Winter Model Discussion - Cold Hunting -12Z 03/01/13

[kumquat]

The considered advice from Ian, was to largely ignore - or, at the very least, don't become too married to solutions at this very specific moment in time. It's because there is obviously a consensus at Exeter, that downstream SSW influence is going to over-ride what we currently see as outputs from NWP.

Perhaps I worded it badly but that was what my "none the wiser" alluded to - for those specific reasons, in this specific set of circumstances. (BTW I was not suggesting, by any means, that the MO professionals are intrinsically none the wiser! Of course they are (the wiser), although I agree my comment was rather throwaway and careless.)

All I'm saying is I'm constantly (to the point of it sounding like a broken record) hearing repeated calls about "re-reading Ian F's posts" and ignoring all other out put past T+x and my point is that this thread exists exactly for that reason.

Now I agree with you that it's probably a waste of time but it's been many people's waste of time here for years.

Edited January 4, 2013 by kumquat

[SnowBallz]

Dont the met office have a MR-LR view Snowballz? surely they look out further than seven days for potential pattern changes?

Of course they do. But - obviously - it's at odds with what the current NWP output is showing, hence the advice. I think that's where the value of experienced, professional meteorologists plays its hand; algorithms are only able to compute to a certain degree, and within pre-determined boundaries. However, a human being is not so closely confined, and is therefore able to form a different informed view.

I should imagine that the professionals at Exeter have a 'hypothesised evolution', which - as this current period and (SSW) phenomenon progresses - they would expect to slowly influence the more normalised NWP output. Indeed, I would take an inference from Ian's advice, that the 'first test' of the hypothesis may well be bearing the fruit which the professionals foresaw - hence reasonable enough confidence to advice caution regarding current NWP output.

Of course the risk is that the hypothesis is flawed. But isn't that the inherent nature of meteorology, ie: somewhat trial and error? I would say that this current hypothesis is on trial, and - should the principle be proven - then you can begin to develop more encompassing algorithms, therein - to a degree - extending the agility of NWP. That's always the common goal. Therein, I totally agree with Ian, that's is a very exciting time ahead...

[johnholmes]

Looking at it from another angle and this refers me back to the empirical data we used to use in the Met O prior to computer models when trying to forecast significant events 24-72 hours down the line.

In this case the development of a Scandinavia anticyclone.

Looking at my very old forecast notes and then at the Met O output post 72 hours almost all the criteria for this developing and for it persisting beyond 24 hours once formed seem to be met!

That would suggest the ridge and surface high to be NE of the UK.

Interesting to see just where they will initially be in that time scale of 72-144 hours, maybe a bit beyond that?

[Troubleatmill]

Ensembles are still all over the place, so i think now is the time to listen to GP and see how things transpire over the next few days, certainly a few members coming on board and what looks for certain is that we are seeing the end of this zonal pattern that has plagued us since mid December.

Edited January 4, 2013 by Nick JB

[The Eagle]

The upper and middle stratospheric modelling is unbelievable at this stage and is as clear a signal as you could get for a Greenland ridge.

So now it's a Greenland high and more likely a northerly? Have you given up hope now of anything developing in to substance by 192hrs?

[Troubleatmill]

Of course they do. But - obviously - it's at odds with what the current NWP output is showing, hence the advice. I think that's where the value of experienced, professional meteorologists plays its hand; algorithms are only able to compute to a certain degree, and within pre-determined boundaries. However, a human being is not so closely confined, and is therefore able to form a different informed view.

I should imagine that the professionals at Exeter have a 'hypothesised evolution', which - as this current period and (SSW) phenomenon progresses - they would expect to slowly influence the more normalised NWP output. Indeed, I would take an inference from Ian's advice, that the 'first test' of the hypothesis may well be bearing the fruit which the professionals foresaw - hence reasonable enough confidence to advice caution regarding current NWP output.

Of course the risk is that the hypothesis is flawed. But isn't that the inherent nature of meteorology, ie: somewhat trial and error? I would say that this current hypothesis is on trial, and - should the principle be proven - then you can begin to develop more encompassing algorithms, therein - to a degree - extending the agility of NWP. That's always the common goal. Therein, I totally agree with Ian, that's is a very exciting time ahead...

Ah i see where you are coming from now Thanks for that

[ChartViewer]

Nicely predicted -AO Ensemble forecast

[Village]

I see more of a Scandinavian based H/P with a coll over the southwest between the Azores H/P which will eventually break down. Coldest air in the southeast of the UK going forward and warmest in the northwest.

[Jason M]

Looking at it from another angle and this refers me back to the empirical data we used to use in the Met O prior to computer models when trying to forecast significant events 24-72 hours down the line.

In this case the development of a Scandinavia anticyclone.

Looking at my very old forecast notes and then at the Met O output post 72 hours almost all the criteria for this developing and for it persisting beyond 24 hours once formed seem to be met!

That would suggest the ridge and surface high to be NE of the UK.

Interesting to see just where they will initially be in that time scale of 72-144 hours, maybe a bit beyond that?

Very good point. Just as someone who has had an interest in this since being a kid, the current output from say day five onwards just screams Scandi High.

I'm surprised really that this isnt being developed agressively and early by at least some of the ensembles. I do wonder if things could switch very quickly.

Jason

[Weathizard]

Interesting 6Z ens. A real flip from the 0z ens within 192-216hrs I feel. Had a look through most of them and there is some stunners but the majority are cool and dry, with the building blocks firmly in place for heights to the North.

Will be interesting to see where the 12s go today. Anyone else noticed that when we have a poor OP the ens tend to be better and when the OP is good, the ens tend to climb off the boat? Very strange I've noticed it a lot recently, even lasts months debacle had similar.

[-uksnow-]

Very good point. Just as someone who has had an interest in this since being a kid, the current output from say day five onwards just screams Scandi High.

I'm surprised really that this isnt being developed agressively and early by at least some of the ensembles. I do wonder if things could switch very quickly.

Jason

It has been noted by some that perhaps until the SSW has occurred in a couple of days time the outputs will have a far worse grasp on what's coming, therefore I think you could well be right about a sudden change.

[bradymk]

looking at output i think we are going to see a gradual cooldown over the next two weeks while HLB assembles itself to the north with fog/frost possible at times but then into the 3rd week is when i see the potential for some very cold weather, beginning the 21st to 23rd. However with the volatile output i wouldn't be too surprised to see big upgrades shorter term with a quicker trop response. 6z ensembles were crackers synoptic wise

[Ian Brown]

I would just advise strong caution and hope people are not building their hopes up. Lest we forget it was only last month that we had the METO ‘uncertain’ in their longer range outlook and the ECM 32 dayer going for cold.

All this was turned on it’s head in the space of 24-36 hours with the Norwegian shortwave and a strong jet streak coming out of the US. A sudden game changer.

Now we have the METO again stressing the same ‘uncertainty’ and the ECM 32 dayer once again going for height anomalies around Greenland.

Remember we need to get the block in the right place and you only have so many shots at this before another signal comes in and chances are gone.

[nick sussex]

I'd be very surprised to see anything like the GFS 06hrs operational run come close to verifying.

This really goes against what you'd expect with the PV splitting and the background strat warming. For this reason its really not worth people worrying over it.

There is still alot of uncertainty with the initial response from the SSW and because of this I wouldn't rule anything out.

The actual reverse zonal winds haven't even occured yet so before we rule out a quick tropospheric response we best wait till after the weekend.

If you think about how often you might see a major SSW, generally once every two years so for nearly all the time the NWP is dealing with start conditions which have a normal west/east zonal flow above 60n.

Now here you have a reversal of that taking place between 72 and 96hrs. The Feb 2009 event caught many forecasters out because of the rapid initial response, the models didn't prog the big retrogression in the pattern till very close in.

I'm not saying we're definitely going to see this same quick effect but until the SSW has actually ocurred then its best to view the output with even more caution than normal.

Edited January 4, 2013 by nick sussex

[AWD]

EC London ens;

The Op similiar to the GFS, both heading down a colder route.

EC Op at T240;

EC mean at T240;

Expect possible westward corrections in the pattern within the next few EC runs.

Still a cluster going colder at the end of the EC De Bilt short ens;

Finally, differences between the ECMWF & GFS 500mb anomaly charts. ECMWF reluctant to lower heights to our south & build heights to our north/north west compared to the GFS which has a trough to our west & strong heights to our north;

Conclusion - I still don't know! Lots to play for & plenty of different potential routes we could take mid month.

Edited January 4, 2013 by AWD

[bluearmy]

awd, on those ecm ens : the blue line is the gfs op run, not the ecm control.

[AWD]

awd, on those ecm ens : the blue line is the gfs op run, not the ecm control.

I knew that, half asleep. Sorry, only had 3 hours sleep!

[MR EXTREMES]

Looking at it from another angle and this refers me back to the empirical data we used to use in the Met O prior to computer models when trying to forecast significant events 24-72 hours down the line.

In this case the development of a Scandinavia anticyclone.

Looking at my very old forecast notes and then at the Met O output post 72 hours almost all the criteria for this developing and for it persisting beyond 24 hours once formed seem to be met!

That would suggest the ridge and surface high to be NE of the UK.

Interesting to see just where they will initially be in that time scale of 72-144 hours, maybe a bit beyond that?

or it could well be that surface high being located over the uk or even slightly to the east and in this case cooling with night frost and low daytime minima depending on how long suface high sticks around.

to be honest better than wet and windy mild rubbish and certainly clears the air im sitting on the fence and a suface high over the uk could well be the end result.

not taking away the massive expectations of some real wintry weather i always found the settle cool to cold then wintry a favourate of mine which is also a common feature when it happens here in the uk.

and to add europe is pretty dam cold and there clearly a surge of cold air due to be pushed into the scandi area in the next 7 days so if the setup does transpire for us then a north northeast flow would be better than easterly until cold is set in beyond germany ect ect.

[karlos1983]

Hi all

I have been taking a back seat since December's major upset, still watching each run with hope and my addictive nature toward model watching both playing a part.

I am commenting now for 2 reasons, the first, being this is first time really, since model watching, that I will have seen this (potential) setup, so I am extremely intrigued as to how it will pan out and will mainly be watching and learning from the experienced members of the Forum, rather than attempting to comment on something I have no knowledge of. (SSW)

Secondly, for anyone with my level of knowledge (which is growing year by year), I am advising extreme caution, it is extremely rare you will see a chart like this verify! All I am saying is wait, until the change is afoot, and that we are in a reliable time frame, i.e. cross model agreement at T+60. I am trying not to be negative at all

That said, it is an extremely exciting time for model watching and I shall be here as always.

Now over to you experts!!

[MR EXTREMES]

A cracking 06z GEFS ensemble mean which sits well continuity wise with the 00z GFS and ECM runs. Not overly cold at face value but get the synoptics into position first....

The split tropospheric vortex looks like following the strat lead at this range. The fundamentals being residual vortices over North America and Siberia with a ridge over the Arctic. The balance of energy post split in these two vortices being the key modelling issue at present. Todays runs have placed a bit more emphasis on the North American vortex whereas yesterdays were favouring the Siberian / Scandinavian one.

What doesn't seem to be an issue here is long term. Strat lead pulls the North American vortex further and further west and south. We should continue to see the tropospheric vortex pull away from Greenland allowing for height rises (06z op an outlier here!).

The upper and middle stratospheric modelling is unbelievable at this stage and is as clear a signal as you could get for a Greenland ridge.

u seem far more confident about this outcome compaired to november onwards so is this a done deal?

are u able to put your neck on the line and say were in a far better situation than before christmas?

regards excellent stuff gp.

[snowmackem]

Hi, this is bugging me, can someone please tell me what the initials NWP stand for, I know I should know and probably look silly for asking,

Ta!

[Timmytour]

Hi all

I have been taking a back seat since December's major upset, still watching each run with hope and my addictive nature toward model watching both playing a part.

I am commenting now for 2 reasons, the first, being this is first time really, since model watching, that I will have seen this (potential) setup, so I am extremely intrigued as to how it will pan out and will mainly be watching and learning from the experienced members of the Forum, rather than attempting to comment on something I have no knowledge of. (SSW)

Secondly, for anyone with my level of knowledge (which is growing year by year), I am advising extreme caution, it is extremely rare you will see a chart like this verify! All I am saying is wait, until the change is afoot, and that we are in a reliable time frame, i.e. cross model agreement at T+60. I am trying not to be negative at all

That said, it is an extremely exciting time for model watching and I shall be here as always.

Now over to you experts!!

I'm going to name that set up the Atlantic Flying Swan and hope that, later this month, she is indeed flying in a north west direction while looking east

[ChartViewer]

T144

T168

T192

Hopefully by this time next week we are at least waking up to something more seasonal, frosty and at least having to wrap up when going to work!!.....Hate mornings going to work in Winter that are damp, mild and murky.

Central, Western Europe also cooling down nicely.

[AWD]

Hi, this is bugging me, can someone please tell me what the initials NWP stand for, I know I should know and probably look silly for asking,

Ta!

Numerical Weather Prediction

[MisfitDog3]

Continuing with the Model thread Winter themed Bingo: Just nailed 'Scandi High' and 'Extreme Caution' today....

The set up seems to be more convincing then the December debacle...in that there are more building blocks in place. I suspect we'll see a clear and dry cold picture as High Pressure builds from the east, rather than widespread snow...but possibly some very low night time temps.