Models, teleconnections and nowcasting

[knocker]

A quick glance at the first two weeks of February from the EC weeklies update

01 > 08

Salient points

Aleutian ridge

Vortex northern Canada with associated troughs central North America and north west Atlantic

Strong westerly upper flow exiting the eastern seaboard south of the latter across the Atlantic

But abating and backing a tad in the east, courtesy of the positive influence of the European subtropical high just to the east of the UK with the latter just influenced on the western periphery

Tending towards a NW/SE split

08 > 15

Not dissimilar upstream

Downstream the Atlantic trough and European subtropical high have moved a tad west

Which facilitates more influence from the latter over the UK

 

Edited January 3, 2020 by knocker

[knocker]

The North Atlantic 500mb and surface analysis for midnight

The fronts and associated rain currently over central southern areas of the country will clear the south east by late morning. Resulting in a dry day with sunny intervals apart from northern Scotland where there will be frequent wintry showers and a gusty wind, courtesy of a cold front associated with the deep low over western Norway

Dry for most areas tonight with some patchy frost but continuing with wintry showers and longer periods of rain over northern Scotland

Saturday will be dry day with sunny intervals for most but another deep low has tracked north into the southern Denmark Straits and a warm front associated with this will bring rain to western Scotland and N. Ireland

Over saturday night and through Sunday there is a lot going on in the west with the vortex slipping down the Labrador Straits and another deep low tracking north in mid Atlantic. Back in the UK the frontal system mentioned above soon clears but another front associated with the aforementioned low will bring some persistent rain to the north west with strengthening winds

By midday Monday the low is south east of Iceland and the associated cold front sweeps east across the country bringing heavy rain and strong gale force winds, which could be severe in the north Meanwhile another deep low has dropped into the western Atlantic

Over the next 24 hours this low tracks north east and deepens to be south of Iceland whilst the frontal system moves across the UK again bringing some very strong winds and heavy rain to the north but also some very warm air generally

 

Edited January 3, 2020 by knocker

[knocker]

According to the gfs the next five days is dominated by the vortex and associated deep troughs to the north west and the resilient subtropical high to the south east. Thus the Atlantic is an ideal environment for cyclogenisis and thus more unsettled weather for the UK, with once again the north bearing the brunt. Best not to get too wrapped up with detail at the moment but strong winds and heavy rain are quite likely at some stage

[knocker]

The fronts still aligned across central southern England at 0600 but cleared the far south west

[knocker]

A glance at the ecm next week keeping in mind that with all the energy swanning around in the Atlantic the detail will be elusive

 

Edited January 3, 2020 by knocker

[knocker]

The ext EPS mean anomaly this morning has the Atlantic vortex/trough a tad further east and thus the European subtropical high follows suit.

[knocker]

Another look at next Tuesday

And hey ho, blue sky and Cu here

Edited January 3, 2020 by knocker

[knocker]

As has been noted previously the vortex over Greenland creates an ideal baroclinic environment for cyclogenisis in the western Atlantic

Edited January 3, 2020 by knocker

[knocker]

To me the ext mean GEFS anomaly indicates that the percentage play is for a continuation of the pattern that is quite likely in the nearer time frame, That is a strong upper flow exiting the eastern seaboard that backs quite sharply in mid Atlantic, courtesy of the continuing resilience of the subtropical high Thus active cyclogenisis taking place in the western Atlantic will track north east and thus a very much a NW/SE split over the UK

Edited January 3, 2020 by knocker

[knocker]

The comments above also apply to the EPS but with the major caveat that earlier comments, alluding to the fact that the precise position and intensity of the trough/ridge in the Atlantic/Euro sector is critical, should also be noted, as the EPS has everything a tad further east and less amplified. Thus the NW/SE split is not quite so cut and dried

The NAO and AO updates from the weklies

 

Edited January 3, 2020 by knocker

[knocker]

Outlook - Pretty much a stand off between the energy and active cyclogenisis to the W/NW and the resilient ridge to the south east with the UK in the middle

The North Atlantic 500mb and surface analysis for midnight

Some rain and showers over western and northern Scotland this morning, courtesy of a couple of cold fronts, nut this should move away north through the day before cloud and rain from another frontal system moves in from the west.Elsewhere cloudy with sunny intervals with lighter winds as the ridge becomes more influential

The rain over western Scotland may pep up a tad this evening and the early part of tonight as the warm front tracks east.

Over Sunday conditions stay the same over much of the country but a trailing front across northern Scotland, linking the old system to a developing west of Ireland will bring more persistent rain  here and perhaps to N/ Ireland.

Overnight and through Monday the aforementioned low develops rapidly and is 956mb south east of Iceland by midday whilst the cold front tracks east over the UK bringing heavy rain and strong winds

This front quickly clears east but another low to the west undergoes rapid cyclogenisis as it tracks towards Iceland and the associated frontal system will bring more strong winds and heavy rain to the north through Tuesday whilst at the same time importing some very warm air into the country with temps way above average.

On Wednesday the vortex is dragging some very cold air into Greenland, even by ice-sheet standards, and nearer home the front has cleared to the east but is trailing close to the south coast so some rain here whilst showers and quite strong winds continue over northern Scotland

 

 

 

Edited January 4, 2020 by knocker

[knocker]

By Thursday the gfs has tracked the low to the south west into southern Ireland

And over the next five days the Atlantic remains an active cyclogenisis environment so continuing unsettled as regards the UK but still tending towards a NW/SE bias.

[knocker]

No surprises with the ext GEFS but previous comments vis the position and intensity of the trough/ridge in the Atlantic/Euro sector still pertain

[knocker]

The ecm also tracks the low north east on Thursday

but in general the 5-10 period is dominated by strong winds and cyclogenisis in the Atlantic whilst the the European subtropical high edges a tad east. Thus still indicating a NW/SE bias across the UK

 

Edited January 4, 2020 by knocker

[knocker]

Further comment on the ext mean EPS output this morning unnecessary except perhaps becoming more generally unsettled in western regions

[Blessed Weather]

This winter's persistent negative EPO and consequent Alaska/Aleutian ridging seems to be on steroids according to the ECM forecasts and appears to be driving a semi-static 7-wave (Rossby/planetary wave) pattern around the northern hemisphere. I think for the best chance for a change in pattern it's a case of looking for the Alaskan/Siberian (or Scandi) ridge combo to split the TPV and generate the vertical wave propagation to disturb the SPV, hopefully even sufficient to bring about a SSW in early February. To this extent I was fascinated by the AO and NAO charts posted by @knocker earlier - both indices plummet into negative around the 13th Feb - a SSW earlier Feb??

ECM mean 500 height anom 11th Jan - 13th Jan:

ECM NH 500 anom 4th Jan 0z for 14th Jan: 

EPS AO and NAO forecasts:

EDIT: I should also add that the MJO also offers the possibility of a February pattern change and neg AO/NAO if (thanks to neutral IOD) it can finally reach favourable Phases 6, 7, 8, 1 at reasonable amplitude in late January (then add 7 - 10 day lag), as the latest ECM forecast suggests possible:

 

Edited January 4, 2020 by Blessed Weather
MJO scenario added.

[Griff]

@Blessed Weather I won't quote your entire post, but thanks again for another interesting read. Very difficult to interpret these things as a novice.

 

Out of curiosity, when does early winter give way to mid winter? 

 

In the bleak mid-winter
Frosty wind made moan;
Earth stood hard as iron,
Water like a stone;
Snow had fallen, snow on snow,
Snow on snow,
In the bleak mid-winter
Long ago.... 

 

[Blessed Weather]

4 minutes ago, Griff said:

@Blessed Weather I won't quote your entire post, but thanks again for another interesting read. Very difficult to interpret these things as a novice.

Out of curiosity, when does early winter give way to mid winter?

Thanks for the kind comment. Taking Dec/Jan/Feb as the winter months, then I guess mid-Jan is mid-winter.

[Catacol]

4 hours ago, Blessed Weather said:

This winter's persistent negative EPO and consequent Alaska/Aleutian ridging seems to be on steroids according to the ECM forecasts and appears to be driving a semi-static 7-wave (Rossby/planetary wave) pattern around the northern hemisphere. I think for the best chance for a change in pattern it's a case of looking for the Alaskan/Siberian (or Scandi) ridge combo to split the TPV and generate the vertical wave propagation to disturb the SPV, hopefully even sufficient to bring about a SSW in early February. To this extent I was fascinated by the AO and NAO charts posted by @knocker earlier - both indices plummet into negative around the 13th Feb - a SSW earlier Feb??

ECM mean 500 height anom 11th Jan - 13th Jan:

ECM NH 500 anom 4th Jan 0z for 14th Jan: 

EPS AO and NAO forecasts:

EDIT: I should also add that the MJO also offers the possibility of a February pattern change and neg AO/NAO if (thanks to neutral IOD) it can finally reach favourable Phases 6, 7, 8, 1 at reasonable amplitude in late January (then add 7 - 10 day lag), as the latest ECM forecast suggests possible:

 

Would agree with all this, though the AO/NAO plunge in Feb was only the control run?

However the timeline you out together here Malcolm I think is our only real hope this winter season now for some proper cold.

[MP-R]

2 hours ago, Griff said:

@Blessed Weather I won't quote your entire post, but thanks again for another interesting read. Very difficult to interpret these things as a novice.

 

Out of curiosity, when does early winter give way to mid winter? 

 

In the bleak mid-winter
Frosty wind made moan;
Earth stood hard as iron,
Water like a stone;
Snow had fallen, snow on snow,
Snow on snow,
In the bleak mid-winter
Long ago.... 

 

I’m still wondering when autumn gives way to early winter!

[knocker]

All very odd as I went out early this morning expecting a dry, albeit cloudy day and have spent it dodging large Cu/Cbs and heavy showers

??

 

[knocker]

Windy with heavy rain on Monday and then impressive surface temps on Tuesday

Before the next low sweeps in on Thursday

And continuing unsettled in the 5-10 period as the European subtropical high loses amplification

 

Edited January 4, 2020 by knocker

[knocker]

Continuing very amplified upstream with a very strong Aleutian ridge but less so in the Atlantic/euro sector and with the trough taking closer order more generally unsettled than has been hinted at of late

[Dorsetbred]

Interesting perspective of mild, but not overly mild on Tuesday when viewing this

Weather for the week ahead - BBC Weather

WWW.BBC.CO.UK

---

After a relatively quiet spell of weather, next week looks more unsettled with strong winds and rain at times but we'll also see above average temperatures.

 

[knocker]

25 minutes ago, Dorsetbred said:

Interesting perspective of mild, but not overly mild on Tuesday when viewing this

Weather for the week ahead - BBC Weather

WWW.BBC.CO.UK

---

After a relatively quiet spell of weather, next week looks more unsettled with strong winds and rain at times but we'll also see above average temperatures.

 

Well the ecm is not quite as high But the winds in western Scotland are probably more relevant

 

Edited January 4, 2020 by knocker