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Model output discussion - late November


Paul

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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire

Good stuff.

And further highlights the ECM's overall worthyness....as per I may add!!

@ for our part

@Blessed Weather

Edited by tight isobar
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Posted
  • Location: Camborne
  • Location: Camborne

The salient points of ext GEFS mean this evening

Vortex over northern Canada with associated subsidiaries Aleutian Islands and north Scandinavia

Ridges Russia and Alaska and thus some amplification across North America but nothing particularly anomalous

But the pattern change has resulted in a very strong upper flow across the Atlantic, particularly in the east with a squeeze between the trough and the subtropical high

This would indicate an unsettled period

gfs-ensemble-all-avg-nhemi-z500_anom_5day-5979200.thumb.png.a92278923d45b24971d2cecfd2f80c1a.pnggfs-ensemble-all-avg-nhemi-t850_anom_5day-5979200.thumb.png.92531060d709a2844de423ff5a959812.pnggfs-ensemble-all-avg-eur-t2m_c_anom_5day-5979200.thumb.png.4d1cf58d00bd0d8551299eb74862fc16.png

 

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Posted
  • Location: Stoke Gifford, nr Bristol, SGlos
  • Location: Stoke Gifford, nr Bristol, SGlos
49 minutes ago, Blessed Weather said:

 

Final thought, forecasting for our small island, on the edge of the Atlantic and continental Europe, inevitably gives its own challenges to the models.

Oh yes! For any post read by any NW member bookmark this segment. It will really help to manage your weather expectations for these wonderful islands we live in.

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Posted
  • Location: st albans
  • Location: st albans
10 minutes ago, knocker said:

The salient points of ext GEFS mean this evening

Vortex over northern Canada with associated subsidiaries Aleutian Islands and north Scandinavia

Ridges Russia and Alaska and thus some amplification across North America but nothing particularly anomalous

But the pattern change has resulted in a very strong upper flow across the Atlantic, particularly in the east with a squeeze between the trough and the subtropical high

This would indicate an unsettled period

gfs-ensemble-all-avg-nhemi-z500_anom_5day-5979200.thumb.png.a92278923d45b24971d2cecfd2f80c1a.pnggfs-ensemble-all-avg-nhemi-t850_anom_5day-5979200.thumb.png.92531060d709a2844de423ff5a959812.pnggfs-ensemble-all-avg-eur-t2m_c_anom_5day-5979200.thumb.png.4d1cf58d00bd0d8551299eb74862fc16.png

 

that will make a change then ….could do with some rain …...

i wonder if all three vortex segments can co exist ? scandi, Aleutian, Canada ……. suspect one of those wont verify in the 9/14 day period

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
1 hour ago, Blessed Weather said:

 

Next a look at the verification stats for model performance in America and Canada published by the Canadian Met Office. Their graph compares the error rates at Day 5 and runs from 2017 up to Sept 2019. The latest results have the top models in the following order:

  • ECM Europe (best)
  • Met Office UK
  • GFS (old) America
  • ICON Germany
  • JMA Japan
  • CMC Canada (worst)

180585446_VerificationgraphCanMetSep2019.thumb.jpg.0f36546fd9c0fbea4f995c94691e48db.jpgSource: https://weather.gc.ca/verification/monthly_ts_e.html

Some interesting observations on the graph. First is that the models all show fewer errors in the summer months than in the winter. Secondly it appears that every year it is the months of Nov and Dec that give the biggest headache for the models and the highest error rates each year, no doubt caused by the dynamics of the weather waking up from its summer slumbers, for example as the increasing temperature gradient between the rapidly cooling northern areas interacts with the warmers temps lingering further south and fires up the Jet Stream.

Good post.  Just wanted to pick up on the statement in bold, because the site that I use shows the opposite, the models are worse in summer than winter.  The measure is different, it's the 500mbar geopotential height anomaly correlation (higher is better) here for NH day 5 for GFS and ECM going back ages:

image.thumb.jpg.60f18727fd5466b1fe8ccaf90bb915dc.jpg

Clearly shows better performance in winter (and, as an aside, the improvements over the years!).  

Interestingly, the picture in the SH is unclear i.e. no clear seasonal signal.

image.thumb.jpg.ee60a85d8ec5663376a262f74abca872.jpg

Edited by Mike Poole
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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire

Vertical slant...still think those uppers are being underplayed @96+ hrs...

And with the dropline around the Russian slot...there's room for argument!!!

ECH0-144.gif

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Posted
  • Location: sheffield
  • Weather Preferences: cold ,snow
  • Location: sheffield
2 hours ago, lassie23 said:

 

Slightly better 168hour chart on EC.ridging better and low digging in atlantic.ptobably same outcome as the 6z

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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
22 minutes ago, bluearmy said:

that will make a change then ….could do with some rain …...

i wonder if all three vortex segments can co exist ? scandi, Aleutian, Canada ……. suspect one of those wont verify in the 9/14 day period

Unfortunately sods law will prevail and it will be the wrong one - it won't actually be the one that is progged to be the weakest on that chart!

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Posted
  • Location: STEVENAGE, HERTS (100M ASL)
  • Location: STEVENAGE, HERTS (100M ASL)
4 minutes ago, bluearmy said:

more polar profile shenanigans on the ec op and the murr trough to our west perhaps showing what might change around nw Europe in the mid term 

Certainly 1 step closer to a scandi cut off high on this run!

47A0D3E1-D535-4A5E-9E58-41B2F1CD4D40.png

Edited by Tim Bland
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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire

Fools rush in where angels fear to tread comes to mind!!..

The models have big diagnostic problems with vortex...and height placement..

And let's not forget...minor adjustments...are of mass scale....

In our-tiny domain!!!

ECM0-168.gif

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

There's plenty of Arctic potential during the first half of December in the GEFS 12z as there was in the 6z, hopefully the wintry trend will continue!❄❄❄

Edited by JON SNOW
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Posted
  • Location: Heckmondwike, West Yorkshire
  • Location: Heckmondwike, West Yorkshire
8 minutes ago, Mike Poole said:

The purple one finger salute from the vortex at T216 on ECM:

image.thumb.jpg.2f8b8cbc46fcbe5612acd08d77dc0050.jpg

I have a feeling it will be more a case of the grand solar minimum that will be giving the one fingered salute to the vortex. 

Screenshot_20191126-185812.png

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Posted
  • Location: Essex, Southend-On-Sea
  • Weather Preferences: Warm, bright summers and Cold, snowy winters
  • Location: Essex, Southend-On-Sea
8 minutes ago, Tim Bland said:

Certainly 1 step closer to a scandi cut off high on this run!

47A0D3E1-D535-4A5E-9E58-41B2F1CD4D40.png

Glad someone mentioned it that’s about as close as we could possibly come to having something decent in the next 10 days. Just a little more of a dig west and we would have been seen a different following chart. 

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Posted
  • Location: Hadleigh, Suffolk
  • Weather Preferences: An Alpine climate - snowy winters and sunny summers
  • Location: Hadleigh, Suffolk
17 minutes ago, Mike Poole said:

Good post.  Just wanted to pick up on the statement in bold, because the site that I use shows the opposite, the models are worse in summer than winter.  The measure is different, it's the 500mbar geopotential height anomaly correlation (higher is better) here for NH day 5 for GFS and ECM going back ages:

(SNIPPED)

Thanks Mike. I was scratching my head here, trying to think through why a heights anomaly correlation would give a different seasonal result to an RMS error rate. Then I looked at your charts again and twigged it's showing a 3-month mean correlation for Day 5. Maybe that's got something to do with it but to get to the bottom of it I wonder if you could pm me the methodology (or link) used to produce those charts. Ta.

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Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl

The gefs still showing a 5/6 day colder spell, and at last, much drier too.(graph is for C.England.)

gfs-ens_apcpna_eu_3.thumb.png.cc5c544612362c36384cd98769ced4ec.pnggfs-ens_T2maMean_eu_3.thumb.png.9657633a3eadc4d772ffae14e28c6db5.pnggraphe6_1000_271_95___.thumb.gif.5f31e8d42783e69bc55dc71f3130db77.gif
 

Thankfully a change to all the rain and cloud we have had for a seemingly long time.Some brighter days and night frosts as we go into Winter proper.

 

 

 

Edited by phil nw.
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Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire
36 minutes ago, Mike Poole said:

The purple one finger salute from the vortex at T216 on ECM:

image.thumb.jpg.2f8b8cbc46fcbe5612acd08d77dc0050.jpg

All that slight bit of transient amplification is doing is allowing a more seamless rise in pressure across Europe in the longer run. We will not get enough amplification to promote a Scandi high so it's pointless. 

As a result, ECM ends as bad as you could get, with the jet roaring away well to our N and a strong Euro HP. As +NAO as you could get!

At least with the jet angled more NW to SE at a lower latitude, we were in the game for some PM outbreaks. 

Look at the image above and the profile over Canada and the States- it's completely flat, combined with the vortex located over that area...that is not a good combination going forward.

Edited by CreweCold
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Posted
  • Location: sheffield
  • Weather Preferences: cold ,snow
  • Location: sheffield
2 minutes ago, CreweCold said:

All that slight bit of transient amplification is doing is allowing a more seamless rise in pressure across Europe in the longer run. We will not get enough amplification to promote a Scandi high so it's pointless. 

As a result, ECM ends as bad as you could get, with the jet roaring away well to our N and a strong Euro HP. As +NAO as you could get!

At least with the jet angled more NW to SE at a lower latitude, we were in the game for some PM outbreaks. 

Tbh I've never known an Atlantic ridge cause so much excitement but what ever floats your boat!!! Yes the PV still looks like producing a fair amount of rain etc,not welcome

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Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
7 minutes ago, CreweCold said:

All that slight bit of transient amplification is doing is allowing a more seamless rise in pressure across Europe in the longer run. We will not get enough amplification to promote a Scandi high so it's pointless. 

As a result, ECM ends as bad as you could get, with the jet roaring away well to our N and a strong Euro HP. As +NAO as you could get!

At least with the jet angled more NW to SE at a lower latitude, we were in the game for some PM outbreaks. 

Look at the image above and the profile over Canada and the States- it's completely flat, combined with the vortex located over that area...that is not a good combination going forward.

Yes I was actually making the same point re ECM, as I said finger up from the vortex, not to it.

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