Model Output Discussion 4th Dec.2013-12z onwards.

[forecaster]

This December must be like a holiday for meteorologists! Very easy to forecast and unlikely to shift anytime soon! UKMO and GFS in perfect agreement a tell tell sign of mild weather. Karyo

No, fog is probably the hardest thing to forecast, or low cloud. Both could be an issue under such situations. Were this set up to occur in summer though, it would be relatively straightforward.

[Frosty.]

No, it will make the pattern very flat and hard to achieve any meaningful amplification that is required for a cold spell here. Karyo

It wouldn't be flat all the time if the atlantic fires up..I would say winds would be north of west at times with colder incursions, we can't just assume it would be mild all the time. I'm not talking about cold spells, more like polar maritime incursions behind cold fronts.

[karyo]

No, fog is probably the hardest thing to forecast, or low cloud. Both could be an issue under such situations. Were this set up to occur in summer though, it would be relatively straightforward.

That's for the southeast! The majority of the country looks like getting a mobile southwesterly.

[karyo]

It wouldn't be flat all the time if the atlantic fires up..I would say winds would be north of west at times with colder incursions, we can't just assume it would be mild all the time. I'm not talking about cold spells, more like polar maritime incursions behind cold fronts.

Ok but those brief incursions have no chance to bring any cold uppers away from Scotland unless there is some amplification in the Atlantic. Here we are looking for a straight southwesterly with low heights in the Atlantic and persistent high pressure in the continent.

 

Karyo

[Frosty.]

Ok but those brief incursions have no chance to bring any cold uppers away from Scotland unless there is some amplification in the Atlantic. Here we are looking for a straight southwesterly with low heights in the Atlantic and persistent high pressure in the continent.

 

Karyo

At least it would be better than what we will be getting in the next 7-10 days, i'm hoping for something like the 6z op & control run later in FI, cold weather close to christmas.

[Ian Brown]

It wouldn't be flat all the time if the atlantic fires up..I would say winds would be north of west at times with colder incursions, we can't just assume it would be mild all the time. I'm not talking about cold spells, more like polar maritime incursions behind cold fronts.

 

That is dependent no Bartlett setting up with the jet permanently SW to NE. Sure if the jet is a bit further South then you can get some variation, but with comparisons being made to the late 80s and late 90s winters, you often didn't even get that.

[Bolton67]

funny how last month and the month before we see a sharp increase in solar activity could be that feb could be our best bet as solar activity has declined a little so mid jan start of feb we could see something more exciting from the model out puts.I feel uptick in solar activity has a strong effect on the strength of the vortex and jet stream output.I don't believe we are going to see anything exciting for a long time yet.

Seriously, when is your negativity going to stop ? So by your logic, we should all log out and come back in late January? Please can I remind you it's the 7th of December. Edited December 7, 2013 by lancs_northants

[That ECM]

A strongly zonal set-up establishing on the GFS, we are now in the sort of situation where charts out to around T216 will have a reasonable level of accuracy.

This post deserves more credit. He got a bit of a roasting for saying " a long way back to cold". Much thought in how to use a chart and say the same thing differently!! In honesty tho who could disagree. Meant in good humour IB.

[Mucka]

Well with the output being poor for cold fans at the moment I guess I am allowed to clutch a very thin straw?

Just the smallest hints in GFS ensembles that we will have a chance of more amplified pattern later in the month.

We are talking deepest FI here but don't write a white Christmas off just yet.

If it does take shape it may well be another mid Atlantic ridge and yeah we all know how that turned out last time, but next time...

 

We know its bad when it gets to looking within the ensembles in dep FI just for the threat of a beneficial pattern change but that's where we are I'm afraid.

I'll keep an eye on it and see if a signal develops.

[Ian Brown]

Seriously, when is your negativity going to stop ?So by your logic, we should all log out and come back in late January?Please can I remind you it's the 7th of December.

 

ER is only being realistic, we are on a slow descent to zonality with the killer combo of a deep PV and Euro High, with some forecasters talking of a record +ve January AO. 

[Tamara]

Well with the output being poor for cold fans at the moment I guess I am allowed to clutch a very thin straw?

Just the smallest hints in GFS ensembles that we will have a chance of more amplified pattern later in the month.

We are talking deepest FI here but don't write a white Christmas off just yet.

If it does take shape it may well be another mid Atlantic ridge and yeah we all know how that turned out last time, but next time...

 

We know its bad when it gets to looking within the ensembles in dep FI just for the threat of a beneficial pattern change but that's where we are I'm afraid.

I'll keep an eye on it and see if a signal develops.

Yes I agree. It rather highlights what I have been suggesting today about the upcoming pattern being perhaps a transient one through December. Far too early to tell when the present changes in the Pacific and movements of the vortex are only just beginning. but it underpins some of the thoughts written today about the further outlook

[Yozzer]

 

 

Bet that brings back some memories eh John?

[johnholmes]

Bet that brings back some memories eh John?

 

It is easy to go off some folk!

[Mucka]

Yes I agree. It rather highlights what I have been suggesting today about the upcoming pattern being perhaps a transient one through December. Far too early to tell when the present changes in the Pacific and movements of the vortex are only just beginning. but it underpins some of the thoughts written today about the further outlook

 

That was a very good call Tamara and it has been proved such.

I think we were quite close to getting a cold pattern setting up though, only narrowly missing the Scandi ridge linking up and that would of made a real difference but the proof is in the pudding and this particular pudding turned out quite flat.

 

I agree the next blocking episode may be another transient ridge but if we can get one strong enough and further West we could get a decent cold shot pre Christmas.

If, could, maybe, sigh.

Edited December 7, 2013 by Mucka

[Cecil Hogmanay Melchett]

ER is only being realistic, we are on a slow descent to zonality with the killer combo of a deep PV and Euro High, with some forecasters talking of a record +ve January AO. 

who are these forecasters Ian?

[Tamara]

That was a very good call Tamara and it has been proved such.

I think we were quite close to getting a cold pattern setting up though, we only narrowly missing the Scandi ridge linking up and that would of made a real difference but the proof is in the pudding and this particular pudding turned out quite flat.

 

I agree the next blocking episode may be another transient ridge but if we can get one strong enough and further West we could get a decent cold shot pre Christmas.

If, could, maybe, sigh.

We we would like to see a resumption of the poleward Alaskan ridge because it will relocate the vortex back to the Siberian side and encourage the wave 2 activity into the stratosphere we are going to depend on to break up this entrenched vortex as we get deeper into the winter. On that basis, we want the upcoming spell with the vortex over Greenland and Canada to prove as transient as possible. Fortunately the analogues are also on our side in this respect following late autumn/early winter periods of Aleutian High dominated patterns. Also it gives some excuse to pick out some of the deepest and most tentative GFS hints of the possible way ahead

[Summer Sun]

GFS 12z has all of the UK above average till the 15th

 

Anomaly

 

 

Expected temperatures

 

[Captain Shortwave]

Worst chart of the season so far, jet tilted SW/NE with a train of lows all guaranteed to take a track between Scotland and Iceland. 

Whatever happens tomorrows ECM will be better 

Edited December 7, 2013 by Captain shortwave

[Summer Sun]

ECM isn't looking as unsettled as UKMO later next week the only place prone to any rain really is Scotland and even here it won't be much

 

 

T216 shows something slightly cooler pushing in to the west

 

 

Nasty low to end ECM's run over Scotland with another one lining up behind it

 

Edited December 7, 2013 by Summer Sun

[TSNWK]

ECM 216 240 are text book zonal Bartlett. Simples.

[Catacol]

Suggestions made yesterday have firmed up in the models today. US wave 2 warming 12/13 Dec sees tropospheric response with heights rising out of Canada:

 

 

Vortex shift towards Scandy/Svalbard and the warming that started over the US is forecast to be a bit stronger and long lasting today focused at around 20hPa - see here:

 

 

FI GFS then has it right for me a few days later, with most of the vortex energy displaced East and continued warming to our west encouraging the rebuilding of the mid atlantic high. General shift of heights to the W and NW visible here 19 Dec:

 

 

From here the question will be what happens out over Siberia. I mentioned yesterday that GFS has a suggested warming, and its still in the runs today:

 

 

 

For me this means mild zonal will be short lived. My reading of trop responses to forecast warmings would suggest a flow more NW than SW by Dec 20 and then the potential for some wet and windy weather for Xmas week - snow over northern hills, near normal for the rest of the UK. I wouldnt rule out a northerly with a bit more chill to it at that stage if heights over the mid atlantic can build sufficiently.

Edited December 7, 2013 by Catacol_Highlander

[Methuselah]

As far as I can see - and, whether we like it or not - we have a spell of zonal weather to contend with...Will it last forever? I doubt it! 

[Catacol]

ER is only being realistic, we are on a slow descent to zonality with the killer combo of a deep PV and Euro High, with some forecasters talking of a record +ve January AO. 

 

I dont see it that way. Evidence from the season so far is that regular shunting from warming events is ongoing, and I think is likely to remain ongoing. Even if we fail to get a major SSW in Jan/Feb I doubt we will see sustained zonal patterns and instead we will see amplification of the pattern continue with more NW and N action ongoing. We can only be a bit vague at this stage to be honest, but a flat bartlett for a month would require a very quiet strat pattern - and while we have not broken the vortex yet we have seen plenty of minor warmings and the aleutian high shows signs of being a semi permanent feature this winter. In simple terms I think it is an error to apply the NH patterns of the 89 - 08 period to years following 08. We have seen a change in general circulation patterns and nothing in 2013 has suggested that these have returned to the pre 08 pattern. A flat pattern for a week or so looks odds on, but to extend that to the end of January seems a long shot in interpretative forecasting terms.

 

I note you still refuse to post any data to back up your statements. If I were marking your A level essays you would be scraping a grade E at best.

[Richie V]

I'm off on one again....

expect by tues for ecm and gfs inparticular to throw up some unbelieveable violent lp solutions.

First hints on the latter frames of the ECM this eve.

[Tamara]

I dont see it that way. Evidence from the season so far is that regular shunting from warming events is ongoing, and I think is likely to remain ongoing. Even if we fail to get a major SSW in Jan/Feb I doubt we will see sustained zonal patterns and instead we will see amplification of the pattern continue with more NW and N action ongoing. We can only be a bit vague at this stage to be honest, but a flat bartlett for a month would require a very quiet strat pattern - and while we have not broken the vortex yet we have seen plenty of minor warmings and the aleutian high shows signs of being a semi permanent feature this winter. In simple terms I think it is an error to apply the NH patterns of the 89 - 08 period to years following 08. We have seen a change in general circulation patterns and nothing in 2013 has suggested that these have returned to the pre 08 pattern. A flat pattern for a week or so looks odds on, but to extend that to the end of January seems a long shot in interpretative forecasting terms.

 

I note you still refuse to post any data to back up your statements. If I were marking your A level essays you would be scraping a grade E at best.

The basis of what Ian is saying here is made on the assumption that the Aleutian High is not a semi permanant feature this winter, and has been a front loaded one that has kept the pattern more amplified before the background +AO signal takes over from mid December onwards.

 

However as has been documented, there are indeed reasonable grounds for thinking that the upcoming unfavourable Pacific pattern will be transient. The forecasters, that Ian allude to, do not stress any confidence at all that any raging flat +AO pattern will continue through the heart of the winter and expect, overall, the amplified Pacific pattern to hold sway with just transient interruptions.

 

I think it is right to point out what can go wrong, much as I posted on the other thread today, but that should only be within the context of a balanced overview of the pro's and con's of any given situation and the most likely way the pattern will proceed

Edited December 7, 2013 by Tamara תָּמָר