Short range model discussion - into 2018

[knocker]

Much as predicted with the frontal system tracking east across the south, very wet and quite breezy in the early hours on Friday

And the upper trough over the Atlantic at midnight with strong flow along the southern flank

Edited December 18, 2018 by knocker

[Stuie]

2 hours ago, knocker said:

Much as predicted with the frontal system tracking east across the south, very wet and quite breezy in the early hours on Friday

And the upper trough over the Atlantic at midnight with strong flow along the southern flank

That last chart, signs of pressure building much more western than previously modeled? Or just a trough being created with the LP?

[knocker]

40 minutes ago, Stuie W said:

That last chart, signs of pressure building much more western than previously modeled? Or just a trough being created with the LP?

Not really. Both the gfs and ecm start having a bit of bother nearer T132

[knocker]

Outlook - remaining unsettled under the auspices of low pressure but a pattern change signaled at the end of the period.

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

Yesterday's cold front has cleared into the North Sea but the UK remains with the circulation of the complex low pressure area to the north west of Ireland. Troughs embedded with this circulation will bring squally showers, quite likely with some hail and thunder in the mix. to many areas through today and this evening and overnight. Initially in the far south east and south western regions but through the afternoon and evening a more concentrated band will effect most areas as an occlusion pushes east over the Irish sea. Eastern regions will remain pretty dry and Temps around average.

A not dissimilar story tomorrow with stray bits and pieces of occlusions in the flow and thus heavy showers more concentrated in west and north west regions, But by 1800 a band of rain is approaching Cornwall as the next frontal system moves in from the west.Temps again around average.

Although the UK remains under the influence of low pressure through Thursday night and Friday the stirrings of the aforementioned pattern change are becoming evident over the east coast of North America. Meanwhile back on the farm heavy rain from the frontal system will track north east through Thursday evening and Friday morning accompanied by a freshening wind. A marked N/S temp contrast.

On Saturday the stirrings continue with the Bermuda high surging in the western Atlantic which squeezes and re orientates the upper trough to the west of the UK which does at least give the UK a temporary respite with a transient ridge and thus a sunnier and drier day.with temps a tad above average.

The pattern change continues on Sunday with the trough pushed a tad further east which allows more frontal system egress to the UK and a band of rain to track SW > NE with temps again a tad above average. It is worth mentioning, en passant, that it was around here that the models struggled yesterday with the trough/ridge interaction.

And on to the NH profile at T120

Edited December 19, 2018 by knocker

[knocker]

Sat image at 1315. After fine start to the morning with some Cu and Cb around a sheet of As arrived

Early morning sun shining on developing Cu this morning

[knocker]

Heavy showers will continue to effect many areas through this evening and overnight but in particular western areas over England and Wales at first switching by the early hours to the north west as showers coalesce Frost unlikely apart from the far north of Scotland

Edited December 19, 2018 by knocker

[Stuie]

Evening, Knocker.

Great post (13hrs ago). Just looked at the latest Fax chart for Friday and the LP does swiftly shoot over NE. Winds gusty in the south and damp but Saturday looks Ok and but Sunday rain for most (Sunday fax not updated)

I do find those Fax charts tricky to read!

 

Edited December 19, 2018 by Stuie W
Trying to learn

[knocker]

23 minutes ago, Stuie W said:

Evening, Knocker.

Great post (13hrs ago). Just looked at the latest Fax chart for Friday and the LP does swiftly shoot over NE. Winds gusty in the south and damp but Saturday looks Ok and but Sunday rain for most (Sunday fax not updated)

I do find those Fax charts tricky to read!

 

The 96 and 120 fax charts update later in the evening's. One of the reasons I prefer to leave any more detailed posts to morning.

Edited December 19, 2018 by knocker

[knocker]

outlook - unsettled but becoming calmer and drier as a pattern change gets underway during the period

The NH 5000mb profile and surface analysis for midnight and the 0300 WV image.

Today another showery day but the emphasis will shift from more southern and central regions to the west and north west as embedded troughs slide around the circulation of the low to the north west of Scotland. Temps around average. But by 20 rain from a complex frontal system approaching from the south west is just nudging Cornwall

The main belt of rain the progresses east along the south of Wales and England and it could be quite heavy and windy around the triple point

But a band of rain associated with the occlusion will track north east during the early hours and through Friday giving a wet day in many areas before clearing the north east by mid afternoon. A fairly marked N/S temp difference resulting from this

Through Friday evening and Saturday the pattern changes mentioned earlier are well underway resulting in a sunny intervals and showers day for the UK with temps a tad above average

The evolution of the next few days, in particular the trough/ridge interaction, appears to have been causing one or two headaches, and continues to do so. On Sunday, with the trough now positively tilted  west of Ireland, a frontal system tracks north east in the quite strong flow along it's south east flank, to bring cloud and patchy rain to Wales and many parts of England. A very marked N/S temp divide.

A not dissimilar day on Monday but with the trough to the west now tending towards a negative tilt as the ridge builds over the UK and a weakening front straddled across southern areas brings some cloud and patchy rain here. Again a marked N/S temp contrast

And the NH profile at T120

 

 

Edited December 20, 2018 by knocker

[BlueHedgehog074]

Just an example at 120 hours, but the 00Z runs from the GFS, ECMWF, UKMO, GEM and ICON all pretty much agree to a drier spell developing towards the big day.

GFS

ECMWF

UKMO

GEM

ICON

Some slight variations of the High Pressure theme, otherwise a generally dry for all. While it could be quite chilly and frosty, especially during the morning, it would probably feel quite pleasant in the sun and calm winds. More so the further South in the U.K you are. Could be a really nice day for going strolling.

Not a snowy day some from the Hunt For Cold thread would like, but not a bad Christmas present from Santa. ?

Edited December 20, 2018 by DiagonalRedLine
Make one or two changes to post

[knocker]

The midday analysis

[knocker]

Although leas frequent showers will continue this evening over northern areas, particularly western Scotland.  But by 21000 a band of heavier and more persistent rain will already be effecting southern Ireland and Cornwall. This associated with a new frontal system that's part of a major upper trough dominating the Atlantic.

The triple point of this system will scoot along the south overnight accompanied by heavy rain and quite strong winds, perhaps reaching gale fores along the Channel coast, before clearing the south east by 0600, But the band of rain associated with the occlusion will continue to track north east to be over the north of England and southern Scotland  by midday Friday.

Edited December 20, 2018 by knocker

[knocker]

outlook - Remaining unsettled at first but a pattern change during the period results in much more benign weather by the end.

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

The moderate rain currently effecting the south east will clear quickly this morning leaving the odd shower in it's wake and still quite breezy for a while along the south coast. But patchy rain/drizzle will continue to effect the Midlands and the north as the waving occlusion straddles the country. Sunny intervals and showers over Scotland. Quite mild with temps above average, particularly in the south.

But as can be seen a wave is forming on the occlusion to the west and this will scoot across the country this evening accompanied by some heavy rain, mostly concentrated on an area south of Carlisle. This will have cleared by the early hours leaving clear intervals and showers.

So once all the fronts are out of the way a bright and breezy day on Saturday with the odd shower thrown in, which may be more frequent in N. Ireland and south west Scotland, courtesy of the stray lingering occlusion. Another relatively mild day/

But now the pattern change mentioned earlier is well under way with the subtropical high pressure zones amplifying and the atlantic trough caught in the middle of the pincer movement. The result of all this is that frontal systems are pushed north east across the UK along the eastern flank of the trough bringing cloud and patchy rain over Saturday night and through Sunday, along with some quite warm air, but not reaching Scotland which should remain sunny. A marked N/S temp contrast

The trough/high pressure fandango continues apace and by Monday a ridge is established over the UK , But with weakening fronts around remaining cloudy with perhaps some patchy rain/drizzle in the south. Again quite a steep N/S temp gradient.

A similar story on Xmas Day but likely some regional variations vis cloud and temperature with the high cell now centred just to the south east

And on to the NH profile at T120 which illustrates the pattern change

Edited December 21, 2018 by knocker

[knocker]

The wave on the trailing front and accompanying area of heavy rain, that is out to west at the moment, will whip across central parts of the UK this evening on the very strong upper flow running around the Atlantic trough, clearing the east coast by 0200. There will be quite strong winds south of the fronts for a while this evening. After this more showers will effect western regions,

Edited December 21, 2018 by knocker

[knocker]

Outlook - Once the weekend is out of the way a change to drier and more benign weather as the pattern change becomes established,

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

Apart from some showers around in the west of Scotland, courtesy of an occlusion lingering close by, most of the country will have a dry and clear start to the day and this will continue through the day and this evening, with perhaps the showers dying out somewhat by then, thanks to a transient ridge,.But by late evening rain will be into Cornwall as the next frontal system approaches from the south west.

This system is quite a complex double structure which slides ENE across the country, thus the first area of rain tracks north east through Sunday morning and early afternoon to be followed by another band that swings across the south from midday onwards. All of this introduces some much warmer air so a very much N/S divide by the end of the day.

By now the pattern change is virtually complete and the ridge established over the UK, but fronts from the trough in the Atlantic, now neutrally tilted, are still straddled across the south thus cloud and patchy rain here whilst elsewhere staying dry. Temps a tad below average apart from the south west

On Xmas Day the high cell is centred over Belgium with the energy banging on the door in the west. Thus the country in a gentle south west flow portending a pretty cloudy day with temps around average but with some regional vagaries, Perhaps some patchy rain/drizzle from the weakening warm front that the aforementioned energy has forced around the block,

A not dissimilar day on Wednesday so remaining generally cloudy with perhaps some rain/drizzle in western regions and temps a tad above average.

And on to the NH profile at T120

[knocker]

A curling warm sector on Xmas Day behind a weak warm front. so pretty cloudy The obligatory Sc at 3000 feet and even some medium cloud thrown into the mix down in Gods Little Acre.

[knocker]

Total Cs cover here with quite a few contrails, The midday Modis

[knocker]

There will be some residual showers around still this evening over western Scotland, otherwise dry in most areas. But the complex frontal structure away to the south west will become more organized and track north east towards the UK. This will bring rain into Cornwall by midnight which will move north east across the country, heavy at times, to reach southern Scotland by midday. A clearance for a time behind the first front before more rain arrives in the south west.

[Stuie]

Think you can safely say Knocker that the week as pretty much panned out as posted early on in the week, nice work.

[jy]

Wont be around early next week Knocker,so have an enjoyable Xmas and thank you for keeping this superb part of the forum going,down to earth,no nonsense stuff,keep up the excellent work.

[knocker]

Cheers jy, have a good one

[Rocheydub]

1 hour ago, knocker said:

Cheers jy, have a good one

Indeed. Love your posts knocker. No bias, just honest to goodness synopsis. Thank you for all you do for NW community! Happy Crimbo!

[knocker]

Outlook - The next 48 hours sees the final piece of the pattern change jigsaw slip into place with high pressure becoming established in the vicinity of the UK, portending a spell of dry and quiescent period of weather

.

The surface analysis for midnight and the WV image for 0300

As can be seen cloud currently covers most of the UK and there is a lot of rain under this. This rain, which will be heavy at times, will linger over the north of England before clearing into the North Sea by mid afternoon with Scotland remaining dry and sunny. But at the same time further rain will effect the south west as the second front straddles the south and this will likely persist until the early hours of Monday before fading south with the front. Elsewhere a dry night and quite chilly in Scotland with a widespread frost Monday morning. Quite a temp contrast today with the warm air encroaching the south. This could well be the last substantial rain for a while

So Monday, after a frosty start with the odd fog patch around with be generally dry if not overly warm but with fronts fairly adjacent parts of Wales and south west England could well see some patchy rain/drizzle.

A not dissimilar story for Xmas Day as the high cell becomes centred to the south east the weakening warm front meanders across western parts of the country thus cloudy with patchy rain/drizzle in these areas whilst the north and east remain dry. Temps a tad above average in the west but cooler in the east.

By now the high pressure is well established, not forgetting there is still a lot of energy exiting the eastern seaboard into the Atlantic before hitting the buffers of the block and weakening as it runs around the northern flank  But the positioning of HP is such that warm air is advected into western Europe whilst the colder air slips south away to the east.

So Wednesday and Thursday another couple of quiet and relatively warm days, if predominately cloudy, with the odd spot of drizzle in the north from the decaying front that is still lingering

And the NH profile at T120

 

Edited December 23, 2018 by knocker

[knocker]

Much milder air into the south

[SilverWolf]

Hi Knocker,

Thank you so much for all your efforts on this thread this year. I’m a landscape gardener so always need last minute weather updates - I always come to this thread as you  do your summaries so early in the morning! As much as I enjoy the hunt for cold thread, this thread is much more ‘useful’ for me.