228 replies to this topic

[Snow Guy]

I found the trends of the vortex and Russian high further west, heights over greenland and the vortex displacing quite promising.

[The PIT]

GFS heading back to average to slightly above average with each run. Need to keep an eye on the feature at T111 in case it winds up more. Otherwise any cold air spends too much time over the Atlantic to bring anything of note.
Yet another reality check for ice age hunters.

[Snow Guy]

Radiating Dendrite, on 17 January 2012 - 16:48 , said:

Not sure where you are getting that from.

The jet was much better positioned in the hi-res run compared to the 6z with better amplification.

The canadian high is also seen to be continuing its development which is a good sign and the PV was shifted further west yet again.

It went wrong in FI, but the GFS always flattens the pattern in FI.

If people cannot see that the gfs low res is a joke then i give up, every run it just goes against the set up pre 192.

[ANYWEATHER]

ukpaul, on 17 January 2012 - 16:49 , said:

GFS very disappointing, building blocks are being put in place but only leading to relentless zonality (and not even of the cold sort). If it is getting the signals then either the competing ones are much stronger or we are in the wrong place pretty much every time to benefit, we should be seeing a change now in output according to changes in NAO, PV etc. but none of this seems to cut any ice (literally!)

Yes a powerful Jetstream looks like resetting itself across the Uk as in previous weeks, apart from this brief and welcome respite of the last 5 or 6 days. Little sign of anything substantially Wintry in the forseeable future, but as I mentioned yesterday the Scottish Mountains picticularly look like getting Plastered with some substantial snow as frequent Polar Maritime air picticularly for Scotland looks pretty much the case in the Near future, based on the recent output.

[Harsh Climate]

Snow Guy, on 17 January 2012 - 16:56 , said:

If people cannot see that the gfs low res is a joke then i give up, every run it just goes against the set up pre 192.

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

[nick sussex]

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.

[No balls like Snow Balls]

Could be pretty stormy down Eastern side of UK on Sunday according to 12z GFS at T120.


or could be Stormy on Monday Further North according to UKMO, take your pick, disagreement at T120 between UKMO and GFS.






Good heights still over Greenland in high res part of run on GFS. Did not bother looking into FI.

Edited by No balls like Snow Balls, 17 January 2012 - 17:14 .

[Buzzit]

Radiating Dendrite, on 17 January 2012 - 16:52 , said:

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]

Buzzit, on 17 January 2012 - 17:02 , said:

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

hgt300CA2SYRSCnorn.png

To this

hgt300CAI1Q683ff.png

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

They look indentical to me?

[happy days]

Buzzit, on 17 January 2012 - 17:02 , said:

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

hgt300CA2SYRSCnorn.png

To this

hgt300CAI1Q683ff.png

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.

[Tim Mellors]

nick sussex, on 17 January 2012 - 16:59 , said:

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]

happy days, on 17 January 2012 - 17:22 , said:

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]

NorthNorfolkWeather, on 17 January 2012 - 17:39 , said:

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 by Paceyboy, 17 January 2012 - 17:43 .

[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 by shedhead, 17 January 2012 - 17:51 .

[phil n.warks.]

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.

[CreweCold]

shedhead, on 17 January 2012 - 17:48 , said:

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.

[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]

Buzzit, on 17 January 2012 - 18:09 , said:

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 ??