Short range model discussion - into 2018

[knocker]

There is fog here at the moment with the sky obscured but looking at the 1300 chart you can see the moderate rain to the east and south east whilst further north already appears to be in showery conditions.

Edited February 14, 2018 by knocker

[knocker]

So we did sneak into the warm sector down here thus the fog

Edited February 14, 2018 by knocker

[chrisbell-nottheweatherman]

29 minutes ago, knocker said:

So we did sneak into the warm sector down here thus the fog

I see the Met Office found a small area around the low without fronts, so filled it with a couple of troughs.

[knocker]

1 hour ago, chrisbell-nottheweatherman said:

I see the Met Office found a small area around the low without fronts, so filled it with a couple of troughs.

It's becoming a tricky just saying the front will track west-east across the UK these days . you can see the cold front skirting SE Ireland and roughly the triple point on the 1415 Modis and the 1500 geo.

Edited February 14, 2018 by knocker

[chrisbell-nottheweatherman]

2 minutes ago, knocker said:

It's becoming a tricky just saying the front will track west-east across the UK these days . you can see the cold front skirting SE Ireland and roughly the triple point on the 1415 Modis.

I'm amazed by how well-defined the triple point is.  Thanks for pointing it out.

[knocker]

Anyway once the front(s) have cleared east later this evening the winds will abate apart from in N. Ireland and western Scotland where wintry showers will persist over night. Quite a spread of min temps tomorrow but feeling cold in the north in the still fresh winds.

 

[knocker]

A quick run down on tonight's medium term anomalies which are not in fact much different to yesterday and still in fair agreement.

So still Siberian vortex lobe, east pacific ridge and Hudson Bay vortex, And the twin troughs associated with the latter, one SW through central Canada to the SW United States and the other south east into mid Atlantic with high pressure over the south east U.S. Still a highly amplified pattern with strong upper westerlies leaving the eastern seaboard but the amplification continues in the Atlantic arena with strong ridging east of the trough north through the UK with another trough to the east. All resulting in the aforementioned upper flow turning sharply north into eastern Greenland/Iceland and stalling any west-east movement, thus depressions forming in the favorable environment will drift N/NE. Which of course all means that the UK will stay under the influence of high pressure portending a dry period with temps a little below average leaving the key question, where will the surface high cell reside. At the moment according to the EPS to the N/NE of the UK but this the det. runs will need to sort.

[knocker]

As a general overview today sees the start of a few days that will be dryer, with less wind and not as cold. This does not rule out weak fronts being forced east around, or even through, the burgeoning high pressure from the south west.The 500mb GPH and and wind barbs for Saturday 00 illustrates this quite well with the trough to the NE, high to the SW and the energy flow along the interface that does this forcing. Having said that we are not talking anything dramatic.

Anyway a little more detail.A much better day today for most of England Wales with less wind and plenty of sunshine. Maybe the odd shower in the southwest and west Wales. But the western regions of N. Ireland, Scotland and north west England will still be quite windy with frequent wintry showers of rain, sleet, hail and snow with the odd blizzard in the mountains and feeling very cold here after an icy start to the day but temps rising to 8 or 9c further south. This will continue overnight but generally easing by morning where it will be another cold start to the day.

So sunny with little wind for most areas on Friday as the high pressure is in charge but still fairly windy in the north with some wintry showers but much less frequent but by evening an occlusion and patchy rain will have reached N. Ireland and western Scotland. This patchy rain will continue to affect the north west over night and into Saturday.

The rest of the country will remain dry with light winds but by 1800 (keeping in mind the opening remarks) a small wave that has formed to the west has arrived to the north west of Scotland with a weakening front  and this front will track south east overnight and into Sunday so although no longer very active will bring cloud to most areas, albeit it will be quite mild.

 

Thus we arrive at Monday more or less where we came in but some rapid transitions are afoot and there we must leave it.

 

Edited February 15, 2018 by knocker

[knocker]

It can be seen from the 06 fax that the weather in NW Scotland is pretty lousy.

And if you like keeping track of current conditions at different places the METO WOW site is quite nifty

https://wow.metoffice.gov.uk/

[knocker]

The 1100 Modis illustrates Scotland bearing the brunt and the midday geo shows nothing sinister lurking in the woodshed apart from a weak system away to the south west.

Edited February 15, 2018 by knocker

[knocker]

A chance of thundersnow in the NW/W of Scotland in the next few hours according to the METO

[knocker]

The wind and wintry showers associated with the deep low over Iceland and the associated occlusion will continue this evening and overnight in NW Scotland but will abate somewhat by morning. Where, after a widespread frost, most places will have a fine day with little wind but still perhaps the odd shower or two in western Scotland.

But by 00 saturday a weakening occlusion has pushed east and is already bringing cloud and perhaps some patchy rain/drizzle to western parts but leaving a mainly dry day for most of the UK.

What is interesting here (well I think so) is the strong low level jet (energy) leaving the south eastern seaboard thanks to the squeeze between the vortex trough to the north and high pressure in the Gulf of Mexico. Ideal for a spot of cyclogenesis.

Over Sunday and Monday staying dry and very mild but probably cloudy in most places courtesy of a couple of weak fronts pushing across the country courtesy of the aforementioned events in the western Atlantic,

 

 

Edited February 15, 2018 by knocker

[knocker]

To supplement the above the updated fax for Sunday

[Andy Bown]

Thanks Knocker. A few days ago I really thought we were looking forward to a settled period starting today, but no, several troughs brought showers today and fronts will be turning up over the weekend! Drizzle is guaranteed.

When will we be front and trough free!!??

[knocker]

3 minutes ago, Andy Bown said:

Thanks Knocker. A few days ago I really thought we were looking forward to a settled period starting today, but no, several troughs brought showers today and fronts will be turning up over the weekend! Drizzle is guaranteed.

When will we be front and trough free!!??

I know it's blasted annoying, so hoping to make the most of tomorrow and hopefully Saturday

[knocker]

Interesting ecm this evening

At t72 the deep low tracking NE/N in mid Atlantic promotes the Azores ridging north east adjacent to the UK but which is interrupted by the warm front associated with the latter crossing the country.upon which a wave forms which is over south east England by T96. Quite a key intervention as it happens.

The cold front associated with the same system then tracks east bringing rain  to the UK by midday Tuesday whilst the low pressure to the south east consolidates.

 

Edited February 15, 2018 by knocker

[knocker]

And so on to this evening's anomalies in this interesting current evolution.

They do not in fact shed much light although they are in pretty good agreement. I won't repeat the upstream spiel as nothing has changed except to reiterate that is still a very strong westerly jet leaving the eastern seaboard thanks to the vortex/trough to the north and the high pressure in the Gulf of Mexico. But thanks to the impressive amplification in the Atlantic arena it gets no further than mid Atlantic before turning south westerly, then southerly and thus depressions formed in this favorable environment will tend to track NE/N. It is this amplification that is the problem, or to be more precise. the precise alignment of the trough/ridge/trough trio which to a great extent will dictate the position of the high cell relative to the UK upon which the sanity of so many depends. Assuming of course that it's not too late, I think it's safe to say it will be dry and colder than average but the det runs will need to sort the detail.

[knocker]

This morning sees the continuation of the battle between the air, a combination of Pm and Tm, and systems from the west driven by the twin energy flows leaving N. America and the Pc air to the east, with the UK tending to be the battle zone. This has been see sawing of late and this morning is no exception with the gfs siding with the former in the short and medium term. Nothing definitive here.

Today after a widespread frost will be dry, sunny and with little wind in most places the exception being N. Ireland and Scotland where it will be cloudier and breezier. Max temps in the 7-8C range. But during the day cloud and rain associated with an occlusion will affect N. Ireland and Scotland and track south east continuing overnight which could give some light snow on high ground.

Saturday will be mostly dry and sunny but cloudier in the west with perhaps some patchy drizzle thanks to the weakening occlusion and some wintry showers in NW Scotland. And Saturday is not a bad illustration of the two energy flows and different airmasses to the west.

As can be seen from the last chart another frontal system is on it's way from the west and duly crosses the UK on Sunday bringing with it cloud and patchy drizzle albeit quite mild with temps reaching the giddy heights of 12C in places.

This cloudy, mild air with the odd patch of drizzle continues though Monday and Tuesday as the high cell dominates but things are stirring away to the south west in the vicinity of the cut off upper low but there we must leave it.

 

 

 

Edited February 16, 2018 by knocker

[knocker]

The latest fax update for 1200 Sunday has the warm front down NW England, Wales and Cornwall which fits in okay with the above and the usual Exeter convolutions for Scotland and N.Ireland. And the latest surface analysis

[knocker]

Interesting that the ecm has a wave on the warm front at 1200 Monday not a million miles away from the where the latest fax chart has it  And at T96 has it over central France but crucially the upper trough and cold front west of Ireland has split the ridge . The two actions in combination allow the high cell to the north east along with the low pressure to the south to initiate an easterly flow over the southern UK with the ridge to the west curtailing any east bound energy. This then establishes the dominance of the high cell over southern Scandinavia and is not a long way from it's position yesterday evening.

 

Edited February 16, 2018 by knocker

[chrisbell-nottheweatherman]

3 hours ago, knocker said:

The latest fax update for 1200 Sunday has the warm front down NW England, Wales and Cornwall which fits in okay with the above and the usual Exeter convolutions for Scotland and N.Ireland.

What the heck sort of occlusion is that over SW Scotland?  I understand the warm sector, but I can't visualise what's happening in terms of airmasses at the triple point where two occlusions join a warm front or what's happening at the other triple point where another warm front joins one of the occlusions!

Edited February 16, 2018 by chrisbell-nottheweatherman

[knocker]

Best not to ponder too much Chris. Anyway a very nice high res. Modis at 1145 courtesy Dundee Satellite Receiving Station

 

Edited February 16, 2018 by knocker

[knocker]

As I  mentioned earlier, and no doubt others have mentioned elsewhere, the gfs and ecm start diverging very early, around T72 or even earlier so that by Tuesday 00 the differences are quite marked and the way is paved for the starkly different evolution. These charts are not particularly detailed but the difference in the handling of the European low and blocking of the energy to the west by the ecm, allowing the Scandinavian HP to ridge south west is evident. And from it was all downhill. Just to throw in the UKMO for good measure

Edited February 16, 2018 by knocker

[knocker]

A band of rain, perhaps some snow over the high ground in Scotland, will move south east on the weakening occlusion overnight which will linger over the south west and central areas of England in the morning. Drier and brighter elsewhere but showers in the NW of Scotland.Just to note a veil of Cs has recently encroached here with some Ac courtesy of said front as indicated on the Camborne 1200 sounding.

[knocker]

And the later Modis for 1330