Model Output Discussion 01/09/17

[nick sussex]

On the face of it some interesting synoptics from the GFS but in terms of weather on the ground for coldies it doesn’t deliver .

The blocking is too far to the nw and the low filling over the UK will just deliver rain, by the time the limpet low manages to clear se another overblown GFS special develops to the sw.

The outputs at present are a case of having several chances to score from 3 yards out and ballooning these chances  over the goal.

[booferking]

2 minutes ago, Man With Beard said:

Might be our best hope of cold. The Atlantic gets stuck to our west rather than on top of us and heights build around the top linking eventually with Greene high.

Sounds tricky but certainly possible.

That,s how the ECM  evolved last night hopefully it show similar tonight again.

[Paul_1978]

3 minutes ago, nick sussex said:

On the face of it some interesting synoptics from the GFS but in terms of weather on the ground for coldies it doesn’t deliver .

The blocking is too far to the nw and the low filling over the UK will just deliver rain, by the time the limpet low manages to clear se another overblown GFS special develops to the sw.

The outputs at present are a case of having several chances to score from 3 yards out and ballooning these chances  over the goal.

It doesn't need to deliver right now though Nick? For me it's about getting the building blocks in place for late Nov/early Dec, which is certainly what's happening. 

[Cheshire Freeze]

2 minutes ago, Paul_1978 said:

It doesn't need to deliver right now though Nick? For me it's about getting the building blocks in place for late Nov/early Dec, which is certainly what's happening. 

But building blocks don't really exist in this instance. We're against the clock RE the strat vortex and it's engaging with the trop. 'Building blocks' won't cut it here, we either need the cold when all said and done or we suffer a fate we all know too well. 

I think this has been hinted at over the last day or two by people like Tamara.

[northwestsnow]

Liking the look of UKMO 144 this evening-

Dry, cold and frosty just as suggested by the pro's.

Hopefully ecm will be similar at 144 and we can see how things would progress- imho it would be a positive evolution for coldies

The trough over Italy/Balkans could well be our saviour

Edited November 9, 2017 by northwestsnow

[nick sussex]

7 minutes ago, Paul_1978 said:

It doesn't need to deliver right now though Nick? For me it's about getting the building blocks in place for late Nov/early Dec, which is certainly what's happening. 

I think these same building blocks have been going up for the last few years , this is the slowest house build in living memory ! Lol

In the UK you only get so many chances to score. If there’s blocking there the UK needs to take advantage before the opportunity passes.

 

[Frosty.]

Exeter is getting the building blocks in place for coldies further down the line (mogreps / GloSea5 etc), hopefully will continue!..very encouraging and I'm certainly not going to get hung up about individual operational runs. I think there are good signs for the majority on here with the start of the meteorological  winter just over three weeks away! 

Edited November 9, 2017 by Frosty.

[BLAST FROM THE PAST]

Well for me there is nothing to be concerned about yet.  PV to move Over us and to the east, HP to NW, second half but mainly last 10-12 days of Nov target date. Every chance we may see southerlies before northerlies.  All in the ball park........still.  A week is a long time in weather not just politics....

 

 

BFTP 

Edited November 9, 2017 by BLAST FROM THE PAST

[Interitus]

29 minutes ago, CreweCold said:

But building blocks don't really exist in this instance. We're against the clock RE the strat vortex and it's engaging with the trop. 'Building blocks' won't cut it here, we either need the cold when all said and done or we suffer a fate we all know too well. 

I think this has been hinted at over the last day or two by people like Tamara.

Longer term maybe, but on the contrary to a raging vortex it is really surprising that more mention hasn't been made of the GLAAM actually dropping through the floor in relation to forecasts of Arctic and cross-polar high pressure - 

Less angular momentum shows weaker AO, polar air mass convergence -> high latitude high pressure = this is the source of the interest in the charts at the moment.

[Paul_1978]

47 minutes ago, CreweCold said:

But building blocks don't really exist in this instance. We're against the clock RE the strat vortex and it's engaging with the trop. 'Building blocks' won't cut it here, we either need the cold when all said and done or we suffer a fate we all know too well. 

I think this has been hinted at over the last day or two by people like Tamara.

To be honest I read Tamara's last post on Tuesday and I couldn't make head nor tail of it so I couldn't comment on that!

However a negative AO, negative NAO, easterly QBO all being in place, for me, bodes well. And not looking too far ahead is good for one's sanity.

I don't see any reason to be too despondent - we're seeing great charts at the moment and I'm enjoying the output.

[tight isobar]

A nice clean evolution 12z ecm.

192 the waa placement is spot on @greenland..

Also likely to go 3-way split in pv-polar vortex....

With morphing eastern canadian sector.

'Cannot upload snapshots!!!!'

Edited November 9, 2017 by tight isobar

[Allseasons-Si]

The ecm decides to ditch the idea of heights to the east of the trough on this run and goes with the gfs,just watching that cross polar flow establish on the next frame,could be another stonker coming up.

[nick sussex]

Looks like the ECM has dropped its previous trend and is following the GFS.

The issue at present is whether we’ll see low pressure get far enough to the east se to allow some colder conditions to move in or whether there  this will become slow moving over the UK.

[sebastiaan1973]

32 minutes ago, Interitus said:

Longer term maybe, but on the contrary to a raging vortex it is really surprising that more mention hasn't been made of the GLAAM actually dropping through the floor in relation to forecasts of Arctic and cross-polar high pressure - 

Less angular momentum shows weaker AO, polar air mass convergence -> high latitude high pressure = this is the source of the interest in the charts at the moment.

Please read this tweet and the converstion.

 

[knocker]

The ecm has the wave just approaching the west coast of Ireland around Charlestown Saturday 00 and it swings down through central Wales by 06 and into N west France by 12. Thus rain Wales and SW and southern England, At 06 the front orientated NW Wales .Easbourne with the dew points to the SW 50/52F and to the NE 42/42.

Edited November 9, 2017 by knocker

[Daniel*]

Very good IMO I’d assume there’d be a cut off Greenland high on the next frame.

[Allseasons-Si]

Winds all the way from NE Asia/Alaska to the uk and trough looks like dropping SE.

[snowy weather]

1 hour ago, Steve Murr said:

The low pressure in the atlantic to get stalled out & a ridge develop North out if France to scandi - setting up a Scandi block which later allign with the canadian high

Cool thanks mate 

[SMU]

We will take the ECM tonight

not quite Nirvana but pretty damn good at day 10

 

[blizzard81]

Great run from the ecm tonight and would mark an incredible consecutive run of Sunday northerly plunges. Four in total from October 29th to Nov 19th. The first two already verified, third one nailed on for this coming Sunday and the fourth showing on the ecm day 10 chart. 

[Allseasons-Si]

Nothing wrong with the final chart from ecm,trouble is though it's at day ten again

[Frosty.]

A much more wintry end to the Ecm 12z compared to the 00z..I'm very happy with this!..strong height rises to the nw and a nicely aligned scandi trough..locked in cold with an increasing risk of snow...BANK!! :-)

[Daniel*]

1 minute ago, Allseasons-si said:

Nothing wrong with the final chart from ecm,trouble is though it's at day ten again

Nice to finally see some very cold Arctic air  primed in our direction plunging southwards, there would be wintry precipitation to rather low levels in Scotland beyond this would spread south. Pleased with the operational 8/10 I’d score it. 

[Tamara]

51 minutes ago, Interitus said:

Longer term maybe, but on the contrary to a raging vortex it is really surprising that more mention hasn't been made of the GLAAM actually dropping through the floor in relation to forecasts of Arctic and cross-polar high pressure - 

Less angular momentum shows weaker AO, polar air mass convergence -> high latitude high pressure = this is the source of the interest in the charts at the moment.

Best that I interject at this point.

That is a GEFS forecast which has a low angular momentum bias, notwithstanding that the background pattern is inclined to La Nina

In my opinion its rather the opposite way around with regard your post. What has been happening is effectively "destructive interference" with the La Nina state. There is currently a relatively higher GLAMM state than seen since mid summer - but still only taking total global atmospheric angular momentum a little above -1SD.

The atmospheric decoupling from the ocean base state is the result of a significant eastward propagating MJO wave during October

Its feedback loops from the eastward propagating tropical convection in October that added westerly wind inertia into the atmosphere, boosting atmosphere angular momentum tendency. There is a text book lag time of about 3/4 weeks for the amplification mechanisms created by this amplitude convection to manifest in the atmospheric circulation. Look at the massive leap in AAM tendency starting from the beginning of Octobers high amplitude wave which culminated  mid month. From -4SD to +3SD - quite some ying-yang elastic band effect set in motion   NWP is now showing the fruits of the considerable consequential amplification injected into atmospheric circulation taking into account that lag. 

The westerlies added to the system negate the overriding net total of easterly trades in global windflows which are a product of La Nina and consequent low atmospheric angular momentum.

The rossby wave trains from tropical convection propagate polewards and help to perturb a fledgling vortex. On the basis of the size of the October bounce in AAM tendency no surprise to see an early season vortex struggle.

The question is what happens when the MJO feedbacks wane, and the downstream tropospheric amplifying mechanism is lost. This allows the typical La Nina pattern(with low atmospheric angular momentum) to dominate with the jet flowing over the anomalous Nina ridges in the Pacific and Atlantic - possibly at the same time as vortex intensification occurs. That is not a ticket to a -NAO/-AO combination in the future. Quite the opposite - we can't be thanking crashing GLAMM for setting in motion the processes for "building blocks" to a sustaining cold pattern

Time will tell of course, but the pattern indicated by the models heading through this month to the approach of start of winter could simply be a vortex pre-intensification phase characterised by cooling upper layers in the stratosphere descending and flushing out the warmer troposphere/lower stratosphere negative zonal anomalies.

There is unlikely to be any further assist from the MJO until later in December, based on periodicity of the next likely amplitude MJO wave (45 to 60 days). And with La Nina consolidating and the wavelengths changed with the new season, a next amplitude wave could well have a lot more on its plate in terms of making headway across the Pacific to help amplify the pattern downstream

The North Pacific ridge, characteristic of La Nina, will likely dictate the downstream pattern to a further Atlantic ridge - and La Nina favours increased polar jet flow heading over the anomalous circumglobal ridges. The ticket to a -NAO is a southern stream c/o rossby waves triggered by convection passing the dateline. That comes with a weak Nino signature which is not at all likely to be present this side of the New Year, at the least

 

Edited November 9, 2017 by Tamara

[phil nw.]

Both GFS and ECM continue to have the same idea with the Atlantic ridging coming off Newfoundland around day 7 but as we can expect some variations on detail further on.

The main issue in week 2 is how much amplification we actually get in the Atlantic,more the better as we have more chance of clearing any cut off low pressure further south and east bringing us into a much colder Arctic feed from the north or north east.As Steve M pointed earlier we are just about there on the ECM by days 9/10.

So many possibilities on how this spell of amplification will work out for us wrt our chances of an early taste of Winter.

A look at the day 12 gefs stamps on the jet stream

shows how many outcomes the models are wrestling with in week 2-a disjointed and weakened Atlantic flow.

An Interesting period coming up starting with the next colder spell coming our way from tomorrow continuing through the weekend.

T72hrs.

Some fascinating charts to follow over the next couple of weeks to see if cold lovers get lucky this time.

Edited November 9, 2017 by phil nw.