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phil nw.

Model output discussions pm 31/12/15

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3 minutes ago, karyo said:

Everything I see in the models today is in agreement with the met office update from yesterday. A possibility for a brief cold spell preceded and followed by mild weather. 

You forgot to mention wet also with above average rain fall for the west there is no mercy when it comes to mother nature.:wallbash::wallbash:

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16 minutes ago, karyo said:

Everything I see in the models today is in agreement with the met office update from yesterday. A possibility for a brief cold spell preceded and followed by mild weather. 

Incorrect and wrong thread but there forecasts do not state mild at all.

More average temps in-fact. Please continue with meto discussion in the relevant threads, Thanks. 

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im surprised that some more seasoned chart watchers are getting despondent about that individual runs show.

the mean upper trough is expected to shift eastward, the uk is likely to get flooded with cold pm air. but this scenario is often not one that lasts. so expecting a lengthy cold spell out of the emerging possible synoptical pattern is pretty unrealistic imho. especially when you throw in to the mix a re-emerging azores high , which is only of use (for cold) if it links with the greenland high. if it doesnt, then the jet will steer systems over its northern flank and over the uk.

personally id be surprised if this expected cold snap lasted longer then around 3-4 days.

 

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1 minute ago, mushymanrob said:

Personally id be surprised if this expected cold snap lasted longer then around 3-4 days.

Which is what's expected during a cold spell and that's what the models are showing before heading back to something average. Not the balmy temps of late.

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As for the reload in the 6z, we often see the GFS doing that in the far FI as it doesn't pick up the shortwaves at this range and the northerlies look like happening quite easily. When the event moves in the semi reliable timeframe, shortwaves and weaker heights further north spoil our chances.

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Don't think we have really learnt anything after the 06z either way, waiting for the ensembles to give an idea, hopefully a few more than the 00z will be tending cold and not a few less

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It certainly look colder next week with some wintry showers around

gfs-1-174.png?6gfs-1-198.png?6gfs-1-222.png?6gfs-1-252.png?6

As the week progress the high builds over the UK more so becoming much drier for a time

gfs-0-252.png?6

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As a boy in the New Forest in the 50/60's I longed for snow. There were barren years, but it often seemed to arrive around half term in February. Current charts  suggest some cold interest, but if we want an early snow fest it will have to be a virtual one.

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More shortwave drama, I would have banked these charts a few days ago, when the mother of all storm was shown, even if it's only a quick northerly I would take that then high pressure to dry us all out, long term the PV is in ruins and all the signals point to chances a plenty for cold and some white stuff come late Jan early Feb. :cold:

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14 minutes ago, karyo said:

As for the reload in the 6z, we often see the GFS doing that in the far FI as it doesn't pick up the shortwaves at this range and the northerlies look like happening quite easily. When the event moves in the semi reliable timeframe, shortwaves and weaker heights further north spoil our chances.

Hi Kayro

I'm merely taking what I see from the output at face value, regardless of its historical verification. It certainly helped me when I was a "beginner" and I was not sure what could happen looking at the broader NH picture/profile. It wasn't until I saw these potential reloads get scuppered by shortwaves nearer to the time etc, that I started to get a bit more experience of Model watching as to what you state. You are more than likely correct RE the Shortwaves and the GFS tendencies to deal badly with what looks like a clear cut Northerly, but it can be a lot to take in for beginner's.  

Cheers

Karl 

  

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4 minutes ago, karlos1983 said:

Hi Kayro

I'm merely taking what I see from the output at face value, regardless of its historical verification. It certainly helped me when I was a "beginner" and I was not sure what could happen looking at the broader NH picture/profile. It wasn't until I saw these potential reloads get scuppered by shortwaves nearer to the time etc, that I started to get a bit more experience of Model watching as to what you state. You are more than likely correct RE the Shortwaves and the GFS tendencies to deal badly with what looks like a clear cut Northerly, but it can be a lot to take in for beginner's.  

Cheers

Karl 

  

No problem Karl, I got excited on numerous occassions in the past to be treated with disappointment in the end. Of course, occassionally those charts can come off but the percentage is sadly low.

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I must say, that I've never been fussed by all the 'shortwave hysteria'. I appreciate model 'downgrades' can be somewhat tiresome; but computers cannot 'downgrade' the weather...:D

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Reasons to be cheerful:

Lagged significant tropical convective signal from tropics on course to sub tropics to kill +NAO regime

Cooling underway of Nino 1.2 (eastern) region, whilst further imminent WWB to sustain warmth in Central Nino regions. MJO return to Indian Ocean later this month should underpin this trend of cooling of eastern region, and help the process along of 're-shaping' the forcing from the Pacific towards a centrally controlled one which teleconnects to adjustment of Nino H500 pattern of heights south of Greenland (destination ultimately perhaps Iceland into February)

The latest Kelvin wave activity assures yet further westerly wind additions to the atmosphere supplied from the Pacific to sustain +AAM WAA bombardment on the polar vortex.

Large implications follow on from next MJO cycle as it potentially moves back towards the Western Pacific through February. Especially as the matured Nino evolves favourably in terms of forcing a cold later winter pattern. Yet more poleward rossby wave bombardment - with the AO already well established and tanked -ve

The long wave pattern suggests that an evolving -NAO moves from west based, initially, to a more central/eastern the closer we get to February. With the vortex displaced away to our NE and a -AO/-NAO pattern being carved out, there is only one way for the jet stream to ultimately head. Underneath us.

Putting all the factors outlined together,and on the basis we have achieved a -AO flip already, with the polar field carved across from one side to the other, and time suggested to be borrowed for the first half of winter  +NAO regime  - it appears counter-intuitive and hard to envisage as we head into the second half of winter (and increasingly then towards the last third of winter) how we return sustainably  to a south westerly regime post Atlantic amplification. Something has to surely give sooner or later.

I would continue to think that even if somehow the upcoming phase of change towards a colder pattern we see, at last, this winter, manages to contrive an 'almost but not quite there' scenario' - with heights evolving to our NW (and then perhaps N as we get into Feb)  Ultimate arrival looks something like the models are trying to concoct right now and resembles attempts towards something along the lines of 1983.

 

archivesnh-1983-2-8-0-0.pngarchivesnh-1983-2-10-0-0.pngarchivesnh-1983-2-15-0-0.png

 

Its a case of whether we get here sooner than this sort of timeline or round about the same time. There remain decent chances we could get there sooner. The upcoming amplification maybe just an Hors-d'oeuvre rehearsal

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A brief idea from me

Cold and pattern change looks very likely within 6 days to me that is using the anomaly charts. I don't pretend to know a great deal beyond 15 days.

usual links

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

http://www.cpc.noaa.gov/products/predictions/610day/fxus06.html

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32 minutes ago, Tamara said:

Reasons to be cheerful:

Its a case of whether we get here sooner than this sort of timeline or round about the same time. There remain decent chances we could get there sooner. The upcoming amplification maybe just an Hors-d'oeuvre rehearsal

Precisely T.

The obsession with shortwaves is delusional IMO, as is the reliance and buying into ops for anything beyond day 5 in this current set up. The modelling is getting to grips with the speed of the upper trough moving across North America in the medium range. The fact that this delivers more of a mid Atlantic ridge is no surprise here.

I like the GFS op which echoes nicely the ensemble guidance we're getting, and which reflects the longer term thinking on the GWO. It delivers a cold pattern, which will remain cold for some time after, it obliterates the Euro ridge. It also exercises the sub-tropical jet over Mexico. It is here that those critical fluxes in momentum will manifest themselves subsequently in terms of the North Atlantic profile. The fact that the GFS is playing around with this idea (and the ridge close to Greenland) in the extended range should be noted.  GEM Ensemble and EC EPS means look very good over the Arctic in the extended.

Timing wise, I'm actually advancing my thinking on NAO flip to around the 23rd-26th January period.

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Well looking at the GEFS Purbs at +180 timeframe it is hard to argue we won't see a northerly and much colder conditions of some sort next week. 

http://www.meteociel.fr/modeles/gefs_cartes.php?ech=180&code=1&mode=0&carte=1

Scrolling through them all is not disheartening in the slightest. Purely talking for our cold next week, not the prolonged nature of it. 

 

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Nothing to get to phased about this morning' as evolution to cold is just that...evolving! 

The recent modelling of possible split-polar vortex via cross polar flow has somewhat diminished "given" however waa into point Greenland still remains optimistic. Large lobe stagnant vortex in/and around top Canada remains the fly in the ointment' in thw craved Atlantic block.

This is still very much open for function as the NCEP stress in last night's analysis. And as things stand it an open book in regardsto getting a window of opportunity to get heights into that area (greenland) atm its threading a rope through the eye of a needle scenario. ...but as again coming model evolution could turn the rope into a cotton thread' and send waa to meet the Arctic high...then a whole different nw euro/uk picture will evolve......and tge root to cooling be comes the root to the freezer! 

Resolve is not nearly there ....yet!

gfsnh-0-360.png

gfsnh-0-384.png

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1 hour ago, Glacier Point said:

Precisely T.

The obsession with shortwaves is delusional IMO, as is the use of ops for anything beyond day 5 in this current set up. The modelling is getting to grips with the speed of the upper trough moving across North America in the medium range. The fact that this delivers more of a mid Atlantic ridge is no surprise here.

I like the GFS op. It delivers a cold pattern, which will remain cold for some time after, it obliterates the Euro ridge. It also exercises the sub-tropical jet over Mexico. It is here that those critical fluxes in momentum will manifest themselves subsequently in terms of the North Atlantic profile. The fact that the GFS is playing around with this idea (and the ridge close to Greenland) in the extended range should be noted.  GEM Ensemble and EC EPS means look very good over the Arctic in the extended.

Timing wise, I'm actually advancing my thinking on NAO flip to around the 23rd-26th January period.

I think ignoring shortwaves and the ops in this setup is delusional.

 The ability to forecast on a global scale is therefor of great value if you can generally pinpoint the locale of the blocking highs for the winter + the phase changes + on top of that there's 'some' value in putting together a forecast for the projected phases of the -AO & -NAO then that's of 'some' use as well - but it only goes so far- & specifically to the UK becomes only a loose connection- & whats clear is no one so far has much clue about 'change' in phases - again just using reanalysis charts to try & pattern match when the stratosphere may or may not change. Anyone can do that with enough time on their hands.

Interestingly though the current pattern wasn't forecast by me, you or anyone for that matter - Every single weather forecast / er continued the global very strong westerly flow well into Jan - when infact the biggest kara ridge for some years developed. It was only then when the teleconnective parameters started to react to the change & was it seized apon - IE cause & effect.  Not forecast then change.

The operational Models - at day 5 + 6 into 7 have NEVER suddenly produced a Greenland high - Every single one that's landed including the 2010 one has been well modelled in advance around day 7 & 8 into 9 - that's because the pattern that drives in its pretty easily spotted by both the GFS & ECM.  So is there going to be a Greenland high suddenly appearing today at day 6/7 on the ECM or GFS 12z. NO. No chance. so the use of the operational & the ECM mean is not delusional today - your assessment is miles off.

Even the UKMO @ 144 @ day 6 is telling us 0% chance.

UN144-21.GIF?05-06

because the amplitude of the wave & the residual flow of the eastern seaboard means the energy is moving E or ENE - not North or or North west.

The best we do here is an atlantic ridge holding the atlantic at bay for 1 day- but looking at the amplitude on the UKMO is already struggling to reach Greenland.

As for again writing of the shortwave pattern - again I don't agree. ( how can you forget the December NW forecast that got smoked 2-3 years ago when the models plumped a shortwave over Norway & scuppered the block)

 The shortwave pattern is everything to the UK as with our size on the worlds map the UK needs only lives in a small corridor for cold & that means theres no room for variance in the track. There have been so many occasions in the last 5 years where the models have got to day 7 with a block showing cold for the UK only to resolve the shortwave pattern at day 6 & 5 to find that the cold either stops short of the UK from the east or is steered away from the UK - anyone that's been on here more than a year will know & anyone been here more than say 5 years would essentially file your comments in the bin.  Shortwaves that form around / under the main block are responsible for funnelling the coldest air on one direction - but they also limit the area that the cold covers, so more concentration of cold - less coverage has been the trend for the last 5 years-

You only need look at the Kara ridge to show this in action - when the super high started in the models as a clean high, only to see day 6 & 7 a shortwave get modelled to come under the base- its clear as a bell over Norway on this chart

ECH1-24.GIF?00

so in terms of this upcoming cold spell binning the ops is incorrect for day 6-8 as we already know there no Greenland high in the mid term, it will be a polar high & an atlantic ridge with an amplitude probably south of Greenland, meaning that at days 8 + 9 into 10 the pattern will slacken off for the UK & the atlantic will have an impact - The more circular the atlantic high the further east the milder air will reach - possibly even east of the UK, if it can be sharp enough to reach Greenland then the inflection point ( like yesterdays ECM 12z ) may send the energy more southward across Ireland brining snow-    History tells us that eastward is more favoured than southward.

Also again critically on something you dismiss is highly impactful to the UK for the penetration south of the cold, the depth of the cold & the speed at which its delivered..- as the modelling of the shortwaves around 144-168 from GFS V ECM although only separated by a few hundred miles are why the shortwave pattern is critical

ECM1-144.GIF?05-12

good alignment for cold -

gfs-0-138.png?6

bad alignment for cold.

So - in Summary, I think your post is way off the mark - both in relation to the formation of the Greenland high ( as its already toast ) & the part the shortwave pattern plays for the UK--- 

S

 

 

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In light of Steve M's post;

I must admit the wording from GP on shortwaves and using the op runs seems a bit strong.

I'm hoping he meant something along the lines not getting too hung up on what a specific run shows the shortwave features to get up to. Odds are there's at least one interfering with things and toppling the ridge, but how quickly that removes the colder air is another matter. In other words, the focus should be on how the broad pattern evolves, then factoring in how shortwaves may interact with it.

 

A can't sympathise with respect to long-range forecasting using teleconnections, however. It wouldn't be much use if we never even tried. Learning by mistakes is unfortunately a large part of progress in this field of meteorology. Last winter was all about a chance of changing things but really did require everything to come together just right. This season we look to have more wiggle room for late Jan into Feb, so I'm feeling more hopeful, which is a nice change.

 

- and to be fair to GP, I see no prediction of a blocking high over Greenland for mid-month in that post, more a suggestion that the mid-Atlantic ridge might behave a bit differently to what the 00z op runs (for example) have showed us.

Looking at the current ensemble spreads, this seems like very sound advice to me.

Not the most-on topic of posts I know mods, for which I do apologise. In an attempt to improve its relevance, here's the 06z GEFS plot for London which highlights the large spread of outcomes at hand:

MT8_London_ens.png

This shows the potential for that mid-Atlantic ridge to put up more of a fight than the op runs show.

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I'm a fan Steve - but I think this post is fired rather from the hip and without sufficient thought. I wouldnt argue about the potential impact of shortwaves on the broad pattern - I remember that Dec non-easterly very well - but 3 things you have got off target here:

1. GP said ops behind 5 days in this setup are of little use. Assuming we are agreed that we are in unusual times with such a huge AAM forcing coming into the mix then I think your blast is off target. Nobody would surely say that op runs beyond 5 days are on no use at all. In fact if you scroll back through a few of Stewart's earlier posts he actually refers to them.

2. To suggest that Stewart is one of those irritating "forecasters" who waits for a clear signal and then puts out a forecast and claims success afterwards is nonsense. Maybe again you ought to scroll back through posts made in December... when EC32 was screamiing westerlies, and Knocker's anomaly charts were again and again posted up as indicating dominant westerlies... and in the midst of all that you might find the posts that challenged the modelling of the MJO... and climaxed a week or so ago with specific reference to a brief northerly phase mid Jan. Note brief northerly phase. Where was the prediction of a Greenland High in mid Jan? You are imagining it.

3. Finally note the dates on Stewart's specifics. Full NAO flip 3rd week of Jan. This was the same as was stated earlier in Dec. Third week in January. NOT next week.

 

So - without wishing to sound like the interpretative analyst that I am - you need to make sure you have your information accurately at your fingertips before firing off and describing a very respected long range forecaster with a considerable record of success as "deluded."

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For reference in terms of what I said - there has been significant change in the models ( most notably the GFS ) which swung the cold west- all that was missing was a higher amplitude wave in the atlantic

Projected GFS day 6 thurs 1pm

gfs-0-138.png?12

 

Probable verification

gfs-0-48.png?6

 

Upper Air projected

gfs-1-144.png?12

 

Upper air probable verification

gfs-1-66.png?6

 

For London then I make that a swing 8 degrees & for most 4-6 degrees.

Not quite enough for the full on Cold & snow-  but you would have to be Stevie wonder not to see the difference.

 

 

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I understood GP's post in that it was comments offered in relation to broad hemisphere movements towards a negative NAO. Shortwaves are relevant, but not until we get the negative NAO pattern in place. GP's advice is quite sound, sit back, crack open a beer and watch the pattern unfold. We have plenty of time to worry about shortwaves in due course, but not right now. 

 

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One thing the models have definitely underdone is the MJO. Numerous forecast modelling has had it little amplified and returning to the COD. 

Yet it continues now fairly well amplified into Zone 7 through 8.

I wonder therefore if the Atlantic ridge next week will prove more resilient. 

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just a note that the extended eps manage to retrogress the Atlantic anomoly back towards se greenland

hence the low upper anmmoly remains throughout the run over nw Europe though more marked across scandi

so the current direction of travel has the initial ridging not as amplified or sustained as might be hoped but thereafter, the likelihood that the core of the blocking will stay/revert mid Atlantic and be far enough west to allow the dreaded short waves to head south at a longitude which keeps at least some of the UK in the cold air.  We are definitely in the raffle and we could even have a ticket from the winning book!!

 

 

 

 

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Only just catching up with the outputs. Putting aside the debate re shortwaves which I'm sure you'll be relieved about given my past obsession of them!

The ECM quite disappointing this morning, it moves that lobe of PV west across Greenland and this isn't want we want to see.

Unfortunately there is no agreement between the big 3 upstream at T144hrs. The GFS 00hrs run was quite nice because the idea of a shortwave dropping se from Greenland is a possibility.

We're not seeing deep and amplified low pressure upstream to deliver some WAA into Greenland , we really need a good interaction between south/north streams of the jet over there and one system running ne up the west side of Greenland.

Overall it still looks on course to become colder, I think to prolong the cold without a proper Greenland high is going to need some more upstream amplification to help pull back the PV and allow some shortwave energy to run se under the UK with the Arctic high hanging on to the ne.

 

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