Model Output Discussion 29th December - Into mid-Winter.

[carinthian]

58 minutes ago, Polar Maritime said:

Some very cold surface temps with hard frost especially in the South over the weekend and into next week. -7/8/9c certainly possible with some locations hovering around freezing all day as -4/-5c uppers sit over England.

And the chance of a possible snow flurry..

PM , would that not be a laugh if the snow hot spots on that chart came off... namely snow starved Preston, Manchester, North Notts...would be welcome after such a drab time up there in the old industrial northlands.

C

[Seasonality]

5 minutes ago, stodge said:

Morning all

Well, I see general agreement from the OP runs overnight and this morning for the cold and settled conditions to be eased away early next week in favour of a milder, more Atlantic based set up. Yes, the breakdown has been delayed 48 hours or so from the earlier output but by Wednesday next week it's hard to imagine an outcome other than milder air over the whole of the British Isles with rain approaching from the Atlantic.

We knew this would happen and it's going to have to be enjoyed/endured (delete as appropriate) for at least 14 days. I'm more than encouraged by what I'm seeing in the furthest fringes of GFS FI at this time.

The initial rebuild of the PV over NE Canada/Greenland in response to the Siberian warming may not be of too long duration or of great strength (whether it's an actual SSW or not is a question for others) but it will leave us under Atlantic domination for 10-14 days.

After that, I see signs of the PV weakening further and the "possibilities" for a pattern change - to what, I don't know, and, to stress, absolutely no guarantee such a change will be favourable for fans of snow or cold. We could quite easily finish up with a block bringing mild SW'lies and that would be that.

The next 7 days of model watching aren't going to be fun or pretty for those looking for winter but we have more than a third of "official" winter remaining and never rule out the possibility of lowland snow in early March - it's happened many times before.

But none of the models go out far enough to show 2 weeks of Atlantic domination from Wednesday next week? Bold call considering how weak the Atlantic has been so far.

[Severe Siberian icy blast]

7 minutes ago, stodge said:

Morning all

Well, I see general agreement from the OP runs overnight and this morning for the cold and settled conditions to be eased away early next week in favour of a milder, more Atlantic based set up. Yes, the breakdown has been delayed 48 hours or so from the earlier output but by Wednesday next week it's hard to imagine an outcome other than milder air over the whole of the British Isles with rain approaching from the Atlantic.

We knew this would happen and it's going to have to be enjoyed/endured (delete as appropriate) for at least 14 days. I'm more than encouraged by what I'm seeing in the furthest fringes of GFS FI at this time.

The initial rebuild of the PV over NE Canada/Greenland in response to the Siberian warming may not be of too long duration or of great strength (whether it's an actual SSW or not is a question for others) but it will leave us under Atlantic domination for 10-14 days.

After that, I see signs of the PV weakening further and the "possibilities" for a pattern change - to what, I don't know, and, to stress, absolutely no guarantee such a change will be favourable for fans of snow or cold. We could quite easily finish up with a block bringing mild SW'lies and that would be that.

The next 7 days of model watching aren't going to be fun or pretty for those looking for winter but we have more than a third of "official" winter remaining and never rule out the possibility of lowland snow in early March - it's happened many times before.

Sorry but completely disagree there. How an earth can you call zonal for at least 14 days? Firstly we were meant to be in mild air a lot quicker than The reality, with various models barking up the wrong tree with the mjo for example been misread by the mods so that alone brings question marks on where we all go from here, granted the PV is strong at the minute but that doesn't completely rule out a mid lat high; which has the capability of ridging into Norway/scandi just enough to filter cold air down on its eastern and southern flank, zonal is by no means a sure bet, but if we see it I'm beginning to think a 2/3 day affair rather than 2/3 wk one. 

[stodge]

17 minutes ago, jvenge said:

GFS, GEFS, ECM and ECM EPS are all keen on keeping the AO and NAO comfortably positive going towards the end of the month.

Yes, not sure that's an entirely accurate summation.

The AO has been positive all winter, remains so and may go higher (to +3) as we go into February.

The NAO is a different story - it has had negative spells (such as now) and the forward forecast has a lot more scatter. I'd say neutral to weakly positive to month end but with much uncertainty.

The PNA is positive now but drops back to neutrality by month end.

[Summer Sun]

Looking like the high will be putting up a good fight against any west or south westerlies

[bluearmy]

17 minutes ago, jvenge said:

GFS, GEFS, ECM and ECM EPS are all keen on keeping the AO and NAO comfortably positive going towards the end of the month.

No surprise but keep your eyes on the extended AO - a big spread in the neg direction will reveal ens members heading for a QTR to the poss  SSW

 

[stodge]

5 minutes ago, Severe Siberian icy blast said:

Sorry but completely disagree there. How an earth can you call zonal for at least 14 days? Firstly we were meant to be in mild air a lot quicker than The reality, with various models barking up the wrong tree with the mjo for example been misread by the mods so that alone brings question marks on where we all go from here, granted the PV is strong at the minute but that doesn't completely rule out a mid lat high; which has the capability of ridging into Norway/scandi just enough to filter cold air down on its eastern and southern flank, zonal is by no means a sure bet, but if we see it I'm beginning to think a 2/3 day affair rather than 2/3 wk one. 

Thank you for the comment.

I didn't use the word "zonal" by the way - I don't see a zonal outlook but a more Atlantic-dominated set up (there is a difference).

I do agree there is a possibility the HP will be more resilient than the models are suggesting and as I acknowledged the breakdown scheduled for Sunday/Monday is now looking more like Tuesday/Wednesday next week but I see nothing in the OP runs this morning to suggest either ridging into Scandinavia or a link to the Russian HP - there may be a number of the Ensemble members that suggest that. I also see broad cross-model agreement to T+168 at this time.

The driving force is the regeneration of the PV on the Canadian/Greenland side from Siberia. The return transfer of energy across the Pole "may" be the first response to the warming on the Siberian side and if so it's entirely to be expected. None of this says we can't benefit from any warming later but a warming on the Eurasian side (as distinct from a Canadian warming) doesn't do us any favours initially. In the depths of FI there are encouraging signs but given the lag on these I'm happy with my view of 10-14 days of milder Atlantic weather from the middle of next week.

Yes, the models haven't covered themselves in glory this winter and I may be wrong.

As someone once said, more runs are needed and let's see if the 06Z OP continues the trend.

[jvenge]

12 minutes ago, stodge said:

Yes, not sure that's an entirely accurate summation.

The AO has been positive all winter, remains so and may go higher (to +3) as we go into February.

The NAO is a different story - it has had negative spells (such as now) and the forward forecast has a lot more scatter. I'd say neutral to weakly positive to month end but with much uncertainty.

The PNA is positive now but drops back to neutrality by month end.

Of course much uncertainty, it changes almost every run, but the last ones are putting it positive, just varies how much and when.

 

7 minutes ago, bluearmy said:

No surprise but keep your eyes on the extended AO - a big spread in the neg direction will reveal ens members heading for a QTR to the poss  SSW

 

Could always hope the control run of the GEFS is right for both ;-)

[Hammer50]

I do not see any incursion from the Atlantic for the foreseeable future if anything we are going into the freezer for some time to come especially with the ssw in the next few weeks and the continued cold out to the east Spring is going to be very late this year.

[TEITS]

Going to add my opinion on the model output but this is purely based on past examples rather than any scientific reasoning.

When we have a pattern that the models suggest i.e Atlantic Vs Blocking then at the timeframe such as +168 onwards, the models including the ECM will always try and send the energy from the Atlantic NE and be very reluctant to go SE (undercut). The ECM +192 does send some energy SE. Only inside +144 do the models start suggesting the possibility of undercutting. This is why E,lys can appear rather suddenly.

At this moment in time the E,ly is a long shot. Between +96 to +144 we need to see further adjustment with greater amplification and with the low in the Atlantic being further W. However considering the changes we have seen in the past +72 hrs I wouldn't be so bold in saying mild, zonal for the next 2 weeks!!

[mb018538]

As others have pointed out - models are increasingly confident of a massive drop in zonal winds by the turn of the month (and SSW), so this could well lead to something very interesting by the middle of February. Not guaranteed of course, but at least gives us a shot.

[bobbydog]

There seems to be a few doubters regarding the SSW. (understandably so maybe) they are modelled more consistently than trop events, so consider this-

29th January 2017

27th January 1991

4th February 2017

6th February 1991

Within a couple of days either way and almost identical

Does this not inspire a little bit of confidence that we might be on the verge of what we have all been waiting for?........

[jvenge]

3 minutes ago, bobbydog said:

There seems to be a few doubters regarding the SSW. (understandably so maybe) they are modelled more consistently than trop events, so consider this-

29th January 2017

27th January 1991

4th February 2017

6th February 1991

Within a couple of days either way and almost identical

Does this not inspire a little bit of confidence that we might be on the verge of what we have all been waiting for?........

When it gets to within 7 days on the GFS and ECM, without chopping and changing along the way, yep :-D

[bobbydog]

3 minutes ago, jvenge said:

When it gets to within 7 days on the GFS and ECM, without chopping and changing along the way, yep :-D

Tick that box then  the warming I have illustrated is underway at 7 days. There is a minor one as well at 5 days

[ITSY]

6 minutes ago, jvenge said:

When it gets to within 7 days on the GFS and ECM, without chopping and changing along the way, yep :-D

The other thing I would look out for are gradual hints of incursions into the trop polar vortex at the back end of FI. Notice that even on the midnight GEFS, the Op and 6 ensemble members ended with significant trop level attacks on the vortex at our level - most completely not related to the UK, but interesting as a sign for how long it may take for the affects of any warming to propagate downwards...

[bluearmy]

Comparing hemispheric temperature charts at 10hpa has no real bearing on what follows in the trop 

need to view the heights rather than the temps and at levels below 10hpa after the warming 

[bluearmy]

Don't look at the 18z gfsp week 2 if you are of a nervous disposition 

interesting to see another gfs fi throw up a ridge mid Atlantic which becomes cut off toniur north thereafter 

i noted the strat modelling kicking up a high anomoly to our north/northeast around day 8/10

pieces of the jigsaw and they may all be disconnected but on the other hand ......

 

Edited January 19, 2017 by bluearmy

[bobbydog]

5 minutes ago, bluearmy said:

Comparing hemispheric temperature charts at 10hpa has no real bearing on what follows in the trop 

need to view the heights rather than the temps and at levels below 10hpa after the warming 

Either way BA, a warming on that scale will have a significant effect on the trop. 

Seeing it being forecast is warming my cockles anyway.... 

[Singularity]

The MJO sure did book it across to phase 1 on the H-W plot yesterday.

GEFS suddenly became keen to race it across to the Pacific but at low/negligible amplitude between phases 3 and 6. Under that scenario I expect we'd be looking for the 7/8 transition to pull us out of a less than inspiring pattern as we set off into Feb. Most likely it would by the 2nd week - but this is making a lot of assumptions and in any case the professional input from NCEP suggested yesterday that something more like the CANM mean is more likely to unfold. ECMF is currently splitting the difference while UKME is very energetic as usual during times of increasing MJO amplitude - but it could actually do quite well if the models are indeed over-reacting to interference from other equatorial phenomena.

Short-term, the models are already enthusiastic enough with MJO amplification that it seems it would be some going to get enough more in the upstream pattern to slow or stall the low moving NE from Florida in the 6-8 day range, but of course there's always the chance that the process by which the amplification propagates east is not being handled quite right. So the potential remains. Best outcome of all would see that low held up and then interacted with by another low further west in the U.S. as you could see more mid-Atlantic amplification to help disrupt the major troughs in that area.

If instead the Atlantic jet remains relatively unperturbed then what with stratospheric support for blocking to our E/NE we could well be locked into a balmy SW flow for a time much as the longer-term model guidance has been suggesting for many days now. Something we'll just have to accept if it happens.

[jvenge]

 

1 minute ago, bluearmy said:

Don't look at the 18z gfsp week 2 if you are of a nervous disposition 

interesting to see another gfs fi throw up a ridge mid Atlantic which becomes cut off toniur north thereafter 

i noted the strat modelling kicking up a high anomoly to our north around day 8

pieces of the jigsaw and they may all be disconnected but on the other hand ......

 

I might be unpopular for saying so, but I don't bother with the 06z and 18z at all. I think for the 06z it's a case of no other models with output at the time and then when the 12z comes along, you have UKMO and ECM as well. Then with the 18z, by the time I'm awake, the 0z is already out...

[TEITS]

Good example of how low pressure undercutting can make all the difference.

[Nouska]

27 minutes ago, bobbydog said:

Either way BA, a warming on that scale will have a significant effect on the trop. 

Seeing it being forecast is warming my cockles anyway.... 

Hi, BB the 1991 analogue does make a single chart entry in the upstream analogues.

From reanalysis I did yesterday on the past January SSWs - 2006 looks a good match for geopotential heights at time of reversal. The map below shows the forty five day surface anomaly following the event in 2006.

Nothing remarkable in CET figures for February but looks like it was a cold March. The summer that followed would be nice to see again, though!

 

 

[Seasonality]

High pressure still looking strong.

[sebastiaan1973]

Well. The end of februar 2006 was (very) cold for the continent. 

38 minutes ago, Singularity said:

The MJO sure did book it across to phase 1 on the H-W plot yesterday.

GEFS suddenly became keen to race it across to the Pacific but at low/negligible amplitude between phases 3 and 6. Under that scenario I expect we'd be looking for the 7/8 transition to pull us out of a less than inspiring pattern as we set off into Feb. Most likely it would by the 2nd week - but this is making a lot of assumptions and in any case the professional input from NCEP suggested yesterday that something more like the CANM mean is more likely to unfold. ECMF is currently splitting the difference while UKME is very energetic as usual during times of increasing MJO amplitude - but it could actually do quite well if the models are indeed over-reacting to interference from other equatorial phenomena.

Short-term, the models are already enthusiastic enough with MJO amplification that it seems it would be some going to get enough more in the upstream pattern to slow or stall the low moving NE from Florida in the 6-8 day range, but of course there's always the chance that the process by which the amplification propagates east is not being handled quite right. So the potential remains. Best outcome of all would see that low held up and then interacted with by another low further west in the U.S. as you could see more mid-Atlantic amplification to help disrupt the major troughs in that area.

If instead the Atlantic jet remains relatively unperturbed then what with stratospheric support for blocking to our E/NE we could well be locked into a balmy SW flow for a time much as the longer-term model guidance has been suggesting for many days now. Something we'll just have to accept if it happens.

Phase 1 and 2 have high pressure displaced to the north. Altough phase 1 less than phase 2. 

Edited January 19, 2017 by sebastiaan1973

[jvenge]

3 minutes ago, Seasonality said:

High pressure still looking strong.

Toasty...

A long way out, though, and PROBABLY wouldn't get that warm.