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This is the focused model discussion - please only post about the model output. 

For a more laid back, bantery model discussion please use the Cold hunt - models and banter thread.

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If anyone wants confirmation of short-term forecast volatility, then look no further than the latest Fax charts.

T+96 for Tuesday shows a developing Low over the Bay of Biscay:

20190125_2104.PPVM89.thumb.png.c8e4e1e7dd1209d8da33c1b63592975e.png

T+120 for Wednesday only 24 hours later - BANG - and the Low is gone:

20190125_2104.PPVO89.thumb.png.6a9973a805c1399fe9c4975d6ed90156.png

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The warmer air creeping east today with the font And to digress for a moment. I was in a taxi just now and the driver started wittering on about how he loved cold weather. I thought, '

Interesting morning and really encouraging IMO in terms of the set of model suites we were looking at on Thursday and Friday being chipped away at then collapsing into something else late Friday into

What we need to see is exactly what you are seeing here, though by pacific trough I'll translate that as Aleutian low. We need the pattern to retrogress to pull the power out of the Canadian lobe, and

Posted Images

Following on from the above with the gfs and the transition is not seamless. By 1200 Thursday the trough has tracked south east just to the west of Ireland and the aforementioned front, on which an intense little wave has formed, is moving north east  along with the belt of rain, sleet and snow along the leading edge. Over the next 24 hours the trough realigns over the UK and France and there is a lot of wintry unsettled weather around on another very cold day. This is of course subject to change

gfs_z500_vort_natl_23.thumb.png.3f99f3069e52cde71d577aafb7a5b31a.pnggfs_z500_vort_eur_27.thumb.png.7bc73c3991fc7274d50ff52a348c33b8.pnggfs_ptype_slp_eur2_27.thumb.png.556e59cd0997e2e9bbc3d9aca008dfab.png

Edited by knocker
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The ecm has the trough, with a deep surface low, west of Ireland by Thursday midnight with frontal rain already effecting there. In the next 18 hours the low moves east over Ireland as the front traverses the country with strong winds effecting many areas. Dew points fall progressively lower from the Midlands north so at this stage possible snow down to lower levels along the northern edge of the front as it moves ENE Over the next couple of days the low fills slowly and drifts east so a couple of cold unsettled days with wintry showers

t120.thumb.png.87dedc12cc511eab0915bf592cd38f5b.pngt138.thumb.png.a704f7697b96eec1dcda0c3ead122d3c.png

Edited by knocker
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Thanks for the brilliant analysis' @knocker finding the other thread moving a bit too quick to find the posts required to form a reasoned opinion.  Especially with so many models that we have rolling these days, so it's nice to see some succinct posts which alongside the chart viewers can get a more reasoned opinion.

Looking at the 0z gfs the energy companies will be rubbing their filthy mitts right out to t384 at the continuous cold showing with only a couple of charts across the whole suite devoid of blues AND pinks somewhere across the UK.

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1 hour ago, geordiekev said:

Thanks for the brilliant analysis' @knocker finding the other thread moving a bit too quick to find the posts required to form a reasoned opinion.  Especially with so many models that we have rolling these days, so it's nice to see some succinct posts which alongside the chart viewers can get a more reasoned opinion.

Looking at the 0z gfs the energy companies will be rubbing their filthy mitts right out to t384 at the continuous cold showing with only a couple of charts across the whole suite devoid of blues AND pinks somewhere across the UK.

Certainy the EPS looking at below average temps but the period below the coldest as it creeps up from there

index.thumb.png.2dd260afd3b1c3eb2ba06d091c6e260b.png

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Hello friends!

Can someone please tell me where I can find the actual chart for this forecast skill verification.... I've been searching for an hour or so, but can't find the source... /Sorry for a bit offtopic ;) regards

 

image.jpg.bfe843b5b130019599e59e5e903bf8

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Ringing any bells yet..??.

As much as i hate using ANY precip charts other than +24-out..

As an example..

The low sits exactly as quoted yesterday..with leading top snow..(not transitional)...

Southern england!!

This b4 and in between a few other cracks @the [email protected] other parts up-n- down the land...

If many dont see some fairly decent lying snow across nxt week..i'll eat my socks!!!!!

 

gfs-1-84.png

Screenshot_2019-01-26-09-56-41.png

Screenshot_2019-01-26-09-57-09.png

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Most of the posts on Netweather are interpreting the enormous variety of model outputs to predict the most likely weather conditions over the next few days or even two weeks ahead, but it seems to me that only those members like Knocker and a few others who concentrate on the short term (24 - 72 hours ahead) are likely to get it right.  Here are some examples of model variations over only a 10 day period showing the northern hemisphere for today as predicted 10 days ago compared with the actual conditions this morning:

                       Charts from the 16/01 for 26/01            Same model, actual conditions on the 26/01

ECM        image.thumb.png.b0cb99ed000db10bce96cb3cf1ad5bf7.png    image.thumb.png.a16f7aec3d7bde8965000f9ed89d8e73.png

GFS        image.thumb.png.992a18c1080bc7923966559b6dc063c0.png    image.thumb.png.7ee416d2e01f6d36958b00cb74807ba7.png

GEM       image.thumb.png.6d3aaa3ae0cc741884f5e3cc48f17e70.png    image.thumb.png.85ea69ed601437c170ab0776b195e54d.png

Perhaps not surprisingly none of these models either agreed with each other or were able to accurately forecast today's northern hemisphere conditions, and their predictions were in fact quite wide of the mark with only the ECM getting anywhere near the right solution.  As far as the detail in our small area of the world is concerned the 10 day outlook in these examples was quite misleading.  It just proves to me that although long term trends might be deduced from the model output, beyond 72 hours almost anything can happen locally and we should not be surprised if actual snowfall is not seen in the charts until it's almost on top of us.

Edited by Sky Full
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Morning all ?

Sky Fall makes a valid point about model volatility and accurately which is always worth noting but there is a game changer emerging in the medium to long term and those looking beyond whether it will snow on Tuesday might have first seen it on some of yesterday's runs but ECM picks it up this morning:

ECM 00Z OP at T+240:

ECM1-240.thumb.gif.b1f99f31edb52157f9be83d7fe029a51.gif

It's not the big LP south of Iceland or the small area of heights to the west of Norway nor even the Azores HP but the small LP forming to the west of the Azores HP. This is a critical feature going forward as it initiates a change in the pattern, For the last few weeks, our LP have been spinning off the Canadian PV lobe and deepening past the tip of southern Greenland but this LP is sourced from the tropical Atlantic.

Here it is on the GFS 00Z outputs:

OP:                                                            Parallel:                                                  Control:

gfs-0-240.thumb.png.97d8d767e23810e0d9e51f6f41246f57.pnggfs-0-240-p.thumb.png.a3838b9ef73e57008933ab79bc9b6e98.pngControl-240.thumb.png.058bd39057b4c27bee7d0186aa389872.png

The LP does what all the other LP have failed to do - first, it breaks the flow of LP from the PV - it's a sign the PV is weakening and pulling away west into Canada but second as it comes NE heights are raised to the east and north-east so all three of OP, Parallel and Control end on an anticyclonic note. The Parallel ends with a 1050MB HP over the North Sea and more than a hint of retrogression. with the PV having transferred across towards Eurasia. GEM shows the small LP as well.

It's one to watch and could be the pattern for a cold anticyclonic February dominated by HP to the east. Whether it develops as a true HLB or it's MLB based to the east remains to be seen but it's the direction of travel that IDO hinted at a couple of days ago as well.

 

 

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1 hour ago, Vikos said:

Hello friends!

Can someone please tell me where I can find the actual chart for this forecast skill verification.... I've been searching for an hour or so, but can't find the source... /Sorry for a bit offtopic ;) regards

 

image.jpg.bfe843b5b130019599e59e5e903bf8

Yes, here, then click the 'go' button next to 'Height' 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/ 

 

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@Sky Full It's a fair point you make, and I've reflected alot on this in the past week - but when I've gone back through my posts I've seen that there was some very good performances by the ensembles, which I think got clouded by op variations.

Those who saw my posts earlier in the month might remember that even on the 7th January, I noticed the ecm ensembles were particularly bullish on 22nd January being a snow risk for many. Over the next 10 days, the ensembles consistently picked 22-24 January as being cold enough for snow. This has actually verified. 

True, there were reasonable signals - at times - for cold either side of these dates, but these were a little more shaky. 

So while the impression may be of there that the models failed last week, that's not entirely true - the better lesson perhaps is, as ever, not to get sucked in by every change in the op runs until nearer the time ?

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Also just to add to that Man with Beard I remember noting a while back that the ECM ensembles were picking up signals for a possible snow event on the 29-31st of the month. Based on what is happening now, that signal is seemingly proving to be a very good one. Of course uncertainty over exactly how it evolves still, but the trend was there even a solid 6-7 days ago when the easterly was falling apart.

EDIT- Here is what I said on Tuesday morning:

"What is interesting is there is more than a hint again of possible snow event around the 29-31st. This was also highlighted yesterday on the 12z ECM ensembles, though I've not seen the 00z ECM ensembles to see whether that has held."

Edited by kold weather
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14 minutes ago, Man With Beard said:

@Sky Full

So while the impression may be of there that the models failed last week, that's not entirely true - the better lesson perhaps is, as ever, not to get sucked in by every change in the op runs until nearer the time ?

Wise words, but I'd expect that from someone with a beard such as yours!

In terms of forecasting beyond the short range, to me I think it's about guidance rather than pronouncing an exact setup. Past the 4 day range synoptic SLP charts can vary; not necessarily enormously on a hemisphere scale, but small differences in SLP have a big impact locally. That is why looking at the 500mb charts is always a good idea as it gives an idea as to the overall pattern and helps to ascertain probabilities for a particular outcome at a lower level. If we see a deep low pressure system developing on SLP charts, then do the 500mb charts across other models and previous runs back up the signal?

Of course, 500mb charts are also subject to change, but much less than their SLP brethren. Going even further out, it's a case of trying to figure out what drives the pattern higher up which is where analysis of teleconnections and the stratosphere come into play. This is really at the edge of understanding at the moment (I think!) and the best we can do is to estimate general patterns going forward. We're a long way from being able to nail down SLP at a range greater than 8-10 days (as the CFS clearly demonstrates), but we can at least give probabilities on overall patterns which drive outcomes.

Unfortunately, many people seem to think that longer range forecasting should be like short-term forecasts with details such as PPN type and temperatures accurately predicted. Anybody who takes the time to study the subject more closely knows that this is simply not possible and the best that can be said is 'likely' or 'probable'.

Overall it's a fascinating area of interest and I enjoy being able to discuss the weather in detail with people who aren't simply making polite conversation. I particularly appreciate the efforts made by those who go into great detail about their thoughts and analysis and help others such as myself to continually learn new things!

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4 minutes ago, kold weather said:

Also just to add to that Man with Beard I remember noting a while back that the ECM ensembles were picking up signals for a possible snow event on the 29-31st of the month. Based on what is happening now, that signal is seemingly proving to be a very good one. Of course uncertainty over exactly how it evolves still, but the trend was there even a solid 6-7 days ago when the easterly was falling apart.

EDIT- Here is what I said on Tuesday morning:

"What is interesting is there is more than a hint again of possible snow event around the 29-31st. This was also highlighted yesterday on the 12z ECM ensembles, though I've not seen the 00z ECM ensembles to see whether that has held."

We had the 23rd signal and then the 30/31st.  Both have proved to be more than interesting from a way off.  Not seeing another one which may reflect that this weeks deep trough could be the last one as we descend into more slider territory against the developing ridging to our ne 

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3 minutes ago, bluearmy said:

We had the 23rd signal and then the 30/31st.  Both have proved to be more than interesting from a way off.  Not seeing another one which may reflect that this weeks deep trough could be the last one as we descend into more slider territory against the developing ridging to our ne 

Yes. Certainly seems to be backed up by the 8-14 day 500mb height anomalies (which as mentioned in the other thread were given a 5/5 confidence score by forecaster yesterday). 

IMG_20190126_122026.thumb.jpg.bfad05eeb6ec16464690d4d2b82ec226.jpg

Still a gap in above average heights between Greenland and Azores High, so certainly suggestive of energy squeezing across the Attlantic and running into the above average heights to our north east. Certainly seems to back up what the Met Office were saying yesterday.

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1 minute ago, bluearmy said:

We had the 23rd signal and then the 30/31st.  Both have proved to be more than interesting from a way off.  Not seeing another one which may reflect that this weeks deep trough could be the last one as we descend into more slider territory against the developing ridging to our ne 

Nick - just a quick question and minute of your time please - i haven't looked at the strat for a while so have looked at the GFS 6z stratospherically after seeing that there is a huge difference between the BBC and Met Office 30 dayers, to my untrained eye, it looks to me like any downwelling wave left will equate to still a strong Northern arm with no cold uppers to tap into anyway, in other words the scandi high just out of reach, now i know the caveats - it will still be a weak upper vortex so may not be able to prevent the trop doing what it wants, plus i would't be fooled by the lack of frigid uppers on recent graphs as it could just be a waiting game while the pattern orientates favourably, usually also i would plumb for Met Office over BBC, particularly now BBC have stopped using them, however, on this occasion i would just go with the BBC milder outlok (60-40 or 70-30), thats just based on the 6z GFS strat charts though, i am asking you this question specifically because i know you do pay attention wrt these type of evolutions, plus you said even March 1st might be too soon for increased upper westerlies to influence the pattern lower down.

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1 hour ago, stodge said:

Morning all ?
....... there is a game changer emerging in the medium to long term and those looking beyond whether it will snow on Tuesday might have first seen it on some of yesterday's runs but ECM picks it up this morning:

It's ...... the small LP forming to the west of the Azores HP. This is a critical feature going forward as it initiates a change in the pattern, For the last few weeks, our LP have been spinning off the Canadian PV lobe and deepening past the tip of southern Greenland but this LP is sourced from the tropical Atlantic.
                                    ...................
It's one to watch and could be the pattern for a cold anticyclonic February dominated by HP to the east. Whether it develops as a true HLB or it's MLB based to the east remains to be seen but it's the direction of travel that IDO hinted at a couple of days ago as well.

But....can we be sure this feature will form at all......?

Here are the northern hemisphere charts at +240 (5th February) from this mornings output:

ECM       image.thumb.png.255b12d06e49451db0f49893d24bd701.png

GFS        image.thumb.png.b5f706e86a832a2fbe3b987af93395fe.png

GFS (p)  image.thumb.png.5d9484b722ef9b7ef5144d4b103afeff.png

GEM.      image.thumb.png.8fd52dbb6b9a54fbc6ff9203cdf6fe26.png

Not much agreement there......the only common trend in our location seems to be that the Azores high has been flattened and Atlantic is back in charge with everything coming from the west.  No sign of blocking and no easterly or northerly elements.  Perhaps this is the trend we should expect for February?  As ManWithBeard, JohnHolmes and others have been saying for a long time, the ensembles must be consulted for guidance at this range.

 

 

Edited by Sky Full
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The movement I see on the ECM ensembles between D8 and D15 (quite consistent over the past three days) are a slight relenting of the euro trough (though not completely) and a tendency to better heights to the north - but exact location of heights well away from being forecastable. Latest 00Z clusters maintain this theme (D10, then D14) :

ec-ens_nat_z500scenarios_2019012600_240.

ec-ens_nat_z500scenarios_2019012600_336.

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28 minutes ago, feb1991blizzard said:

Nick - just a quick question and minute of your time please - i haven't looked at the strat for a while so have looked at the GFS 6z stratospherically after seeing that there is a huge difference between the BBC and Met Office 30 dayers, to my untrained eye, it looks to me like any downwelling wave left will equate to still a strong Northern arm with no cold uppers to tap into anyway, in other words the scandi high just out of reach, now i know the caveats - it will still be a weak upper vortex so may not be able to prevent the trop doing what it wants, plus i would't be fooled by the lack of frigid uppers on recent graphs as it could just be a waiting game while the pattern orientates favourably, usually also i would plumb for Met Office over BBC, particularly now BBC have stopped using them, however, on this occasion i would just go with the BBC milder outlok (60-40 or 70-30), thats just based on the 6z GFS strat charts though, i am asking you this question specifically because i know you do pay attention wrt these type of evolutions, plus you said even March 1st might be too soon for increased upper westerlies to influence the pattern lower down.

We saw a tweet the other day about glosea and notable downwelling waves in feb (fwiw, I know this to be correct) ......... we have now seen the 30 dayer take on the type of wording seen last feb a few weeks before the end of month beasterly ....... I wouldn’t pay too much attention to the bbc 30 day forecast - they need to be quite specific on conditions each week and I suspect they take their cue from the latest ec46/clusters.  Back end of the eps are sniffing decent ridging to our north and northwest (as per @MWB  clusters above).  it’s been a painfully slow downwelling and if we don’t actually benefit from these reversal waves then there is an argument that the SSW interfered with a positive (for cold) MJO cycle which would have likely brought some decent wintry conditions in January. Now that would be unlucky!  

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23 minutes ago, bluearmy said:

  it’s been a painfully slow downwelling and if we don’t actually benefit from these reversal waves then there is an argument that the SSW interfered with a positive (for cold) MJO cycle which would have likely brought some decent wintry conditions in January. Now that would be unlucky!  

That is the fear. MetO long term musings are starting to become a fairly key crutch for those looking to see a pattern change from westerly to more easterly. 

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