phases you will see the upstream energy tugged a bit further east.

 

Theres also the recent trend of bringing another lobe of high pressure towards Svalbard which could help, we need to see agreement on how the low sinks and how much if any energy is left to the north after that happens.

Edited by nick sussex

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Its likely there will be some phasing of energy spilling east off the PV and some residual left to the north, unless that is the block is further west. Its not a disaster if there is some phasing but it depends on where that takes place to the north, if its going to happen you want it to be as far west as possible because as the energy phases you will see the upstream energy tugged a bit further east. Theres also the recent trend of bringing another lobe of high pressure towards Svalbard which could help, we need to see agreement on how the low sinks and how much if any energy is left to the north after that happens.

any news on latest NAM nick or GME??

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Well, the met office didn't sit on the fence in nov / dec 2010 did they, that was a very strong wintry signal..I thought this was too judging by the models, including their own ukmo model which has looked very wintry for the last 3 days in a row..so why is it only significantly wintry for the far north of scotland?

Worth keeping in the back of our minds that a 500 mile shift east in the models = no snow for most. It's not a done deal at this range so the Met can't really hype it up just yet, that's my thinking.

Though I nearly passed out when I saw Snowking's snow depth charts!

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Well not long to the 12Z, there’s great excitement in here today.Looking forward to the runs slightly nervous but fingers crossed.It would be great to get a Boom! From Steve and Frosty could do with an upgrade.I might get so excited my SNOW-ICE will melt?PS(not till April)

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any news on latest NAM nick or GME??

NAM looks better than the earlier GFS06hrs run upto T84hrs, a bit more amplified upstream and it looks like the low is further se, the GME is not as good as this morning but is still similar to the GFS06hrs although with better heights to the ne at T72hrs. Not long to wait now, lets hope we get agreement on the low track, the shallower the better in terms of depth.

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I think there will be a lot of disappointed people in here next week (Coldies) ! Will give a full explanation later :-(

well given current model evolve, some may end with egg on faces, againtthere maybe some under evaluation of the evolve. 12z should shed a little more light.

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NAM looks better than the earlier GFS06hrs run upto T84hrs, a bit more amplified upstream and it looks like the low is further se, the GME is not as good as this morning but is still similar to the GFS06hrs although with better heights to the ne at T72hrs. Not long to wait now, lets hope we get agreement on the low track, the shallower the better in terms of depth.

thanks nick and what a nailbiter this is turning out to be!!

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