Short range model discussion - into 2018

[knocker]

Interesting jet configuration around the amplifying trough/ridge complex stretching from N. America to the UK on Saturday. Cetainly some snow on the higher ground down to Wales I would think and even low levels in Scotland.

Edited October 22, 2018 by knocker

[knocker]

I am sure that everyone is aware of the rapid pattern change in a couple of day’s time, courtesy of events upstream, so no need to dwell. And talking of upstream, cat 4 hurricane Willa is about to hit Mexico, hopefully without dire consequences.

Back to the present and the 500mb and surface analysis for midnight.

As can be readily seen there is a squeeze going on between the trough and the high cell and thus some strong NW winds over Scotland during the night which will move down over the north east of England during the day. Could well be 50-60mph gusts in exposed areas. The winds will abate by evening Added to this the front(s) will also move a tad south so patchy rain/drizzle, mainly over Scotland. Elsewhere there has been some high cloud down as far as the Midlands but further south fairly clear with some mist/fog patches. These will clear quickly leaving a sunny day for much of wales  and central/southern England.

Still some patchy rain around overnight, still mainly in in Scotland,  but the winds continue to abate.

The patchy rain/drizzle is persistent over western Scotland on Wednesday and still breezy here but elsewhere the high pressure becomes more influential and although there will be a fair amount of cloud around a quite pleasant day and warming up a tad. Best make the most of it.

By Thursday the transition is well underway with the trough over NE North America and the high pressure amplifying in the western Atlantic. Thus another trough and cold air is tracking south east towards Scotland with the cold front just west of the Hebrides at midday. From here it will track south east with rain into Scotland and N. Ireland by evening but elsewhere cloudy with some sunshine and temps generally around average.

Over Thursday night and through Friday the wave that has formed on the front becomes quite a vigorous feature as it tracks into southern Norway as the cold front continues to track south east accompanied by colder air and showery rain. But behind it is the following occlusion that hails the northerly arctic air and this very unstable regime will initiate frequent squally wintry showers with snow on the high ground in the north

By Saturday the northerly regime covers the whole of the UK with possible the winds reaching gale force in some areas so quite a nasty wind chill. A continuation of squally wintry showers that will likely be of snow on the high ground in Scotland and possible further south

The position at midnight Sunday finds the upper trough forced south as the ridge to the west comes under increasing pressure and it's a case of "where do we go from here"?

Edited October 23, 2018 by knocker

[knocker]

From late morning quite a lot of thick Ci and some high Ac here. The Sat image is the high res. MODIS for 1321 UTC (courtesy Dundee Satellite Receiving Station)

 

[knocker]

This evening and overnight still quite windy in northern and eastern areas but abating through the early hours, And still some patchy rain around in th north of Scotland. Elsewhere drier but probably quite a bit of cloud around so what with this and the wind quite mild night/

Edited October 23, 2018 by knocker

[knocker]

Today marks the last day before the transition to another regime and much colder air gets underway in earnest as can be seen below.

The 500mb and surface analysis for midnight

As can be seen everything is already in place for the upcoming transition with the upper trough in position over Greenland with the surface low and cold front in the Denmark Strait and south of Iceland. Meanwhile nearer home the high pressure is still in charge but due to the orientation of the high cell and the proximity of another front it will still be quite windy over Scotland today with some patchy rain/drizzle which may also occur in western regions further south during the day. But elsewhere, and where the cloud breaks, not a bad day and fairly mild. But by 1800 the aforementioned low has tracked west of Norway and the waving cold front is over the Hebrides

By midnight the front has nudged south with some patchy rain into western Scotland and still quite breezy.

By midday Thursday the waving front is straddled across northern Scotland and heavier and more persistent rain will effect most of Scotland and the north west of England by evening. But further south where there will be less cloud and lighter winds still a not bad day with temps around average or a tad above.

Overnight and through Friday the developing wave will track east to southern Sweden whilst the cold front tracks south east accompanied by patchy rain and with colder air in it's wake, clearing the south coast by midday. But in the now strong northerly airstream there are other fronts/troughs tracking south in the circulation and these will bring wintry showers with them, snow on the hills in the north, and even colder air.

The very cold air is well established by Saturday with widespread frosts and a nasty wind chill in the strong winds, Plus some very heft showers which will be concentrated more in the north and around the coasts with a mixture of snow. hail and thunder

But by Sunday the ridge that has amplified to the west has come under pressure from a new upper trough tracking east and has ridged north east across the UK thus negating the northerly flow and though still a cold day, a tad warmer in the south east with much of the wintry shower activity confined to eastern coasts and the south east

And this is the state of play at T120

Edited October 24, 2018 by knocker

[knocker]

Today, the high pressure that has been with us for quite some time, makes it’s exit. Giving way to a new regime of much cooler and unsettled weather that may be with us for a while.

The 500mb and surface analysis for midnight

A cloudy and mild start to the day in many places but this will a break somewhat over England and Wales during the day, particularly over eastern areas to give not a bad day. But the wave forming on the front to the west will continue this process and track east to be over northern Scotland by 1800. Thus rain will effect western Scotland by mid morning and spread to the rest of Scotland, N. Ireland and northern England by evening.

During this evening and over night the associated cold front will track south east introducing much colder unstable air with frequent heavy wintry showers in it's wake which are likely to be of snow over the high ground in all areas.

 

The front clears the south coast by midday leaving the the whole of the UK in a cold northerly with quite a nasty wind chill with frequent showers, of snow over the high ground in the north, which are rather concentrated there and in coastal areas

A similar story overnight and through Saturday with the surface wind veering a tad as changes are afoot out west with a very frost start to the day.

The changes mentioned above continue through Sunday and pressure on the ridge from a new upper trough realigns it north east across the UK cutting off the northerly flow and restricting the showers to the east coast. Where it in fact gets quite windy in the south as this reemerging pattern has also forced the original trough south where a surface low has formed on our old front over south east France and thus the strong easterly component to the wind in the south

My take on what happens on Monday was covered in a post last evening but to briefly to reiterate. Burgeoning high pressure in the western Atlantic forces the new trough south east which reinforces the similarly amplifying European high, All of which leaves the UK in a slack area of low pressure which portends broken cloud with sunny intervals, perhaps still some showers along the east coast, and still temps significantly below average, albeit fortunately little wind.

The NH profile at T120

Edited October 25, 2018 by knocker

[knocker]

Some interesting cloud formations on the HR Modis at 1130 UTC. Early St has gone from down here but a lot of thick Ci and some Sc.

The 1200 geostationary gives broader view with colder unstable air to the north west

Edited October 25, 2018 by knocker

[knocker]

The witching hour is upon us The cold front will make steady progress south during this evening and overnight, approaching the south  coast be 0600. Behind much colder air which will gradually veer and strengthen and frequent wintry showers, which will often be in organised bands.

Edited October 25, 2018 by knocker

[knocker]

The 500mb and surface analysis at midnight indicating the colder air quickly becoming established. And the Lerwick sounding as it's in the even colder air behind the occlusion as the wave moves into the North Sea.

As can be seen the cold front and band of patchy rain is already half way down the country at midnight and during this morning it will clear the south coast leaving the whole of the country in the unstable colder air with temps way down from of late. Frequent squally showers are already into N. Ireland and western Scotland and these will become more extensive during the day, mainly over exposed western and eastern coastal areas They will fall as sleet or snow over the higher ground in the north and there could well be some thunder in the mix as well.

The strong northerly wind will continue overnight as will the squally showers in the north and exposed coastal areas and becoming more concentrated in eastern areas as the wind veers a tad. Falling as snow over the high ground in the north Elsewhere with clear skies a widespread frost by morning.

Saturday is going to be a lousy day as the strong northerly wind continues with more frequent squally showers of just about everything including snow on the high ground probably in all parts of the UK and hail and thunder in exposed areas elsewhere but becoming more prevalent in the south east as the wind continues to veer.  Feeling very cold

Over Saturday night and through Sunday the northerly wind gets cut off as the high pressure to the west ridges north east across the country under pressure fro another upper trough pushing east in the north west. Thus the surface wind continues to veer and the showers become confined to eastern coastal regions. Another very cold day but fortunately not so windy

By midday Monday it's all happening. Strong ridging in the western Atlantic drives the aforementioned trough south east which not only reinforces a similar amplification of the European ridge but activates the low pressure to our south associated with our old friend the original waving front. All of this results in another cold and clear day for the UK with still some residual showers along the east coast.

Essentially on Tuesday the energy in the west runs up against the strong block to the east bringing all longitudinal movement to a halt which drives one trough down to Biscay and the other north into the North Sea which could well result in some windy and wet weather along eastern Britain. Elsewhere mainly dry with some scattered showers around in the west and another cold day.

The NH profile at T120

Edited October 26, 2018 by knocker

[knocker]

A further indication of shower distribution and intensity tomorrow?

[knocker]

The odd shower or two as the cold front is still to clear the south east on the 0900 geostationary image

[knocker]

And for a change super typhoon Yutu

http://rammb-slider.cira.colostate.edu/?sat=himawari&z=0&im=12&ts=1&st=0&et=0&speed=130&motion=loop&map=1&lat=0&opacity[0]=1&hidden[0]=0&pause=0&slider=-1&hide_controls=0&mouse_draw=0&follow_feature=0&follow_hide=0&s=rammb-slider&sec=full_disk&p[0]=16&x=11008&y=11008

[knocker]

Hey Ho, an unstable and cold NNW airdtream at midday

[knocker]

With reference to the above the Camborne sounding supports the fact of only quite small Cu here for the last few hours

[knocker]

If anything the northerly wind will strengthen this evening and overnight and the showers will become concentrated over northern Scotland, N. Ireland and western/eastern  coastal areas of England and Wales with a convergence line lurking over west Wales and Cornwall by morning. The showers over Scotland could well be of snow to low levels bringing ice int the equation but elsewhere likely rain/hail. For other areas a clear night with widespread fros

t.

Edited October 26, 2018 by knocker

[knocker]

After the weekend the next detail to sort concerns the low tracking North into the North Sea at the beginning of next week.

This evening's fax has it SE France 12 Monday which pretty much agrees with the ecm

And then, which will effect eastern coastal regions and perhaps some snow in NE France

 

Edited October 26, 2018 by knocker

[knocker]

Changeable weather over the next few days with temps remaining below average

The 500mb and surface analysis for midnight

Squally showers overnight, of snow over the high ground in Scotland but rain and rain/hail in the N. Ireland and and coastal regions of Wales and England. Note the Pembroke Dangler in the south west. These will tend to die out over N Ireland and Scotland during the day and become more concentrated along the east, south east coasts and central southern England as the wind veers somewhat. Elsewhere after a very frosty start very crisp and sunny but feeling very cold.

Showers continuing in the east overnight as the wind also continues to veer with the ridge edging across in the north. A widespread frost by morning

The ridge becomes more influential through Sunday but still very breezy in the south and once again showers of rain/hail. possibly some sleet, concentrated over eastern regions. Another very cold day but generally the wind has abated so less wind chill

By Monday the changes that have been mentioned in previous posts are underway with the amplification of the subtropical high in the western Atlantic forcing the next upper trough south east that also serves to reinforce the European ridge to the east of the UK  At the same time activating the low pressure to the south where a wave has formed on our old front over south east France. All of which results in calm and bright, but still cold, day for most with a few showers lingering along the east coast.

By Tuesday both troughs are caught in the pincer movement of the amplifying ridges and thus any longitudinal movement ceases resulting in the aforementioned  wave over France, deepening and tracking north into the southern North Sea. This will bring strong winds and possibly heavy rain to eastern regions but, obviously, the precise track of the low is the key to the extent of this.Whilst this going on elsewhere another dry and cold day after a frosty start

By Wednesday the North Sea low has filled and tracked north to be off the Norwegian coast and the Atlantic trough has taken closer order with a slack low pressure area to the south west and a waggly front up the Irish Sea. All resulting in patchy rain/showers in the west and dry with sunny intervals elsewhere and still cold

And the NH profile at T120

Edited October 27, 2018 by knocker

[knocker]

A cold morning

[knocker]

Nice geostationary image at 0900 UTC. We've still got the Dangler

Edited October 27, 2018 by knocker

[knocker]

High res. sat at 1100 UTC

[knocker]

Terrific image from the 1300UTC high res. MODIS (courtesy Dundee Receiving Satellite Station) The Dangler still operating down here and we had a pretty violent hail shower abut an hour ago.

Tropopause around 400mb!!

Edited October 27, 2018 by knocker

[Atmogenic]

1 hour ago, knocker said:

Tropopause around 400mb!!

sorry for my ignorant comment but what's so exciting about that? 

[knocker]

7 minutes ago, Atmogenic said:

sorry for my ignorant comment but what's so exciting about that? 

Well I wouldn't say it was exciting but it's good indicator of the northerly Arctic air. It's not often as low as that at this time of year and with a 500mb temp 0f -36C

[knocker]

Trough digging way south Weds.awaiting disruption, with strong WAA into Europe

[Atmogenic]

5 hours ago, knocker said:

Well I wouldn't say it was exciting but it's good indicator of the northerly Arctic air. It's not often as low as that at this time of year and with a 500mb temp 0f -36C

oh ok thanks for explaining