Model Output Discussion 01/09/17

[Frosty.]

Overall I'm very impressed with the latest model trend towards even colder weather from the north as we go through next week with a real arctic wintry flavour to the uk weather, especially to exposed northern and eastern areas with showers becoming increasingly wintry with snow in places, especially on hills and frosts becoming widespread with icy patches following late showers..I couldn't ask for more really considering its still autumn for almost another week..let the good times roll!

[karlos1983]

That post is worth linking, very interesting read, you have to appreciate anyone taking the time to come to these conclusions. Hats off.

 

[stodge]

Afternoon all

I'd argue the one thing we don't want to see is a warming from the Eurasian side as the PV will then consolidate over the Canadian side.

More excellent model output this morning for those not looking for blowtorch SW'lies. I do think the final position and orientation of the HP has to be resolved. The GFS 06Z OP holds the HP close to the British isles before retrogression begins while ECM begins retrogression much earlier.

[Snowy L]

50 minutes ago, stodge said:

Afternoon all

I'd argue the one thing we don't want to see is a warming from the Eurasian side as the PV will then consolidate over the Canadian side.

More excellent model output this morning for those not looking for blowtorch SW'lies. I do think the final position and orientation of the HP has to be resolved. The GFS 06Z OP holds the HP close to the British isles before retrogression begins while ECM begins retrogression much earlier.

Important not to look at the temperature graphs when trying to see where the vortex is. The warming is coming from Asia, but the vortex is being pushed into Eurasia by high pressure from the Alaskan side.

[booferking]

CFS takes the blocking to a new level next week the bar is set let's see what the 12z bring to the table.

Edited November 25, 2017 by booferking

[Dennis]

AO and NAO latest

[terrier]

Well just got home from work and read back some great discussion on the output. Think we could see some Stella charts a little later. Gfs ecm ukmo all with a cold outlook. The only slight gripe I would have is can’t really see much in the way of snow away from coastal areas and hills. But as ever let’s see what this evenings output has to say. Happy hunting folks 

[Guest]

WINTER 2017/18 REPORT No. 2 WITH NOVEMBER 24th INPUT

In my first report (on Wednesday – see page 192) I focussed on some of the reasons for the lack of any decent cold uppers. I looked at the current temperature profile of the Arctic. The exceptional relative warmth there is very worrying and making it that much harder for the UK to tap into a deep cold source. I felt that we would need a sustained and direct Arctic flow to enhance our chances. Several of the more recent model runs have indicated that this might be possible suggesting rather lower 850s – still nothing exceptional but seemingly going in the right direction.

I concluded that I would be looking out in the models for the Arctic airstream to veer slightly more into a north easterly quarter in order to drag down a colder pool into Scandinavia and/or Europe and this in turn might feed into the UK. Yesterday’s GFS and ECM 12z runs and last night’s GFS 18z run hinted at this possibility.

On Thursday, I posted some comparisons between the current type of set up and those in the early stages of the epic 2010 cold spell (see page 199). The really significant cold then came in on a Polar Continental airstream sourced initially from the Arctic and later from western Russia and Siberia. The 2010 event was exceptional and the earliest severe winter cold for 120 years. There was a substantial pool of deep cold (surface and uppers) to tap into and it may be very difficult to see a repeat of this even with very similar synoptics but I’ll examine what might be possible.

I shall briefly update the Arctic indicators (slightly better news on Svalbard forecast temperatures) and then examine the current and predicted temperature and snow cover conditions in Siberia, Russia, Scandinavia and Europe.

Arctic Sea Ice News and Analysis:

In the last two days the overall ice extent for late November has hit a new record low, actually below the previous record low levels of 2012 as can be seen in the charts below:

These chart shows the current extent of the sea ice (as on November 24th) in relation to the 30 year means.

     

Source: National Snow and Ice Data Center (NSIDC)

Here’s the link for the latest monthly report (from November 2^nd) and the current charts:

http://nsidc.org/arcticseaicenews

Arctic Current Sea Surface Temperatures (SSTs):

It is too soon to update these, so please refer to the charts I posted in my long report on page 192.

Svalbard 10 Day Maximum Temperature Forecast (November 25th) :

The good news is that the forecast temperatures for the Svalbard stations that I monitor are "mostly" (for day 5 and day 8 several degrees lower than those forecast just 2 days ago. I summaries the D1, D5 and D8 values for each station with the previous values (from the November 22^nd forecast) shown immediately below. I also show the website link for each station so that you can view the full details and monitor future changes.

Central/West Svalbard – Longyearbyen 28 m asl:   

http://www.yr.no/place/Norway/Svalbard/Longyearbyen/forecast.pdf

November 25^th Forecast:   Nov 26th  -5c;   Nov 29th  -9c;   Dec 3rd  -4c.

November 22^nd Forecast:   Nov 23rd  -6c;   Nov 27th   -7c;   Dec 1st  -4c.

North-West Svalbard – Ny-Alesund:  

http://www.yr.no/place/Norway/Svalbard/Ny-Ålesund/forecast.pdf

November 25^th Forecast:   Nov 26^th  -5c;   Nov 29^th -17c;   Dec 3^rd -8c.

November 22^nd Forecast:   Nov 23^rd  -6c;  Nov 27^th -10c;   Dec 1^st -5c.

Central South Svalbard – Sveagruva:   

http://www.yr.no/place/Norway/Svalbard/Sveagruva/forecast.pdf

November 25th Forecast:   Nov 26^th -9c;  Nov 29^th -14c;   Dec 3^rd -9c.

November 22nd Forecast:   Nov 23^rd -5c;  Nov 27^th -12c;    Dec 1^st -9c.

Please note that the links above will update automatically at frequent intervals throughout the day. They are the Norway met office’s predictions. We need to be aware that these are only a forecast that is subject to change and I am told that the Arctic surface temperature forecasts are not completely reliable even at quite short range. 

The temperatures were above freezing for a week or so earlier this month but they have fallen well below freezing during the last few days and are set to remain at these levels or fall further during the next 10 days. Nevertheless, the temperatures are still above their 30 year means. To put the above figures into context, here is a link to the main Longyearbyen site:  

http://www.yr.no/place/Norway/Svalbard/Longyearbyen/statistics.html

This shows monthly means and actual highest/lowest temperatures recorded during the last 13 months. Svalbard has been seeing “maximum” temperatures often running at 5c to 10c above their long term average throughout most of the last 4 years. This is reflective of the warming Arctic and the near record low sea ice cover.

European 2m Surface Temperatures:

             Current "live"                             Nov 25th 0650                        Nov 24th   1450                        Nov 24th  0650                        Nov 23rd 1450

      

Note that it is important to allow for min/max temps when comparing the charts. The 0650s are usually close to the minimums and the 1250s are usually close to maximums.

Northern Hemisphere Surface Temperature Charts:

a) Current – 0100 on 24/11/17:

  GFS 24/11/17  0100 18z T+6

 

 b) Cross Model Comparison for 0100 on 1/12/17:

      GFS  Nov 25^th 6z T+138            GEFS ens mean Nov 25^th 0z T+144               GEM Nov 25^th 0z T+144                      NAVGEM  Nov 25^th 0z T+144       

                                                

Note: I adjusted the chart times on the GFS and JMA to match the correct forecast time.            

If you compare the current and day 6 charts the main area of Northern Hemisphere deep cold remains over Siberia, with less widespread and less intense cold in North America. There is little change over Greenland and in most of the Arctic Ocean. 

Northern Hemisphere 850 Temperatures:

a) Current – 0100 on 24/11/17:

    GFS 24/11/17  0100 18z T+6  

     

b) Cross Model Comparison for 0100 on 1/12/17:

        GFS  Nov 25^th 6z T+138          GEFS ens mean Nov 25^th 0z T+144      UKMO  Nov 25th 0z T+144                ECM  Nov 25^th 0z T+144  

                                          

       GEM Nov 25th 0z T+144               NAVGEM  Nov 25th 0z T+144             JMA Nov 24th 12z T+156   

                        

Note: I adjusted the chart times on the GFS and JMA to match the correct forecast time.         

I show the charts for December 1st as this should be after the second incursion of Arctic air around midweek and with the first signs of possible veering of the air stream. With so much uncertainty, I do feel that going any further into FI will not be useful.  The charts are broadly similar but there is quite a variation on the depth of the cold. If we are to see a more polar continental air stream, then it is likely that more of the Siberian cold would move towards us. How far and how deep is still very uncertain.

Northern Hemisphere, Asian and European Snow Cover:

I show animations for snow cover and sea ice changes. These are produced by the National Ocean and Atmospheric Administration (NOAA).  When you go to their site you can change the date range and go back over 10 years. You can change the speed and pause on any particular day. These are brilliant, very informative charts and great to play around with. I’ve re-set the links below to show the last 2 weeks from November 10th to November 24th but you can change the dates on the site and choose your own options.

a) Animated Northern Hemisphere Snow Cover Changes (updated by NOAA November 24th):

https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/nh/20171110-20171124

              November 24th chart:                               November 10th chart:

                                        

b) Animated Europe and Asia Day Snow Cover  (updated by NOAA November 24th):

https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/ea/20171110-20171124

           November 24th chart:                                  November 10th chart:

                         

North Asian snow cover has been well above average since mid-October. During the last 2 weeks it has grown steadily and expanded southwards and westwards into Eastern Europe as well as the Middle East. Europe had been almost snow free. Northern and central Scandinavia is snow covered and this has been steadily spreading southwards in recent days (note that the high central plateaus usually have pretty complete snow cover for most of an average winter). Meanwhile, the extensive snow cover over the northern USA has receded and is mostly confined to Canada due to mostly milder conditions there recently.

Overall, it is not difficult to see why it is so hard to achieve prolonged cold and wintry weather from an Arctic airstream and there is a lack of cold available over much of the northern hemisphere. Siberia and most of north Asia does currently have a decent cold pool at the surface and uppers. We’ll need the right synoptics to get this to move towards the UK. The models showing a long fetch direct north-north-easterly could import this cold via Scandinavia. Alternatively, if the airstream veers further east with a flow established from the north-east or east we may be able to establish a deepening European cold pool and then tap into that. This is what happened in 2010 (as well as for many other prolonged cold spells) and does seem to be the best chance of importing much deeper cold air with far less modification over land.

My analysis does not make any assumptions on what will happen (the models may continue to flip flop) and I merely show what we might need to achieve a memorable early winter cold spell based on current conditions. If the “generally” predicted  (by most recent model runs) synoptic pattern is sustained for a prolonged period then at least we have a chance. I shall review some of these indicators in a week or so and check on the progress (or lack of it) and produce another updated report then. Meanwhile, an exciting time with great potential for us coldies and surely a really fascinating period for all weather enthusiasts and professionals.

Edited November 25, 2017 by Guest
Check links and charts + spelling corrections

[Daniel*]

9 minutes ago, terrier said:

Well just got home from work and read back some great discussion on the output. Think we could see some Stella charts a little later. Gfs ecm ukmo all with a cold outlook. The only slight gripe I would have is can’t really see much in the way of snow away from coastal areas and hills. But as ever let’s see what this evenings output has to say. Happy hunting folks 

Looking at the fax charts for early next week it does not scream bone dry, moisture signal is there not isolated either. Scotland may see an organised period of snow quite snowy for Scotland it looks into next week, plenty of troughs and possible disturbances moving south in a clearly quite unstable northerly airstream. 

Edited November 25, 2017 by Daniel*

[karlos1983]

This is not good, 12z still to roll out and I’ve got no likes left  

So far so good. Lee having nightmares that this shortwave won’t eject cleanly

Edited November 25, 2017 by karlos1983

[Singularity]

12z   06z 

Trying to take it easy but can't resist showing the slight increase in Arctic heights plus marginally increased coverage of Greenland by the yellow shading 

[Derecho]

Sorry, posted the previous message in the wrong thread!

Back on topic, the 12z has a slightly negative tilt (108h) but pretty much identical

06z                                                            12z

 

Edited November 25, 2017 by Quicksilver1989

[karlos1983]

*keep* no idea who Lee is.

+96 and the cold air has arrived! 

would imagine the snow showers will be packing into northern Scotland 

[Met4Cast]

Very slightly more amplified GFS 12z so far, nothing major but every little helps, the further North the high can get, the better for down the road. Fantastic Jet Stream profile 

[Mucka]

2 minutes ago, Daniel Smith said:

Very slightly more amplified GFS 12z so far, nothing major but every little helps, the further North the high can get, the better for down the road. Fantastic Jet Stream profile 

Yes marginally better in every respect early doors than the 06z so should be a good run.

Slightly better ridge, slightly stronger arctic high, better upstream amplification, slightly better undercut, slightly better ridging to the East. 

 

Edited November 25, 2017 by Mucka

[Pembroke Dangler]

-10 line moving into Scotland and widely -8 at 850 if the precipitation hits at night anywhere could have snow down to sea level 

[Ice Day]

Another good run so far, virtually every frame has been an improvement versus the same time on the 6z, which is good to see.  The east would surely be getting some snow at 114?

 

Just great charts to herald in the start of winter proper

[karlos1983]

UKMO needs to get on the naughty step though 

It’s ok, but it’s not quite carling. 

Edited November 25, 2017 by karlos1983

[Singularity]

Trust UKMO to be difficult with that little secondary low!

  
GFS meanwhile is of great interest yet again, as the focus of low heights is held further west in Canada due to less development of the LP on the eastern flank of the vortex lobe. Could do with that low just SW of Svalbard dropping down across Scandinavia. At +138 it seems to be trying to do that...

[northwestsnow]

8 minutes ago, Pembroke Dangler said:

-10 line moving into Scotland and widely -8 at 850 if the precipitation hits at night anywhere could have snow down to sea level 

Looks bitterly cold that chart but quite slack so limited snow imo...frost on the other hand will be starting very early...like 5pm

[Mucka]

5 minutes ago, northwestsnow said:

Looks bitterly cold that chart but quite slack so limited snow imo...frost on the other hand will be starting very early...like 5pm

Don't worry mate, this run should only go one way once that Greenland trough drops. 

Incredible block developing.

Edited November 25, 2017 by Mucka

[northwestsnow]

The normally reliable ukmo model seems to be all over the place at the moment...the 00z run was a lot better than the 12Z!!!

[karlos1983]

This is developing very nicely indeed. Could be a jaw dropper. Yes “Jaw”

[Met4Cast]

Just now, northwestsnow said:

The normally reliable ukmo model seems to be all over the place at the moment...the 00z run was a lot better than the 12Z!!!

And the 00z was a lot better than yesterdays 12z. 00z runs seem to be inline with the other models whilst the 12z UKMO run seems to throw a wobbler. Very strange

[Ice Day]

Certainly looking a bit different at 168.  The cold uppers have left us but maybe more to come from the north/north west?