Short range model discussion - into 2018

[knocker]

Looking pretty dry over the next five days apart from west Wales, NW England and in particular NW Scotland but no big surprise there.

[knocker]

The 1200 geostationary courtesy Dundee Satellite Station.

 

[knocker]

Friday still remains the 'window' between a front tomorrow that fragments over the UK and the next frontal system arriving on Saturday which tracks around the high pressure which is centred too far to the south west.

Edited January 24, 2018 by knocker

[knocker]

Before looking at the short term detail a quick observation vis the well sign posted forthcoming medium term pattern changes if I may. NOAA, the GEFS and EPS anomalies have been very consistent of late regarding this and without going into detail can be summed up thus.

A strong EPO ridge into Siberia in conjunction with an active Vortex lobe N. Canada and trough down the eastern US results in a highly amplified pattern upstream with a strong jet running south of the trough out of the eastern seaboard and across the Atlantic. Downstream the Azores attempts to ridge ridge north but with limited success for two reasons. Firstly the aforementioned energy suppresses northward movement and secondly it phases with the European trough that has become positively tilted south of the UK which tends to orientate the ridge north east over the UK. Thus portending settled and drier weather except possible the far north. I'll just post last night's NOAA charts as an illustration of what I mean as it is not really within the remit of this thread.

Right back to the short term. A much better day today after yesterdays wind and rain which can essentially be split into two halves. The eastern pert of the UK will generally be dry with little wind whilst the west will be subject to squally showers, particularly in N. Ireland and Scotland where thunder and hail could be involved. But these will also die out overnight and into tomorrow as a transient ridge moves east associated with some amplification to the west and the upper trough deconstructing in the vicinity of the UK

So make the most of Friday as by Saturday the eastbound energy has suppressed the ridge allowing fronts associated with a low south of Iceland to cross the UK bringing rain to most places.

These clear quite quickly  and by Sunday the HP is attempting to ridge again but as can be seen systems are still sneaking around the top and a front is already impacting the north by midday Sunday and proceeds to track south.

As can also be seen, which of course complicates matters further, the aforementioned front is associated with our perennial cut off low to the south west and another energy channel, albeit it's journey south across the UK is driven from the north west. And there we must leave it.

 

 

Edited January 25, 2018 by knocker

[knocker]

The very recent update of the fax for Saturday shows an intense low to the north west of Scotland and a wet and windy day for all as the fronts cross the country

Edited January 25, 2018 by knocker

[northwestsnow]

3 minutes ago, knocker said:

The very recent update of the fax for Saturday shows an intense low to the north west of Scotland and a wet and windy day for all as the fronts cross the country

Indeed.

Lets hope things settle down a bit thereafter, far to much rain round these parts for my liking this last few days ..

[knocker]

This morning's NA sat. image, apart from showing the showers down the western side of the UK, clearly shows the wodge of cloud south of greenland that divides the trough to the west and the ridge.

It is this trough that tracks quickly east, suppressing the ridge that bodes a wet and windy Saturday

[knocker]

The midday geostationary again highlighting the showers down the western side of the UK which I can verify as just had a heavy hail shower here.

Courtesy Dundee Satellite Station

 

[swebby]

1 hour ago, knocker said:

The midday geostationary again highlighting the showers down the western side of the UK which I can verify as just had a heavy hail shower here.

Courtesy Dundee Satellite Station

 

This and the radar show the troughs and 1st occluded front as plotted on the 12utc fax. Looks reasonably dry between the two occluded fronts.

 

[knocker]

A dry and quiet day tomorrow but by 1800 the forces from the west are gathering with a jet running around the south of the trough in the western Atlantic joining forces with the vortex energy stream resulting in systems tracking around the high pressure that is centred too far to the south west.

Thus by 1200 Saturday we have the resulting low south east of Iceland with the dissociated fronts bringing wet and windy conditions to all.

Edited January 25, 2018 by knocker

[knocker]

As I mentioned yesterday morning the expected forthcoming pattern change has been well signposted and i feel it worth mentioning again this morning, illustrated by a couple of the the GEFS anomalies, as it puts where we are going in the short term  into perspective.

As can be seen in the 2-7 range upstream there is a strong high cell in the Bering Sea area, the Canadian vortex and a fairly flat flow across North America  This results in a strong westerly upper flow across the Atlantic around the high pressure to the south which becomes influenced in the eastern Atlantic by the cut off upper low in the western Mediterranean. Quite important because quite early on in the piece the interaction between the east bound energy and the orientation of the high pressure is paramount.

But as can be seen as we move quickly into the 5-10 period upstream becomes much more amplified with the EPO ridge and the N. American trough which in turn reflects on the downstream high/trough axis but that is for another thread.

So back to the here and now. Not a lot to add to last evening. Today will be a much better day, less wind and sunny intervals for most so enjoy as the next complex frontal system is on it's way by late this evening. (Don't know where Exeter find all these fronts ) These duly cross the UK on Saturday bringing rain and strong winds, perhaps gales in Scotland, leaving sunny spells and squally showers in the their wake.

By 1200 Sunday the high pressure is semi in charge with the UK in a fresh, quite mild, westerly flow and dry for most areas. The exception being northern Scotland where the influence of the cut off low way to the south west is being felt with a front trailing from there around the high pressure into Scotland. The two energy flows can be clearly seen on the 500mb chart.

A wave forms on the front and tracks into Norway though Monday whilst the energy in the northern arm exerts some control and the front itself tracks south bringing rain with it as it travels and leaving cooler brighter weather in it's wake

From this point we are rapidly entering the arena where we started this morning so best left here.

[James1979]

A great thread/read, so nice to be able to read about weather in the more reliable timeframe, thanks.

Edited January 26, 2018 by James1979

[knocker]

The 0600 analysis and satellite clearly showing the system that will cross the country tomorrow

[knocker]

Warm front west of Ireland at 1200 with associated cloud at around 12, 000 feet and warmer air aloft already indicated on the midday Valentia sounding

[knocker]

And at 1800

 

Edited January 26, 2018 by knocker

[Ukwoody]

4 hours ago, Sweatyman said:

What is this? The Knocker thread?

No far from it, but He does kindly post most days.  So does John Holmes and a few others normally

 

[Rocheydub]

Indeed, and I'm very grateful to knocker for his opinion on the output. It's my first port of call when I log in here these days!

[Sweatyman]

Indeed ! Said in jest.carry on knocker

[Rocheydub]

This evening.

[knocker]

Along the theme of yesterday last night's NOAA to get some general context. I wont go into detail, much the same as yesterday, but the 6-10 is very pertinent to the the near time evolution with the HP/trough axis in the eastern Atlantic. The divergence of the upper flow in the later period, although of much interest, will be subject of discussion elsewhere.

Today the front(s) and rain currently affecting the west of the UK will move east during the morning becoming quite patchy further south but heavy in Scotland where there may well be severe gales later as the low pressures to the NW merge and track ESE to be north of the Shetlands by midnight.

The gales abate overnight and Sunday sees the UK in a brisk, moist, and relatively mild airstream but heavy rain is impacting Scotland courtesy of the front previously discussed associated with the low away to the south west which briefly subjects the UK to two energy flows.

The front is forced south overnight Sunday through Monday as the main energy flow out of the eastern seaboard exerts itself clearing the south coast by Monday evening.

By 1200 Tuesday we are at the beginning of the upstream pattern changes and the Atlantic is the scene of the battle between the east bound energy leaving North America and the high pressure to the south with the UK at the coal face of this interaction, This is quite well illustrated taking three charts for that that time.

flash forward another 24 hours and with the HP amplifying north as part of this interaction and thus the trough tracking south east you can see where the NOAA anomaly is coming from, albeit slightly earlier, but illustrated very well by the GEFS 2-7 this morning. And this sets the tone, so to speak

Edited January 27, 2018 by knocker

[knocker]

deleted

Edited January 27, 2018 by knocker

[knocker]

The 3-7 ecm det. anomaly illustrates very well the troughs to the NE and SSW are influencing the upper flow in the eastern Atlantic

Edited January 27, 2018 by knocker

[knocker]

Looking at the pattern change upstream as mentioned above from the Pacific angle with the knock on affects downstream such as the strong jet exiting south of the trough over N. America

 

Edited January 27, 2018 by knocker

[chrisbell-nottheweatherman]

2 hours ago, knocker said:

Looking at the pattern change upstream as mentioned above from the Pacific angle with the knock on affects downstream such as the strong jet exiting south of the trough over N. America

 

Presumably, this is likely to fire-up a fairly flat jet over the Atlantic.  If I might ask a question in order to clarify something; in your main post this morning you mentioned a brief period during which the UK willbe affected  by two energy flows - are you referring to the warm front lingering over the E corner as the cold front swings in to the Western Isles?

Cheers.

[knocker]

9 minutes ago, chrisbell-nottheweatherman said:

Presumably, this is likely to fire-up a fairly flat jet over the Atlantic.  If I might ask a question in order to clarify something; in your main post this morning you mentioned a brief period during which the UK willbe affected  by two energy flows - are you referring to the warm front lingering over the E corner as the cold front swings in to the Western Isles?

Cheers.

Not specifically to two fronts Chris although one is associated with the trailing front to the south west along which waves are forming. But that is down the east side of the Bermuda ridge and the other flow is around the north of the ridge from the eastern seaboard and eventually become dominant.