Short range model discussion - into 2018

[knocker]

9 minutes ago, JeffC said:

I think I'm sort of dyslexic when it comes to reading some of these charts, but I can decipher it when given a different slant on it - Is this the warmer pool you're looking at Knocker?

https://earth.nullschool.net/#current/wind/isobaric/850hPa/overlay=temp/orthographic=146.60,60.53,327/loc=178.122,64.141

 

Yes Jeff that shows the transport from the Pacific into eastern Russia into the Arctic very well.

[Methuselah]

Purple alert! Purple alert! Lesser spotted +ive SLP seen near Iceland!

[JeffC]

20 minutes ago, knocker said:

Yes Jeff that shows the transport from the Pacific into eastern Russia into the Arctic very well.

Cheers, if you click on the 10 Hpa it shows that interesting warm patch in the strat but only at that level...

[knocker]

Once the fronts clear the south coast tomorrow the UK will be in a very windy. and colder, north westerly, particularly in the north, with frequent wintry showers concentrated over Scotland where they will be of snow, even down to low lying areas

Edited January 30, 2018 by knocker

[knocker]

The overiding theme in the short and medium term remains unsettled and can be summed up with periods of rain, sleet or snow generally in the north, followed by squally wintry showers.Because of the expected pattern that develops temps will be below average. A brief word regarding this pattern in the medium term.. There was good agreement last night between NOAA and the GEFS and EPS anomalies and upstream the key players vis the UK weather are the intense Canadian vortex with associated troughs down N. America and ESE through Iceland. Thus a very strong westerly upper flow leaving the eastern seaboard which diverges in the eastern Atlantic courtesy of some positive anomalies and ridging in northern Scandinavia and, in particular, the combination of the Azores high pressure and the trough positively orientated to the SE/S of the UK Thus the westerly flow abates somewhat and veers north west very close to the UK. This fairly long preamble was me leading up to saying worth keeping an eye on this this morning as the short term should start leaning in this direction. Just the NOAA chart to illustrate this.

Back to the short term.

Once yesterdays fronts have finally cleared today the UK is left in the very windy north westerly circulation of the intense low situated north east of Scotland thus frequent squally wintry showers, particularly in the west and north where they will be of snow, even down to the low ground, A perturbation in the flow may bring more concentrated showers as it tracks down the western coasts.

Essentially these cold and showery conditions pertain though tonight and tomorrow although by 00 Friday with the low slipping down the North Sea and the Azores ridging to the west the surface wind will have veered northerly and thus shifting the main area of the showers to the north and the east coast.

Friday could well be the best day of the week as the ridge moves in portending dry and sunny with lighter winds, albeit maybe a frosty start, But by 00 Saturday a rather complex picture is emerging with an upper trough over Greenland stretching towards the UK with it's associated surface fronts already impacting N. Ireland and Scotland, with another upper trough positively aligned to the south east of the UK.

The front and rain, snow on the higher ground in the north, track south east through Saturday but the upper trough is in the process of deconstructing under pressure from renewed ridging by the Azores and waves are forming on the front and by 1800 an enclosed low has formed and is over Yarmouth.

By 1200 Sunday the low has drifted SW into northern France and with the Azores ridging north east the UK is in two airmasses but the latter is under intense pressure from much energy eastbound from the eastern seaboard. But here we must leave it.

 

 

Edited January 31, 2018 by knocker

[knocker]

The ecm has the frontal wave a little further west over the weekend thus the low is forming over south west England by 12 Saturday.and by midnight is over central France with the Azores ridging north east. So in fact not dissimilar to the gfs in the end

Edited January 31, 2018 by knocker

[knocker]

Perhaps interesting to note the brief amplification and introduction of the colder air to the east and south of the UK at the end of the week is associated with the formation of the vortex/cold trough combo over N. America And you could almost say a direct line to the Asian cold

.

 

Edited January 31, 2018 by knocker

[knocker]

Current surface analysis. Just had a brief but violent hail/rain shower here and not very pleasant out there with some hefty snow showers in western Scotland and NW England.

[knocker]

The gfs 06 analysis for 12 Saturday shows some sig, differences with the fax.

Edited January 31, 2018 by knocker

[knocker]

Moving on a little from an earlier chart I find this not without interest as it illustrates a few things.

The massive positive temp anomaly in eastern Russia and the eastern Arctic as warm air is pumped up from the Pacific. A very cold lobe of the vortex in NE North America with an exceptional temp gradient in the western Atlantic with associated massive WAA into the Denmark Strait whilst to the east there is the cold air that has plunged south just to the east of the UK.

All is thus ready for a lobe of the American cold to swing south east with frontal systems preceding it for the det runs to sort the detail.

[knocker]

The midday geostationary (courtesy the Dundee Satellite Receiving Station) shows very clearly the low to the NE; the showery regime to the west: and the decaying front over southern England.

[knocker]

3 hours ago, knocker said:

Moving on a little from an earlier chart I find this not without interest as it illustrates a few things.

The massive positive temp anomaly in eastern Russia and the eastern Arctic as warm air is pumped up from the Pacific. A very cold lobe of the vortex in NE North America with an exceptional temp gradient in the western Atlantic with associated massive WAA into the Denmark Strait whilst to the east there is the cold air that has plunged south just to the east of the UK.

All is thus ready for a lobe of the American cold to swing south east with frontal systems preceding it for the det runs to sort the detail.

And moving on a tad

 

Edited January 31, 2018 by knocker

[knocker]

The wintry showers will continue overnight and into tomorrow but become mainly concentrated in the north and western coastal areas as the wind veers northerly as the low drifts down the North Sea and the Azores ridges to the west. Still windy in the north but abating later.

Friday not a bad day after a frosty start with sunshine and light winds as the ridge drifts across. But by late Friday evening the front approaching from the west is already over western Scotland and Ireland. It will move steadily east during Saturday with rain,sleet and snow affecting most areas, It is going to marginal for snow so best left to a later time as it quite possibly could end up being a nowcast in some areas.

[knocker]

Merely an observation and it's not specifically short term although it most certainly impinges on it.

Looking at the ecm anomaly this evening it would appear, to me anyway, that the anomalies last evening were not a million miles wrong with the overall pattern although of course they appeared to have missed the big trick. Which appears to have been the change of orientation of the Canadian vortex combined with WAA into the Arctic from the Pacific and the Greenland/Iceland area which intensified and realigned the high pressure over the Arctic leading to the CAA southward plunge to our east which has establishes much colder air in the vicinity of the UK. So although the Atlantic pattern is much the same as previous, albeit the Azores ridge relegated to some extent, it becomes a slightly different ball game. Anyway, just a thought

Edited January 31, 2018 by knocker

[Ukwoody]

so sorry, knocker but what exactly does that mean forcast wise? I'm a bit lost

 

[knocker]

4 minutes ago, Ukwoody said:

so sorry, knocker but what exactly does that mean forcast wise? I'm a bit lost

 

Well I wasn't really concerned with the weather as it's outside the remit of the thread woody but essentially you are looking at a strong jet east bound from the eastern seaboard running around the Azores high veering north westerly in the eastern Atlantic and over the UK thanks to the influence of the trough to the E/SE thus it will be unsettled in the UK as systems follow this route with temps below average. As always when getting an idea of the pattern from the anomalies the det runs will need to sort the detail as time progresses.

[knocker]

Today a low north east of Scotland will drift south and be 982mb in the Denmark area by 1800. Thus the UK in a strong NW/NNW airstream, perhaps gales force in exposed areas in the north and accompanied by squally wintry showers, of snow on the high ground in the north, which will be mainly confined to to western coastal areas. These will continue through the night and also affect eastern coasts as the surface veers northerly. Elsewhere it will be clear with frosts by Friday morning

Tomorrow will probably be the best day for a while with the ridge nudging in from the west and the low continuing to fill over norther Germany most of the UK will be dry and quite sunny and feeling not too bad in the light winds, Any showers confined to the east coast and the south west,

But complications are afoot. The amplification that is taking place with the Azores high pressure ridging strongly north east and the trough to our east dropping south, which incidentally sets up the conduit for the colder air, is temporarily interrupted by a trough driven east by the energy leaving the eastern seaboard resulting in the associated front being over Ireland and just west of Scotland by 00 Saturday.

The front will slowly tracks east but with little waves forming along it it doesn't get that far and by 00 Sunday one such wave has formed a small over low western France and the front has dissipated, The $64, 000 question is will it bring rain or snow on it's travels? Even at this stage difficult to be definitive about this as it's going to be very marginal

Sunday a quieter showery day, albeit quite cold, as the ridge reasserts itself and this renewed amplification once again produces some very intense thermal gradients with strong WAA into the Arctic east of Iceland and CAA down the east of the UK courtesy of the aforementioned conduit. But there is still a huge amount of energy to the west but it must be left here.

 

Edited February 1, 2018 by knocker

[knocker]

The latest fax reaffirm the front making little eastward progress on Saturday

 

Edited February 1, 2018 by knocker

[knocker]

Confirmation of the earlier comment vis today

And not bad agreement on the position of the front 12 Saturday but the development of the shallow wave as the front fizzles out perhaps causing a slight headache.

 

[knocker]

The 06 gfs more or less agrees on the front on Saturday fizzling out with patchy rain, perhaps some snow on the higher ground but it does bring the colder air into the south east early Monday as the next front approaches. The question is what will happen to the warmer moist air as it is squeezed. Will it mix out?

 

Edited February 1, 2018 by knocker

[knocker]

A couple of the GEFS mean anomalies from the 06 run at T24 & 96 which illustrate quite well the WAA into the Artcic and the continuing role of the intense Canadian vortex and the CAA plunge south into western Europe.

Edited February 1, 2018 by knocker

[knocker]

The surface analysis for 1500 and the geostationary for same time. Courtesy of the Dundee Satellite Receiving Station

[knocker]

Leaving Saturday aside for the moment and looking slightly further ahead. One of the key questions as the cold front approaches on Monday may concern how much of the warm moist air preceding the front gets mixed out as the front struggles and slows against the cold block in the east. The front could start to fragment and a potential quite widespread snow event become more patchy.

[knocker]

The ecm has the UK dry Sunday and Monday but quite a stiff ESE breeze over the south on Sunday thus quite a wind chill. Max temps for Sunday 4-5C but 7C in N. Ireland. Tuesday 3-5C but around freezing in N. Scotland.

[knocker]

Just a personal opinion but guessing/estimating lapse rates to calculate a surface temp from 850mb temps is very hit and miss and at best will only give you an approximation. At worst in can be miles out.