Short range model discussion - into 2018

[The PIT]

4 hours ago, knocker said:

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.

The other thing to consider is freezing rain which could also been the result if the temps don't get mixed out.

[knocker]

Birds eye view this evening with the GEFS 850mb anomaly showing the intense thermal gradient in the Atlantic, courtesy the Canadian vortex, and the strong WAA running north through Iceland and the conduit of the CAA plunge south over western Europe at T72. And subsequently the warm air being squeezed out by T96.

 

[shotski]

2 minutes ago, knocker said:

Birds eye view this evening with the GEFS 850mb anomaly showing the intense thermal gradient in the Atlantic, courtesy the Canadian vortex, and the strong WAA running north through Iceland and the conduit of the CAA plunge south over western Europe at T72. And subsequently the warm air being squeezed out by T96.

 

That’s a shame.....

[knocker]

1 hour ago, shotski said:

That’s a shame.....

Yes it is rather as it reduces the chances of a decent snowfall as the front mixes out

And moving on a quick glance at a forecast sounding in East Anglia 1200 Sunday is a good illustration of CAA in the boundary layer.in the cold NE wind.

Edited February 1, 2018 by knocker

[davehsug]

23 minutes ago, knocker said:

Yes it is rather as it reduces the chances of a decent snowfall as the front mixes out

And moving on a quick glance at a forecast sounding in East Anglia 1200 Sunday is a good illustration of CAA in the boundary layer.in the cold NE wind.

I still can't sqare the temperatures showing for Sunday, with the 850s on almost all of the models. 7C in the South East with -10 850s? At this time of year, -10 should alwayd equate to surface sub zero, so somebody's wrong. Is it the models or the forecasts?

[knocker]

5 minutes ago, davehsug said:

I still can't sqare the temperatures showing for Sunday, with the 850s on almost all of the models. 7C in the South East with -10 850s? At this time of year, -10 should alwayd equate to surface sub zero, so somebody's wrong. Is it the models or the forecasts?

I must admit I haven't been following this closely but the gfs this evening is generally showing 3-4C at 1200 Sunday for the south east and the 850s are a little variable and -10C would probably be the extreme. Although is not out of the ordinary for these surface temps. As I said earlier Dave guessing lapse rates, particularly in a known CAA situation is really to be avoided if possible,

[knocker]

Today, all things considered, will be quite pleasant for most and after a frosty start in places sunny and light winds will be the order of the day as the transient ridge briefly influences proceedings. Showers will be much less frequent and probably confined to the east coast and the tip of SW Wales and south west England. By early evening the front that is approaching from the west will be along the west coast of Ireland and will move gradually east during the evening bringing some rain to N. Ireland and western Scotland, Wales and  Western England

Overnight and through Saturday morning the front will move slowly east bringing patchy rain to Scotland Wales and western England and falling as snow on the higher ground in the north (this is not definitive as it will be marginal in some areas) but the front is starting to fragment as a wave forms on it and the eastern parts of the UK will remain dry.  Thus by evening precipitation has largely died out and the shallow wave is over north west France and the southern half of England is a NE surface wind.

Sunday will be dry for most as the Azores ridges north east to the high pressure over Scandinavia but with low pressure to the south of Britain the southern half of England will remain in a fresh NE wind which could produce some wintry showers in the south east. Temps generally in the 3-5C range.

This remains the situation early Monday but by 1200 the next front is approaching NW Ireland and over the next 24 hours it will track south east across the western half of Britain bringing rain sleet and snow. This is going to be another tricky one regarding where and how much snow so no point in me attempting detail at this stage

Edited February 2, 2018 by knocker

[knocker]

The ecm max temps on Sunday generally in the 4-5C range, 7C in N. ireland.

Monday generally in England 3-4C but 0-2C Wales, northern England and Scotland.

Tuesday 1-3C in England and Wales. 0-2C in Scotland, 3-4C in N/ Ireland and 5c in Camborne. But dew points are very low this where the marginality is evident.

[knocker]

Keeping in mind what has already been said some ecm surface charts for T,48,72.96 and 850mb temp anomaly and wind vectors

Edited February 2, 2018 by knocker

[knocker]

Current surface analysis; latest fax for 06 tomorrow and forecast freezing levels for 12

[knocker]

Tuesday continues to look marginal although at the moment less so than tomorrow with the temps and dew point lower but it still depends on how much oomph is left in the front.

[knocker]

Excellent illustration at T60 of the different airmasses involved in this current pattern.

The cold front running south from Iceland with the very cold air associated with the Canadian vortex piling up behind whilst the warmer air tracking NE from the western flank of the Azores high pressure precedes it. Further east the UK is in a col between two high pressure cells with stagnant cold air settling in the very slack gradient whilst the low pressure to the south just about brings an easterly component to the very south of England,

Wind it on 24 hours and the warm air has been absorbed, the UK become appreciable colder and the PM behind the front is being modified bt warmer air sweeping north around the high pressure. The front will carry on tracking east but the question is  how much is left in the tank?

[knocker]

Ecm max temps for Sunday 4-5C but quite a wind chill in the south in the fresh NE wind.

Monday quite similar minus the wind.

Tuesday 0-3C  and the front attempting to push further east during the day fragments, so again marginal, so lets settle for patchy rain and snow,

[johnholmes]

I have to say I do get the feeling that the cold spell is not going to be as marked as it seems to have suggested from various models at times. Just going to have a look at the 500 mb NOAA for this evening, back in a minute, oh and the latest Met Fax charts

 

Edited February 2, 2018 by johnholmes

[johnholmes]

Well here are the Fax charts. On the first few I assume the eastern occlusion shown heading west is Exeter showing where they feel the coldest air is, ie: east of this front?

http://www.weathercharts.org/ukmomslp.htm

I know the 6-10 day chart is outside the 72h even at the start but it may give us a clue to what the overall upper air pattern is most likely to be.

I have to confess I am not sure what forecast I would give based on this, and the 6-10 has been similar for several days. It has a strong flow from the Gt Lakes area/Alaska into the west of the UK. Will surface high pressure become the dominant feature over the UK or will it be unsettled. Got to be honest and say I am unsure of what to go for.

In the heat of the main thread there is a fair amount of up and down as usual but the overall trend on the 3 main models, post 72h, seems to me to have this surface ridge from the SW then the Atlantic starting to play a more major part. Mind you the Atlantic is often predicted to push in too early, so this may be one of those occasions.

Sorry not able to give any more definite guidance.

Interesting model watching, although probably not what deep cold and snow lovers would prefer to see.

Edited February 2, 2018 by johnholmes

[knocker]

I was looking at the NOAA earlier John in the context of comparing it with this evening's GEFS and EPS so I'll just throw them into the ring as well. It does appear to me that the cold air conduit is blocked in the east and the cold air in situ is thus shunted south. Still that's one impressive vortex

Edited February 2, 2018 by knocker

[johnholmes]

You could be right k, it just does not look like a really cold spell from an easterly point to me, it is there to some extent for 24-48 hours but not longer term?

Edited February 2, 2018 by johnholmes

[knocker]

Today the occlusion already affecting the western half of the UK will wander slowly east whilst dissipating thus patchy rain, and sleet, the latter mainly on the higher ground to the north, and similarly some snow in Scotland. A small wave that develops on it will be over N. France by evening. Showery brighter weather behind already in to N. Ireland. The cold front to the east which is nudging west will also tend to peter out as it nears the east coast Temps ranging from 7C in the south west to 3C further north.

Tomorrow a much brighter day albeit quite cold with temps 4-5C at best and there may be some brief flurries in the south and  east in the fresh north easterly wind

The clear skies and light gradient continues overnight in most areas leading to a widespread frost Monday morning but by midday the next front is approaching from the north west introducing a warmer south westerly airstream to N. Ireland and Scotland.

Through the rest of Monday and through Tuesday the front will track south east across the UK but it is rapidly losing it's identity so a rather similar scenario to today with patchy rain sleet, snow on the higher ground but clearer colder weather behind also in the mix

From here we await a repeat performance but that's for another day

 

Edited February 3, 2018 by knocker

[knocker]

Nothing to add detail wise from the ecm so just the surface and 850mb temps anomaly and wind vector charts for T24, 48, 72

[knocker]

Quite an interest scenario looking at the 2-7 GEFS and EPS anomalies this morning.

Strong Canadian vortex elongated SE to encompass Greenland/Iceland with Azores high pressure suppressed with a strong westerly jet running  across the Atlantic, But as the flow reaches the eastern Atlantic close to the UK it diverges quite sharply with the northern are tracking  NNE around the east European ridge and a rather peculiar slack upper low over N. Scandinavia. The southern arm turns sharply south courtesy of the positively aligned upper trough S/SE of the UK. Where precisely this divergence occurs is important and will dictate how far active systems will progress east.  Temps remaining below average.

[johnholmes]

Yes I commented in the other thread about ec-gfs and noaa both showing a pattern that diverges much as you suggest k. I am at a loss to know just how that divergence is going to affect the surface weather. An interesting pattern for sure over the next 2 weeks.

Close in, the 72h period and the Fax charts are going to be the best overall guidance I would suggest. Talk of snow etc will be uppermost in most folks minds but I cannot see any widespread heavy snow. Localised low level falls are possible but may not be apparent until a few hours before they occur!

[ghoneym]

Latest Meteogroup short range charts

[knocker]

The analysis at 06. Currently 3C and light rain Manchester and 2C and light rain East Midlands but you can check a few Metars here

http://meteocentre.com/surface-weather-station/metar-synop.php?ids=EGNX%3A-99999&type=dec&lang=en&stn=EGTE&map=uk&syn=03839

[knocker]

The latest fax has the CF slipping through from the east overnight so the possibility of some flurries in it's wake.

Edited February 3, 2018 by knocker

[knocker]

The midday fax chart and the 12 geostationary courtesy Dundee Satellite Receiving Station. The sat. image, apart from confirming a cloudy UK, clearly shows the front in the North Sea and the little feature over the Contentin Peninsula. Plus the showers over Cornwall with one currently in progress

Edited February 3, 2018 by knocker