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Model output discussion - heading into 2018

Paul

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Not much to add atm im on the fence a bit in regards to the models, but next week looks a lot more interesting than this week, which has been totally benign....

How ever my only thing to add is, everything most of time gets pushed south. Could turn into a bit more interest next week imo, but we shall see

Edited by Snowjokes92

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6 minutes ago, Snowjokes92 said:

Not much to add atm im on the fence a bit in regards to the models, but next week looks a lot more interesting than this week, which has been totally benign....

How ever my only thing to add is, everything most of time gets pushed south. Could turn into a bit more interest next week imo, but we shall see

I think you will find that the polar front jet actually gets adjusted further north most of the time. The models (especially the GFS) have a bias to overplay the extent of any southerly trajectory. 

Edited by mulzy
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Well the much derided EC snow depth charts again show the peak district/pennines and much of ulster/wales with snow on the ground between boxing day to the 28th..

Will be interesting to see if that signal is maintained over the coming 24-28 hours...

 

Edited by northwestsnow
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33 minutes ago, Nick F said:

Having browsed the extended EPS, they appear to be retrograding the tropospheric PV back over northern Canada in the means? Still we are left with a SWly 500mb mean flow though, but means could smooth out the potential for some members building heights to the northeast in the extended. Will need to see the  clusters later I guess of any credible hints of what 00z GFS op shows in FI.

The slp probability charts provide for that nick and show less than 10% support (as per standard). Of course there could be some upper ridges with surface pressure below 1030mb but they would have pressure higher to the south and therefore not be the type of feature we would be searching for re Scandi highs 

I certainly wouldn’t discount the potential for this to evolve beyond two weeks 

there remains a disconnect with the gefs on this 

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1 minute ago, TEITS said:

Following my earlier post I shall explain more.

What I noticed on the GFS yesterday for the New year is a trend away from the SW,lys becoming SSW,S,ly. This is due to a new trend appearing where the trough in the Atlantic is digging further S. This increased amplification allows the dreaded Azores HP to become our friend instead of enemy. Check the chart below to see what I mean.

GFSOPEU00_228_1.png

Note what happens afterwards. The flow slowly veers from a SW,ly to S,ly to SE,ly.

GFSOPEU00_237_1.pngGFSOPEU00_264_1.png

This is text book because sometimes a S,ly can be a precursor to an E,ly. Now im not predicting a bitter snowy E,ly yet but my method has always been instinctive based on years of following weather patterns. A new trend could emerge from a SW,ly to an E,ly. Even the Berlin ensembles which have been dreadful recently are starting to show these colder runs.

t850Berlin.png

Well teits i hope you are onto something...as blue says above its 10% chance on the eps so its a long shot 

:)

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3 minutes ago, northwestsnow said:

Well teits i hope you are onto something...as blue says above its 10% chance on the eps so its a long shot 

:)

I do think this general evolution makes sense and the eps do ‘dig’ the upper trough to our west but there remains too much strength in the northern arm, the mean flattens out and the probability charts show a Euro ridge much more the likely consequence. 

Perhaps a more likely week 3 direction of travel ??

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1 hour ago, bluearmy said:

sadly it isn't really - the extended eps are not showing the little drop of low anomoly post day 12 this morning, nor is there a small upper trough sinking to our se. Micro changes globally  but changes where they are important to us.  any troughing to our south is purely transient at the moment 

the eps are still below 10% on high mslp over scandi at day 15 whilst gefs show around 30% 

whilst there are still wintry surprises more than possible in the cool zonal outlook, there is little to hang your hat on searching for any deep cold. 

These "extended eps" (whatever they are - never seen them) seem to change every single day. Are they meant to be taken seriously as an indicator? Seems to be more ups and downs with them than a fiddlers elbow.

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14 minutes ago, Summer Sun said:

UKMO extended remaining unsettled with some strong winds and widespread rain

ukm2.2017122900_168_lant.troplant_prp_fcst.gentracker.thumb.png.b729ebe1a208e8ebbe2857ecf4dc03ba.png

The bearer of good news as ever Summer Sun :D.

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17 minutes ago, TEITS said:

Following my earlier post I shall explain more.

What I noticed on the GFS yesterday for the New year is a trend away from the SW,lys becoming SSW,S,ly. This is due to a new trend appearing where the trough in the Atlantic is digging further S. This increased amplification allows the dreaded Azores HP to become our friend instead of enemy. Check the chart below to see what I mean.

GFSOPEU00_228_1.png

Note what happens afterwards. The flow slowly veers from a SW,ly to S,ly to SE,ly.

GFSOPEU00_237_1.pngGFSOPEU00_264_1.png

This is text book because sometimes a S,ly can be a precursor to an E,ly. Now im not predicting a bitter snowy E,ly yet but my method has always been instinctive based on years of following weather patterns. A new trend could emerge from a SW,ly to an E,ly. Even the Berlin ensembles which have been dreadful recently are starting to show these colder runs.

t850Berlin.png

My take exactly. These have been showing in increasing (albeit low) quantities in the ens over the past few days. What has changed (for this scenario ) is a slight shift back west in the forecast WAA ridging north. Prior to that, still very interesting, more of a proper Euro high was being pumped up with the subsequent ridging going into Russia setting up more of a Eastern Scandinavian/Russian block. Potentially still nice but much harder to tap into.

if we get the digging of the jet further south and west, so much the better.

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3 minutes ago, Paul_1978 said:

These "extended eps" (whatever they are - never seen them) seem to change every single day. Are they meant to be taken seriously as an indicator? Seems to be more ups and downs with them than a fiddlers elbow.

Couldn’t agree more on this. Operational runs are often discarded because of the so called background signals, I’m sure they take them into account anyway. You can’t go wrong with the ECM to day 5, anything else is just complete fantasy. 

 

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26 minutes ago, Summer Sun said:

UKMO extended remaining unsettled with some strong winds and widespread rain

ukm2.2017122900_168_lant.troplant_prp_fcst.gentracker.thumb.png.b729ebe1a208e8ebbe2857ecf4dc03ba.png

WONDERFULL!!!!:closedeyes: MERRY XMAS SS

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10 hours ago, blizzard81 said:

It's 21st Dec but don't worry, I know you can't wait for Christmas lol. Anyway, I happen to think early Jan won't be the right off most on here seem to think. I remember the early to mid 80's winters when a potent cold spell was often preceded by a polar maritime spell. The classic forecasters would often say "if you think it is cold now, wait until next week" :)

Nice to see things have moved on positively this morning. The ecm is a bit of a party pooper in the middle part of the run. However, it shows quite a good snow event for northern England on boxing day at just 4 days out. A better end to the run as well. I have a feeling gfs is onto something in the 10 to 12 day timeframe with a pressure build over scandi. Well done to Tamara, GP, Catacol etc if so. 

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image.thumb.png.3ed5290f74a7e7df19c8c7b95f4a4ec0.png

I am not the best at reading charts and I hope my posted charts show up as I see them on my computer :-)

At day 5 the differences on the Alaskan ridge between the 3 main models we can see look very different, UKMO and GFS the closest and ECM slightly different by not building the secondary ridge behind the first poleward attempt.

The GFS has a more organised low pressure system passing above the UK and the UKMO has a slack low directly over us, the differences I appreciate might just be timing.

To the more learned posters here, would that not suggest that even day 5 currently indicate that this is where FI starts? 

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42 minutes ago, bluearmy said:

The slp probability charts provide for that nick and show less than 10% support (as per standard). Of course there could be some upper ridges with surface pressure below 1030mb but they would have pressure higher to the south and therefore not be the type of feature we would be searching for re Scandi highs 

I certainly wouldn’t discount the potential for this to evolve beyond two weeks 

there remains a disconnect with the gefs on this 

Ah well, it's a straw to clutch, but an outsider obviously at the moment, given that the trop and strat PV look to cool and strengthen in an unfavourable position for any sustained cold in the UK/Ireland and certainly HLB is off the cards for a while.

At least we have the Christmas period coming up to divert our minds onto other things and perhaps forget about our impending slide into domination by the trop PV and zonal express, with the possibility of some better signals showing up in the New Year. 

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4 hours ago, snowfish1 said:

A great finish by gfs on its latest run showing a cold pool to the east ready to pile in!! Interesting times ahead this winter compared to last few. I have a "feeling" about this one don't you ? 

Aye snowfish, I certainly have a 'feeling' about it: Oh no, not again!:D

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42 minutes ago, bluearmy said:

I do think this general evolution makes sense and the eps do ‘dig’ the upper trough to our west but there remains too much strength in the northern arm, the mean flattens out and the probability charts show a Euro ridge much more the likely consequence. 

Perhaps a more likely week 3 direction of travel ??

As I've often said on here, the route to very cold starts from very mild. The scenario of HP developing in Iberia and moving NE into Scandinavia is one we've seen before - I believe that's how the 62-63 winter got started. It doesn't happen often - usually we get MLB rather than HLB as the northern arm of the jet has enough strength to hold the HP to the south so it gets as far north as Germany or southern Denmark.

Now, for those of us in the SE that's no bad thing if you want cold because even an MLB with the right orientation can bring colder clearer air in from the Continent. Obviously, fans of snow would need an HLB to deliver anything more than snow grains and snizzle.

The current output suggests nothing more than a transient MLB at best but it's very early days and a direction of travel mentioned by a number of forecasters in their LRFs.

I did think yesterday the signal for sending heights back into Europe had been muted or perhaps delayed beyond New Year - this morning I'm not so sure.

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gfs-0-132.png?6

The Wintry potential is still there for boxing day onwards, more so for the north and as per usual higher ground (But not exclusively)

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11 hours ago, Catacol said:

1. MJO forecasts are fading fast, but observed as opposed to predicted magnitude still seems disconnected to me. However even taking into account a possible underestimation of amplitude we have begun to see some gloomy suggestions of westerly influence. The trop influence on the strat is flipping just at the wrong time - downwards propagation of strat anomalies now the dominant player and this timing perfectly with a return to the pole of the main start vortex after spending much of December displaced to Asia. End result, taking into account lag time, would be a growing trend for Atlantic awakening... and right at the time the Pacific signal wanes. One wonders whether this is “luck” or whether it is another part of the intricately linked global climate system referred to Paul above

Three words - "Extratropical MJO initiation".

The simple assumption that the tropics drives everything is false, in particular the role of the extratropics in firing up or dampening down MJO phases seems to be totally ignored.

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Mein Gott, this looks unpleasant...Calls for a rocket-powered Pogo Stick!

h850t850eu.png

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51 minutes ago, Paul_1978 said:

These "extended eps" (whatever they are - never seen them) seem to change every single day. Are they meant to be taken seriously as an indicator? Seems to be more ups and downs with them than a fiddlers elbow.

The "extended eps" are the ECM ensembles D11-D15. Look, anyone who follows my posts knows that I am quite prepared to be critical of models when they get it wrong, but I think criticism of the extended eps in the past two months is being quite unfair. 

Much better to give a solid example of how it has done. I chose 26th December since it is a period now firming up on the ops. Here's what the ensembles said about it last night:

ec-ens_nat_z500scenarios_2017122112_120.

And here's what the ensembles were showing 11th through to 15th December. Bear in mind that clusters to the top and left are the largest, and clusters to the right/bottom are smallest (and more likely to be outliers)

ec-ens_nat_z500scenarios_2017121112_360.  ec-ens_nat_z500scenarios_2017121212_336.  ec-ens_nat_z500scenarios_2017121312_312.  ec-ens_nat_z500scenarios_2017121412_288.  ec-ens_nat_z500scenarios_2017121512_264.

Considering these were D11-D15 charts at the time, I am quite content with their performance. True, they made one reasonably large error, which was to not see the Arctic heights spreading as far as Greenland. But consider what they did get right. Troughing close to the UK (correct). Not particularly keen on Scandi heights (correct). Generally SW/W pattern but with plenty of large enough clusters presenting the chance of the trough pulling through enough for a temporary NW. 

Based on just these 5 runs, I was very confident by 15th December that the period just after Christmas would be low pressure dominated with an outside chance of a marginal snow event if all fell into place. I was very confident there would be no big freeze or Scandi High. This all looks like being proven true. Now if ensembles can give me this broad detail at such a long range, I am pleased with that. (Perhaps I thought there was room for it to be a bit stormier than currently forecast on the ops, but still looking like gales on western coasts, so that wasn't completely wrong either.)

But the key is, I looked for a consistent pattern over a few days. There usually is one if you look. TBH - the period after New Year is one exception where I can't really see the pattern after D12 - but that's not usual.

What am I trying to say? Simply to stop knocking the ensembles this winter! They are doing a good job if you use them properly!! :)

 

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High 1036 over Greenland

High 1029 over Northern Europe linking into Scandinavia?

Low pressure heading into Spain

Azores high slipping SW

Encouraging signs or just a temporary position?

 

Fax Tuesday 27 Dec 2017.png

Edited by snowblizzard
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4 minutes ago, Ed Stone said:

Mein Gott, this looks unpleasant...Calls for a rocket-powered Pogo Stick!

h850t850eu.png

Why??

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00z EC and 06z GFS below showing a heavy snow signal for northern England and Northern Ireland Boxing Day evening/night on northern flank of low pressure system clearing east over central areas. Too far off to know whether the low track will be further north or south though and whether it will be cold enough for snow to fall and settle at lower levels. But some upland areas of the north could see spell of quite heavy and disruptive snow.

Reminds me of an evening in January 1995 when I was in Leeds at the time studying, when a similar system crossing central areas in a zonal flow had some snow on the northern edge and brought the city to a standstill.

gfs_ptype_thick_uk2_19.thumb.png.77f5215f44cd5bbd5fad95a6e00acef3.pnggfs_ptype_thick_uk2_20.thumb.png.ab06feda61e5056ac442bd82d2f09e68.png

Edited by Nick F
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