Models, teleconnections and nowcasting

[knocker]

As seen last evening the next critical period would appear to be, after the passage east of the midweek trough, the phasing of the subsequent troughs in mid Atlantic along with further amplification of the subtropical high in the wake of the previous trough. The position midday Friday

According to the gfs over the next three days the troughs duly merge with surface lows evolving in mid Atlantic and tracking north east. But the ridge is quite resilient and they make little impact on the UK and in fact the trough starts to deconstruct as the ridge continues to amplify. The upshot of all this is that most of the UK will stay dry and a lot warmer than of late with the exception of the far north west. If of course this pans out

Edited March 30, 2020 by knocker

[knocker]

Skipping the waffle the ecm take on the weekend

 

[knocker]

Clear skies here first thing, then a sheet of Sc wandered across which has since cleared, Some patchy cloud creeping in elsewhere I see

[knocker]

The preamble and detail for the weekend from this evening's ecm is not hugely different to this morning so I wont run through it all again except to say by Monday the frontal rain is a tad further east, but that's too far away to worry about that detail

 

[knocker]

The end of this week will se a brief interruption of the high pressure dominance

By midday tomorrow a trough that has broken away from the tpv is over Iceland and from there will track east  The cold front associated with the latter starts to move south across Scotland accompanied by rain and a strengthening wind. Further south fairly cloudy but dry

Over Wednesday night and through Thursday the Iceland trough duly moves east and merges with the tpv resulting in the surface wind veering over the UK with further fronts tracking south in the circulation. This introduces colder air in the North with snow showers in Scotland and perhaps gales along western coasts, But note yet another breakaway trough moving south along the eastern flank of the intense high pressure over Greenland

[knocker]

Over Friday and Saturday the aforementioned trough continues south and phases with the troughs further south which results in sundry surface low centers in the Atlantic with the main one south of Iceland. But at the same time the subtropical high amplifies so initially only N. Ireland and Scotland remain under the influence of unsettled weather

But as can be seen, according to the gfs further developments occur under the umbrella of the main trough with a surface low to the south west of Ireland by midday Sunday qith some quite warm air adverted into much of the UK Best left here I feel

Edited March 31, 2020 by knocker

[knocker]

Needless to say developments under the new Atlantic trough with the ecm are completely different, albeit not significantly regarding the UK weather for the weekend

Edited March 31, 2020 by knocker

[knocker]

In the ext period it still appears to be whether the re-alignment of the tpv, particularly the trough in the north west Atlantic will allow any signifant amplification of the Subtropical high in the east. At the moment the jury is still out on that

Edited March 31, 2020 by knocker

[knocker]

The gfs 06 follows on from the midnight re the low Sun/Mon

[knocker]

A simplistic overview of the NH anomaly charts from the EC weeklies update for the last half of April would simply be that the tpv alignment is not far away from what is being indicated in the ext period at the moment  The difference being that the Atlantic has withdrawn a tad and the subtropical has thus got more traction in the east. Hopefully this portends a more settled and drier spell

[knocker]

After the troughs merge in the Atlantic at the end of the week it is pretty much a battle over the weekend of the surface features in the Atlantic against the ridge and the gfs has been relatively consistent with this

Edited March 31, 2020 by knocker

[knocker]

The ecm has a different take on the formation and track of the surface low to the west of the country over the weekend but it still has a front sweeping across

[knocker]

And talking about diurnal variation. The radiation inversion at Nottingham on the midnight sounding with no wind

surface 1015mb temp 4.8C DP 0.8

.............1013mb temp 13.2C DP 7.3

Edited April 1, 2020 by knocker

[knocker]

The North Atlantic 500mb and surface analysis for midnight

Today the cold front associated with the low to the north slips south over Scotland and this will bring some rain and strengthening winds in the north whilst further south it will remain dry, perhaps the odd shower, albeit a lot cloudier than of late.

Not much change overnight except a further extension of the tpv tracks east across Iceland and it will become very windy in the north with wintry showers by morning as further fronts swing across

By tomorrow the wind will have veered in the north introducing colder air and heavy wintry showers with hail and snow in the mix

By Friday the well documented change is underway with a further extension of the tpv tracking south and phasing with the Atlantic trough whilst the subtropical high once more amplifies from the south Some rain in the north otherwise dry

Over the weekend it is the development of the surface features that are of interest, namely the Atlantic lows and the ridge and the result is advection of some very warm air and heavy rain encroaching N. Ireland and western Scotland by Sunday afternoon

 

Edited April 1, 2020 by knocker

[knocker]

According to the gfs over the next couple of days the low to the south west drifts across the UK and fills rapidly whilst another ridge develops; So showery giving way to drier conditions but best left there

[knocker]

The ecm doesn't really make much of the low to the south west Sun/Monday, it develops the one south of Iceland a lot more, but it does have a shallow wave tracking north east as the front crosses the country

 

[knocker]

The position of the Atlantic trough, relative to the ridge, would appear to be of some importance for two reasons.

1, the advection of warm air into the UK

2. How far will Atlantic frontal systems push east?

 

[knocker]

The North Atlantic 500mb and surface analysis for midnight

The ext of the tpv continues to move east into Scandinavia through today resulting in some very strong winds over northern Scotland and in particular the Shetland Isles. And as the associated fronts track south east it will become much coder in the north with frequent heavy showers of rain, hail and snow in Scotland. In short very wintry. Further south more cloud than of late, maybe the odd shower, but a tad warmer

Tonight the winds will abate but the wintry showers will continue in the far north and and a widespread frost here by morning. Less cold in the  south under the cloud blanket

Still some wintry showers in the north on Friday as an occlusion tracks south but elsewhere dry but mainly cloudy.

By Saturday the well documented phasing of the troughs has taken place in the Atlantic resulting in a complex area of low pressure west of Ireland. Whilst at the same time the subtropical high ridges over the UK and into Europe. Ergo staying dry and a tad warmer in most places

The area of low pressure becomes more concentrated on Sunday as it tracks north and the movement drags some very warm air up from the south whilst the associated front brings some rain into western areas

By Monday the low has intensified to be 953mb NE of Iceland whilst the UK remains more or less under the high pressure.The frontal rain will still effect many western areas over Sunday night before generally clearing through Monday

Edited April 2, 2020 by knocker

[knocker]

Over the next couple of days, according to the gfs, the trough/ridge pattern is well established which results in:-

1) another system tracking north east bringing some rain to western areas.

2) Continued advection of warmer air from the south

 

Edited April 2, 2020 by knocker

[knocker]

Once the front is out of the way on Monday the ecm is also cooking with gas next week

[knocker]

Very unpleasant at Lerwick at lunchtime/ Temp 2.8C and a steady 30kts from the NW

[johnholmes]

Just a 'pirie' blow as they call it

[knocker]

The gfs has some rapid cyclogenisis in mid Atlantic next week which, apart from generating WAA into Europe, has a weakish wave on an associated front tracking NE bringing some wet weather to the NW. For the moment anyway

Edited April 2, 2020 by knocker

[knocker]

I haven't posted the ext anomalies of late because the GEFS has been the fly in the ointment, perhaps this has changed in the last 12 hours

[knocker]

Not total agreement between the ext anomalies but all definitely singing from the same hymn sheet. Namely the alignment of the tpv, in particular the NW Atlantic trough, is conducive to the subtropical high amplifying in the east portending quite settled weather with temps nudging a tad above average.