Short range model discussion - into 2018

[knocker]

looking at the Camborne midday sounding you could say we were in the colder aitmass

And a nice image of the low at 1300

Edited December 7, 2018 by knocker

[knocker]

The frontal rain cleared the east coast early this afternoon leaving the the whole of the UK in a very strong WNW wind that will reach gales force, possible severe, i exposed areas with frequent heavy squally showers. These will be concentrated in western regions, and in particular Scotland, as the wind  veers somewhat as the low drifters east into the North Sea. By early morning probably some upper cloud encroaching the south west from the next frontal system.

The 1600 chart

 

[Sky Full]

2 hours ago, knocker said:

.......

And a nice image of the low at 1300

That's an amazing satellite image there - you could hardly have drawn a more perfect spiral showing the air circulation around the low, or a straighter line to pick out the leading edge of the front.  I'll never get tired of the patterns created in nature....

[knocker]

Outlook - A slow transition to drier, calmer and cooler conditions is underway but in the mean time very wet and windy for many over the weekend.

The 500mb NH profile and the surface analysis for midnight

At the moment the wind is abating somewhat but still quite a few showers around in western and northern areas. But during the morning these will become more concentrated in western areas as the next frontal system approaches and spread east during the afternoon. At the same time the wind will start to pick up again, particularly in the south west and along the Channel. coast. Still quite mild

This evening and overnight the frontal system quickly clears away to the east with showers now more concentrated in the south west.  However the transition is underway with the subtropical high ridging the west and an occlusion is tracking south over Scotland with the onset of a northerly wind with much cooler air behind, All of which cause a squeeze in the south and thus the wind will pick up further here with severe gales in exposed areas

The wind will finally ease in the south through Sunday morning and the showers become less frequent through the day but the aforementioned front is still tracking south along with the colder air and thus the showers over Scotland could now be quite wintry.

By now, with the transition well underway, the battle begins in earnest between the energy exiting the eastern seaboard and the emerging subtropical high with  the UK at the coal face, This results in a much quieter and cooler day on Monday with a frosty start. The aforementioned occlusion is now fizzling out but further fronts are struggling east under the pressure from the associated deep depressions swinging north to the west. And they will introduce some patchy rain.

And this essentially is the scenario over Tuesday and Wednesday.as more intense depressions track NNE,(we are talking about an 150kt jet here) with fronts struggling across the UK giving some patchy light rain, as the ridge is nudged a tad further east.

And the NH profile at T120

[knocker]

The 0600 analysis

[knocker]

The low and associated fronts that have brought grotty and very windy conditions to much of the UK today are racing east and by 0600 tomorrow the low will have phased with the main low over southern Norway leaving the trailing occlusion across the north Midlands, Behind which, with the subtropical high ridging to the west, the wind veers northerly and quite importantly introduces colder air..

So the frequent squally showers will continue through this evening and overnight but tending to move south and become more concentrated in the west  and as the colder air becomes established showers over northern Scotland will be of snow over the higher ground, The other corollary of the shifting pattern is an increase of the surface wind, generally south of the front, but in particular in the south west and along the south coast, and it could reach severe gales in exposed areas.

Edited December 8, 2018 by knocker

[knocker]

Outlook - from today becoming calmer, drier and a tad cooler as a slow pattern transition takes place

The 500mb NH profile and surface analysis for midnight.

This initially this is a follow on from the above. The frequent squally showers and very strong winds (60mph gusts here), mainly south of the north midlands, will both decrease during the morning with just a few showers in the west and over northern Scotland.. Thus by the afternoon a dry and fairly sunny day for most albeit a tad cooler as the occlusion has finished it's journey south and the ridge is building to the west.

And this is largely the story this evening and overnight and with the wind abating quite a widespread frost by Monday morning.

Thus Monday starts sunny in most areas but events are evolving in the Atlantic with which we are now familiar and a warm front is struggling east which brings cloud and patchy rain to the north west during the afternoon.

This battle between the pressure exerted by the energy distribution to the west and the ridge/block is essentially the scenario for the rest of the week with the UK in no mans land. So overnight Monday and through Tuesday the warm front continues to struggle east giving some very patchy rain whilst intense depressions track north in mid Atlantic. And by evening a cold  front associated with these is nudging into Ireland bringing cloud and more persistent rain to the west.

W now enter the uncertainty arena through Wednesday/Thursday' Another intense low tracks north west of Ireland and it currently remains problematic as to how far east the aforementioned weakening cold front will get in it's struggle against the block and thus also any rain, or snow on the higher ground,

And the NH profile at T120

 

Edited December 9, 2018 by knocker

[knocker]

The current analysis

[knocker]

The midday chart. The wind finally easing here after a pretty rough18 hours

[knocker]

The MODIS image at 1240

[knocker]

Outlook - a much quieter period than recently. less windy and a tad colder, as a slow pattern transition gets underway

The NH 500mb profile and surface analysis for midnight and the WV image for 0300

A few residual showers still around associated with the dying occlusion (see sat. image) but otherwise a frosty start in many areas after a clear night. The showers will fizzle out and most areas will have a dry and sunny day as the ridge builds but during the afternoon cloud will increase from the west as the weak warm front, associated with the complex low pressure area in the Atlantic nudges in. Could well bring some patchy rain/drizzle in the NW. Temps a tad cooler in the north east

The cloud and patchy rain/drizzle  will ingress further east overnight but over northern Scotland and around East Anglia still some frost patches.

Apart from the NE ans E Tuesday will be generally cloudy with still the odd patchy drizzle in places, and this is reflected in the temps, but by late afternoon more persistent rain is effecting N. Ireland and the south west associated with a cold front attempting to edge in from the west.

Overnight Tuesday and through Wednesday the energy in the west continues to push the front against the blocking ridge without a great deal of success and thus the rain becomes intermittent and confined to western regions. Temps around average

Over Thursday and Friday the energy continues to apply massive pressure on the ridge. In fact it does achieve a technical knockout by establishing a separate high cell to the north east, but further amplification of the subtropical high north east gives temporary support and further ingress east of the front is thwarted, although perhaps some rain in the south west Thursday evening from the little wave around the Brest peninsula, until rain does effect the north west by Friday evening. Until then dry and quite chilly in most areas in the south easterly breeze.

And the NH profile at T120

 

Edited December 10, 2018 by knocker

[knocker]

The 0600 chart

[lottiekent]

Going to following this thread with interest the next few days.

[phil nw.]

T72hrs for Friday 1200hrs and GFS  shows the cold to the east and the Atlantic mild lurking to the west with the UK in the middle.The -5C uppers extending into the centre of the UK by this time already signs of the milder air coming in over Ireland though.

Low pressure winding up south of Iceland with approaching rain and strengthening south westerly winds.

[johnholmes]

Just to give a bit of interest re the search for cold, better renamed perhaps as the search for snow in back gardens!

When I can find my link to 'will it snow' or 'How to predict snow' I will post it in here as it may generate some interest. It does work if you use it correctly and don't 'fiddle' any answers!

So if anyone has the link can you drop it in here for me please?

many thanks

 

 

[phil nw.]

Looking quite raw tomorrow in a stiff and cold south easterly wind.

Fax and GFS 850hPa temperature charts for 12 noon Thursday

The colder air getting across the UK behind the cold front heading west.

[johnholmes]

Just to give a bit of interest re the search for cold, better renamed perhaps as the search for snow in back gardens!

No forecast from me and it is approaching 24 hours outside the 'short range model discussion', but never mind.

Take the latest ppn predictions from whichever source you use. If it shows no ppn for you thendon't bother trying with this system any further. If it shows ppn then carry on.

Use this link to check, using the nearest model output for you. The nearer to T+00 then the more probable it will be closer to what actually falls, thus the short range models come into play from T+48 hours down.

The link is

 

With thanks to Polar Maritime for searching and finding it

and it does work pretty well!

 

[phil nw.]

Another cold day tomorrow then we see a change coming in by the weekend.Saturday and the charts for mid-day show frontal systems into the UK bringing rain with them and milder Atlantic air behind.

Quite a decent chance of snowfall over higher ground for a time as the rain hits the cold air- shown by the latest medium range NW model.

The freezing level quite low ahead of the change rising as the milder air takes over in the south west.

[Nick F]

A look at GFS forecast skew-ts show the potential for snow turning to freezing rain over N England on Saturday evening, as per Met Office warning. A warm nose moves in from the west (occluded front?) aloft noted by temp above 0C diagonal line above surface temp around freezing. So snow perhaps melting aloft as warm nose moves in between 750-850mb falling to surface that's around 0C and potentially freezing on contact.

[Polar Maritime]

A very interesting day tomorrow, Severe gales a bitting wind chill and blizzards for some.

[phil nw.]

The UK fax's for Saturday 12z and Sunday 00z show fronts pushing into the cold air and taking a number of hours before making headway across the UK.As PM mentioned above some quite inclement weather with some heavy rain ,gusty winds and indeed snow in parts as the battle between the 2 air masses commences.

Finally by Sunday pm the UK turning milder as the fronts clear to the north east.

and by Monday 00z T72hrs shows the UK into the Atlantic pattern 

The UK by then expected to be into a south westerly flow and temperatures back to around average,

 

Edited December 14, 2018 by phil nw.

[Nick F]

Another look at tomorrow's freezing rain risk over higher ground of N England and southern Scotland, two forecast skew-ts from and cross sections for N England from GFS at noon and 6pm tomorrow show the 'warm nose' of air aloft above 0C spreading in from the west over surface temps that are around 0C above, say, 200-300m, so snow potentially melting in this less cold layer before the cold rain reaches surfaces on the ground which are potentially at or below 0C and freezing on contact:

Saturday noon                                             Saturday 6pm

 

                                                     

 

Edited December 14, 2018 by Nick F

[Sky Full]

Eight hours of strong winds to move across the UK from 5:00pm tonight as predicted by the ICON:

I would not want to be on a boat or an oil rig in the North Sea tonight looking at the above.  My thoughts go out to anyone who has to endure these conditions at sea.

[knocker]

Fascinating geostationary image at midday showing the wave and frontal structure across western Ireland

A lot of moderate/heavy rain around at 1300

And the high res. MODIS at 1340

 

Edited December 15, 2018 by knocker

[knocker]

Cold front now through here

Interesting midday Nottingham sounding. The possibilities with the warm air aloft and low level inversion vis freezing rain are apparent  If not here, elsewhere

Edited December 15, 2018 by knocker