Model Output Discussion - The Start Of Winter

[Mark Neal.]

We don't have the parallel pub run for a few days,but the normal 18z is a touch more amplified and showing a pretty chilly end to the weekend.

gfs-1-96.png

Yes and Still strong hints that Scotland and Northern England could see Snow with elevation and Wintry mix potentially even to lower levels. Keeps the seasonal feel going!

http://images.meteociel.fr/im/5641/gfs-2-96_bun7.png

Edited December 3, 2014 by Mark N

[johnholmes]

Surely it's better than looking at one run in isolation?

 

what I was inferring  is compare like with like down to 144h-168h, ie 12z to 12z, below that then okay the balance starts to swing towards checking each run as the latest data takes over in terms of accuracy. Even then it is a good idea to see how like for like is going. Never ever use just one run on any model.

[Cloud 10]

Latest fax charts for Sunday and Monday look wintry with the 528 dam line clearing the UK with troughs embedded in a cold unstable northwesterly.

 

[TheGrittersAreOut]

I wonder if theres something up with the UKMO. Once again it has the most amplified upstream solution compared to the others, we saw with the recent will it won't it northerly that it was too amplified and then had to backtrack.

 

Theres also a divergence across the NWP upstream with low pressure development at T144hrs, with the UKMO having a very weak feature compared to the ECM and GFS.

 

I don't normally (ever  ) post but over the past few years I've learned a huge amount about weather modelling from all of the experts on this forum - fascinating stuff.

 

Following up to Nick's comment, what I've not seen mentioned is the major upgrade to the Unified Model that the UKMO rolled into production in the late summer. For many years the UM was what's called a 'spectral model'. These models are difficult to make scale well on today's supercomputers so about 12 years ago a dynamical core called the new dynamics was introduced. This in particular removed the need for fast fourier transforms to manage divergence in the solution around the poles. This dynamical core has always required a lot of artificial damping to reach a solution quickly enough. This summer they released a much upgraded version of this core called ENDGame - there's a discussion of it on the UKMO website.

 

I know that a lot of work has been going on within the UKMO to make sure this core is performing well - perhaps some of the over amplification that Nick references above is one consequence of this change,

 

Interestingly, the ECM is still a spectral model - and they are very proud of this. They believe their dynamics are more accurate as a result of their persistence with this type of numerical solver.

 

Keep up the good work all!

 

TheGrittersAreOut

[nick sussex]

Quite a big difference between yesterdays outputs and todays and all within the T144hrs timeframe:

 

So take last nights UKMO 12hrs run at T144hrs:

 

 

Then tonights to T120hrs

 

.

Then last nights to T120hrs:

 

 

And tonights to T96hrs:

 

 

You can see there the big increase in amplitude over the ne USA.

 

This has been one of those changes that sort of went under the radar, the GFS 18hrs run has also trended more amplified, however the ECM is flatter but it could be that this colder plunge could be a bit better than first thought, the UKMO fax charts are not without interest and they go with the UKMO raw output, of course they might change yet again but I wonder whether we could squeeze even a bit more amplitude given tonights trends:

 

 

You can see above  at T96hrs the 528 dam line about to clear the south coast.

 

Then at T120hrs below still most of the UK within the 528 dam and if this verifies as the winds fall light overnight Monday it could be the coldest night of the winter so far:

 

 

 

 

 

 

 

:

Edited December 3, 2014 by nick sussex

[blizzard81]

It's not an easterly as you'd like to see it. Continental flow around a s euro trough. mobile run throughout with Atlantic ridge occasionally joining with blocking to our east and then depressions dropping in and sinking.

Thank you, goes cold very cold in the last 3 days with little or no precipitation though.

[phil nw.]

It looks we are heading for a typical early Winter unsettled and westerly type of weather for the next couple of weeks.

The anomaly NOAA chrts that Knocker posted earlier and the mean charts below all show a +nao pattern with the low heights over Greenland/Iceland and the Azores high.

 

Not a mild flow though as the mean jet pattern is trending on a southerly path which means very often the UK is on the colder/polar side of the flow as can be seen by the 850hPa temperatures in the above images..

 

Surface temperatures look around or just below the seasonal average but with some steep lapse rates in the polar air some quite significant snowfall is quite likely higher up over parts of Scotland and possibly some other northern and western mountains..Add in the prospect of strong winds or gales at times then blizzard conditions are quite possible at elevation.

For many of us though it promises to be just a normal December outlook no deep cold but feeling chilly with rain or showers when the Atlantic systems come through with some frosts on any calmer and clearer nights between the fronts.

Although the pv looks fragmented wrt the coldest(purple)segments there's still enough energy in the area to our nw which continues to drive our weather.

In many  Winters past with a +nao we would eventually see the setup turn into a milder sw flow as the AH drifts east and the jet orientates sw-ne but at the moment this doesn't look likely as the models continue to dig some low pressure se into Europe.  

[johnholmes]

If you look at Met Fax charts, the 96H and the 120h, on the link below, show both issued this evening at the same time which is fine. What is rather odd is the huge change in pressure in about the same area?

At least 50-60mb. It just seems looking at the sequence 72-120h a bit odd. Must have a close look at the jet stream to see if that throws any light on the subject. At the moment I cannot see how or why such a large change unless I am totally misreading dates/times etc?

http://www.weathercharts.org/ukmomslp.htm#t120

The number of thickness lines supports it but I am lost as to why such a huge increase in the thickness advection.

Any ideas folks?

[blizzard81]

Quite a big difference between yesterdays outputs and todays and all within the T144hrs timeframe:

 

So take last nights UKMO 12hrs run at T144hrs:

 

UK3.gif

 

Then tonights to T120hrs

 

UK4.gif

.

Then last nights to T120hrs:

 

UK1.gif

 

And tonights to T96hrs:

 

UK2.gif

 

You can see there the big increase in amplitude over the ne USA.

 

This has been one of those changes that sort of went under the radar, the GFS 18hrs run has also trended more amplified, however the ECM is flatter but it could be that this colder plunge could be a bit better than first thought, the UKMO fax charts are not without interest and they go with the UKMO raw output, of course they might change yet again but I wonder whether we could squeeze even a bit more amplitude given tonights trends:

 

fax96s.gif

 

You can see above  at T96hrs the 528 dam line about to clear the south coast.

 

Then at T120hrs below still most of the UK within the 528 dam and if this verifies as the winds fall light overnight Monday it could be the coldest night of the winter so far:

 

fax120s.gif

 

 

 

 

 

 

:

Yes Nick, quite big changes at very short range. The trend of today is upgrade to cold in the short term.

Past experience tells me that when we see this upgrade at short notice (which isn't very often by the way)

then the knock on effects in the mid to long term tend to be even greater. Watch this space is what I say

[Severe Siberian icy blast]

Quite a big difference between yesterdays outputs and todays and all within the T144hrs timeframe:

 

So take last nights UKMO 12hrs run at T144hrs:

 

UK3.gif

 

Then tonights to T120hrs

 

UK4.gif

.

Then last nights to T120hrs:

 

UK1.gif

 

And tonights to T96hrs:

 

UK2.gif

 

You can see there the big increase in amplitude over the ne USA.

 

This has been one of those changes that sort of went under the radar, the GFS 18hrs run has also trended more amplified, however the ECM is flatter but it could be that this colder plunge could be a bit better than first thought, the UKMO fax charts are not without interest and they go with the UKMO raw output, of course they might change yet again but I wonder whether we could squeeze even a bit more amplitude given tonights trends:

 

fax96s.gif

 

You can see above  at T96hrs the 528 dam line about to clear the south coast.

 

Then at T120hrs below still most of the UK within the 528 dam and if this verifies as the winds fall light overnight Monday it could be the coldest night of the winter so far:

 

fax120s.gif

 

 

 

 

 

 

:

Quite agree there Nick , also the changes regarding the Siberian ridge is quite stark don't you think ?particualry last nights 144 next to today's 120?

All in quite an interesting period of weather coming up with some polar maritime air creeping in more frequently next week may well throw a few surprises, I no Cheshire gap streamers can have quite a dramatic effect for the west midlanders when the conditions are ripe , and feel particualy at night there may well be some action .

With things slowly moving forward regarding the dropping of the Asian low been replaced by high pressure backing west again , should allow the next cycle of the SAI to show its hand as we move through the month , maybe just delayed by 10 days of so from the initial expectations .

[Blessed Weather]

Tonight's anomalies all singing from the same hymn sheet that the Atlantic express is running to schedule.

 

 

Hi knocker. May I comment on your post. It was the first sentence about the Atlantic express running to schedule and the chart you posted that got me interested. So I thought I would visit the NCEP website and run the 31 day 500hPa geopotential height anomaly for last December 2013 to get a feel for where we are this year. Comparing that output with your ECM EPS mean chart:

 

NCEP Dec 2013  ECM EPS Ensemble mean for 13 Dec2014

 

If I'm reading the charts correctly, some significant differences with the mean anomaly's your chart shows:

 

- last year's positive heights over Europe replaced with lower heights, 

- last year's negative heights over NE Canada/Newfoundland replaced with positive heights,

- last year's positive heights over Alaska/Aleutians replaced with lower heights.

 

So lots different from last year which IMO suggests this winter will continue to develop differently to last year's Atlantic onslaught?

[knocker]

Hi knocker. May I comment on your post. It was the first sentence about the Atlantic express running to schedule and the chart you posted that got me interested. So I thought I would visit the NCEP website and run the 31 day 500hPa geopotential height anomaly for last December 2013 to get a feel for where we are this year. Comparing that output with your ECM EPS mean chart:

 

NCEP Dec 2013 Nth Hem 500 Anon 01Dec_31Dec2013 b.jpg ECM EPS Ensemble mean for 13 Dec2014 post-12275-0-70487900-1417641695 ECM EPS.png

 

If I'm reading the charts correctly, some significant differences with the mean anomaly's your chart shows:

 

- last year's positive heights over Europe replaced with lower heights, 

- last year's negative heights over NE Canada/Newfoundland replaced with positive heights,

- last year's positive heights over Alaska/Aleutians replaced with lower heights.

 

So lots different from last year which IMO suggests this winter will continue to develop differently to last year's Atlantic onslaught?

 

Well I would tend to agree with that BW. I hasten to add my opening comment wasn't intended to relate to twelve months ago. Have to watch my Ps and Qs in future.

[blizzard81]

Hi knocker. May I comment on your post. It was the first sentence about the Atlantic express running to schedule and the chart you posted that got me interested. So I thought I would visit the NCEP website and run the 31 day 500hPa geopotential height anomaly for last December 2013 to get a feel for where we are this year. Comparing that output with your ECM EPS mean chart:

 

NCEP Dec 2013 Nth Hem 500 Anon 01Dec_31Dec2013 b.jpg ECM EPS Ensemble mean for 13 Dec2014 post-12275-0-70487900-1417641695 ECM EPS.png

 

If I'm reading the charts correctly, some significant differences with the mean anomaly's your chart shows:

 

- last year's positive heights over Europe replaced with lower heights, 

- last year's negative heights over NE Canada/Newfoundland replaced with positive heights,

- last year's positive heights over Alaska/Aleutians replaced with lower heights.

 

So lots different from last year which IMO suggests this winter will continue to develop differently to last year's Atlantic onslaught?

What a cracking post, post of the day without a doubt and goes a long way to stressing how different this winter is

to last. On a side note, I would advise anyone who has a chance to look at the archives for Jan 84. Eerily similar to the

current set up.

[Cheshire Freeze]

Are you serious with this comment?

On the 3rd December?

Not wishing to be abrasive John but if you'd paid any sort of attention to the likes of Tamara, Chiono or Nick you'd understand that my comments were in context of any potential SSW later this month/early next. MJO phases 7 and 8 will potentially create the foundation for this, the MJO circle of doom will not. As far as I'm aware the basis for most of the cold LRFs is said SSW is it not? Hence you can see my logic for what I said......

Also if you'd quoted all of my post, other people may have noted the context of the part of my post you decided to highlight...

Edited December 4, 2014 by CreweCold

[Mucka]

GFS and especially UKMO pretty flat this morning, moderating any potential cold air incursions next week perhaps? Just one run that isn't the best  looking 144 chart for coldies.

 

 

Then again UKMO has been all over the place lately at that range so so not worth taking at face value as yet.

 

We still have Fridays brief flirt with colder uppers and then we get a cold incursion of polar maritime air again later in the weekend which may yet be the best chance of some low lying areas seeing snow falling if not settling this year. 

That sentence puts things into perspective doesn't it? coldies deserve something better soon but it is looking like the last 3rd of Dec at best other than these transient cold air incursions. 

Still That second Northwesterly looks potentially quite potent while it lasts so fingers crossed (especially those of us in the NW who can get lucky with this set up)

 

GEM saves the day as usual in FI with something with a little more wintry interest

 

 

And goes on with what could be quit a cold pattern with a more significant trough to our E and the Azores high squeezed further north and  West

 

 

I won't bother posting GFS FI as it turns into zonal horror show.

Edited December 4, 2014 by Mucka

[Mucka]

Something is afoot!

Just had a browse through GFS ensembles and all bets are off from day 6.

I don't mean there is a cold pattern suddenly looming but there is definitely a spanner being thrown in the cold zonal works!

There is a lot of variation on what will happen when the next deep trough wants to drop SW from around day 5 with conflicting signals wanting the Azores high to ridge in very strongly as with UKMO only even stronger on some GFS ensembles and others that want drop the trough South and force the Azores high West and then the rest that are generally in keeping with previous runs. Example of the three options (obviously much more nuanced but just to give a basic idea of how there is a new signal in the mix)

 

 

 

Of course there will be variation by day 7 but these are BIG variations with visible differences conspicuous by day 5.

Interesting times.

 

If GFS ensemble) FI is to be believed (and it isn't) then the choices seem to be a flattening of the pattern to standard zonal or a true cold zonal pattern to set up(low pressure sliding Nw/SE to the East of the UK)  which I haven't seen for many a year so it would make a nice change.

 

GFS ensemble pressure charts.(check out the sudden explosion of scatter from day 5. That illustrates the uncertainty and variance I was describing.

 

Edited December 4, 2014 by Mucka

[Captain Shortwave]

Not wishing to be abrasive John but if you'd paid any sort of attention to the likes of Tamara, Chiono or Nick you'd understand that my comments were in context of any potential SSW later this month/early next. MJO phases 7 and 8 will potentially create the foundation for this, the MJO circle of doom will not. As far as I'm aware the basis for most of the cold LRFs is said SSW is it not? Hence you can see my logic for what I said......

Also if you'd quoted all of my post, other people may have noted the context of the part of my post you decided to highlight...

The MJO is only one factor, add to that there are many examples of where the weather refused to run to the MJO script so to speak. The big example is January 2011 where we were in MJO phases 6,7 and 8 but the weather certainly did not reflect this. Sure it would be helpful as the MJO would certainly be a good driving force, but it isn't the be all and end all.

 

Models this morning, more or less the same as yesterday

GFS doesn't look as wet as yesterday with the Azores high getting in at times and the stormiest weather staying further north.

UKMO

Again looks further north, though wet and windy weather is still likely

GEM

Probably the most unsettled, though again the stormiest of conditions mid-week staying to our north.

Edit - ECM

ECM showing a fairly undulating pattern with another cooler shot at day7/8 as the deep low clears east.

Edited December 4, 2014 by Captain shortwave

[johnholmes]

Not wishing to be abrasive John but if you'd paid any sort of attention to the likes of Tamara, Chiono or Nick you'd understand that my comments were in context of any potential SSW later this month/early next. MJO phases 7 and 8 will potentially create the foundation for this, the MJO circle of doom will not. As far as I'm aware the basis for most of the cold LRFs is said SSW is it not? Hence you can see my logic for what I said......

Also if you'd quoted all of my post, other people may have noted the context of the part of my post you decided to highlight...

 

apologies, I did not set out to annoy you or mislead anyone. I rarely if ever repeat whole posts, no intention to mislead anyone.

My suggested outlooks are rarely, again if ever, for further ahead than 2 weeks or so. Again nothing yet suggests any marked change, rest assured when it seems a consistent signal I will post in here saying so.The latest NOAA output is shown below and nothing there YET suggests any deep cold in the next 2 weeks, short lived bursts of Pm possibly even Am but no long lasting deep cold yet showing

http://www.cpc.noaa.gov/products/predictions/814day/500mb.php

[Jason M]

Some subtle changes this morning in the longer term charts IMHO. I'm not a great fan of so called cold zonality because it usually becomes mild zonality very quickly! Noticeable this morning that increasing numbers of GEFS are indicating bigger pressure rises to our South and southeast in response to the lump of PV that looks like being sat to our North. The upshot of this is that wind flow starts to be steered more from a SW direction and we get TM air rather than PM.

It's not an overwhelming signal but it's something I noticed yesterday and is a slightly stronger signal this morning. The chart below illustrates where I think we could end up.

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=0&ech=204

It's a 380 hour chart that I've pulled out from the opp run, but there are plenty of other similar charts this morning within GEFS. There are still some northerlies shown but it's the trend away from this that I'm highlighting. Maybe Fergies comment the other day of a signal for warmer temps in week 3 or 4 is starting to be reflected.

Edit link is not the chart I wanted to post as ipad playing up, but just click via link on the 380 chart.

Edited December 4, 2014 by Jason M

[knocker]

A quick observation of the ECM take on the possible storm next week. At T144 the low is 936mb Iceland.  24 hours later it has nipped SE to just north of Scotland, filled to 973mb but has the potential for very damaging gusts in excess of 70kts for Scotland and N. Ireland. Hopefully this will not verify which is more than likely the case. A beady eye tho'. Oh, and also a potential for moderate snow levels in NW Scotland.

Edited December 4, 2014 by knocker

[terrier]

Looking at the model output this morning seems we have seen the low slightly downgraded. Also looks as we head later into next week we start to loose the polar maritime air and gets replaced with tropical maritime. So we should see temps recover to near average or slightly above. Which ties in with met outlook of a warm up into week 3/4.

[Paul]

Just thought I'd take a chance to show off our new model tracker this morning

 

Last 4 00z's from the ECM and GFS are shown - all for the 10th of December at 00:00 - just to see how they're both handling the potential storm next week. Fair to say there's a reasonable amount of uncertainty with it, with the GFS perhaps more consistent over the last few days, and certainly less progressive than the ECM has been.

 

GFS

 

ECM

[knocker]

Shameless advertising when there is serious business afoot locating the cold. Still very neat though.

Edited December 4, 2014 by knocker

[IDO]

Something is afoot!

Just had a browse through GFS ensembles and all bets are off from day 6.

 

 

 

That is the case but more worrying (for coldies) is if you fast forward to D16 and look at the ensembles then, they are very uninspiring:

 

 

A sign that the pattern is long term when even big difference at D6 translate to very little interest at D16.

 

The problem we have is fluid PV lower heights, the mean PV from week 2 heads from Canada to Siberia/N Pacific:

 

 

 

We also have the jet in ascendency in the Asia Pacific region; the control for instance: 

 

This prevents any mid-latitude disruption and keeps a relatively flat upstream wave pattern in week 2.

 

So in that synoptic very little chance of a HLB to develop. So any interest at D6 gets over run by the larger signal in week 2. The big question is what happens when that migration to the Siberian sector concludes? Will it set up shop or continue the mobile theme and move elsewhere?

 

As for ECM it's 8-10 day charts as expected this morning reverts closer to the more consistent GFS 8-12 day output: 

 

In the next 16 days it is all rather average fare for most (especially if you don't live on a mountain) and the London ensembles highlight the average temps for the next 16 days with very low risk of snow:

 

 

So with no strat to trop trigger likely before January and little trop wise to suggest blocking is on the way we continue to lower expectancies for the medium term. It does show that even when at the start of November it looked like potentially a promising 4-5 months of cold nothing can be taken for granted. November had a CET of +2.0c and December is already at +1.5c!

[Snowman.]

That is the case but more worrying (for coldies) is if you fast forward to D16 and look at the ensembles then, they are very uninspiring:

 

Meteociel_-_Panel_GEFS.png

 

A sign that the pattern is long term when even big difference at D6 translate to very little interest at D16.

 

The problem we have is fluid PV lower heights, the mean PV from week 2 heads from Canada to Siberia/N Pacific:

 

gensnh-21-1-240 (1).png gensnh-21-1-384 (2).png

 

We also have the jet in ascendency in the Asia Pacific region; the control for instance: gensnh-0-3-384.png

 

This prevents any mid-latitude disruption and keeps a relatively flat upstream wave pattern in week 2.

 

So in that synoptic very little chance of a HLB to develop. So any interest at D6 gets over run by the larger signal in week 2. The big question is what happens when that migration to the Siberian sector concludes? Will it set up shop or continue the mobile theme and move elsewhere?

 

As for ECM it's 8-10 day charts as expected this morning reverts closer to the more consistent GFS 8-12 day output: ECH1-240 (2).gif

 

In the next 16 days it is all rather average fare for most (especially if you don't live on a mountain) and the London ensembles highlight the average temps for the next 16 days with very low risk of snow:

 

graphe6_1000_306_141___Londres (1).gif

 

So with no strat to trop trigger likely before January and little trop wise to suggest blocking is on the way we continue to lower expectancies for the medium term. It does show that even when at the start of November it looked like potentially a promising 4-5 months of cold nothing can be taken for granted. November had a CET of +2.0c and December is already at +1.5c!

GFS is hinting at wave 1 towards the end of its output. Has been for the past 4 runs or so.

 

http://www.instantweathermaps.com/GFS/2014120400/NH_HGT_10mb_384.gif

http://www.instantweathermaps.com/GFS/2014120400/NH_TMP_10mb_384.gif

Edited December 4, 2014 by SN0WM4N