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Short range model discussion - into 2018

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3 minutes ago, johnholmes said:

Nothing new in that, if any read my comment in the main thread about cold blocks and how they are often difficult to shift

Read that and quite interesting. How about when the atlantic air incoming is itself fairly cold, though? Although zonal is not sort after in the other thread, I can't personally help but being a little impressed at how fortuitous the UK is being with modeled colder zonal/PM. I remember reading something pre winter regarding a correlation between low solar/EQBO in this regard.

 

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I honestly have no knowledge of what you ask about. I would think that less mild air in the Atlantic would find it slightly easier than 'real' mild air to make progress but I don't have any memory of any empirical notes about this when I was working. 

The reason for that is that mild air tends to slide up the cold air it comes against it, large temperature differences making it less dense. With relatively coldish air then there would be less temperature contrast and thus the incoming air would not possibly be displaced over the lower cold air to the same extent.

hope that makes sense?

 

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Just now, johnholmes said:

I honestly have no knowledge of what you ask about. I would think that less mild air in the Atlantic would find it slightly easier than 'real' mild air to make progress but I don't have any memory of any empirical notes about this when I was working. 

The reason for that is that mild air tends to slide up the cold air it comes against it, large temperature differences making it less dense. With relatively coldish air then there would be less temperature contrast and thus the incoming air would not possibly be displaced over the lower cold air to the same extent.

hope that makes sense?

 

Yeah that's what I was assuming as well. Thanks.

 

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Adding to my post earlier

I spent some time looking more closely at the isobars on each of the charts, where has the surface air originated from?

Using the Met O model and after T+72 it is coming from a pretty southerly direction, like the Mediterranean. So whilst the idea of a settled rather cold spell is unlikely to change a great deal for the 3-8 days or so period. The often problem with an easterly is already showing. Air not from eastern Europe/Russia/Scandinavia but southern Europe.

So for really cold air the ridge needs to be drawing surface and upper air from northern Europe. A game of wait and see as it is not doing that for long at the moment.

 

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The issue this year is the lack of real deep cold out east some parts of eastern Europe were seeing 850's down to -20 in early Jan last year this year they could hit +4 in some parts

2016

gfs-1-54.thumb.png.30883a9fc6f3c94e835db301056931de.png

2017

gfs-1-541.thumb.png.5c3b2d475c68912c5e658df74591c5c1.png

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Yes it's quite interesting. On the gfs 06 for midday Sunday the surface flow over England south of the Midlands originates in North Africa.

gfs_slp_uv10m_europe_14.thumb.png.82b9c8e3ec9c2ebddb92d1fb50eecf05.png

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1 minute ago, Summer Sun said:

The issue this year is the lack of real deep cold out east some parts of eastern Europe were seeing 850's down to -20 in early Jan last year this year they could hit +4 in some parts

2016

gfs-1-54.thumb.png.30883a9fc6f3c94e835db301056931de.png

2017

gfs-1-541.thumb.png.5c3b2d475c68912c5e658df74591c5c1.png

As someone who lives in the area impacted by that event last January, I can say it came in fairly quickly and it wasn't overly cold prior to that. -18 and heavy snow for several days.

My general point is that people tend to think that cold in Eastern Europe just plonks itself there at the start of winter, just waiting to be tapped into. The truth is it doesn't. It comes and goes, just like other places. Sometimes it can stay longer and you will always have the 1995/1996 almost 5 months winter, and a few others less severe, but prolonged cold none the less. Mostly, it does just come and go, for varying degrees of time.

 

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@johnholmes posts are like finding a water fountain whilst lost in the desert. 

Thank you so much John not only for your knowledge but your style of explaining which is so much easier to follow than many others. 

The almost emotional attachment people are putting on computer models as if they are living beings is bizarre. 

meantime in the actual models for this weekend here in east central Scotland  we are looking at a max of - 3 and a low of - 10 with uppers of - 8 that may just produce enough showers that create snowfields inland that freeze leading to a decent period of wintry weather. Whatever uppers are produced next week its going to be bitterly cold week in Scotland at the surface and a potential for freezing rain which we have already experienced this winter. 

 

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5 hours ago, johnholmes said:

Well shall we try and make some sense of how the models are treating things out to 72h and perhaps peeking out to 120h?

Below is the UK Met model output on Net Wx

https://www.netweather.tv/charts-and-data/met-office

We can use this and others I'll show to see how their model is dealing with the development/movement of the surface high and also at 500 mb, which is where the real work of forecasting occurs. Get that right and there is a good chance the surface will be near to what happens. Get it wrong then forget any prediction.

It does show the surface feature moving east, perhaps a shade NE comparing 00z with 12z yesterday. The upper trough, watch the 558 black line, has moved east and extended/sharpened somewhat, causing the surface ridge to be moved NE compared to the previous 12z issue. But remember this is partly sequential anyway, 12 hours further on, and to me it looks a reasonable prediction.

N

John, just want to say thanks for a sensible knowledgeable insight.  Still a bit over my head but so much easier to understand then in the other thread - which I have stopped visiting due to the nastiness.  Cheers!

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If I get chance I will do a 12z comparison of the models, that is EC and gfs, as UK Met is not part of this link, so will have to be done separate.

It will not be possible to do a direct comparison from my earlier posts, I think (?), as the link should update itself if you look at it when the 12z data is all out. If that makes sense?T

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Tomorrow midday sees the UK and the eastern Atlantic under a complex upper trough with various surface lows and fronts littered about bringing sporadic rain and some snow in Scotland, Whilst to the west the high pressure is ridging north and then north east towards Iceland.

gfs_ptype_slp_eur3_5.thumb.png.13c1809192c9c5adf45163399f2a2813.pngPPVG89.thumb.gif.b89659773617f978a0a00689a84ab724.gifgfs_z500a_natl_5.thumb.png.79c007ac00b24e273c3ec243b373ca3f.png

Over the next 24 hours the ridge moves east and the extension south towards Scotland forcing the trough south. Crucially the low that has formed between Greenland and Scotland has also tracked east and the associated front marks the boundary between the warm and cold air as the latter now descends on the UK in the resulting North easterly wind.

gfs_ptype_slp_eur3_7.thumb.png.0a736a1739e4ad196a7cd35ea9ae9be4.pnggfs_ptype_slp_eur3_9.thumb.png.e47a36621111346b2bd0fb0515bbc74c.pnggfs_t850a_natl_9.thumb.png.8a14498543292b8f4016e3dfa9670d5d.png

By 12 Sunday the ridge has slipped further south and east resulting in quite a stiff easterly wind in the south of England and max temps around 4C in England and progressively colder further north and around freezing in Scotland.

gfs_ptype_slp_eur2_13.thumb.png.3e26145f900039893185c9b17f4bdec5.png

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Posted (edited)

The ecm has the small perturbation that's on the fax above over Bristol at 06 tomorrow. Could bring some more prolonged rain and strong winds for a time in the south west.

Edited by knocker
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The T48 &72 surface charts from the ecm  Both days max around 4-6C apart from northern Scotland where it will be 1-3C

ecm_mslp_uv850_eur_3.thumb.png.e0c70d7c1106f329876016ce62b4e65c.pngecm_mslp_uv850_eur_4.thumb.png.2917d04f74a6fe8c1834965f98fcdcd2.png

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Posted (edited)

Not sure if I can get much done before things change to the 18Z but will start.

First just to say the low that came across today did give a wide swathe of winds 50-60 mph and some between 60 and 68 mph, link below, with 68 at Aberport  on the Welsh coast the highest.

http://www.weatheronline.co.uk/weather/maps/current?LANG=en&UP=0&R=310&TYP=windspitzen&ART=tabelle&LANG=en&DATE=1515096000&KEY=UK&LAND=UK&CONT=ukuk&SORT=3&SI=mph&CEL=C&UD=0

The track of the low can be followed on this link

http://meteocentre.com/analysis/map-surface.php?date=0&lang=en&area=uk&size=standard

The link to the 00z to 12z model comparison for ECMWF and GFS is below

https://www.netweather.tv/charts-and-data/model-comparison

Met Office 12z is below

https://www.netweather.tv/charts-and-data/met-office

and now the Met Fax charts, not model data directly but not a bad idea to compare the latest charts, prepared by the senior man, to see how they look at the side of any of the models at the same time, especially the UK Met model

https://www.netweather.tv/charts-and-data/met-office

 

So we have all we need to do our comparisons and make comment on them.

Looking at the GFS from t=48h and there are relatively small changes in the trough and surface low pattern south of the UK but the main change, in the upper air, the 500mb 552 DM contour line, start to show at 72h onwards. Note how that ridge is much more marked on the 12z. For ECMWF much the same happens to that upper ridge.

My apologies but being unable to see a larger scale than Net Wx shows for the comparison I am having difficulty in seeing just what is happening to the attendant surface high, certainly it looks further east and north at 12z? For sure its position at 72h, just off the Scottish coast on the 72h Fax is much further NE at 120h. . Checking the Met O charts and they have the centre at 120h furtherNE to what either ECMWF or GFS do.

 

Turning to the Fax charts and we have 3 Fax charts all for 1z Sunday (this at 2051 as I type). The interesting thing here is that the last one 72h has the high some distance east from the previous two predictions for the same time. The current 120h Fax, to be updated in a couple of hours, shows the main centre of the high, south of where the ECMWF and GFS 120h 12z charts suggest. Checking the Met O charts and they have the centre at 120h further NE to what either ECMWF or GFS do

 

GFS on left and ECMWF on right at 120h

 

So it will interesting when the 120h Fax chart is issued this evening to see what the senior man does with the position of the high.

Ah, no charts as they will not copy directly from my word system but you have been given, in most cases, which charts I have been looking at. 

 

No answers provided but take a look yourself at the links and see if you end up with the same thoughts I have.

Fascinating as to what we will have by 72 hours let alone 120 hours and even further out.

 

Edited by johnholmes
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Brilliant idea with the new thread. Excellent !!

ill be staying well clear of the other one and all

the ridiculous F1 nonsense chatter!!! 

 

Thanks agin for setting this one up . 

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Once again sorry things did not work out as neatly as I had hoped. Will try to do better tomorrow, nothing in the morning as I am out from about 8.30am.

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Posted (edited)

T72hrs from the UK charts

fax72s.gifUW72-7.GIF?04-17

Probably the coldest day-nationwide -of this cold snap with the winds at this stage from the cold air further east.The occlusion across the Channel having brought the Arctic air south over the UK.

We can see the warm front running east-west across C.Europe with the warmer Mediterranean air to the south.

Edited by phil nw.
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Posted (edited)

Today sees a complex area of low pressure cover the UK and eastern Atlantic with lows over Ireland and the North Sea and a front moving south over Scotland thus some rain and snow on the high ground whilst further south the odd heavy rain shower. Further to the west in the Atlantic the high pressure is ridging north, then north east,whilst a low forms between Greenland and Iceland.

gfs_ptype_slp_eur3_4.thumb.png.48d2bf23a3f7b7bd5e80b622291cec36.pngPPVE89.thumb.gif.b3db64f1ac2a8e26a742b6dbd19e01ec.gif

By midday tomorrow the pattern change is well under way with the ridge progressing south towards Scotland thus also pushing the upper tough south into western Europe. This initiates a much colder north easterly surface wind over of the UK This process is facilitated by the aforementioned Greenland/Iceland low tracking east with the associated front marking the boundary between the much colder air to the north. Max temps 5-6C in England and Wales but 2-3C further north and quite breezy in the south.

gfs_ptype_slp_eur3_7.thumb.png.40d56eccedab250f152d5be07b2a065a.pngPPVI89.thumb.gif.1b5dfb3e050dadf1da091937e1ab5387.gifgfs_t850a_natl_7.thumb.png.fc20ce18695ddbe79bbca29c19a6871c.png

Over the next 24 hours the high cell continues to slip south over Scotland but at the same time it's starting to adjust to a more NW/SE orientation. This process completely alters the airflow over the UK, cutting off the north easterly and initiating quite a strong easterly in the south which is being squeezed by the low pressure over Spain. Indeed the airmass in the far south  of England could well be sourced in north Africa. As can also be seen the Iceland low is now tracking across Scandinavia taking the front and cold air boundary with it. Max temps on Sunday around the 4-6C apart from northern Scotland where they might struggle to get above 2C.

gfs_ptype_slp_eur2_11.thumb.png.8e657edfc9ed244eca64b1c5a6005150.pnggfs_ptype_slp_eur2_13.thumb.png.19e2e4ba315c64eb09cd495dc678eba5.pnggfs_t850a_natl_13.thumb.png.f0fc35baf1f1b633cbdedd9aef5f850c.png

The coal face awaits but that's for another day

gfs_ptype_slp_eur2_17.thumb.png.5a9a6a1a1715cafe34cac3b77218ec6a.png

Edited by knocker
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The ecm closely follows the gfs. Without going into too much detail here the T24,48 and 72 charts.

ecm_mslp_uv850_eur_2.thumb.png.797634bf83729c05fad0ee9b541a5083.pngecm_mslp_uv850_eur_3.thumb.png.6abb42335c35b478b76bae6856087336.pngecm_mslp_uv850_eur_4.thumb.png.227b9e5140598fbdd392402a8f6bd02e.png

ecm_t850_uv_eur_4.thumb.png.ed34f2f36b2ff51c8eea88201584c16f.png

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Posted (edited)

Just a brief input this morning. First of all thank you knocker as usual for a quick overall guide to the models you show each day.

Out to T+72 and it is colder weather on the way. Beyond that and it does now seem that any blocking is going to be too far away to prevent the Atlantic slowly, probably rather erratically, pushing fronts into the west and longer term over the UK. The anomaly charts I use for the 6-14 day nroad outlook do suggest this, possibly with rather stormy weather at times in that time scale.

So a summary = getting colder for a few days, then less settled and slowly a bit less cold.

links to charts as shown on previous posts, sorry not got time just now to put them in.

UK Met below

https://www.netweather.tv/charts-and-data/met-office

with GFS and ECMWF comparisons with one another for 00z and yesterday 12z below

 

https://www.netweather.tv/charts-and-data/model-comparison

sorry really must dash

Edited by johnholmes
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Arpege model showing some enjoyable 'seasonal' weather to be had from the upcoming settled spell, with a couple of predominantly sunny days and overnight frosts away from eastern and southern coasts. After the excesses of the holiday period, some lovely weather for a brisk walk in the country!

Nebulosite (cloudiness: black is clear sky) for Sun 7th 16.00 and Mon 8th 16.00:

5a4f3f11c2d05_ArpegeCloudSun07Jan16_00.thumb.png.14c8fad6d9d22df70af0c3da3afbd82e.png5a4f3f1b26e0c_ArpegeCloudMon08Jan16_00.thumb.png.82f6a22bccbe7313cb243fd770fc435f.png

Temperature Mon 8th 06.00:

5a4f3f398ed24_ArpegeTempMon08Jan06_00.thumb.png.31dda817bc77273a8cb08dbd8d4edee1.png

 

 

 

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Early tomorrow and the Net Weather MR model shows the complex low sinking away south taking it's damp and cloudy weather of today with it.

viewimage.pbx?type=nmmlo;date=20180105;t

we then see the cold air sink south right down the country after frosts for many overnight.

Sunday is looking much brighter in the crisp and cold air.Afternoon temperatures ranging from 5/7C down south to below freezing in parts of Scotland which by now sees uppers around -8/-9C.

viewimage.pbx?type=nmmlo;date=20180105;tviewimage.pbx?type=nmmlo;date=20180105;t

Frost setting in early Sunday evening but as we go overnight into Monday we can see the warmer air originally from the  Med. heading north across the channel as the high starts to slip away eastwards.The earlier frost already gone from much of C. and S.England/Wales.

viewimage.pbx?type=nmmlo;date=20180105;tviewimage.pbx?type=nmmlo;date=20180105;t

so a drier and quite cold 2/3 days with some sharp frosts and Winter sunshine to come before by Monday we just see signs of a slow and perhaps a stuttering change from the west,but that is for another time.

 

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Posted (edited)

Yes Phil I'm looking for a window tomorrow morning so that I can get down the country park for a couple of hours

overview_028.jpg?2018010506

Edited by knocker
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Posted (edited)

I'm no great fan of model temps but an eye needs to be kept on the mins over the weekend. As the high cell slips south over Scotland Saturday night some very low air and grass mins are expected Sunday morning, particularly in central and northern Scotland, Perhaps in the -10>15C range,

PPVG89.thumb.gif.6db8e6f23ca1adb0edc78d1bdf81363e.gif

Edited by knocker
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Nice to have a sensible thread to look at. Very good agreement as expected at T96 showing the first attack on the block which has already been shifted east by the power of the jet. Sadly no easterly but with a lack of time for deep cold be formed over Europe it wouldn't have been much of a beats any ways.

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