Short range model discussion - into 2018

[chrisbell-nottheweatherman]

3 minutes ago, knocker said:

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.

I see (I think!) - I get that there are two flows in the western Atlantic, but, to my layman's eyes, they appear to merge into a single jet flow well to our west - unless the flow down the eastern flank of the Bermuda ridge then flows around the southern flank of the easternmost of the two cut-off troughs?

[knocker]

24 minutes ago, chrisbell-nottheweatherman said:

I see (I think!) - I get that there are two flows in the western Atlantic, but, to my layman's eyes, they appear to merge into a single jet flow well to our west - unless the flow down the eastern flank of the Bermuda ridge then flows around the southern flank of the easternmost of the two cut-off troughs?

Well I don't think they merge completely at this point as the front is the boundary between the two air masses. As a matter of interest the wave bringing heavy rain to Scotland is causing a certain amount of disagreement. Later the flow from the W/NW becomes dominant as the high pressure moves east and then the flows will merge further west. Well this is my take on it

Edited January 27, 2018 by knocker

[chrisbell-nottheweatherman]

17 minutes ago, knocker said:

Well I don't think they merge completely at this point as the front is the boundary between the two air masses. As a matter of interest the wave bringing heavy rain to Scotland is causing a certain amount of disagreement. Later the flow from the W/NW becomes dominant as the high pressure moves east and then the flows will merge further west. Well this my take on it

I see it now, thanks.  I was allowing my attention to be distracted by the cut-off low near Gibraltar.

Edited January 27, 2018 by chrisbell-nottheweatherman

[knocker]

9 minutes ago, chrisbell-nottheweatherman said:

I xsee it now, thanks.  I was allowing my attention to be distracted by the cut-off low near Gibraltar.

Which is not without importance later but outside this remit of course.

[Interitus]

3 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

 

This is the tweet from other thread -

The question of the jet extension is interesting as in the near forecast it follows the MJO progression. The initial extension may be as above tweet, though this is a little out of date and down thread Sam brings in the MJO. Another thread discusses these extratropical/tropical contributions and is worth a read -

 

[knocker]

On the midday satellite the low SE of Iceland and the looping front currently affecting the UK can clearly be seen. And the trailing front down to the trough between the HP cells that will impact us soon.

[knocker]

And a better view on the 1500 geostationary and why it has remained distinctly gloomy in these part albeit the rain has ceased

Edited January 27, 2018 by knocker

[knocker]

Some very strong winds over northern Scotland this evening as the low drifts ESE towards Norway and noticeable different airmass characteristics with very mild air further south.

 

Edited January 27, 2018 by knocker

[knocker]

The squeeze over northern Scotland

[knocker]

The synopsis at midnight;

Low pressure to the north of the UK with the main low west of southern Norway thus still windy in northern Scotland. A pretty fresh westerly wind further south as well but fresh is probably not the right word as England and Wales are under a Tm airmass with frontal systems to the west

The airmasses are clearly defined and a glance at the Camborne 00 sounding shows the tropopause at 143mb in the Tm air.

So on to the nitty gritty

Today most of the country remains in the Tm air, thus cloudy and mild, perhaps the sun breaking through in the east, the exception being western Scotland where an open wave has formed on the fronts as they track NE bringing heavy rain

Overnight and through Monday the front tracks south leaving a cooler and showery airstream in it's wake but resulting in quite strong winds in the warmer air ahead of it's travels. The front clears the south coast by 1800

We are now entering a period when changes are afoot upstream where the EPO ridge is starting to sniff the coffee and the Canadian vortex/trough becoming established and in the meantime there is a lot of energy leaving the eastern seaboard eastbound and over the next few days this will interact with high pressure and depending how they phase will determine the detail of the weather over the UK. Thus as can be seen by 1800 Tuesday there is low pressure to the NW/N with a low 985mb NNW of Scotland with the associated front bringing heavy rain and strong winds to the north.

But fully in keeping with the above mentioned phasing the high pressure then amplifies in the Atlantic forcing the upper trough south east which veers the surface wind across the UK Wednesday/Thursday resulting in strong winds, possibly gales in exposed areas, and frequent squally showers.

And regarding the pattern upstream mentioned earlier, this morning's GEFS anomaly is quite informative.

Edited January 28, 2018 by knocker

[knocker]

Not much point in looking in too much detail at the ecm in the short term but just to note the similarity between the anomaly and the GEFS above. The EPS is still inclining to the key players in the ext period remaining the intense Canadian vortex and trough to the NW and the diverging upper flow in the eastern Atlantic associated with some positive anomalies and some ridging n. Scandinavia and the positively aligned trough to the south of the UK

[johnholmes]

As k has indicated above interest for coldies is going to be around by Thursday. The period into the weekend being worth watching in my view. Upper air flow is going to be North of West and cyclonic=unsettled so snow for some areas, possibly lowish levels also. Keep an eye on the Met O Fax charts they are probably going to be the best quick guide to the overall pattern. Will it snow etc then GFS will provide lots of highs and lows as back garden hopes come and go.

Interesting period though, especiaily for coldies.

[knocker]

The frontal cloud showing clearly on the midday geostationary, courtesy of the Dundee Satellite Station.

[knocker]

The evolution towards significant blocking over the North Pacific - North Pole is happening as the Madden Julian Oscillation pushes across the Pacific. This isn't a coincidence. The big shift in the North Pacific - N. Pole pattern has significant ties to the tropics. H/t MV

[knocker]

The cold front currently across North Wales and the north of England will continue to track south clearing the south coast by this afternoon. Some strong winds, with cloud and patchy rain in the Tm air preceding it but clearer Pm behind it with the odd shower.

Most of the UK will have a dry and quite clear and frosty night but frontal systems to the west of Scotland and Cornwall will track east bringing rain and strong winds to western Scotland and rain into the south west England and south Wales overnight into Tuesday.. This will move east during the day but the rain will persist over western Scotland, perhaps snow on the mountains, as the front associated with the depression 985mb over the Faeroes moves south east and impacting N. Ireland by 1800.

Thus by 00 the cold front is lying across the borders with a couple of frontal ripples across the south of England and still very windy in the north with frequent wintry showers.

From here some amplification takes place and the Azores HP starts pushing north which impacts the upper trough to the north west and it starts tracking south east. Thus the surface low does likewise which veers the strong surface wind north west and ensues a continuation of the squally wintry showers, particularly in the north and along western coasts.

The low continues to run down the North Sea during Thursday and in the process veering the wind even more but probably concentrating the showers now down the eastern side of the country but the brief respite of a very transient ridge is very short lived as the next low tracks east south of Iceland and the associated front(s) are already impacting western Scotland and N. Ireland by 00 Friday.

We have now reached the stage of the pattern change upstream with the EPO ridge, high cell Siberia and the active vortex/cold trough scenario.

And how this plays out downstream in the medium term continues to be of interest with the the interplay of the Azores, positive anomalies and some ridging in the Svalbard area, and the positively aligned trough to the SE/S of the UK. Where will it all end?

 

[knocker]

The 0600 satellite showing the front trailing down to the cut off low pressure to the south west.

[knocker]

An illustration, again, of why it makes kittle sense to look too far ahead with the current changing upstream pattern. A quick look how the gfs handles the trough leaving the eastern seaboard and the difference in the surface analysis in just six hours even in the short range

 

Edited January 29, 2018 by knocker

[knocker]

Leaden skies here all day and at 1200 the cold front very adjacent.

 

Edited January 29, 2018 by knocker

[knocker]

The overlying theme with the current outputs is unsettled in the short term with the interaction and phasing of the cooler and warmer air with a lot of eastbound energy leaving the eastern seaboard. But, according to last night's anomalies, as the pattern change takes place upstream. the flow will diverge in the eastern Atlantic as the Azores/trough axis becomes more influential initiating a more settled period over, at least, the southern half of the UK and perhaps more as time goes on. But I digress. Temps generally a little below average.

A pretty frosty start in many areas today with some showers in the west of Scotland but there is a shallow wave west of Cornwall tracking east that will bring patchy rain to the south west/ south and up north a frontal system will bring some some heavy rain and strong winds into western Scotland. The fronts and rain will track south east during the evening and overnight whilst the little wave in the south tracks east.

By 1200 tomorrow the fronts will have cleared the south coast leaving the UK in a strong north westerly with a deep low 975mb in the vicinity of the Shetland Isles. Thus squally wintry showers, perhaps of snow in the north, and more frequent there and on western coastal areas.

At this point, keeping in mind my earlier comment, the Azores stars ridging in mid Atlantic forcing the upper trough south east, This of course impacts the surface analysis with the low slipping down the North Sea to be over Denmark by 1800 on Thursday and the strong surface wind will veer northerly in the process with the squally showers tending to die out, apart from down the east coast,  as the ridge moves east over the UK.

But this ridging is extremely transient as a strong jet swinging south of the North American trough and across the Atlantic in conjunction with a deep low over Iceland quickly suppresses it and by midnight Saturday the fronts associated with the aforementioned low are already impacting Scotland and strong winds are once more the order of the day over the UK.

Returning briefly to the opening comment this morning's GEFS anomaly is not supporting the increasing influence of the Azores and the Canadian vortex. trough to the north west starts to dominate which is a little surprising in some respects. It will be interesting to see what the EPS comes up with this morning but that is for the other thread to sort.

 

Edited January 30, 2018 by knocker

[knocker]

The ecm does have a variation next weekend. It forms a more intense little wave on the front as it tracks south east on Saturday and in fact is an enclosed low over N. France by 00 Sunday. And at first glance the ecm det output does seem more in line with last evening's anomalies mentioned in an earlier post.

Edited January 30, 2018 by knocker

[knocker]

The low north of Scotland and the front bringing rain there today stretching across the Atlantic.

[knocker]

A rapid change down here in the last couple of hours with a veil of Cs as the wave, and patchy rain, approaches from the west.

[knocker]

A yellow warning for snow and ice has been issued for Weds for Scotland

 

Quote

Between 03:00 Wed 31st and 18:00 Wed 31st

Following a spell of rain, temperatures will fall quickly allowing ice to form on untreated surfaces. Frequent blustery showers of rain, sleet, snow and hail will then also develop. Some roads and railways are likely to be affected by snow with longer journey times by road, bus and train services. Some injuries from slips and falls on icy surfaces are also possible.

https://www.metoffice.gov.uk/public/weather/warnings#?date=2018-01-30

Edited January 30, 2018 by knocker

[knocker]

Worth pausing a moment and looking at the North Pacific where the massive block is pumping very warm Pacific air into Arctic Russia and the eastern Arctic. Some temps 60F above climatology.

[JeffC]

3 hours ago, knocker said:

Worth pausing a moment and looking at the North Pacific where the massive block is pumping very warm Pacific air into Arctic Russia and the eastern Arctic. Some temps 60F above climatology.

I think I'm sort of dyslexic when it comes to reading some of these charts, but I can decipher it when given a different slant on it - Is this the warmer pool you're looking at Knocker?

https://earth.nullschool.net/#current/wind/isobaric/850hPa/overlay=temp/orthographic=146.60,60.53,327/loc=178.122,64.141