Focussed Model Discussion

[knocker]

18 minutes ago, mushymanrob said:

can i ask

anybody else not able to view the noaa anomaly charts?.. i get a 'insecure' note - page not directing properly.. http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

I'm getting the same using Firefox.

[knocker]

A very marked change with the ext EPS mean anomalies this evening in two days. I'm not even going to attempt any detailed waffle vis the possible surface analysis except to say fairly benign with temps maybe a tad below average.

Edited February 6, 2019 by knocker

[cheeky_monkey]

2 minutes ago, knocker said:

A very marked change with the ext EPS mean anomalies this evening in two days. I'm not even going to attempt any detailed waffle vis the possible surface analysis except to say fairly benign with temps maybe a tad below average.

still looks brutal cold here..which ever way.

[knocker]

20 minutes ago, cheeky_monkey said:

still looks brutal cold here..which ever way.

Yup the coldest air over western Canada

[Singularity]

A big takeaway for me from the 12z ECM is that it managed to let the vortex split take shape again thanks to the powerful ridge from the Pacific side (MJO-driven). None of GFS/GEFS's suddenly very positive AO tendency to be seen there.

 

Question now is whether this very logical pattern trend will actually continue - once again it depends strongly on whether the MJO actually does propagate east in line with the recent model trend. The signals this time around (SST pattern, westerly wind bursts, model ensemble spread) have now become the most focused on an eastward propagation outcome that I've seen so far this winter so there's reason to be hopeful as long as the stratosphere doesn't throw a curveball at us... oh no, now I've gone and done it .

[Rocheydub]

25 minutes ago, Singularity said:

oh no, now I've gone and done it .

You should be ashamed of yourself!

 

It is a very logical pattern trend, although I have a nagging doubt about that vortex core to our north east, that could squeeze everything south for us leaving us the wrong side of the flow (from a coldies perspective)... As always more runs needed.

[knocker]

The NH 500mb and the surface analysis for midnight and the 0300 WV image

The wave duly brought some wet and windy weather last might but much of the rain has now cleared leaving ongoing wintry showers in the south west which will later spread to all western areas. There could well be hail and thunder in the mix, But the rain hasn't cleared everywhere and a band will continue to move east over northern areas through the morning with perhaps some snow down to lower levels in Scotland. And the wind will abate during the day

A very brief respite follows but the rapidly deepening low is approaching from the west and rain from the associated warm front will effect south west regions by 2000 this evening and, along with freshening winds. will track north east through the night  introducing much warmer air in the warm sector at the same time.

By midday Friday the low is 956mb close to N/ Ireland and the cold front is crossing the country with a band of heavy rain. But the wind is now a major factor withvery strong winds in all areas but particularly down western coasts. The front will clear to the east during the afternoon leaving frequent wintry showers in it's wake. more especially over Scotland.

The low continues to track northeast through Saturday evening and slowly filling leaving the UK in a squally unstable westerly airstream with frequent showers, again with the risk of hail and thunder in the mix. Still very windy but slowly easing from the south  But here there is likely to be further rain as another wave has formed to the south west and has tracked north east to be 992mb in The Channel by midnight Sunday

Through Sunday the upper trough slowly moves east and the surface wind veers northerly,thus much looker with still some wintry showers

As the trough continues to move away to SE a ridge builds over the UK portending a quiet, dry and sunny day on Monday albeit after a frost start

Edited February 7, 2019 by knocker

[knocker]

Continuing briefly with the gfs. Essentially the familiar story of the Amplifying subtropical high pressure battling the east bound energy and by t144 a front has manages to push across the country with some rain. The ridge continues under pressure from the west but the orientation is now such that some of the energy can swing around it and advent colder air down through central Europe into North Africa, And this continual  pressure not only distorts thridge by does nasty things to the Atlantic trough.

Edited February 7, 2019 by knocker

[knocker]

So what's the ecm take on this. At t144 it has a weak front fizzling out against the ridge. Thereafter a not dissimilar evolution to the gfs but pushing the energy a tad further east

[knocker]

One senses we are entering a key period vis the end of February. The eps continues to indicate strong upstream amplification but less so in the Atlantic sector where the trough has become much more negatively tilted in response the European ridge aligning positively into eastern Greenland. This is going to be tricky to call regarding detail in the vicinity of the UK

Edited February 7, 2019 by knocker

[winterof79]

32 minutes ago, knocker said:

One senses we are entering a key period vis the end of February. The eps continues to indicate strong upstream amplification but less so in the Atlantic sector where the trough has become much more negatively tilted in response the European ridge aligning positively into eastern Greenland. This is going to be tricky to call regarding detail in the vicinity of the UK

We look like we may finally experience the effects of the recent warming.

If the ridge edges toward Greenland it could get interesting

[Nick F]

9 minutes ago, Nick F said:

Still a fairly decent signal from ensemble z500 means for Scandi high day 10, though EPS mean signal stronger than GEFS.

Taking 00z GEFS z500 mean into the extended and we can see the Scandi height anomaly retogressing towards Griceland area:

This fits in with the standardised MJO composite progression from phase 6 through to phase 8, with height rises over UK (P6) then Scandi high (P7) then Greenland/Iceland high (P8) - MJO progress such as we are seeing advertised by the model RMM plots, GFS most amplified with this, but generally seems to have a better handle on MJO

phase 6-8

With the SSW impact perhaps waning, we may perhaps see less interference with the MJO impact on poleward wave driving 

However, the ENSO base state does have an impact on the kind of pattern response to MJO cycle. Recent ENSO update from NOAA CPC suggests ENSO neutral rather than El Nino: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

ENSO neutral with MJO phase 7 and 8 brings this in the composite:

P7 P8

ENSO El Nino this with P7 and 8

P7P8

... so the models certainly lurching more towards a neutral ENSO MJO 7-8 response.

However, the patterns often never play out exactly to the composites and this has been a strange year with regards to muted pattern response to the MJO cycles through 'colder' phases, likely to do with the SSW interference and there's no guarantee that the SSW may not still be impacting the pattern in next few weeks. So we'll see!

 

[knocker]

Indeed Nick and one fly in the ointment, apparently, is the strongly negative PNA forecast.

[Nick F]

12 minutes ago, knocker said:

Indeed Nick and one fly in the ointment, apparently, is the strongly negative PNA forecast.

We can still get a cold and blocked pattern with a -PNA, would certainly mean less temp contrast along NE North America to fire up the jet stream with all the cold over western N America. 

[knocker]

17 minutes ago, Nick F said:

We can still get a cold and blocked pattern with a -PNA, would certainly mean less temp contrast along NE North America to fire up the jet stream with all the cold over western N America. 

Yes that is true but still a strong jet running south of the trough and exiting the eastern seaboard so how this diverges in mid Atlantic courtesy the ridge/block to the north is just another key element. One thing is for sure it will be interesting to see how the surface analysis pans out with still a fair amount of energy in the mix.

My fly in the ointment was regarding the composites

Edited February 7, 2019 by knocker

[WhiteFox]

17 minutes ago, knocker said:

Yes that is true but still a strong jet running south of the trough and exiting the eastern seaboard so how this diverges in mid Atlantic courtesy the ridge/block to the north is just another key element. One thing is for sure it will be interesting to see how the surface analysis pans out with still a fair amount of energy in the mix.

My fly in the ointment was regarding the composites

Yes, the Pacific pattern seems to be favouring the cut off upper low over Canada; conflicting signals from what I can see. 

I think that the EN neutral composite probably sits best as we have not seen the PNA swing towards positive and no Aleutian Low.

With the Pacific doing its thing, favouring the low over NE Canada, the Sceuro high seems plausible given the push from the west preventing ridging from building too far north.

If the MJO moves into phase 8 (and that GEFS forecast is a huge amplitude) then we may see some forcing on the Pacific pattern which could open the door to Greenland if the Canadian Low pulls away. But, ECM does not favour such a high amplitude for the moment, so perhaps the Canadian low will stay close to its current position leaving the UK in a coldish anticyclonic flow.

It's all about the amplitude: it seems that it would take something big to change the Pacific pattern and the GFS seems to be providing it...

 

[knocker]

The developing low at 30w

[knocker]

Over the next 18 hours the developing low above will undergo explosion cyclogenesis as it tracks north east to be 959mb west of Northern Ireland by 0600 tomorrow. So two things in particular to note'

Number one;- The rain from the warm fronts is initially into N. Ireland and Wales by 2100 before becoming more widespread across western regions and the Midlands by midnight  And  from here effecting all of the country by 0300 with the heavy band associated with the cold front just into western Ireland. Over the next six hours this tracks east with heavy rain effecting all western areas but in particular Wales and the north west of England.

Number two:- As the low approaches the wind will start to pick over south west Ireland the south west approaches by 2100 this evening.and continue to encroach further north east by midnight

But from this point the wind will really start to pep up with south westerly gales in the Irish Sea (probably severe) and western coastal regions with gusts in excess of 70mph in exposed areas. And some particularly nasty conditions over on the west coast of Ireland

It's been very unstable here this morning with some hefty showers around but now a lot of Cs and high Ac as the warmer air is already creeping in aloft

 

Edited February 7, 2019 by knocker

[knocker]

Just to confuse the issue

[alexisj9]

11 minutes ago, knocker said:

Just to confuse the issue

Is that two waves now, instead of just the one in the Channel. Somehow I doubt both will happen, just some confusion, on more north or south.

[WhiteFox]

Excellent satellite picture posted by Marco Petagna on twitter showing the rapid cyclogenesis:

 

[knocker]

There is still a massive amount of energy exiting North America and ,imo of course, slight alterations in the distribution of this will alter the downstream surface analysis in the 5-10 period of every run at the moment. And this, I suspect, may take a while to firm up

Edited February 7, 2019 by knocker

[knocker]

2 hours ago, WhiteFox said:

Excellent satellite picture posted by Marco Petagna on twitter showing the rapid cyclogenesis:

 

And the 1800 WV image

[alexisj9]

2 hours ago, WhiteFox said:

Excellent satellite picture posted by Marco Petagna on twitter showing the rapid cyclogenesis:

 

Where's the second low going?

[WhiteFox]

18 minutes ago, alexisj9 said:

Where's the second low going?

I think they're forecast to phase into the main low. Some very unstable conditions hence the likelihood of secondary waves/lows forming over the weekend.