Model output discussions pm 31/12/15

[northwestsnow]

Fi deserves a huge RAMPPPPPPPPPPPP

Artic winds and snow as the jet digs evermore south, GP are you watching

[Ali1977]

Any chance of this happening ?

[bobbydog]

well i did think the ridge i mentioned would get flattened but it held on and gives us this-

 

[Day 10]

While things are fairly quiet in here I thought I'd look back to 2013 and see how the 3rd January looked then, as you can see not the best looking charts. Fast forward to March and look how things turned out! My point being, I know people are probably thinking March? I don't want to wait til March, but as these charts show below even with January having a setup as it did, at least the spell in March was worth the wait for many. So for me I will always hold out the hope of seeing at least one decent cold spell appear within the next 10-12 weeks, and if you look at it like that still plenty of time for that chance.

Edited January 3, 2016 by Minus 10

[nick sussex]

1 minute ago, Ali1977 said:

Awesome FI

All made possible by the better upstream pattern between T144 and T168hrs.

For newcomers to the thread I'd advise looking at the NH charts rather than the Europe ones. Take a look at the eastern seaboard of the USA T222hrs onwards, see how that low in the southern jet develops and phases with the PV helping to pull this west away from Greenland.

 

[Polar Maritime]

Yes again signs of a pressure rise into Greenland by mid-Month, Drawing a Northerly type flow with snow showers aplenty. Over the next week/10 days we will at least see more average temperatures for the time of year with snowfall over high ground in Scotland and the North, But that goes without yet more stormy/wet weather as Knocker points out below on a cool Westerly flow off the N/Atlantic. Growing chances of snowfall as we move into wk2 as the Jet digs further South pulling colder air with it.

Edited January 3, 2016 by Polar Maritime

[knocker]

Looking at the anomalies at T168 this morning gives a good indication how we could easily cop a nasty storm out of the current pattern. A trough southern US with a ridge NW Atlantic which is spawning possible bombs running up the eastern seaboard at the same time shooting lows towards the UK on the jet, with another low pressure area to the NW of the UK. The stuff of nightmares really. 

In the longer term both the GEFs and ecm at T360 are looking to push the European HP north adjacent or over the UK. I suspect this is the percentage play for a period of more settled weather.

 

Edited January 3, 2016 by knocker

[northwestsnow]

3 minutes ago, knocker said:

Looking at the anomalies at T168 this morning gives a good indication how we could easily cop a nasty storm out of the current pattern. A trough southern US with a ridge NW Atlantic which is spawning possible bombs running up the eastern seaboard at the same time shooting lows towards the UK on the jet, with another low pressure area to the NW of the UK. The stuff of nightmares really. 

Goodness me that looks a bit scarey, still, i'd rather concentrate on the frigid northerly on gfs6z

[nick sussex]

In relation to BA's post the chances of getting to a colder pattern are helped greatly if we don't see the shortwaves attaching to the base of the UK troughing. The effect this has is to push high pressure ne towards southern Europe, these also delay the movement east of the troughing and will try and push this ne.

We get away with it in the GFS 06hrs run but certainly would prefer a higher margin for error.

[Day 10]

Let's hope these charts keep cropping up ever closer

Still out in FI but the ecm 'starting' to show a split vortex too,

Edited January 3, 2016 by Minus 10

[tinybill]

its  fantasy  world  wont  happen but the  gfs is  hinting of possible 5  days of cold weather  just  for the  coldies 

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

 

[Cloud 10]

GEFS 06z control run has very similar ideas to the op. run.

 

[marksiwnc]

[northwestsnow]

1 minute ago, Cloud 10 said:

GEFS 06z control run has very similar ideas to the op. run.

 

Very nice- perhaps some momentum for a pattern change mid month, let us hope !!

[nick sussex]

Looking at the expected pattern over the USA and this is condusive to deliver some wintry weather to western Europe. If we can avoid high pressure being driven too far ne into southern Europe then theres a decent chance of a cold spell.

For the timebeing its this issue that's the main sticking point.

In terms of the pattern over the USA:

THE FORECAST SPLIT-FLOW REGIME OUT OF THE NORTHEAST PACIFIC WILL CONTINUE TO FUNNEL MULTIPLE SOUTHERN STREAM WAVES MOVING ONSHORE THE WEST COAST IN CA AND THEN PROGRESSING EAST ACROSS THE SOUTHWESTERN STATES BEFORE TURNING NORTHEASTWARD INTO THE EASTERN US. BY NEXT WEEKEND, A MORE FULL-LATITUDE MID-UPPER RIDGE IS FORECAST TO STRENGTHEN ALONG THE WEST COAST OF NORTH AMERICA ALONG 130W. THIS COULD SET UP A DECENT COLD SHOT INTO THE CENTRAL AND PERHAPS EASTERN STATES AFTER SUN JAN 10.

The ridge that they mention will amplify the jet, its for this reason that those lows want to turn ne over the eastern USA, its these that we want to engage low heights over western Greenland. The downstream response to that is that high pressure pushing into the Atlantic.

The issue currently is shortwave attachment to the UK troughing and how much this will try and push the pattern ne rather than east/se.

Without that I might be going into a mini ramp! however its best remain cautious until we see that resolved.

[swilliam]

50 minutes ago, bobbydog said:

has anyone noticed how the atlantic train 'slams the brakes on' at around 96hrs. its happened over the last 2 runs and is more pronounced on this one. it decides to find an alternative route - more southerly, which allows a ridge to form behind it, pushing towards greenland. lets see where this goes....

Ye I was going to comment this in that this seems be a major change overnight. The big low in the Atlantic was due to move slowly over us bringing lots of rain and wind. It now seems to to want to stay out in the Atlantic and is if anything moving West rather than east. We do still get LP coming over us but more in the form of trough disruption with and an elongate finger of the LP. I would say this is goodnews for those that have been flooded as whilst not being dry by any means it should be drier.

 

This can be seen on alm models

UKMO

ECM

A couple of days the models were showing the Atlantic low right over us at that timescale.

 

Looking at the NH profile it seems the main reason for this is that the direction of lifting out of the low heights from Eastern Europe is more Northerly and not S Norway. Hence there is no link up with the Atlantic trough and this is not then pulled East

[gottolovethisweather]

I don't like commenting on one run in isolation but the GFS this morning does hint at the possibility of a slightly more widespread wintry event than anything we've witnessed during recent weeks and that is around the 8th January. It will likely be a "blink" and you miss it event but some sleetiness/snow isn't beyond comprehension if I'm honest. Beyond that out into FI, from around about the 13th January onwards, things could turn much colder and potentially snowier across the UK. Shame this doesn't fit into the timeframes of the ECM just yet, but it still is one trend on which to keep an eye on. 

This chart is actually from the 7th January but you can see the crucial 528DAM line attempting to make inroads.

 

As the days unfold, snow chances are increasing up North and the likelihood of snow over rain seems to only grow as we get deeper into FI. Further South over much of England and Wales, Temps are set to be near to slightly below average on the whole and when skies clear (not very often Thanks to much troughing overhead) we might get a seasonal frost by night. An unsettled and windy week coming up and thereafter, perhaps a growing trend towards a "East meets West" battleground scenario as we head deeper into January.

 

Edited January 3, 2016 by gottolovethisweather

[Glacier Point]

Torpedo away !

These westerly winds, induced by the MJO will be fluxed poleward over time (takes around 21 days). On everything we've seen this winter, poleward fluxing has occurred. As soon as those westerlies strike the sub-tropical Atlantic belt, the NAO will flip negative.  The AO being negative should also allow for the MJO to remain highly active, so we may see a further pulses of westerly winds being fluxed poleward after passage of the MJO through the Indian Ocean late January.

[gottolovethisweather]

37 minutes ago, swilliam said:

Ye I was going to comment this in that this seems be a major change overnight. The big low in the Atlantic was due to move slowly over us bringing lots of rain and wind. It now seems to to want to stay out in the Atlantic and is if anything moving West rather than east. We do still get LP coming over us but more in the form of trough disruption with and an elongate finger of the LP. I would say this is goodnews for those that have been flooded as whilst not being dry by any means it should be drier.

 

This can be seen on alm models

UKMO

ECM

A couple of days the models were showing the Atlantic low right over us at that timescale.

 

Looking at the NH profile it seems the main reason for this is that the direction of lifting out of the low heights from Eastern Europe is more Northerly and not S Norway. Hence there is no link up with the Atlantic trough and this is not then pulled East

Yes, the Jet is having a tendency to split at that point in time and one section dives North and the other part SE'wards into central Europe. I had noticed the BBC long-ranger had also shown this prospect over the past couple of days. From T+96 to T+120 hours is where some wintry fun and games might start showing their hand more often in the outputs. As ever, we need to get there before jumping all over it however.

Edited January 3, 2016 by gottolovethisweather

[SteveB]

Hi GP,

Is that torpedo away now or in 21 day's time?

[johnholmes]

1 hour ago, nick sussex said:

All made possible by the better upstream pattern between T144 and T168hrs.

For newcomers to the thread I'd advise looking at the NH charts rather than the Europe ones. Take a look at the eastern seaboard of the USA T222hrs onwards, see how that low in the southern jet develops and phases with the PV helping to pull this west away from Greenland.

 

The question to ask Nick is, how likely at that time scale is this to actually happen? Will it be there at T198h, moved on of course from the actual position shown at 222h. At 240h even at 500mb any model is rarely more than 70% correct. At the surface then it is much less for such detail.

[nick sussex]

Just now, johnholmes said:

The question to ask Nick is, how likely at that time scale is this to actually happen? Will it be there at T198h, moved on of course from the actual position shown at 222h. At 240h even at 500mb any model is rarely more than 70% correct. At the surface then it is much less for such detail.

Yes of course that's well into the future but in terms of the overall pattern expected in the USA its condusive to have low pressure running ne in the eastern USA as that ridge builds into the west USA. We can't be sure of the detail at this range however. NCEP mentioned a few days back an increased chance for nor'easter type lows towards the east USA which would correlate with the jet amplifying in that region.

Currently in terms of cold for the UK I think the complicating factor is any ridge being pushed ne towards southern Europe and slowing the eastwards progression of the pattern as shortwaves phase with the UK troughing.

We'll see what happens with those and for that reason I'm remaining cautious.

[Glacier Point]

torpedo off and running, should acquire its target within 3 weeks.

[Catacol]

12 minutes ago, Glacier Point said:

Torpedo away !

These westerly winds, induced by the MJO will be fluxed poleward over time (takes around 21 days). On everything we've seen this winter, poleward fluxing has occurred. As soon as those westerlies strike the sub-tropical Atlantic belt, the NAO will flip negative.  The AO being negative should also allow for the MJO to remain highly active, so we may see a further pulses of westerly winds being fluxed poleward after passage of the MJO through the Indian Ocean late January.

Hehe - I love it when a plan comes together... By next week the mood in here should change. Personally I dont want the atlantic shut out completely as convective snow showers off the north sea never make it to the west country, so a nice battle royale between arctic and tropical air masses will do nicely please.

I've gone off ensemble means in a fairly major way - but obviously they have use. I'll certainly take this ECM mean for 240h - clear pressure rise over Greenland and troughing to our east. There's sufficient potential in that alone..

 

[Liam J]

Just had a look at the 00z ECM control and at day 10 the UK is in a northerly air flow with a ridge out west up to Iceland so frost and snow (for favoured locations in a northerly) all of the UK in -5c or below 850's and the 522 dam to the south coast. Thereafter the ridge gets toppled and we eventually end up with with heights centred over Spain/SW France leaving the UK in W/SW flow with depressions tracking close to Iceland. Would be drier than recently especially over England and Wales, rain at times for the NW of the UK.