Short range model discussion - into 2018

[knocker]

he gfs still looking at explosive cyclogenesis and severe gales in Scotland on Friday

 

[knocker]

The ecm also going along with some EC. A touch of the left exits?

Edited December 3, 2018 by knocker

[knocker]

Outlook - We at last are losing the upper trough but the respite is but brief as unsettled weather returns, particularly at the end of the week

The NH 500mb and surface analysis for midnight

apart from a few showers,, snow over the mountains, in Scotland it has been a clear night with a widespread frost this morning

And it will remain clear and sunny for most, cooler in the south than of late, with the exception being a continuation of showers over western Scotland and from late morning cloud and then rain will ingress the south west from the warm front associated wit the low to the south west of Cornwall. The rain will then track north east during the afternoon.

The movement of the warm front, and the frontal system behind, will continue through the evening and overnight and some snow may occur on the warm/cold air boundary on the higher ground in north Wales, the Peak District, the Pennines and further north but rather depending on how far north the front gets.

The fronts and rain will continue to edge east through Wednesday, with a heavier band of rain on the cold front, just about clearing the east coast by evening leaving sunshine and showers in it's wake. For a change northern and western Scotland will miss all of this. Warm air will also be reintroduced in the south.

This system clears away quickly Wednesday evening but another system whips though on Thursday giving a breezy day with patchy rain and sunny intervals on what is a very mild day with temps above average.

But whilst this is going on a low is developing along the front at the base of the upper trough to the south west and explosive cyclogenesis occurs as it tracks quickly north east on the very strong jet and by 12 Friday it is 962 mb over northern Scotland. Thus rain and very strong winds with severe gales for a time over exposed areas

The low fills and slips down into the North Sea by Saturday thus for a time quite windy down the east coast but generally sunny intervals and showers although by late afternoon more general rain may well effect western regions from another frontal system.

And the NH profile at T120

 

Edited December 4, 2018 by knocker

[knocker]

This morning's updated fax charts for Thurs/Friday and the ecm for Saturday

 

[knocker]

The occlusion showing on the 0600 WV image.

Edited December 4, 2018 by knocker

[knocker]

I'm not sure whether us lesser mortals should continue to persevere now that the forum heavyweights have made their thoughts clear but I suppose if only for continuity.

We have had As/Ac here since quite early this morning but still no rain as yet. The frontal surface shows up well on the midday Aberporth sounding. The sat image is at 1500

 

[knocker]

Further to the above the frontal rain will shortly be arriving here and will track north east through this evening and overnight. It may fall as snow on the frontal boundary but I suspect only on quite high ground such as in N. Wales for example. Not as cold tonight behind the front(s) but in the clearer air over Scotland another quite severe frost.

[knocker]

The gfs take on Friday's low. Certainly looking at severe gales for a time in the north.

[knocker]

Still no agreement on Friday's low

[knocker]

Outlook - wet and windy before becoming more settled and colder at the end of the period.

The NH 500mb and surface analysis for midnight.

It is a contrasting night with cloud and milder air in the south whilst it is clearer in the north with a quite severe frost likely in Scotland. The 0300 chart illustrates this quite well.

As the frontal system continues to track north east, the rain currently over North Wales and the Midlands will do likewise, possibly snow on the high ground, with the main belt clearing the NE coast by early afternoon. But at the same time the secondary belt related to the cold front will track east across the country and will still be lingering over East Anglia at 1800.  Some showers across the west of England and Wales in the wake of this  A marked N/S temp contrast

The rain will soon clear eastern areas during this evening leaving a cloudy and fairly muggy night for must but by 0300 more rain from the nest frontal system will effect N. Ireland and western Scotland by 0300 moving east.

Through Thursday the fronts from the aforementioned system will traverse the country giving periods of rain/showers and sunny intervals and quite mild., But the important thing to note here is the wave forming on the cold front at the base of the upper trough away to the south west.

This low deepens very rapidly over the next 24 hours and tracks north east through N. Ireland to be north of Scotland by 1200 Friday ( There is always some uncertainty vis a rapidly deepening low)  This will bring rain, followed by squally showers once the cold front is through but, more to the point, very strong winds with severe gales in the north. Temps a tad immaterial but relatively mild.

The main low clears into southern Norway overnight Friday into Saturday bur another low with associated fronts tracks quickly east during Saturday bringing periods of rain followed by sunny intervals and squally showers  Albeit pretty mild apart from Scotland.

By Sunday the transition is underway with the subtropical high amplifying to the west and the surface wind veering northerly initiating the cooler regime mentioned earlier.

And the NH profile at T120

Edited December 5, 2018 by knocker

[knocker]

This morning's update for Friday

 

[Polar Maritime]

Thanks Knocker for the detailed updates in here, Looks like Sunday could be the worst to hit regarding gales especially for the Southeast going by the NetW-MR Model.

[knocker]

Yes PM the ecm is the same. A result of the high amplifying to the west and the trough dropping south to the east

[knocker]

Cornwall attempting to peek out of the clouds on the 1300 MODIS image. Interesting geostationary at 1200 showing not only our trailing front but the mass pf cloud associated with system in mid Atlantic. Still a marked N/S temp contrast

[knocker]

Today's frontal rain will finally clear the east coast this evening leaving a generally cloudy night, with bits and pieces of drizzle/rain, mainly in the west. But from around 0400 heavier rain will effect N. Ireland and western Scotland associated with the next frontal system.And thus milder here than recent nights.

Edited December 5, 2018 by knocker

[knocker]

This evening's update for Friday

 

[knocker]

Outlook - wet and windy becoming more settled and colder

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

It's been a cloudy and mild night generally but rain from the frontal system associated with the deep depression south of Iceland is just about encroaching N. Ireland and western Scotland.and will track south east through northern and western areas through the morning. More persistent rain will effect the south west and Wales during the afternoon as the cold front waves and it is on this that a low is deepening quite rapidly west of southern Ireland. Another very mild day

The low continues to deepen and track NNE through this evening and overnight with the wind picking up whilst the rain moves north east to effect all areas by morning.

by 12 Friday the low is 963mb just west of the Hebrides and much of the rain has cleared with the cold front to the east leaving many squally showers in it's wake in the very strong WNW wind. This wind is the major issue and further north we are looking at severe gales and here the heavy rain will persist.

Over Friday night and through Saturday the low starts to fill and track into southern Norway so the strong NW winds and blustery showers will continue for a while before abating somewhat but on Saturday rain from an occlusion associated with a new low that has tracked east to be west of Ireland will bring more rain to many areas with winds picking up again in the south Another very mild day

The rain clears overnight on Saturday and by now the pattern transition is well underway with the subtropical high ridging in the west and the surface wind veering northerly, abating, and introducing cooler air in the north.

By Monday the ridge has been pushed east to be over the UK by the energy exiting North America, and the upper trough in the Atlantic, resulting in a mainly dry day with light winds but appreciable colder than of late.

And on to the NH profile at T120 which illustrates the last point quite well

Edited December 6, 2018 by knocker

[knocker]

The midday geostationary image. Classic warm sector down here. Low Status, moderate drizzle and thick mist

Edited December 6, 2018 by knocker

[knocker]

The 1500 analysis

[knocker]

The weather over the next 18 hours is essentially linked to the wave depression, currently forming to the west of southern Ireland , and it's rapid  deepening as it tracks north east to be very adjacent to Strornoway, and it's associated fronts as they move north east across the country.

All of this results in the winds strengthening through the night and by tomorrow morning these could reach severe gale in the north with gusts possible up to 80mph in exposed areas. Added to this there will be a lot of rain. The initial pulse will track north east this evening and through the early hours and effect most areas. But this will be followed by the heavy rain on the cold front which will track east through the early hours and tomorrow morning, This will in particular effect southern areas, south of the Humber, and should clear the south east by lunchtime, followed by squally showers. And by this time more persistent  heavy rain will be effecting western Scotland.

[phil nw.]

That low on Friday looks quite a beast with severe gales especially across W.Scotland.

Following the wind and rain over the next couple of days we start to see the Azores ridge pushing into the west by Sunday with the strong winds starting to abate as they turn north west to northerly.

This will bring in colder polar air through the rest of the day with temperatures gradually falling. 

 

 

Edited December 6, 2018 by phil nw.

[knocker]

Outlook - wet and windy becoming calmer, drier and cooler

The NH 500mb profile and surface analysis for midnight and euro chart for 0400

The frontal system associated with the deepening low adjacent to the Hebrides, is currently traversing the country accompanied by heavy rain. Particularly down the western half of England, and all of Wales, associated with the cold front. This will clear from the west during the morning giving way to squally showers which will be very frequent in the north, even coalescing into longer periods of rain, where the strongest winds will also occur with gales and severe gales in exposed areas. A very mild day.

The strong winds will continue this evening and overnight, but moving a tad further south, with a continuation of the squally showers which will gradually become more concentrated in the north

During saturday the low is filling and moving to a position south of Norway thus the wind will abate and veer with the showers eventually dying out but more cloud and rain will start effecting south western areas courtesy of an occlusion associated with another low out to the west. All of which is under the auspices of the upper trough. Temps still okay.

Over Saturday night and through Sunday the pattern change gets underway with the subtropical high amplifying to the west and the upper trough dropping south to the east. Thus again the wind will veer northerly and cooler air will be introduced behind the occlusion which is traveling south. Any showers confined to coastal areas or perhaps the odd snow flurry over the Scottish mountains.

During Monday and Tuesday the ridge, now over the UK, comes under increasing pressure from the complex upper trough in the Atlantic and the massive amount of energy exiting the eastern seaboard. The detail of this has been touched upon in previous posts so will leave it there. Suffice it to say this results in a couple of dry days for the UK with weakening fronts gradually encroaching from the west.

And the NH profile for T120 which illustrates the last point very well

[knocker]

The cold front is through here with some large Cu developing

[knocker]

As I mentioned the cold front is through an now squally showers

[knocker]

The high res. MODIS at 1100 indicates that the front is moving rapidly