Model Output Discussion - cold spell to end Autumn

[MattStoke]

Shallower low on the 18z - 

Compared to the 12z - 

[Dean E]

14 minutes ago, karlos1983 said:

Yes they generally overdo snow accumulations by around an inch I’ve found 

nice one MWB, I will run down the street naked if that happens, (after the watershed) 

After the watershed, bet those 9pm temperatures will be chilly... 

[Had Worse]

3 minutes ago, Dean E said:

After the watershed, bet those 9pm temperatures will be chilly... 

More of a kink in the isobars indicating a trough too.

 

Edit Sorry selected wrong quote.

Edited December 3, 2017 by Had Worse

[feb1991blizzard]

1 minute ago, MattTarrant said:

This is a question for anyone. The alteration of initial data, do the first perturbations have closer initial conditions than say number 20 to the raw operational data? Or does it work in different manner? 

I don't know for definite but I read somewhere on the GEFS that 10 are tweaked to show milder outcome and 10 a colder one, I don't buy into that because they are global models, surely if one place is mild, it will be balanced out by somewhere being cold, I have noticed though when you go through them chasing an amplified pattern - the GEFS usually have a good number in the first few more amplified (particularly with an Easterly) don't know about the ECM as ive only been using them the last few days.

FWIW number 45 on the eps is the best over the widest area, upwards of 10 inches over the whole of the midlands, however, they are great fun but I really wouldn't be paying to much attention to these in a serious manner, one had 10inches sslap bang over Manchester, Manchester had 6 inches in Jan 10 but that was the most in the City Center since 1980-81 so theres basically zilch chance of that happening!!

[snowice]

4 minutes ago, MattStoke said:

Shallower low on the 18z - 

Compared to the 12z - 

Yes it was 770  last run

Edited December 3, 2017 by snowice

[Allseasons-Si]

At 96,there is a shortwave NW of Iceland,wasn't there on there 12z,what will that do to the run further on

gone on the next frame

Edited December 3, 2017 by Allseasons-si

[SMU]

T114 the best yet - all kinky

kink over the SE & snow piling into Scotland on this run

Also the -10c getting closer to London!

[Allseasons-Si]

Temps colder on this run compared to the 12z

Edited December 3, 2017 by Allseasons-si

[Mark wheeler]

[Day 10]

Scotland/Northern England is bloody bitter

[Dean E]

I wouldn't be surprised if a secondary low possibly developing on that Western Side of that Low over Scandi...

A lot of 'kinks' in those isobars are evident. Troughs and fronts evident too

 

[winterof79]

Much colder run already

[andymusic]

Wales gets hammered on the 18z run - nice to see again - again - again - again - might just happen you know

[Methuselah]

Not looking too bad at T+105:

[MattTarrant]

6 minutes ago, feb1991blizzard said:

I don't know for definite but I read somewhere on the GEFS that 10 are tweaked to show milder outcome and 10 a colder one, I don't buy into that because they are global models, surely if one place is mild, it will be balanced out by somewhere being cold, I have noticed though when you go through them chasing an amplified pattern - the GEFS usually have a good number in the first few more amplified (particularly with an Easterly) don't know about the ECM as ive only been using them the last few days.

FWIW number 45 on the eps is the best over the widest area, upwards of 10 inches over the whole of the midlands, however, they are great fun but I really wouldn't be paying to much attention to these in a serious manner, one had 10inches sslap bang over Manchester, Manchester had 6 inches in Jan 10 but that was the most in the City Center since 1980-81 so theres basically zilch chance of that happening!!

Interesting stuff. From some quick research, it seems that the ECM & GEFS use different manners for creating the perturbations. The GEFS uses something called 'Bred Vector' ( https://en.wikipedia.org/wiki/Bred_vector).

[SteveB]

1 minute ago, andymusic said:

Wales gets hammered on the 18z run - nice to see again - again - again - again - might just happen you know

And us in the West country.

[Man With Beard]

26 minutes ago, MattTarrant said:

It wasn't the control which showed this snow event. It was the 1st member. 

Oops sorry!!

[Methuselah]

First -10C 850s of the season to reach the sarf coast:

[Mokidugway]

3 minutes ago, andymusic said:

Wales gets hammered on the 18z run - nice to see again - again - again - again - might just happen you know

That's been pretty consistent ,must be near 10 meters of the stuff forecast for our Welsh friends 

[Guest]

WINTER 2017/18 REPORT No. 3 WITH DECEMBER 3rd INPUT

PART 2: As this is a long report I split it into to two parts. Part 1 was posted much earlier today – now buried on page 117! That focussed on a review of the model output over the last few days and looked ahead to the pattern changes expected later this week and beyond with a closer look at the jet stream and the temperature contrasts over North America and the adjacent Atlantic Ocean. I shall now focus on an updated analysis of the Arctic, European and Asian snow, ice and temperature profiles, with some of my regular features.

While I was writing part 1, the 12z model runs started to be churned out.  In general there has been a real improvement from last night’s 0z runs (from a coldies' perspective) on upgrading the forthcoming northerly as well as the period beyond that. As this thread will probably be knee deep this evening in analysing the latest output (if not the snow next week!), I shall leave this to our regular and occasional posters (for now). Here’s the deal – you concentrate on finding the right synoptics and I’ll search for some deeper cold!!!

In my first full report for this winter on November 22nd (see page 192 of the 1.9.17 model thread)  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 we might see some surprisingly low uppers – possibly -8s generally and perhaps nearer -10s in parts of Scotland.

One GFS run yesterday even showed several spots under -12s. This would be quite exceptional for several reasons – so early in the season, on a northerly being heavily modified after crossing well above average sea surface temperatures (SSTs) and from what “was” (see later) a much warmer than average source. There is a study which suggests that even with a warming Arctic and near record low sea ice extent that the amount of modification is actually quite limited – I’m not quite sure that I entirely agree with that.

Yesterday I replied to another post enquiring whether -12c 850s (if they verified) would be close to a record for Scotland this early in the winter. I looked at a number of early winter cold spells going back to 1878 and showed the 850 charts for the coldest periods during some of these spells (for those interested, see page 101 of this thread). This demonstrated just how rare -12 uppers are even in some of our severest early winter cold spells. Most of the UK’s lowest 850s come in on Polar Continental air streams with a much shorter sea crossing with the south-east usually (but not always) seeing the lowest values. I do still feel that sub -10s will be very difficult (but not impossible) to achieve from the forthcoming predicted northerlies. I would love to be proven wrong about this but widespread sub -8s will do nicely for now!

Arctic Sea Ice News and Analysis:

During last July the Arctic sea ice extent briefly hit a new low for that time of the year challenging the record lows seen in 2012. It reached its lowest point in mid-September when it was the fourth lowest on record. There was a limited recovery during October and early November with only 2012 and 2016 lower. The overall ice extent in late November again fell below the 2012 levels. It does appear to be gaining ground again during the last few days (still below 2012 levels) as can be seen in the charts below:

    Sea Ice extent Dec 2nd       Sea Ice Concentration Dec 2nd      Ice Extent Dec 2nd and 30 year Means             Ice Extent Nov 2nd over Last 6 Winters

                                                                     

Note: for some reason the first three charts did not update properly today but you can view them on the link below.

These charts shows the current extent of the sea ice as on December 2^nd (November 2nd for the last chart) and this is in relation to the 30 year means.

I believe that these particular charts will automatically update even after I’ve posted them!).

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/ 

The next monthly update is due out later this week and I shall probably post this separately shortly after it becomes available.                        

Arctic Current Sea Surface Temperatures (SSTs):

            SSTs  December 2nd         SST Anomalies December 2^nd

         

Source: NOAA Marine Modelling and Analysis Branch

The anomaly chart shows that there is a wide area of open water in the Arctic with well above surface temperatures. The SSTs need to be below the -1.5c threshold (the purple colour). Sea water will start to freeze when it is below -2c but that is for normal salinity. There is slightly lower salt content in the Arctic (mainly due to ice melt) and the threshold is nearer to -1.5c. There are some areas with SSTs well above freezing and the current anomalies are widely over 4c above average and up to 7c above in places although they have fallen very slightly in the last couple of weeks. These higher SSTs are a legacy of the 2015-16 winter when the Atlantic jet stream powered well into the Arctic for much of the first half of winter. This shifted much warmer than average currents right up to the edge of the ice sheet. This strong anomaly has persisted for 3 years and is exceptional and comes on top of the already generally warming Arctic. Unless the SSTs reduce substantially, the anomalies might be carried through to next summer and into a fourth winter.  There is a small area of the North Atlantic, mostly south-east of Greenland with a negative anomaly. SSTs have fallen in recent days in the open water north of Svalbard – I’ll pick up on this shortly.

British Sea Surface Temperatures:

                      December 2^nd                              November 21^st

                    

I was struck by how fast sea surface temperatures around the UK have fallen in recent days since my first winter report on November 21st. This is partly due to the recent Arctic outbreaks and the lack of strong south-westerlies as well as the normal steady decline from the summer to the winter months.

Svalbard 10 Day Maximum Temperature Forecast (December 3rd) :

The very good news is that the forecast temperatures for the Svalbard stations that I monitor are mostly forecast to fall somewhat in the next few days. I summaries the  D1, D5 and D8 values for each station with the previous values (from the November 25th forecast) immediately below. I also show the website link for each station so that you can view the full details.

Central/West Svalbard – Longyearbyen 28 m asl:   

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

December 3rd Forecast:   Dec 4th   -3c;  Dec 8th  -9c;  Dec 12th -9c;

November 25th  Forecast:   Nov 26th  -6c;   Nov 29th  -8c;   Dec 3rd  -6c.

North-West Svalbard – Ny-Alesund:  

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

December 3rd Forecast:   Dec 4th   -4c;  Dec 8th  -14c;  Dec 12th -11c;

November 25th Forecast:   Nov 26^th  -5c;   Nov 29^th -12c;   Dec 3^rd -10c.

Central South Svalbard – Sveagruva:   

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

December 3rd Forecast:   Dec 4th   -3c;  Dec 8th  -14c;  Dec 12th -15c;

November 25th Forecast:   Nov 26^th -10c;  Nov 29^th -15c;   Dec 3^rd -13c.

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 2 weeks ago but fell below freezing towards the end of November. They are continuing to fall back further and will not be far off their 30 year means for this time of year later this week. They look set to remain at these lower levels for at least the next 10 days. 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

Svalbard Airport,  Longyearbyen:

         Temps for last 30 Days                 Temps for last 13 Months                         

                 

  Temperatures, Precipitation and Wind for the last 13 months     

       

 Tabular view for temperature and precipitation per month

Months	Temperature				Precipitation			Wind
	Average	Normal	Warmest	Coldest	Total	Normal	Highest  daily value	Average	Strongest  wind
Nov 2017	-3.6°C	-10.3°C	2.5°C Nov 15	-13.4°C Nov 29	1.9 mm	15.0 mm	0.6 mm Nov 28	6.7 m/s	17.7 m/s Nov 11
Oct 2017	0.5°C	-5.5°C	7.7°C Oct 23	-5.8°C Oct 25	27.4 mm	14.0 mm	18.9 mm Oct 24	5.1 m/s	13.2 m/s Oct 23
Sep 2017	4.9°C	0.3°C	13.3°C Sep 26	-0.7°C Sep 1	20.8 mm	20.0 mm	5.3 mm Sep 19	4.9 m/s	16.3 m/s Sep 23
Aug 2017	6.1°C	4.7°C	11.6°C Aug 2	0.2°C Aug 27	16.2 mm	23.0 mm	7.4 mm Aug 29	4.7 m/s	14.6 m/s Aug 16
Jul 2017	6.9°C	5.9°C	13.1°C Jul 18	2.7°C Jul 4	20.4 mm	18.0 mm	6.5 mm Jul 14	5.5 m/s	13.6 m/s Jul 14
Jun 2017	4.6°C	2.0°C	9.0°C Jun 11	-0.2°C Jun 5	5.6 mm	10.0 mm	1.9 mm Jun 17	4.3 m/s	11.6 m/s Jun 29
May 2017	-3.9°C	-4.1°C	7.3°C May 31	-11.5°C May 9	5.3 mm	6.0 mm	1.7 mm May 15	4.1 m/s	13.9 m/s May 15
Apr 2017	-8.3°C	-12.2°C	2.9°C Apr 29	-21.3°C Apr 1	6.2 mm	11.0 mm	2.5 mm Apr 28	5.5 m/s	15.0 m/s Apr 5
Mar 2017	-11.8°C	-15.7°C	2.5°C Mar 14	-23.5°C Mar 18	15.8 mm	23.0 mm	2.8 mm Mar 7	5.6 m/s	15.6 m/s Mar 26
Feb 2017	-6.6°C	-16.2°C	5.9°C Feb 6	-21.3°C Feb 18	45.4 mm	19.0 mm	10.6 mm Feb 8	6.5 m/s	21.0 m/s Feb 21
Jan 2017	-10.3°C	-15.3°C	2.2°C Jan 16	-21.1°C Jan 31	24.6 mm	15.0 mm	8.7 mm Jan 19	6.3 m/s	17.9 m/s Jan 17
Dec 2016	-6.0°C	-13.4°C	4.8°C Dec 21	-18.5°C Dec 8	22.7 mm	16.0 mm	3.4 mm Dec 20	5.9 m/s	24.8 m/s Dec 29
Nov 2016	-0.7°C	-10.3°C	6.4°C Nov 8	-11.1°C Nov 27	58.0 mm	15.0 mm	41.7 mm Nov 8	5.7 m/s	16.5 m/s Nov 8

The second chart and the table show monthly means and actual highest/lowest temperatures recorded during the last 13 months. The chart has just been updated with the November 2017 figures when the monthly average temperatures were 6.7c above the 30 year mean.  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"                             Dec 3rd   1450                       Dec 3rd  0650                            Dec 2nd 1450                       Dec 2nd  0650   

           

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:

These were shown in part 1 of this report on page 117 of this thread.

Northern Hemisphere 850 Temperatures:

These were shown in part 1 of this report on page 117 of this thread.

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 18th to December 2nd but you can change the dates on the site and choose your own options. I also show the first and last charts below for this same date range.

a) Animated Northern Hemisphere Snow Cover Changes (updated by NOAA on December 2nd):

https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/nh/20171118-20171202

                December 2nd chart                                 November 18th chart

                             

 

b) Animated Europe and Asia Day Snow Cover  (updated by NOAA on December 2nd):

https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/ea/20171118-20171202

              December 2nd chart                                   November 18th 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 and small parts of central and western Europe (not just the mountainous regions) as well as to parts of the Middle East. Europe had been almost snow free. The snow cover over northern and central Scandinavia has now spread to much of the south too 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 northern and central Canada due to the mostly milder conditions there until recently.

Overall, the Arctic indicators show that there has been quite a cooling trend during the last few days. SSTs are very slightly lower, sea ice on our side of the Arctic has expanded (best viewed on the snow cover animated maps from the link above). Svalbard, north Asian as well as central and western European temperatures are falling. In fact a colder pool is starting to develop over western Europe. Asia, European  and Scandinavian snow cover has expanded. So, in the simplest terms, there are some better signs that air streams sourced from or travelling over the Arctic, Scandinavia and Europe are becoming better suited to delivering rather deeper cold. Much will depend on the ongoing synoptics and the broader patterns.

Finally, this is an exciting time with great potential for coldies with some fascinating model viewing continuing as we move further into winter. Next report (no. 4) probably next weekend if I have time.

 

 

 

Edited December 3, 2017 by Guest

[I remember Atlantic 252]

Just now, Ed Stone said:

First -10C 850s of the season to reach the sarf coast:

Yes, Ed, great run, thurs night, through to Saturday, Cheshire Gap chances, cold air reaches us all, midnight Thursday night into Friday

[SMU]

Perfect allignment of the cold so far brings a second bout of -10c over the UK

how close will the slider get....

[Ukwoody]

3 minutes ago, Ed Stone said:

First -10C 850s of the season to reach the sarf coast:

I can see the -10  but how do you work out where the 850 is please??

[andymusic]

2 minutes ago, Mokidugway said:

That's been pretty consistent ,must be near 10 meters of the stuff forecast for our Welsh friends 

Got my husky at the ready - MUSH!!!!!!!!!

[Dean E]

As @Steve Murr alluded to as well, there are many kinks in the flow. Take this with a pinch of salt for now, but in higher res, the 18z +102hr shows a small low forming and moving through the heart of the UK, exiting the south coast..

Edited December 3, 2017 by Dean E