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phil nw.

Model output discussions pm 31/12/15

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I don't really see Jan being the cold spell cold snap judging from the outputs there been few days of possibilities of good blocking but this is slowly declining away although cold northerly or nw is always looking most likely.

so I feel as it stands February looks possibly better for the southern half if we can get a sustainable block over Greenland.

although for us southern folk because the vortex is pretty pumped up it could be close but no cigar.

but further north even Midlands could have period of colder with some wintry weather on offer.

over all some possibles but still don't feel southern south west or southeast don't look exciting but fingers crossed.

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Just to clarify that taking output as a definite beyond 5-7 days in these set ups is going to bring wild mood swings upon ones self.Take the difference here from warmer to colder outlook in the longer term

00z  http://modeles7.meteociel.fr/modeles/gens/runs/2016010500/graphe3_1000_261.94000244140625_23.85999870300293___.gif

 

06z   http://modeles7.meteociel.fr/modeles/gens/runs/2016010506/graphe3_1000_269.94000244140625_34.86000061035156___.gif

 

P.S.

UK Outlook for Sunday 10 Jan 2016 to Tuesday 19 Jan 2016:

Sunday and Monday will be unsettled and often windy with showery conditions interspersed with some more organised spells of rain, and snow on northern hills. The heaviest rain and strongest winds probably occurring in the southwest and the northeast, where large rainfall totals and gales are expected. There is now an increased signal for a brief much colder spell around the middle of next week with widespread overnight frosts. There is likely to be a mixture of sunshine and showers, with the showers falling as sleet of snow to low levels in the north, and perhaps also in the south. Towards the end of next week unsettled and sometimes windy weather with mainly westerly winds may become re-established, although there is some uncertainty. Temperatures should return to near normal.

 

I SHOULD  be on time every day but I am not

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I'm glad we've come together for the most part on the way in which long range and shorter range methods work. My analogy (of sorts) would be that using teleconnections etc. helps to see which way and how far (and with luck, fast) the pendulum is likely to swing, while shorter range techniques on the smaller scale are about resolving all manner of wobbles within what is inherently a chaotic system.

The MJO was a wildcard feature in the long range outlooks for this winter, because it's really not meant to become active during a strong El Nino event. It's effectively a manifestation of the caveats accompanying many pre-season forecasts along the lines 'this particular El Nino has some unique characteristics that are unprecedented, increasing the risk of unexpected developments'. In fact, we already saw one such deviation in December, as the unusually warm Indian Ocean drove tropical convection that, while often disorganised, may have helped to amplify the Atlantic trough + Euro High combination - though I suspect the mid-Atlantic 'Cold Pool' was at least as significant (this tied in with record-low AMO values for 2015).

 

A number of days ago I mused that it might take several bites of the cherry to get the blocking features where we want them to be, and the evidence of the past two days suggests we'll be needing at least two. That's fine when you take into account that Feb has just as much cold potential as Jan and the increasing solar input, while detrimental to sustaining lowland snow cover, and add an extra kick to convective developments in snow-permitting conditions, as I found out in Feb 2009 (or it may have been 2008, it's been too long!).

I really do hope that the cold and snow chasers on here get the rewards they deserve for gritting their teeth through that bonkers December. Arguably I can fit into that group too, though professional obligations mean I am well versed in subduing my enthusiasm :ninja:

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Differences as early as +96 between the GFS and UKMO. Mainly the strength and position of Heights coming out of Canada 

UKMO Modele UKMO - Carte prévisions

GFS gfsnh-0-96.png?12  

 

 

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The low is better tilted on this run and more together not spilit should it help the Greenland high form this time??:fool:

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48 minutes ago, Mucka said:

It really isn't a case of Macro V Micro because one is more valuable for generalisations and long term pattern forecasting and the other for short term and detailed local forecasting (local in this sense means UK weather).

You can't predict long term patterns at the micro scale and you can't predict detail at the macro.

Forecasting the upcoming weather for the UK day 5 to 10 days requires a micro approach for me. That doesn't mean we take every operational run as gospel (as fun as that is) but we do take note of developing trends, especially where there is cross model support.. In that regard the Atlantic ridge has very much been toned down and a Greenland high now looks like a remote possibility though personally I would wait until tomorrow before writing it off completely.

If that is the case then we are looking for any longevity from either a reload of the WAA to the West or the ridge toppling toward Scandi - that is the micro out to day 10 which suggest a cold snap the North but then a messy spell with either renewed MLB or HLB and cold from there or a return to a more mobile flow for a time at least.

This mornings UKM looks like it would give a renewed attempt at forcing WAA toward Greenland post day 6 though  the forcing may well take that more toward Iceland.

Look at the low off US East coast day 6, that would give the second push but it wasn't modeled by ECM or GFS this morning so I will be interested to see if sticks with that and what the angle of amplitude might be. Comparisons 144 UKMO, ECM, GFS

Modele UKMO - Carte prévisionsModele UKMO - Carte prévisionsModele UKMO - Carte prévisions

Certainly it seems we will need more than one bite at the cherry to get the sort of amplification we need for a prolonged cold spell but regardless of how things pan out it will be fascinating viewing (and reading). Winter weather fans really deserve some cheer so fingers crossed for improved output this afternoon, especially from GFS.

The fact that the models are placing that low anywhere from the Carolinas to Nova Scotia tells you everything you need to know about reliability at 144hours at the moment.

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Love all this theory and extended debate, but back to what's coming up ... Today I'm in the "short" cold spell camp. The longevity of the spell, for me, was pinning on the Arctic High making a decisive breakthrough in Greenland. This looks less likely to happen. I think 4 days of temps 2C to 5C nationwide (so snow potential even to low levels at times, if the precipitation is there), and then back to at least a few days of something slightly milder. Just a small chance the Atlantic High will build far enough north to cut off a S or W feed, which would prolong the cold. 

Further out, the dice is getting more loaded for cold as the PV bounces around the AH, but that of course only means a better chance, not a certain chance.

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Is this a chicken and egg situation? It seems if the Heights are to be pushed further east across the Atlantic for a more favourable Cold outbreak, the link up of heights over Greenland doesn't happen, but if the Heights are held out to far west, we get a delay in the cold which comes from the north west and not straight from the Pole. I'm wondering if sustainable cold in this spell is proving fruitless? 

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GFs 12z at 150h is looking promising, greater heights over greenland and just looks better than this stage on the 6z.

Rtavn1501.gif .

 

If you look at around 240h where it has gone wrong on previous runs, we really suffer due to the lack of significant heighs over greenland or svalbard. Without any of these in place it will be very hard to achieve a long sustained cold spell from this set-up.

 

Rtavn2401.gif .

 

IMO like the met office I expect a sharp cold snap early next week, quickly replaced by milder/cool westerlies soon after.

 

I hope I'm wrong and at such a range could quite possible be. 

 

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UKMO not bad at 120

Modele UKMO - Carte prévisions

trough further SE than GFS which may allow for some cold air to wrap around the exiting low and better amplification upstream.

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UKMO 144 cold and snowy?

Modele UKMO - Carte prévisions

Depends how much cold air is left to the NE to tap into.

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2 minutes ago, Mucka said:

UKMO not bad at 120

Modele UKMO - Carte prévisions

trough further SE than GFS which may allow for some cold air to wrap around the exiting low and better amplification upstream.

Yea it looks great some difference even at 96hrs between GFS & UKMO who is right tho.

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Pretty nice UKMO tonight 

 

ignoring the discussion around the ridging to greenland, the UKMO makes the most of getting the core of low east of the UK allowing for the coldest of 850s to surge south-

interestingly energy coming up from the SW at 144 may increase snow potential!

image.thumb.jpg.5df54cff5edf050588e453ec

s

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2 minutes ago, Mucka said:

UKMO 144 cold and snowy?

Modele UKMO - Carte prévisions

Depends how much cold air is left to the NE to tap into.

And finally the sort of WAA we are looking for!

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A good UKMO this afternoon, 

Modele UKMO - Carte prévisions

You can see the day 5 chart teeing this set up, a secondary area of low pressure west of the UK tracks south of the UK at day 5, cold northerly winds digging in across the UK.

Good profile over the Arctic too.

GFS

gfsnh-0-144.png?12

The GFS doesn't really model that secondary low at all so we have low pressure over the UK with near normal temperatures and showers. The GFS does however develop a an area of WAA towards Greenland which is holding up that area of low pressure over Canada which is a positive.  The pattern over us looks very complex though.

Overall the UKMO looks better both in the shorter term and longer term in my opinion.

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1 minute ago, Steve Murr said:

Pretty nice UKMO tonight 

 

ignoring the discussion around the ridging to greenland, the UKMO makes the most of getting the core of low east of the UK allowing for the coldest of 850s to surge south-

interestingly energy coming up from the SW at 144 may increase snow potential!

image.thumb.jpg.5df54cff5edf050588e453ec

s

Were would the high go from there anybody any idea???

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Much better gfs up to t168. Waa shunted further west of Greenland. Better height building and the us east coast low is shunted a bit further west to allow enough waa  to draw the artic high in.

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greenland high appearing at day 7...

 

gfsnh-0-174.png

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5 minutes ago, bobbydog said:

greenland high appearing at day 7...

 

gfsnh-0-174.png

This is the best chance of an Arctic High / Atlantic High link up ive seen from GFS ... maybe I spoke too soon in my earlier post!

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GO ON!!

gem going for gold with height's pushing well up the western side of greenland,that's WAA for ya,although it could turn out to be west baised !

gemnh-0-174.thumb.png.9633fdee6bc5c83d9d

Edit:yup i was right but not complaining with those N hemispheric views:D

gemnh-0-198.png

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4 minutes ago, Man With Beard said:

This is the best chance of an Arctic High / Atlantic High link up ive seen from GFS ... maybe I spoke too soon in my earlier post!

lol... and its gone. the atlantic ridge is even struggling on this run but the arctic high is stretching itself across the pole this time.

gfsnh-0-216.png

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4 hours ago, Allseasons-si said:

GO ON!!

gem going for gold with height's pushing well up the western side of greenland,that's WAA for ya,although it could turn out to be west baised !

gemnh-0-174.thumb.png.9633fdee6bc5c83d9d

 

A Murr style three wave pattern.

GP said he liked GEM for its Arctic modelling. GEM sometimes gives indications to the ECM

 

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for comparison at 144

ukmo    Modele UKMO - Carte prévisions

 

Gfs         gfsnh-0-144.png?12

 

 

Gem   gemnh-0-138.png?12

 

As we can see at 144 Gem and ukmo manage to push more waa into the artic where as the gfs cuts the height rises off over ne usa. 

 

 

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GEM is west based, and has mild SW'ly over the UK

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Reload from the gfs!,did ecm do this yesterday evening

gfsnh-0-240.thumb.png.ea33b82eaef90224be

yes it did,although the gfs is a bit less amplified

ECH1-240.GIF.thumb.png.f1998caed63a724e6

 

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