[Model Output Discussion - Colder but how cold and for how long?]

8 minutes ago, LRD said:

Yes, good points

I am getting a feeling of 2019 at the moment. There was a projected cold spell in Jan of that year that looked like it had potential to become quite severe. That ended in a bit of a damp squib and the prospects of a SSW looked promising for Feb. We all know how that turned out. What was it... 19C/20C right near the end of Feb '19? Remarkable warmth

However, a cold, wintry Feb certainly feels possible at this point in time, although EC46 has backed off that further tonight with high pressure over or very near us looking favoured. It will change, I expect

Feb charts. Week of 5th:

Week of 12th:

 

Whilst the ec46 no longer shows the cold set ups it was doing for feb up until a week ago, it continues to show high anomalies close to nw europe and we know it won’t be accurate. (So perhaps move those anomolies around a bit). If it was showing a climatological average zonal flat westerly with +nao then we’d be wondering what it was seeing next month when set against expectations 

[Model Output Discussion - Colder but how cold and for how long?]

14 minutes ago, CoventryWeather said:

Seen a number of models shift Tuesday's Low southwards - nearly 100miles on the latest ICON, ECM also follows it. 

Some on the ECM/GEFS06z had it as far south as North Wales, so clearly another feature yet to be nailed. Expecting a further shift in this over the next day. 

Not really seeing much adjustment through todays runs 

looks to come in through the isle of arran and exit N of the Humber 

I think that’s been a fairly consistent passage over the last few days modelling. Agree if there has been any adjustment over the past five days then it’s south but annoyingly the nwp has done a good job on this shortwave 

 

 

[Model discussion highlights]

7 minutes ago, mountain shadow said:

According to Matt Hugo, they were shifted due to the Strat Warming!

Yes, that's right. The one thing we look for all Winter has caused a potentially 2 to 3 week snowy cold spell to become a disappointing 36 hour cold and dry borefest.

 

I’m not sure its true that the ssw removes the block 

the strat split which allows the mar to extend north means we end up with a Canadian segment and an Asian segment. This is not the ssw.  This is a consequence of a weak spv and recent warming. It’s not a ssw.  Mike has shown that it’s a consequence of the trop pattern reflecting upwards. 
As the two segments begin to rejoin, we see another Asian warming which encourages the pacific ridge to put pressure the spv which is stretching as it comes back together. Whilst it is stretched, it becomes displaced enough to deliver a reversal of 10hpa zonal flow down to 70N.  The Canadian segment is headed back into the Asian master irrelevant of the ssw that occurs around the 18th. It was modelled to happen before we began to see the level of displacement would actually just reverse the flow. 

the movement back across the n Atlantic of the Canadian segment does indeed happen in tandem with the flattening of the trop pattern. we’re assuming that it’s a trop following the strat but like other recent developments, it’s all seems to happen in tandem, top to bottom (or bottom to top). 

tomorrows cross section of the atmosphere shows it reversed all the way through above 70N. The circle is where we have to see blue for a tech ssw reversal. You can see how this is pretty irrelevant. We have reversal - but not quite at a latitude that would likely see the cold  trough get well to our south. This is where the failure to get the blues down to 60N is possibly an issue next week. 

 

Now to Tuesday and you can see we have an ssw. Woopy do! Judge for yourselves the difference between not having the tech ssw and having the tech ssw. 

 

by day and the blues have drained away with a strong flow at 10hpa top to bottom. Obviously that’s not a string flow in the upper strat but it is down at 500hpa 

 

and a few days later we see the reversed flow back again above 75N (ties in with the Arctic high we saw on that run in fi. 

 

id expect the 12z run to be different by this stage as the polar profile is quite different.  it can’t be easy for the nwp to deal with this inconsistent profile of flow throughout the atmosphere. You’d normally expect the upper strat to be quite predictable. 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5011976

[Model Output Discussion - Colder but how cold and for how long?]

11 minutes ago, blizzard81 said:

Cmon BA. Hurry up..... I'm cooking buffet food and I'm at risk of burning it awaiting your post

Sorry - watching the footy and posting at the same time! 
nothing doing until the back end of jan at the earliest - and that will probably be from a mid lat ridge which could then either drift ne or nw. 

[Model Output Discussion - Colder but how cold and for how long?]

7 minutes ago, mountain shadow said:

According to Matt Hugo, they were shifted due to the Strat Warming!

Yes, that's right. The one thing we look for all Winter has caused a potentially 2 to 3 week snowy cold spell to become a disappointing 36 hour cold and dry borefest.

 

I’m not sure its true that the ssw removes the block 

the strat split which allows the mar to extend north means we end up with a Canadian segment and an Asian segment. This is not the ssw.  This is a consequence of a weak spv and recent warming. It’s not a ssw.  Mike has shown that it’s a consequence of the trop pattern reflecting upwards. 
As the two segments begin to rejoin, we see another Asian warming which encourages the pacific ridge to put pressure the spv which is stretching as it comes back together. Whilst it is stretched, it becomes displaced enough to deliver a reversal of 10hpa zonal flow down to 70N.  The Canadian segment is headed back into the Asian master irrelevant of the ssw that occurs around the 18th. It was modelled to happen before we began to see the level of displacement would actually just reverse the flow. 

the movement back across the n Atlantic of the Canadian segment does indeed happen in tandem with the flattening of the trop pattern. we’re assuming that it’s a trop following the strat but like other recent developments, it’s all seems to happen in tandem, top to bottom (or bottom to top). 

tomorrows cross section of the atmosphere shows it reversed all the way through above 70N. The circle is where we have to see blue for a tech ssw reversal. You can see how this is pretty irrelevant. We have reversal - but not quite at a latitude that would likely see the cold  trough get well to our south. This is where the failure to get the blues down to 60N is possibly an issue next week. 

 

Now to Tuesday and you can see we have an ssw. Woopy do! Judge for yourselves the difference between not having the tech ssw and having the tech ssw. 

 

by day and the blues have drained away with a strong flow at 10hpa top to bottom. Obviously that’s not a string flow in the upper strat but it is down at 500hpa 

 

and a few days later we see the reversed flow back again above 75N (ties in with the Arctic high we saw on that run in fi. 

 

id expect the 12z run to be different by this stage as the polar profile is quite different.  it can’t be easy for the nwp to deal with this inconsistent profile of flow throughout the atmosphere. You’d normally expect the upper strat to be quite predictable. 

[Model discussion highlights]

Just now, steveinsussex said:

Weirdly the met office going for sleet and rain to lower levels in the north on Tuesday?!

 

3.40 mark on here

 

 

Warm sector on a wave that doesn’t originate in the frigid flow 

the shortwaves have spoiled this week for most. 

the nwp has counted down pretty well from a couple weeks out - but the ens means won’t see the shortwaves and they can be effective in cutting off the flow 

in tandem with the n American trough being poorly modelled because it’s not going to dig as far south as predicted and sustain for a few days and we see the Atlantic flattened. A deeper n American trough would have sent WAA downstream and helped keep the ridging to our west. And finally the Arctic field remain unpredictable as ever. 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5011597

[Model Output Discussion - Colder but how cold and for how long?]

Just now, steveinsussex said:

Weirdly the met office going for sleet and rain to lower levels in the north on Tuesday?!

 

3.40 mark on here

 

 

Warm sector on a wave that doesn’t originate in the frigid flow 

the shortwaves have spoiled this week for most. 

the nwp has counted down pretty well from a couple weeks out - but the ens means won’t see the shortwaves and they can be effective in cutting off the flow 

in tandem with the n American trough being poorly modelled because it’s not going to dig as far south as predicted and sustain for a few days and we see the Atlantic flattened. A deeper n American trough would have sent WAA downstream and helped keep the ridging to our west. And finally the Arctic field remain unpredictable as ever. 

[Model Output Discussion - Colder but how cold and for how long?]

Gfs fi has us chasing an arctic ridge again - lucky they can be relied upon! 

[Model Output Discussion - Colder but how cold and for how long?]

2 hours ago, Ali1977 said:

The GFS MEAN has snow to the midlands on Wed, this is mental. I think more moves north are on the cards now 

 

A few examples, and there are plenty more 

The gefs mean also reveals that bringing the precip further north also brings less cold air with the mean precip not all shown as snow

Flicking through timeframes on the gefs members (the most excited about precip getting into s england ) reveals a hochpotch of solutions with plenty of rain involved.  So even getting the moisture in doesn’t guarantee anything. 

Meteociel - Panel GEFS

WWW.METEOCIEL.FR

 

[Model Output Discussion - Colder but how cold and for how long?]

10 minutes ago, MATTWOLVES 3 said:

Yeh thought it might be Nick..fortunately it's only out to day 8..perhaps its just that little further on when the tide turns. Will be hoping for some positives from you regarding the eps and strat in the near future..hopefully Nick!!

Sceuro ridge building late in the eps 

2 clusters late on beginning to look retrogressive 

and wrt to the strat, mean ural ridge and Aleutian low showing week 2 which would spell bad news for any spv recovery 

[Model Output Discussion - Colder but how cold and for how long?]

7 minutes ago, MATTWOLVES 3 said:

Again subtle hints of a few runs trending colder again on the mogreps...come on folks work with me here 

Checking the mslp stamps shows it’s just cool zonal on some runs Matt 

[Model discussion highlights]

Would be a good time for the strat to take the lead …..

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5010641

[Model Output Discussion - Colder but how cold and for how long?]

Would be a good time for the strat to take the lead …..

[Model discussion highlights]

The gfs op is generally inconsistent back end of its runs in the upper strat but the last few runs has it taking the spv to Barents /novaya zemlaya with the axis heading back towards the meridian. 
 

I would expect that could indicate that by the back end of jan we would see another set up similar to what we have this week 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5010574

[Model Output Discussion - Colder but how cold and for how long?]

The gfs op is generally inconsistent back end of its runs in the upper strat but the last few runs has it taking the spv to Barents /novaya zemlaya with the axis heading back towards the meridian. 
 

I would expect that could indicate that by the back end of jan we would see another set up similar to what we have this week 

[Model discussion highlights]

Well I said I’d wait for the 12z eps to check out rogue runs and on a hemispheric level they have delivered 

whilst the low spread persists around low heights over Greenland, the remainder of the polar profile looks very broken vortex with plenty of amplification and high level blocking. . Of course that Greenland vortex is a problem for us but it doesnt necessarily persist there into week 3 and the mean vortex is actually west of Greenland so that’s already a positive. 

whilst the breakdown days 8/10 is a poor end to the weeks chase, I made my peace with that a couple of days ago 

the next chase comes into view - maybe a height rise east of the meridian which then retrogresses 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5009483

[Model Output Discussion - Colder but how cold and for how long?]

Well I said I’d wait for the 12z eps to check out rogue runs and on a hemispheric level they have delivered 

whilst the low spread persists around low heights over Greenland, the remainder of the polar profile looks very broken vortex with plenty of amplification and high level blocking. . Of course that Greenland vortex is a problem for us but it doesnt necessarily persist there into week 3 and the mean vortex is actually west of Greenland so that’s already a positive. 

whilst the breakdown days 8/10 is a poor end to the weeks chase, I made my peace with that a couple of days ago 

the next chase comes into view - maybe a height rise east of the meridian which then retrogresses 

[Model Output Discussion - Colder but how cold and for how long?]

Just now, Mike Poole said:

It does, maybe heading for the snowless breakdown I joked about the models seeking out yesterday.

Joking aside, it’s become a feature of breakdowns over the past decade that they don’t bring a transitional snow event further south. Maybe I don’t recall all the fails of my youth but I’m sure it was a thing in the olden days! 

[Model Output Discussion - Colder but how cold and for how long?]

Just now, Mike Poole said:

The new ridge being thrown up does not on this ICON run connect with the Greenland high, but we are still in a northerly T138:

Interested to see where it goes from here.

Esb low is different at day 6 on 12z icon to most other modelling on 00z 

looks like it will topple a cold high across and flatten 

 

[Model Output Discussion - Colder but how cold and for how long?]

Icon further north at day 4/5

Ec had the low through the channel so perhaps icon drifting towards ec 

less push south with the lower uppers on the 12z icon and a little less lobe split again - presumably this slightly less amplification responsible for less push south on the 850’s. 

all within run to run expectation 

[Model Output Discussion - Colder but how cold and for how long?]

Btw, the 06z ec control is a little more ‘lobe closing’ than the 00z run over Greenland 

[Model Output Discussion - Colder but how cold and for how long?]

Just now, Rob 79812010 said:

Thanks! So may not be so mild that week then??

With the Atlantic still on the warm side (if thats still true ) , I would think surface temps could well be at times. 

[Model Output Discussion - Colder but how cold and for how long?]

3 minutes ago, Rob 79812010 said:

Question for anyone please! Why are the GEFS 850 temps consistently showing average temps or below from 23rd to 28th?? I always think these are fairly reliable but seems to be going against what's being said about that week. Is it still in the balance and that the final week may not actually bea mild week? If high pressure drops south doesn't that then allow the mold south westerlies or are there other things in the mix?? Apologies if this has been explained already. Lot of stuff on here!

Cool zonal rob 

could be ok over decent elevation n england and Scotland 

but cool and wet for most with milder interludes re warm sectors 

[Model Output Discussion - Colder but how cold and for how long?]

48 minutes ago, Gowon said:

 Is it the disruption of the jet that get us to that first week of Feb anomaly chart?

It doesn’t look like it’s a retrogressive pattern  on the weeklies to get from last week jan to first week feb. Therefore I’d assume it’s a rise in heights from the mid Atlantic ridge which reflects a slow down in the jet and ‘other influences’

[Model discussion highlights]

the day 15 eps mean and spreads scream Greenland tpv very loudly and upper ridge into Iberia 

= flat zonal 

now the extended ens have been promising a return to a ne Canadian vortex for some time - it’s taken longer to get there than first modelled but it’s now looking v likely indeed

the only caveat I have is that the trop continues to lead the dance and we know how unpredictable trop modelling is as week 2 progresses. there may be feedback issues that are consolidating a strengthening which may not verify in that fashion.  Having said that, it was noted about a week ago that the modelling wanted to stretch the spv from Barents to e Canada, split it, then return the Canadian segment back to svaalbard. We know from experience that this east - west - east movement of a coupled  spv/tpv will usually fire up the northern arm.  It looks like the split that enables the n Atlantic height rise will also be responsible for the fired up jet as the two segments are rejoined on our side of the NH.  in addition, the split Canadian segment dropping into n America doesn’t help as it increases the temp differential which leads to an even stronger jet. and the displaced nature of the spv our side means that this movement is at a southerly latitude which means the jet is aimed at us.  

as nick alluded earlier, there are sniffs of disruption which could force that jet into Iberia but that’s not what the nwp is showing 

I do have nagging doubts on this but it’s rare that the modelling for week 2 is wrong when there is so much agreement across the nwp  

there currently aren’t enough rogue ens members to justify any doubts  (actually the 06z gefs have a few so maybe need to see what happens on the 12z eps) 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5008588