Model Discussion - January 17th

[Buzzit]

What does the GFS nearly always do to lows in the low-res part of the run..............answers on a postcard!

Sorry cannot fit the answer on a postcard due to the size of the low giving me no room to write one...

May be dumb question but can someone tell me why the jetstream chart goes from this

To this

same thing happened in 6z but occurs at +123 / +126

Thanks

[jimben]

Sorry cannot fit the answer on a postcard due to the size of the low giving me no room to write one...

May be dumb question but can someone tell me why the jetstream chart goes from this

To this

same thing happened in 6z but occurs at +123 / +126

Thanks

They look indentical to me?

[Cecil Hogmanay Melchett]

Sorry cannot fit the answer on a postcard due to the size of the low giving me no room to write one...

May be dumb question but can someone tell me why the jetstream chart goes from this

To this

same thing happened in 6z but occurs at +123 / +126

Thanks

Its as strong a jet as your likely to see across the North Atlantic and is the primary reason why we have see next to no HLB this winter.

I guess the main cause of the almost non stop systems spawning off the Eastern seaboard is the strong PV over Greenland but others may be able to explain the dynamics behind that better than me.

[If Wishes made Weather]

There is a question mark regarding how long that flattish zonal flow will last for in the USA, this from their morning update:

LARGE SCALE UPPER PATTERN OVER NORTH AMERICA INTO NEXT WEEK SHOULD

FEATURE THE LARGE POLAR VORTEX CURRENTLY LOCATED NORTH OF HUDSON

BAY TO SPLIT IN TWO. ONE PIECE WILL RELOCATED WESTWARD OVER ALASKA

WHILE THE OTHER WOBBLES EASTWARD TOWARD BAFFIN ISLAND. THIS WILL

KEEP A RATHER ZONAL FLOW THROUGH THE CONUS WITH POSSIBLE BUCKLING

OF THE PATTERN BY EARLY NEXT WEEK.

This will have an effect on the pattern in the Atlantic re the Azores high and Greenland in terms of whether we see a more amplified trough developing in the ne USA.

Which seems to fit with GP's thoughts and those in the Strat warming dept. I think the points to note in the ealier parts of the run is the attempt of the ridge from the AzH to Greenland and the westward trend of the Eurasian High. Generally pleasing signs if one seeks somewhat colder weather.

[NorthNorfolkWeather]

Its as strong a jet as your likely to see across the North Atlantic and is the primary reason why we have see next to no HLB this winter.

I guess the main cause of the almost non stop systems spawning off the Eastern seaboard is the strong PV over Greenland but others may be able to explain the dynamics behind that better than me.

HLB??

[Radiating Dendrite]

HLB??

High latitude blocking

[Paceyboy]

On the face of it the 12z GFS ensembles dont look all that inspiring.

However, after looking through the ensemble charts, there is a tendency for the strengthening of the Greenland high in the medium term and hence this pushes that azores high further south and allows blocking to enter the north atlantic in the low res frames.

Just a trend to keep an eye on here, nothing too exciting for cold but just shows that the ensemble graph doesnt tell the whole story.

A few easterlies and northeasterlies thrown in too.

Edited January 17, 2012 by Paceyboy

[shedhead]

All in all the 12GFS shows subtle differences from previous runs, but all it actually represents is yet another variation on the very familar theme of late. Any sustained cold spell still looks as far away as it has for the last fortnight and we're again left blowing smoke up the bum of 'potential', rather than seeing any tangible signs of change. UKMO is pretty underwhelming too, still looks like far too much energy close to Cape Farwell at 144hrs to see anything other than rather zonal conditions by the middle of next week, so we're once again looking at ECM to pull something out of the fire come 7pm... I won't be holding my breath though!

Edited January 17, 2012 by shedhead

[BLAST FROM THE PAST]

One has to say that models 'should' be showing effects of the pattern change now, one has to ask the question 'why aren't they?'

BFTP

[phil nw.]

It looks as if all the recent output continues to show the jet flow running pretty much around the UK for the next few days with shortwaves running south east into the continent.

The Azores high still lurking to our southwest which keeps any colder air confined to brief incursions mainly further north and east,where some upland snowfall could occur.

Again the overall pattern shows plenty of evidence that the main core of vortex is on the retreat further west.

but not yet enough in the next 5 days to prevent the Atlantic holding sway just keeping the real cold to our east.

Medium term we should look for some overall trends rather than focus to much on the run to run surface features - to see where the pattern at 500hPa level is likely to go.The Northern hemisphere charts are good for this.

Looking at last nights NOAA 500hPa mean Hts forecast is quite interesting.I have found these to be quite good -,the times i have used them.

Here for example was their forecast on 9th Jan. for 6-10 days ahead--,so around today.

and todays GFS

not bad,maybe it overestimated the cross-polar heights but overall the modelling of the Azores High nearby and the placement of the main troughs and ridges are pretty close to where we are now.

This was last nights and the latest forecasts days 6-10 and 8-14.

The Azores High gone and lower heights around the UK with higher pressure to our north east extending towards Greenland and Iceland.

This pattern isn`t going suddenly appear overnight but we should look for those signs of movement of the upper features over the next few days.

[shedhead]

One has to say that models 'should' be showing effects of the pattern change now, one has to ask the question 'why aren't they?'

BFTP

OK, I'll ask then Blast - why aren't they?

[Cheshire Freeze]

All in all the 12GFS shows subtle differences from previous runs, but all it actually represents is yet another variation on the very familar theme of late. Any sustained cold spell still looks as far away as it has for the last fortnight and we're again left blowing smoke up the bum of 'potential', rather than seeing any tangible signs of change. UKMO is pretty underwhelming too, still looks like far too much energy close to Cape Farwell at 144hrs to see anything other than rather zonal conditions by the middle of next week, so we're once again looking at ECM to pull something out of the fire come 7pm... I won't be holding my breath though!

I agree, both the GFS and the UKMO are a far cry from the 'cold promise' that was showing just a couple of days back. I did think that on Sunday evening when the operational went against its suite of ensembles that something was amiss. Time running out for a meaningful cold snap I'm afraid, especially is all this 'potential' is repeatedly not realised.

[BLAST FROM THE PAST]

OK, I'll ask then Blast - why aren't they?

I don't know....unless we won't see 'local' affect for the UK and the ridging won't come off. I am surprised to see this 'stubbornness'....but then again maybe we are barking up the wrong tree and there'll be no 'net' effect til months end which is way in FI

BFTP

Edited January 17, 2012 by BLAST FROM THE PAST

[shedhead]

I don't know....unless we won't see 'local' affect for the UK and the ridging won't come off. I am surprised to see this 'stubbornness'....but then again maybe we are barking up the wrong tree and there'll be no 'net' effect til months end which is way in FI

BFTP

Well you rather jumped on me last eveing Blast and suggested I was effectively writing off Jan at that time (which I wasn't), but I'm increasingly starting to think we are now gonna have to rely on Feb to deliver any meaninful cold. I was actually hoping you had the answer and were just teasing us a little, so thanks for bursting my bubble so swiftly...

Edited January 17, 2012 by shedhead

[Buzzit]

Regarding my jet stream chart question - what I meant to ask is why are there double the streamlines represented in the second chart when both charts are almost exactly the same and only three hours difference ? Is there something not mapping correctly ?

[SP1986]

Currently, although the high attempts to ridge it always gets knocked back from a powerful jet - this is a fairly normal occurrence and happens fairly often in a variety of NAO/AO setups. It's a very familar pattern actually, perhaps one of the most familiar to our shores. In that respect I'd say whilst it may be appealing to write off the GFS based on background signals, this is not really a good idea at all, if anything, in terms of accuracy, the GFS, despite what people might say, hasn't been that bad at all (with regards to any introduction of a new pattern), whilst the ECM has toyed with a pattern, but hasn't quite got it nailed.

So the point being, it is very unfair to put down the GFS when actually, although not greatly consistent, it has been along the right lines, so far, broadly speaking.

[stewfox]

Regarding my jet stream chart question - what I meant to ask is why are there double the streamlines represented in the second chart when both charts are almost exactly the same and only three hours difference ? Is there something not mapping correctly ?

Well I wont be doing spot the difference again as I didn't spot that , they looked the same to be me but as you say they are not. A mapping error ??

[mcweather]

Much has been said in the various arguments between the models by the more learned people on this forum about how the Meto 6-15 and 16-30 dayers have led the way this winter, interms of longer range prediction. So I for one am very happy with the fact that they are giving credence to the possibilty of a harsh winter outbreak as we head towards the end of January and the fact that if the cold option comes off it will last well into february.

6-15 dayer

There is considerable uncertainty regarding the weather during the last few days of January. The slightly more probable scenario at present is that conditions will remain similar to those described above. However there is also a significant risk of much colder weather becoming established right across the UK, with snow in places and widespread overnight frosts.

Updated: 1310 on Tue 17 Jan 2012

16-30 dayer

The forecast for the first half of February is very uncertain. As with the day 6 to 15 forecast, there appear to be two main scenarios, each equally probable, but which are very different. It is also fairly likely that the prevailing weather type at the end of January will continue into February. The first scenario consists of a changeable westerly or southwesterly type, with rain at times (amounts greatest in the west), and with temperatures noticeably above average for early February, with only occasional frosts. The alternative scenario is that very much colder weather, with winds from an easterly or northeasterly quarter, will prevail well into February, bringing widespread frosts, and snow to some areas. In this scenario it would be the east that was most vulnerable to snowfall.

Updated: 1436 on Tue 17 Jan 2012

The meto models must be giving the chance of cold a very good chance for them even to mention cold and snow at this range.

Still very much game on

Edited January 17, 2012 by mcweather

[BLAST FROM THE PAST]

ECM looked pretty decent going on at T96 then 120 the bomb develops southern tip Greenland. Having said that at T144 that LP makes very little progress eastwards....now could this be a starter?....No here it comes at 168

BFTP

Edited January 17, 2012 by BLAST FROM THE PAST

[Cheshire Freeze]

Currently, although the high attempts to ridge it always gets knocked back from a powerful jet - this is a fairly normal occurrence and happens fairly often in a variety of NAO/AO setups. It's a very familar pattern actually, perhaps one of the most familiar to our shores. In that respect I'd say whilst it may be appealing to write off the GFS based on background signals, this is not really a good idea at all, if anything, in terms of accuracy, the GFS, despite what people might say, hasn't been that bad at all (with regards to any introduction of a new pattern), whilst the ECM has toyed with a pattern, but hasn't quite got it nailed.

So the point being, it is very unfair to put down the GFS when actually, although not greatly consistent, it has been along the right lines, so far, broadly speaking.

Yes Stephen, I think we now have to look to the next 'opportunity' to establish some resemblence of northern blocking....it's been shown over the last week or so that the models can suddenly swing in the space of around 12 hours so all is not lost in that respect. Admittedly this looks a tall order in the mid range given the pattern that the 12z GFS locks us in to; though as the METO further outlook suggests, around the turn of the month could potentially be a timeframe of interest.

[The Northern Ramper]

How do you know it's a joke?? It could be right for all we know

In a stick a tail on a donkey kind of way.

You can tell that it isn't using the same calculations leading upto 192 as it is after, it reverts to type despite anything it puts in place beforehand.

[Frosty.]

The Gfs 12z op run shows a very unsettled pattern for the next 2½ weeks with depressions racing in from the atlantic seperated by brief ridges, a rather flatter pattern, it really is astonishing how this run unfolds, it's like rewinding back to november when we had a very cold strat except now we have had some warming with more to come, the improving background changes will surely consign the FI part of this run to the bin and I remain convinced there are some much colder charts around the corner.

Edited January 17, 2012 by Frosty039

[nick sussex]

That UKMO further outlook is a bit of a mystery.

The cold option suggests some form of northern blocking but its hard to imagine a scenario where both options are equally likely and its the first time I've seen the UKMO paint two such opposing pictures.

Generally if theres a strong signal to develop blocking its picked up across the ensemble suite, I wonder if this is a case of them thinking the blocking could end up in the wrong place.

Interesting ECM 144hrs chart, surely no more drama!

[kev238]

For me, the huge positive of today is the Met Office update. No real sigh of the potential on the gfs, however there must be a real split on the ensembles the Met Office uses suggesting complete uncertaintly as to the prospects in 10 days time.

Therefore, if cold charts do start to appear in the models, i will be taking them a lot more seriously!!

[Tim Bland]

Still lots of chopping an changing on the models. FI starts at 120 hrs. 12z ECM has the uk cold and settled with a ridge building over us at 144hrs whilst UKMO has low close to the East and the next low waiting In The wings out west. Very interesting update from the Meto today will be intrigued how the wording is tweaked in the next few days. Still a chance of snow for Scotland and the north east over the next 5 days.