Short range model discussion - into 2018

[knocker]

On the 12 analysis you can clearly see moderate snow on some stations in the East Midlands and down as far as Surrey.with temps 0C whist to the west moderates rain in the warmer air. Fine margins and as I said earlier the models are never going to get the intensity and distribution of snow area correct.

Edited January 21, 2018 by knocker

[knocker]

An eye needs to kept on this little feature in the early hours tomorrow in areas in the south west on flood alerts. It should be quite short lived as it moves away quite quickly

[knocker]

Once again the gfs is keen on rapidly developing the low as it tracks rapidly north east over Scotland Tues/Weds as it interacts with the jet.

Edited January 21, 2018 by knocker

[knocker]

The ecm differs from the gfs and has Weds low 962mb north of Scotland which could lead briefly to severe gales in the Western Isles gusting in the 60kt region. Not a million miles away from this morning's fax.

[knocker]

A general overall assessment of this week as  wet and windy will not be far from the mark before a pattern change gets underway.

A bit more detail. After yesterdays shenanigans a much quieter and drier day for most with a couple of exceptions. Low pressure north of Scotland is still bringing strong winds and rain to the northern areas there and a frontal wave is currently traversing the south west bringing more rain there. This should clear quickly this morning followed soon after by a clearance in the north leaving a very transient ridge.

I say transient because overnight fronts, associated with a complex low pressure area covering the whole of the eastern Atlantic, are already bringing rain and strong winds to the west which spreads east during Tuesday, the rain heavy in some places, before clearing leaving blustery showers. But this not all. By 1800 another wave is forming in the circulation of the main low west of Ireland.

This low develops very quickly and rapidly deepens as it interacts with the jet and tracks north east to be 964mb over the Hebrides by 0600 on Wednesday en route to south west Norway. This will bring gales to western areas of the UK, perhaps severe in Scotland and gusts in the 55-65Kt range cannot be riled out. Also heavy rain in the north and rain across the rest of the UK as the associated front tracks south east during the day.

As noted the low moves away quickly leaving the UK in a strong, showery, westerly but changes are afoot. The upper trough has been moving steadily east, not before another surface low has nipped across Scotland, and amplification is taking place with the Bermuda high pressure ridging in the Atlantic and the Azores doing likewise north east through central Europe. This achieves in two things. Firstly it disrupts the trough and creates a cut off upper low in the Mediterranean/ N. Africa region and secondly halts the west-east movement of any systems and once more establishes a battle between the twin energy systems leaving Canada and the southern US and the high pressure. The stage is thus set.

Edited January 22, 2018 by knocker

[knocker]

The ecm doesn't deepen weds low quite as much 974mb northern Scotland at 06 but  still gusting 55-60 kt region in the western Scotland and northern England.

[knocker]

The front and moderate rain have cleared here now clear skies.

Edited January 22, 2018 by knocker

[Sky Full]

I find it fascinating to watch the subtle differences between the models even at +72hrs - 

UKMO       ECM 

GFS         GEM  

There is no disguising the Atlantic depressions queueing up to affect our weather in the short term - all in agreement there - but the small differences between the models at this image date can lead to massive disagreement in terms of what they are predicting in 10 days time.  It is certainly worth making calculated guesses (forecasts?) but in reality anything can happen post +72hrs.....

[knocker]

A front and rain will impact western regions later tonight and and move east overnight and through the morning and post the passage windy with showers

But by 1800 tomorrow the forecast intense low is beginning to evolve to the west of Ireland and is already 988mb and over the next 12 hours it deepens considerable to be 962mb over the Hebrides. This will bring heavy rain and strong winds, perhaps briefly severe gales in the west of Scotland. Still somewhat dependent on the precise track and intensity. The associated front will track south east of the rest of Britain during the day so wet and windy everywhere else as well.

[knocker]

This early deconstruction of the Atlantic trough that results in low pressure to the SSE could well be quite important as the Canadian vortex gains much oomph in the ext period and the westerly upper flow splits in the eastern Atlantic with one arm swinging sharp SSE.

Edited January 22, 2018 by knocker

[damianslaw]

1 hour ago, knocker said:

This early deconstruction of the Atlantic trough that results in low pressure to the SSE could well be quite important as the Canadian vortex gains much oomph in the ext period and the westerly upper flow splits in the eastern Atlantic with one arm swinging sharp SSE.

Split flow looks likely as we end the month - might we see cold from the 'back door' so to speak, i.e. a cold flow anchoring down from the NE into Europe creating a deep cold pool - plausible.

[knocker]

Today there will be outbreaks of rain in many areas, and quite windy, as a front crosses the country from west to east. Post the passage of the front there will be blustery showers, mainly in the western coastal regions, in the resulting W/SW airflow

But by this evening the next low to the west is getting organized, as can be seen on the above fax chart, and tomorrow is going to wet and very windy in all areas. A quick look as to how this develops with this morning's gfs.

As already noted by 1800 it is poised to the west of Ireland and over the next 24 hours it tracks rapidly north east and deepens to be east of the Shetlands 957mb by 1800 tomorrow, This will bring heavy rain the very strong winds to the UK as it swings past close to Scotland en route and the associated front tracks south east across the UK. Winds could well gust in the 50-60kt region. Even at this late stage the track and depth of the low are still open to some adjustment

Once the low has cleared, the eastern Atlantic, including the UK, is under the influence of the upper trough that has edged east and another surface low impacts Scotland with more rain, but the amplification mentioned yesterday is underway with high pressure ridging in mid Atlantic and north east through central Europe.

By 1200 Friday as the whole pattern edges west the trough is deconstructing leading to a cut off upper low in the Mediterranean area, but at this stage there is still enough upstream energy to drive systems around the Azores HP before fragmenting in the region of the UK

This could well be a key moment in the evolution because by 1200 Saturday the high pressure is consolidating in the vicinity of the UK with the twin energy flows split much further west. Thus the durability of the high pressure in keeping, what is still an impressive amount of energy leaving North America, at bay will certainly influence the detailed evolution of the weather over the UK in the medium term.

It is outside of the remit of this thread but keeping in mind the above it's worth looking at this morning's GEF anomalies and the role of the cut off low. Of course this is not saying this is how it will turn out.

 

Edited January 23, 2018 by knocker

[knocker]

The MSL charts from the ecm for T24,48 and 72 The point above  vis emery/resilient HP remains centre stage

 

[Nick F]

Could be some pretty wild weather for a time tomorrow, as deepening low clips the far north of Scotland bringing gusts of 70-80mph here, while associated active cold front sweeps SE across England and Wales bringing a swathe of gales ahead/along it and a band of squally rain.

EC has a deep low of 961mb just N of north of Scotland around noon

A look at the EC charts for 9am to noon GMT tomorrow indicates gusts in excess of 80mph for NW Scotland, 50-60mph across England and Wales as the cold front passes through

Strong jet parallel to the cold front moving SE with mild and moist air ahead of it and strong deep layer shear supports a convective squall line to move through, perhaps with a narrow line of intense rainfall

So could be some disruption tomorrow from the winds in particular. No warnings out from Met Office yet though, maybe the fire in the offices delaying any yellow alerts?

 

[knocker]

Quite a narrow band of very strong winds at the 500mb level in the squeeze with the upper ridge on the 06 gfs

 

[knocker]

Just to add the METO have issued a warning for wind and rain

https://www.metoffice.gov.uk/public/weather/warnings#?date=2018-01-24

[knocker]

The Geostationary at 1500. Storm gathering to the west. Courtesy Dundee Satellite Station That blasted cloud and rain hung around here all day.

Edited January 23, 2018 by knocker

[knocker]

 

[knocker]

Icons latest take on Georgina

[knocker]

One goesn't wont the ecm to be right as it's showing gusts in excess of 80kts in the western Isles for a brief time tomorrow morning.

[knocker]

 

[knocker]

It would appear that Georgina hasn't as yet developed into an individual enclosed system and is not as deep as the models were predicting. Still looking at strong winds and gales in many places and moderate/heavy rain, currently over Scotland and N. England, moving south east during the day clearing the south east by 1800, Behind the front a strong westerly wind and squally showers which is already the name of the game in N. Ireland.

This continues overnight but by midday tomorrow the much mentioned amplification is underway with the twin HP systems, the Bermuda and Azores, surging north and north east respectively whilst the upper trough over north west Europe begins to deconstruct. But the UK is still under he influence of low pressure as a filling low drifts east so still showery and windy

The trough continues to deconstruct as the Atlantic ridge continues to nudge east over the UK thus Friday becomes the best day for a while as the winds and showers abate 

But the ridge is somewhat transient as it comes under pressure from the quite intense upstream energy and the analysis at 1200 on Saturday epitomizes  the forthcoming evolution in the medium term. We now have a cut off upper low in the Mediterranean as the result of the deconstruction and the Azores high pressure attempting to push north/north east but coming under constant pressure from the twin energy flows emerging from Canada and the southern States that are tending to merge in the western Atlantic. This tends to result in a compromise as can be seen on Saturday with weak fronts pushing through thus changeable conditions but very much tending to a N/S split and quite wet and windy in the north. A characteristic of this pattern

This can be summed up quite neatly by looking at this morning's GEFS 5-10 anomaly.

 

Edited January 24, 2018 by knocker

[knocker]

Georgina has deepened 11mb in the last 5 hours as it tracks north of Scotland

[knocker]

[knocker]