Model output discussion - the beast arrives

[SMU]

1 minute ago, MattTarrant said:

Very GOOD ICON RUN! 

I shouldn't post a snow chart but hey we have a right to be excited. 

 

Is that ICON 12z?

[Summer Sun]

12z ICON keeps it all snow until 1pm on Friday for virtually all of the south and south-west

Could be a major event this would significant snow and blizzards possible

Edited February 25, 2018 by Summer Sun

[MattTarrant]

1 minute ago, Steve Murr said:

Is that ICON 12z?

Yep . Sorry poor cropping of image on my part haha. 

Edited February 25, 2018 by MattTarrant

[Guest]

2 minutes ago, Alderc said:

Why the scepticism? In Dec 10 the temp rose here from -7c under endless blocked and cold conditions to +10c in less than a day. With a NNE trajectory the cold could be brushed aside very rapidly. That being said still plenty to play for. 

It's just against the grain at the moment with other models now preferring the low to stall to the SW before being pushed east. NMM doesn't follow that script.

[Summer Sun]

ICON going less cold in the later stages

12z

00z

 

[Derecho]

6 minutes ago, Summer Sun said:

12z ICON keeps it all snow until 1pm on Friday for virtually all of the south and south-west

Could be a major event this would significant snow and blizzards possible

Yup ICON shows a very complex evolution and I would agree that it would all fall as snow upto 1pm Friday, surface cold is pushed northwards so would perhaps turn to sleet or freezing rain in the far south, but staying as snow elsewhere with a weakening weather front as the uppers mix out.

Would be quite the event for many if that came off.

Edited February 25, 2018 by Quicksilver1989

[Guest]

ARCTIC TEMPERATURE, SEA ICE AND SEA SURFACE TEMPERATURE PROFILES AND ANALYSIS

It's over 3 weeks since I last produced one of my Arctic reports and this one is overdue. I have been distracted by certain other events! I will include my usual features as well as look for anything going on up in the Arctic that might have some relevance in terms of the broader picture going forward. I will start off with a brief review of the latest prospects going forward before I focus on the Arctic.

Renewed Uncertainties in the Day 5 to Day 10 Term Model Output:  

Well they say that 24 hours is a long time in politics and at times like this, it certainly applies to the model output and even every 6 hours for those who scrutinise every GFS run! Even while I was writing out yesterday's long report about the longevity of this cold spell, many of the other models were starting to align rather more to the GFS solution with a faster breakdown. The Met Office still retain their very cold outlook and many on here will be hoping that they stick to this. Their 0z UKMO output, unfortunately only goes up to day 6 and does show the LP making slight inroads into the block and slowly pushing northwards the coldest 850s at day 5 and day 6. Their charts have been posted a few times already, so I won't repeat them here now. There is much uncertainty and this has been alluded to by some posters. I particularly liked @stodge's summary this morning (on page 157).   EDIT: I see that the MetO updates have changed slightly whilst I was writing this report.

I am very conscious that this thread is currently running at an extreme emotional fever pitch and that some will be very disappointed if things go pear-shaped whilst a few others will welcome it. I will attempt to inject some balance into this post and I do not wish anyone to be too gloomy or too excited. I "may" have been a little too bullish in my last post (now buried on page 140 of the 20.2.18 MOD thread). I gave valid reasons and evidence for my views and these "might" still hold sway during the critical period through next weekend. Some are saying that the SSW (sudden stratospheric warming) impact was too strong and progressive and everything is pushing westwards far too quickly. This takes the block towards Greenland and the -NAO also becomes west based with HP in the west Atlantic. This would allow LPs and warmer air to advance from the south-west. How far and how quickly is what the models will struggle with for several more days at least and there may well be some significant swings. I still see that the main arm of the jet steam is shown to continue well to the south of us and mainly on a a fairly straight west to east trajectory. There are just a few small break away streaks that the GFS push towards the UK at times but no real energy to push those LPs right through us. To counter this we have further impacts from the stratosphere with another warming taking place right now. This second warming "should" reinvigorate the flow reversal. The very much weakened Canadian vortex lobe is being pushed across to the Siberian side and this is shown in most of the model output. Here are the GEFS panels from their 6z run (current at the time of writing):

                               Now                                                          Day 3                                                        Day 6                                                        Day 9                                                       Day 12

          

Right now it is still the initial SSW impact that is displacing the Canadian vortex. By day 3 it's shifting across the pole and by day 6 it has found its new home over Siberia. By day 9 (roughly when we might expect some impacts from the second warming) there starts to be a much wider spread of outcomes but most ensemble members still show the vortex over Siberia and many have intensified it and some show it spreading south-westwards towards Europe again. By day12 things become very uncertain with a much wider range of outcomes. Several members show part of the vortex back in Canada but most just show a spread over Asia, Siberia and towards Europe. A few make it all the way through Europe and one (perturbation 14) has it engulfing the UK. This is all far too uncertain at this distance. We simply do not know how this will pan out. The secondary warming impacts might not follow the initial one at all; it might disrupt the current reversed pattern and/or re-set the blocking in a different place; it might enhance or re-invigorate the current blocking. We'll need to rely on the strat guys to keep us fully updated on this fascinating and highly unusual period.  

Back to this week. The deep cold is just about to invade us from the east. many of us will see some significant snowfall and with the very low uppers, sub zero surface temps and extremely low dew points, it will be the dry and powdery stuff which will all settle and drift in the biting winds. Then we have the critical period at the end of this week. We might see a very messy break down; it might be temporary; it might be that the deep cold cannot be displaced at all; it might be pushed northwards but then it returns very rapidly southwards. There may be a blizzard, there may be an intensification of the shower activity and there may even be a period of freezing rain. It will be absolutely fascinating to watch this all unfold and even the nowcasts might get this one quite wrong such is the nature of the opposing forces. Now on to my "more" routine Arctic report.

Current and Short Term Arctic and Northern Hemisphere Temperatures:

With so much uncertainty, i will not go beyond day 5, which is the critical period anyway and subject to considerable change. There is pretty good consistency up until then. Remember, I'm focusing on the Arctic in this particular report, so I'll hardly comment on the UK temperatures which are being heavily covered in other posts anyway.

2 M Surface Temps:  GEFS 6z T+0 0700 Sunday, Feb 28th                 850 Temps:  GEFS 6z T+0 0700 Sunday, Feb 28th

                                                            

There is plenty of evidence of the impacts of the SSW. Much of the cold is being displaced towards the middle latitudes. There is currently a wedge of surface temps in the 0c to 4c band extending right up towards the North Pole. The lowest  values are over Greenland, Siberia, Russia, stretching towards Europe ans also in north-east Canada. The distribution of 850 temps is quite similar to the surface temps with the highest values through Arctic and across the pole and the lowest value in the long lobes over Canada and Siberia, Russia and Europe.

2 M Surface Temps:  GEFS 6z T+120 0700 Friday, Mar 2nd                 850 Temps: GEFS 6z T+120 0700 Friday, Mar 2nd 

                                                         

By day 5 we see that Greenland and north-east Canada have warmed up with the cold transferring slightly to north-west Canada but mostly across the pole with the cold over Siberia intensifying. This does very much follow the displacement of the Canadian vortex that I referred in the opening part of this post. There is a similar transfer of the lowest 850 temps with the lowest values stretching from Siberia to northern Russia. The deep "upper" cold over north-eastern Europe and northern Scandinavia is shown to weaken slightly but there remains an areas of sub -16s and an unusual band of sub -8s to sub -12s stretching westwards from eastern Europe, through northern Britain and way out beyond the mid Atlantic. Again this is reflective of the pattern reversal.    

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 through November and December with only 2016/17 lower at that stage of the winter.  This trend continued throughout January and into early February but just in the last couple of weeks, there has been a small spike with the current recovery just slightly above 2016/17 again. With the SSW displacing much of the Arctic cold right now this might change again. All in all, a very worrying trend with such low ice build up as can be seen in the charts below:

                                  

Source: National Snow and Ice Data Center (NSIDC)

The first three charts show the current extent of the sea ice as on February 24th  (although I believe that these particular charts automatically update even after I’ve posted them). This is in relation to the 30 year means. The last chart which compares each of the last six winters to the mean is only updated monthly and goes up to February 5th. The latest monthly update (for February) was published last week and makes a fascinating read. Please use the link below which also shows all the charts plus much more:

http://nsidc.org/arcticseaicenews/

Arctic Current Sea Surface Temperatures (SSTs):

                   SSTs  February 24th                          SST Anomalies February 24th

        

Source: NOAA Marine Modelling and Analysis Branch

The anomaly chart (on the right) shows that there is a wide area of open water in the Arctic with well above average sea surface temperatures. The SSTs need to be below the -1.5c threshold (the purple colour on the left chart). 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 8c above in places. These anomalies are actually very slightly less than they were a month ago. Unfortunately, although the SSTs have fallen slightly in the last couple of weeks (the normal seasonal decline through the winter months), they are still quite extreme. 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 that 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 just south and south-east of Greenland with a negative anomaly.

 More on Arctic Temperatures - a Brand New Site:

I must thank @ghoneym who came across an excellent new site on Arctic temperatures and referred me to it only this morning. This site is being created by Zachery Labe and is still under construction. It is an educational site with free access and no copying restrictions, so we can all refer to it. Here is the link:  http://sites.uci.edu/zlabe/arctic-temperatures/

Zachery has an impressive CV and there are links to many of his papers. I really look forward to watching this site develop. I shall dig out a several of his fascinating charts right now:  

             

The first chart shows the 2018 2m surface temps compared to the 1958 to 2002 mean average across all of the Arctic from 80N to the North Pole.The other charts speak for themselves and show up the extraordinary increase in the rate of warming during this decade against a back drop of rapid rises during the last 30 years.

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

The forecast temperatures for the Svalbard stations that I monitor are currently above freezing with some rain! They are set to fall rapidly during the next few days and this is for the same reason that I demonstrated earlier - the transfer of the lowest temps from the Canadian side to the Russian side of the Arctic due to the SSW. Once that change is complete, we may well see Svalbard temps rise again. I summarise the  D1, D5 and D9 values for each station 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

February 25th Forecast:   Feb 26th +3c;  Mar 2nd  -11c;  Mar 6th -13c;

North-West Svalbard – Ny-Alesund: 

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

February 25th Forecast:   Feb 26th +3c;  Mar 2nd  -14c;  Mar 6th -16c;

Central South Svalbard – Sveagruva:  

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

February 25th Forecast:   Feb 26th +2c;  Mar 2nd  -16c;  Mar 6th -19c;

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.

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 Temperatures for the Last 30 days          Svalbard Airport,  Longyearbyen Temperatures for the Last 13 months    

                                                                                     

 

Svalbard Airport,  Longyearbyen Temperatures, Precipitation and Wind for the Last 13 months days

Months	Temperature				Precipitation			Wind
	Average	Normal	Warmest	Coldest	Total	Normal	Highest  daily value	Average	Strongest  wind
Jan 2018	-5.5°C	-15.3°C	6.0°C Jan 13	-19.2°C Jan 3	27.3 mm	15.0 mm	18.6 mm Jan 14	5.6 m/s	15.4 m/s Jan 17
Dec 2017	-4.9°C	-13.4°C	2.6°C Dec 20	-19.6°C Dec 30	16.6 mm	16.0 mm	5.7 mm Dec 21	5.9 m/s	18.9 m/s Dec 28
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

 

The last two charts/tables show monthly means and actual highest/lowest temperatures recorded during the last 13 months. This has just been updated with the January 2018 figures when the monthly average temperatures were 9.8c 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.

Overall, the temperature profile of the Arctic is extremely worrying.  The second lowest ice-build up on record (almost the lowest), record high sea surface temperatures with the anomalies going even higher in some parts and high temperatures around Svalbard.

I'll be back with some much shorter posts during this week focusing on the incoming cold.

Edited February 25, 2018 by Guest
Correct typos and check charts & links

[SMU]

If people remember my post from 2 days ago about the allignment of the upper air cold pool being closely linked with the final outcome for the low-

12z GFS alligns further south ( reflected over the UK with more isolines )

12z first

[Catacol]

No definitive answer provided by ICON - still absolutely touch and go. Best case scenario IMBY remains snow showers on Tues/Weds and then blizzard on Thurs/Fri with cold air hanging on. Worst case remains dry through Tues/Weds and then rain on Thursday night into Friday. Many scenarios in between.

You'll forgive me if I declare that if the dry to rain scenario comes to pass I am likely to shut down for the winter and retire until November such will be the disappointment. A background scenario like this that fails to deliver, after years of waiting, will be the end of me even given the potential chance for more snow down the line this month. Never ever contemplate a move to lowland SW England if you like opportunities for frost and snow.

Fingers crossed for a decent evolution this week and that I'll still be online come Saturday. :-)

[That ECM]

Ukmo t96. Block  north west looks stronger I think but I might just be willing it

[Frosty.]

Midweek is looking very pleasant on the Gfs 12z!..sub 505 dam anyone?

[SteveB]

2 minutes ago, Catacol said:

No definitive answer provided by ICON - still absolutely touch and go. Best case scenario IMBY remains snow showers on Tues/Weds and then blizzard on Thurs/Fri with cold air hanging on. Worst case remains dry through Tues/Weds and then rain on Thursday night into Friday. Many scenarios in between.

You'll forgive me if I declare that if the dry to rain scenario comes to pass I am likely to shut down for the winter and retire until November such will be the disappointment. A background scenario like this that fails to deliver, after years of waiting, will be the end of me even given the potential chance for more snow down the line this month. Never ever contemplate a move to lowland SW England if you like opportunities for frost and snow.

Fingers crossed for a decent evolution this week and that I'll still be online come Saturday. :-)

I feel your pain Catacol, But I think there will be plenty of chances this coming week.

We have this tomorrow

This Tuesday

 

 

 

[Summer Sun]

First of the 12z's complete ICON is bitterly cold until the end of the week with a significant snow event for the south and south-west still very possible late Thursday and into Friday

Less cold air then arrives through the weekend and into the 1st full week of March but ground temps still on the chilly side

[WalsallWeather123]

ARPEGE 12z has rain for far south, then snow further north. However the precipitation is much further east compared to ICON. Still a lot to be resolved.

[Mike Poole]

UKMO looks quite a bit further south with the low at T96

Edited February 25, 2018 by Mike Poole

[Rayth]

Well no matter what , we have seen unprecedented things in the past two weeks and that’s not just these stellar Synoptics for this week , a @Tamara ramp of a GFS 12z , posters basically hacksawing the country in half North/South causing a netweather independence referendum and now @Catacol’toy throwing’ even though our nation won yesterday for the first time since 1962/63 ( see what I did there)

anyway the beast was nailed by the models and now I’m facing 5 weather warnings including an amber ! 

Stay safe guys !

Mother Nature sharpens her teeth this week 

[inghams85]

The speed of retrogression lots slower around Greenland and it's baby steps to the MOGREPS solution I spoke about yesterday. Things are getting there people.

[SMU]

5❄️❄️❄️❄️❄️

from UKMO 120

blizzards ! no rain anywhere

Edited February 25, 2018 by Steve Murr

[stokepa31]

3 minutes ago, Mike Poole said:

UKMO looks quit a bit further south with the low at T96

Agreed, Greenland high is beefing up a little and closing the gate a bit

[inghams85]

2 minutes ago, Steve Murr said:

5❄️❄️❄️❄️❄️

from UKMO 120

blizzards ! no rain anywhere

Yes Steve, things getting very interesting again were seeing a slow shift towards what was expected 3 days ago

[Ayrshire weather]

On a more enjoyable note this weather event has improved my health... ? 

I now get at up at 6am every morning before I was very lazy so just shows how enjoyable weather can be and how much excitement has came with this beast! 

[Catacol]

3 minutes ago, inghams85 said:

The speed of retrogression lots slower around Greenland and it's baby steps to the MOGREPS solution I spoke about yesterday. Things are getting there people.

Which is, of course, what it is all about. Slower retrogression and we cash in through to next week. I hope snow comes soon so that next weekend looks less relevant. It's a real pity that all the focus is on the sudden sense of a quick breakdown rather than snow that might be around the corner. 

This is going to run and run though - stamina required.

[inghams85]

Remember the MOGREPS solution of a low skating along the channel. Look at the UKMO 144. We're nearly there. The MET have called this very well so far

[That ECM]

4 minutes ago, Steve Murr said:

5❄️❄️❄️❄️❄️

from UKMO 120

blizzards ! no rain anywhere

Steve, please explain why there would be no rain anywhere. Genuine question.

[MattTarrant]

5 minutes ago, Steve Murr said:

5❄️❄️❄️❄️❄️

from UKMO 120

blizzards ! no rain anywhere

Look at the 850hPa...