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Model Output Discussion - cold spell to end Autumn


Message added by Paul

Please only post model discussion in this thread. 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

Thank you!

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1 hour ago, EML Network said:

The same posters on here always trying to see what they want to and hopecast. 

I have to chuckle when I see so much attention on one LP system, of course it's path is going to be modelled differently from run to run and I understand why so many people are interested, but the path is more or less clear..this will move pretty much straight across the UK from NE to SE cutting a thin sausage shaped wedge, Snow more likely from Wales in the West drawing a line to Lincoln in the East and anywhere North of that is in the firing line. 

 

I’m sorry but thast very misleading.

The path is not clear at all on this system,as even the professional meteorologists are saying they have no confidence at all in the path of the system yet and watch for updates over the next few days.The only clear thing is that somewhere will see falling snow from this system.

And if the path is clear to you why do you think it’s going to be modelled differently run to run:gathering:

 

 

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You know what - I havent seen 1 hopecast on here. People have put all their points of view across in a pretty good mannor- infact its been pretty good debate. The only post that sticks out a mile

Still coming slowly off a cautious fence Long term total global atmospheric angular momentum trends can tell you a lot about pattern changes due to the effects the rises and falls in global wind-

Afternoon All - A frantic few days on here with pages & pages of posts flying through in a matter of hours- I think we have 2 main discussion points at the moment-  1) The short to

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10 minutes ago, Steve Murr said:

Back to the here & now & before the 12s set off on their hopecasting voyage - here is the snowfall accum chart for T48 Euro 4-

A pretty impressive coverage for the UK in particular the favoured spots of the NW midlands - but Ireland ! wheres our Irish contingent - snow all the way down to dublin-

Maybe even a few flurries in London again !

IMG_2189.thumb.PNG.cc389baa5fe2d201b1df32a6650452bb.PNG

More importantly Steve, have you checked for PPI yet?

6 minutes ago, Jayfromcardiff said:

Them charts don't make sense, the METO have issued warnings for 2-5cm widely across NW England, Wales etc but the above doesn't reflect.

 

I'll just watch the radar when it comes I guess.

From the chief forecaster's assessment I read yesterday, he/she did mention that due to the nature of showers there could be some very wide variance in totals across short distances (as you would expect with showers) - but I agree that the warning then goes on to say widespread 2-5cms. They tend to lean more heavily on the UKV in these situations I believe due to its superior resolution, and I know from past experience that the Euro4 can be a bit hit and miss when projecting showers. @Nick L might be able to enlighten us a little more about what the UKV is showing (if it has come into range yet)?

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1 hour ago, Man With Beard said:

I'm not sure a post like this is fair. I take your point about a mainly rainy week coming up after about Tuesday - I suppose people like me don't focus on that because it's just bog standard weather. But when we have models trying to place a 200 mile wide band of snow over various parts of the country, I don't see any problem with focusing on that, or reporting that, or to suggest ones own location might be affected by it?

For us on the south coast, yes it's a bit different, we need something extra special and I'll be astonished if we see lying snow from this - but from 30 miles inland and northwards, well why not speculate?? When I lived in the North Downs area (75msl) we saw all sorts of surprise snowfalls from synoptics not as good as these!

Northern areas have their own dilemma too of course - if the GFS is right, the whole band of precipitation will miss them to their south!!

Look at the Meto forecast. They are going cold with rain/sleet/snow and only short mild spells for the south.  I expect all models to upgrade the cold over the next few days.  Anyone who thinks the GFS zonality for the week before Christmas may need to check back in a few days.  Won’t see mild again in 2017 (except the extreme south west).

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7 minutes ago, ShortWaveHell said:

Would the models associate high pressure with warmer temps ? Wondering if this is a high pressure coming from the continent (east)  

These would be south westerly or westerly wind types dragging warmer air to the uk, not a continental air-mass/source unfortunately. Long way off, so not to be worried about to much atm.

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I think a forecast of 2-5cm snow depth could well be wide of the mark for areas which are prone to the Cheshire Gap streamer. I know from experience, living in a prime spot for that streamer, that 10cm+ can be lying even at modest levels of elevation.

 

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Regarding possible height rises to our north or northeast later in week 2, it looks to have little to do with any push sw of the Siberian ridge. 

It would be due to a push ne of the Atlantic higher heights finding a receptive environment not to be toppled (mainly due to polar ridging in the right place). Some members are helped by ridging from the w Russian block 

so that argues against any ‘beast’ being unleashed in week 3 as uppers will be unlikely to be as low as would be the case with a sw push of the Siberian ridge. Of course that could follow on if a conducive  hemispheric pattern establishes.

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11 minutes ago, Mark N said:

I'm sure the Met Office don't base there forecast/warnings off just the Euro 4 alone. Remember a number of times Ian Fergusson said the Euro 4 was modified/blended when in situations like this before.

The Met Office use UK4? And a blend of others things probably. Much more higher resolution than Euro4 which is probably the best model the public have access to.

 @Nick L spill the latest. :wink:

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2 minutes ago, tvh3382 said:

Look at the Meto forecast. They are going cold with rain/sleet/snow and only short mild spells for the south.  I expect all models to upgrade the cold over the next few days.  Anyone who thinks the GFS zonality for the week before Christmas may need to check back in a few days.  Won’t see mild again in 2017 (except the extreme south west).

Thats a heck of a claim so early in any given month, even if it came from the met whom i doubt would of used the words ' wont see mild again in 2017'. prety sure most if not all on here dont see any kind of weather being in control the week before xmas. No-one including the Met know this weekend yet! :)

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8 minutes ago, tvh3382 said:

Look at the Meto forecast. They are going cold with rain/sleet/snow and only short mild spells for the south.  I expect all models to upgrade the cold over the next few days.  Anyone who thinks the GFS zonality for the week before Christmas may need to check back in a few days.  Won’t see mild again in 2017 (except the extreme south west).

Are you new to this tvh? 

 

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1 minute ago, Daniel* said:

The Met Office use UK4? And a blend of others things probably. Much more higher resolution than Euro4 which is probably the best model the public have access to.

 @Nick L spill the latest. :wink:

They use the UK4. I remember the Euro 4 was many a time supposedly modified by Chief Forecaster or something along those lines, Ian Fergie mentioned it a few times in here and on twitter mainly due to its shower distribution/snow signal!

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8 minutes ago, snowking said:

More importantly Steve, have you checked for PPI yet?

From the chief forecaster's assessment I read yesterday, he/she did mention that due to the nature of showers there could be some very wide variance in totals across short distances (as you would expect with showers) - but I agree that the warning then goes on to say widespread 2-5cms. They tend to lean more heavily on the UKV in these situations I believe due to its superior resolution, and I know from past experience that the Euro4 can be a bit hit and miss when projecting showers. @Nick L might be able to enlighten us a little more about what the UKV is showing (if it has come into range yet)?

The nature of showers varying widely is just them covering all bases in case somewhere gets a dumping of snow or somewhere in the middle of the warning area gettting nothing. As with so many things nowadays, they are terrified of the feeble minds not being able to cope with one or the other. We used to be much more stoic. ?

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28 minutes ago, Seasonality said:

Oh Steve! You are a one... But back to the debate about the slider low, from memory is Wednesday not much too far out to judge the track with any sort of certainty? Was it the March 2013 snowfall that ended up causing record falls in the channel isles after being forecast to hit the mainland only days before? Not saying it will happen again but worth noting in that at this stage there is no point getting worried or putting the champagne on ice as the case may be. 

Yes 2013 drifted south... 

Today event is 78-96 across the UK

I would say the margin of error is 100 Miles north of current GFS track & 200 miles south - net 300- 

The next 36 hours that will refine down to a margin of about 150 miles either aide then the last 24 hours probably 50-100 miles. Post that is radar watch...

 

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11 minutes ago, tvh3382 said:

Look at the Meto forecast. They are going cold with rain/sleet/snow and only short mild spells for the south.  I expect all models to upgrade the cold over the next few days.  Anyone who thinks the GFS zonality for the week before Christmas may need to check back in a few days.  Won’t see mild again in 2017 (except the extreme south west).

Hi tvh3382, good to have you back posting with us again!!

Is your forecast purely on the basis of the METO forecast, or do you have a theory for this based upon the models?

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On the face of it, the models look either good, very good or great for generally cold prospects looking beyond the arctic shot with a continuing chance of snowfalls and below average / cold temps with frosts and ice..proper winter instead of the usual default mild zonal mush..I'm happy and all coldies should be!:santa-emoji:

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1 minute ago, Mark N said:

They use the UK4. I remember the Euro 4 was many a time supposedly modified by Chief Forecaster or something along those lines, Ian Fergie mentioned it a few times in here and on twitter mainly due to its shower distribution/snow signal!

The issue with the Euro4 it goes OTT with the coverage/area of PPN I find it’s still a good tool. 

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4 minutes ago, Steve Murr said:

Yes 2013 drifted south... 

Today event is 78-96 across the UK

I would say the margin of error is 100 Miles north of current GFS track & 200 miles south - net 300- 

The next 36 hours that will refine down to a margin of about 150 miles either aide then the last 24 hours probably 50-100 miles. Post that is radar watch...

 

Steve - wouldn’t you want to wait for the 12z to make the judgement that there is only a 100 mile envelope north of the 06z ? 

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21 minutes ago, Seasonality said:

Oh Steve! You are a one... But back to the debate about the slider low, from memory is Wednesday not much too far out to judge the track with any sort of certainty? Was it the March 2013 snowfall that ended up causing record falls in the channel isles after being forecast to hit the mainland only days before? Not saying it will happen again but worth noting in that at this stage there is no point getting worried or putting the champagne on ice as the case may be. 

I believe it started off modelled over France and then actually corrected further and further north until by T72 it was programmed to hit the southern counties, and then was touch and go until the very last second. Kent/Sussex got a good whack from it. Another example of a slider correcting slightly north without a block in place to its east.

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35 minutes ago, Jayfromcardiff said:

Them charts don't make sense, the METO have issued warnings for 2-5cm widely across NW England, Wales etc but the above doesn't reflect.

 

I'll just watch the radar when it comes I guess.

Hi Jay. that chart is just up to 6am on Friday, before a lot of the fun and games begin. :)

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40 minutes ago, Jayfromcardiff said:

Them charts don't make sense, the METO have issued warnings for 2-5cm widely across NW England, Wales etc but the above doesn't reflect.

 

I'll just watch the radar when it comes I guess.

What the Met Office says in the text of the Weather Warning is:

"During winter weather which brings snow showers, it is not uncommon for snow amounts to vary considerably across short distances. On Friday and Saturday, the snow showers could lead to snow accumulations which vary markedly across the warning area."

That seems fair enough to me. My interpretation of it is: snow in Britain is the most difficult weather to forecast accurately, and we just can't be sure what will fall where as what. This whole area is 'possible' for enough snow to cause disruption, so we're putting out a warning so people know in advance that it might happen. Making no promises, though!

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GFS 06z just expanding that little wedge of heights a little more which is key to guiding that first low more south easterly and at the same time delay the phasing with the trough to the east.I wonder if the 12z.s will maintain this trend,often we see this happen with the cold already established over us as it  proves a little harder to shift.

Anyway a very interesting period coming up with snow showers coming in on the cold Arctic flow from Friday before the anticipated diving low coming in from the nw later in the weekend.Where will the boundary be for the snow?This will not be clear yet but just for fun the latest from NW extras medium term model shows this-a snapshot at 9pm Sunday

viewimage.pbx?type=nmmlo;date=20171206;tviewimage.pbx?type=nmmlo;date=20171206;t

not be taken as gospel as over the next 48hrs i am sure some adjustments will show to the general tracking of this.

Looking at 06 ens pretty solid agreement out to around the 16/12 of surface cold continuing-Aberdeen and Warks 2m temp.

viewimage.pbx?type=ens;date=20171206;timviewimage.pbx?type=ens;date=20171206;tim

After that the Op.run goes mild against the general grouping.Looking at gefs stamps on the jet pattern modeled for 16/12/17

viewimage.pbx?type=ens;date=20171206;tim

We can see some want to flatten out the Atlantic ridging but still a number are sending the jet south around or just west of the UK.A typical pattern when in a battle between the Atlantic mildness and the cold further to the north and east.Enough amplification upstream of course is the key and with each set of runs showing this ebbing and flowing the current pattern will keep us guessing for days to come i am sure.

 

 

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1 hour ago, Steve Murr said:

Back to the here & now & before the 12s set off on their hopecasting voyage - here is the snowfall accum chart for T48 Euro 4-

A pretty impressive coverage for the UK in particular the favoured spots of the NW midlands - but Ireland ! wheres our Irish contingent - snow all the way down to dublin-

Maybe even a few flurries in London again !

IMG_2189.thumb.PNG.cc389baa5fe2d201b1df32a6650452bb.PNG

We're here alright! It certainly peaked my interest, haven't had lying snow here since December 2010, and I've been waiting for the Hi-res models to come in range. I'd imagine we may get a few flakes now at this stage, but the Dublin snow shield is a very strong beast! More to watch and fingernails shortening already!

 

I will have Hirlam and Euro 4 worn out!

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13 minutes ago, pyrotech said:

Interesting to see the changes from ECM and GFS for Sundays low

Starting with GFS 

06z Tuesdaytues06.thumb.gif.f813a2b73762259f8c1b05b368676d52.gif

12z Tuesdaytues12.thumb.gif.fce1fb368c0c0fa8e89fc7ef1463e8be.gif

18z tuesdaytues18.thumb.gif.2aae70c8f6276f2277aecb6a941883ee.gif

00z wed     wed00.thumb.gif.d3b44ea6bf2c65822f52a13d292af977.gif

06z wed   weds06.thumb.gif.8898da4d9d2b093279d12cdc6ef25e09.gif 

 

ECM

 

mon 12zecm12mon.thumb.gif.10d49b59da43fd76407a521c131f3419.gif

Tues 00zecm00tues.thumb.gif.3de852e409a8698744271623002b7db5.gif

Tues 12zecm12tues.thumb.gif.f7dfe4b689ccd1264a796a4b6819a13b.gif

wed 00zecm00wed.thumb.gif.35fa8e9725e43c89e86a0b4f6bed8d6c.gif

tues06.gif

Can’t really assess ec as two charts are for midnight rather than noon. We know yesterday’s 00z run was far ne 

here are the two missing ec ones

C59A6BF0-34AF-4D73-9398-0F6FA24A5DAF.thumb.jpeg.c4eb2c2ce3bdaea092b4bd742eaa8e60.jpeg

3033C722-FBC5-4016-A5A9-023989B2CCE6.thumb.jpeg.82e5a98a40b1162e84060f991f8531e6.jpeg

Edited by bluearmy
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2 hours ago, karlos1983 said:

28F82FA7-2253-4964-81B4-072C5DE2965E.thumb.gif.e85eb8523379618701693315efc11016.gif

its been a while since we’ve seen that much scatter towards the end of the run. Certainly more support for the warmer members than 12 hours ago when I posted yesterday’s 12z graph. One to watch.

The ensemble for de Bilt has much less spread, so London is probably on some warm/cold battleground 

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