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Model output discussion pm 13/01/2016

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Rather than helping to weaken the vortex over greenland, it looks like alex is going to help to invigorate it! Looks like GP has put his negative nao back at least a week!

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54 minutes ago, Minus 10 said:

I know it's only the gfs 6z but that vortex is looking angry again, I though it was supposed to be on the wane?

gfsnh-0-192.thumb.png.3f03acc16bd2e11e18

Let's hope it just hasn't got a clue what's going on!

not necessarily the worst position for the vortex and at face value, you might even say thats a good chart-

archivesnh-1991-1-31-0-0.thumb.png.a1c82

31st Jan 1991...

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20 minutes ago, Yarmy said:

If you look at all the ops, they all show this. Over the next 48 hours It rides up the west flank of the ridge over us and then merges with the approaching Atlantic low. The exact timing and path is presumably what's causing the short-term confusion thereafter. 

Regardless, in the medium term (T168+) the vortex intensification over Greenland with a SW flow for us has more or less unanimous cross-model support.

ECM

ECH1-168.GIF?15-12

 

GEFS mean

gensnh-21-1-168.png

 

GEM ENS mean

gensnh-21-1-168.png

 

It's ok to say that FI is T72 so ignore everything beyond or whatever, but the signal for the above is overwhelming. If there's a Torpedo in the water, now would be a good time for it to appear on the sonar.

 

 

I'm not seeing how it would tie up with another low if its still at hurricane force, initial maps showed a downgrade to a storm but currently Alex is still shown at hurricane force when reaching greenland.

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Chris1986 ,  perhaps you need to let Alex go now. he will shortly become an ex hurricane (he may already have undergone that change) and be absorbed into the Atlantic trough over the next 24/36 hours.    Those NOAA charts showing a white H do NOT indicate him still being a hurricane. 

gfsp 00z shows a more snowy occlusion heading east early next week than the gfs op did.

Modelling still looks messy and unconvincing. 

 

 

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4 minutes ago, bobbydog said:

not necessarily the worst position for the vortex and at face value, you might even say thats a good chart-

archivesnh-1991-1-31-0-0.thumb.png.a1c82

31st Jan 1991...

Yup Jan 2013 and March both had the PV in similar locations. A canadian PV isn't necessary bad and usually promotes sliders as pressure rises NE.

Edited by SN0WM4N

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image.thumb.png.fbe2baa20851f08c3053f9f0

 

the 06z ensembles show that the op run is faster than others to push the cold air out of the way; however, the end result is the same...

if only we could have that blue run...

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Tbh I don't see an awful lot of change in the outputs this morning, slightly stronger heights which slows the Atlantic down but less cold air does manage to come in regardless of that. The UKMO has finally backed down now but as I suspected, showing a slower evolution to milder weather. Now IF we can get the blocking and any weather front coming in at a favorable angle, we just might see some frontal snow on Monday if we are lucky and at this range, its hard too say whether we will or not. 

The significantly milder air is being held at bay for a little longer thanks to the slightly more resistant heights but is still forecast by the GFS and ECM to eventually come in and we get a strengthning PV to boot. I'm sorry but at the moment that is the reality of what the models are showing and have been showing for a good while now, I stress there is uncertainty on the timing of any breakdown but after that, the outlook does seem quite strong on bringing not just milder weather our way but exceptionally mild weather in from mid week onwards. 

Of course, despite this strong signal, the exceptionally mild weather is not guarantee too happen because of the uncertainty in the shorter term but whichever way you look at the outputs, it will turn less cold next week with the prospects of it turning significantly milder from midweek onwards, I'm sure I said that yesterday... So for me, little change in the output apart from slight variations which you would expect.

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3 minutes ago, Great Plum said:

image.thumb.png.fbe2baa20851f08c3053f9f0

 

the 06z ensembles show that the op run is faster than others to push the cold air out of the way; however, the end result is the same...

if only we could have that blue run...

 

Ensembles GEFS Peb 2 would be that blue run it keeps us cold the whole way through and easterly reload a couple of times if only one would say.

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One thing to note from all outputs in the longer range is that pressure does remain somewhat high over the UK so we are unlikely to replicate December's washout for most. Instead, i imagine that most of England will probably stay rather dry with current outputs.

 

ECMOPEU00_240_1.png

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A quick look at the ECMWF model for Monday evening suggests that there could be a period of snow to lowish levels ahead of the approaching occluded front. It may turn to rain behind it though for low lying areas. 
The contours are a forecast snow level which dynamically changes based on how heavy the model precipitation is (heavier snow can penetrate closer to the ground). The front moves through after dark. 

A separate feature moves through Scotland on the weekend bringing a convincing signal for snow to low levels in the west. 

occluded front 18th jan.PNG

feature 17th jan.PNG

 

Imagery ECMWF via MetraWeather.

Edited by forecaster

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50 minutes ago, booferking said:

 

Ensembles GEFS Peb 2 would be that blue run it keeps us cold the whole way through and easterly reload a couple of times if only one would say.

Its funny how that outlier sticks out all alone with no support. Many moons ago we had the reverse situation just before the implosion of a possible cold spell. I remember it vividly it was the brown ensemble member which was a huge mild outlier which tragically verified! In this case we have a blue huge cold outlier.

Not meaning to big this up and no I haven't been drinking at this hour! but the upstream pattern shown over the USA is possible , its the bit over Europe that's more uncertain.

THE PATTERN IS EXPECTED TO REMAIN PROGRESSIVE THROUGH THE END OF NEXT WEEK...WITH THE FLOW LARGELY COMPRISED OF 2 OR MORE STREAMS OF LOW AMPLITUDE AND SHORT WAVELENGTH. SOME GROWTH IN AMPLITUDE...POSSIBLY PHASING...IS GENERALLY AGREED UPON BY THE GUIDANCE TO DEVELOP NEAR OR EAST OF THE PLAINS/LWR MS VALLEY BY DAY 6/THU...WHICH COULD RESULT IN A SIGNIFICANT LOW CROSSING THE SOUTHEAST AROUND DAY 7/FRI. ALSO GENERALLY AGREED UPON BY THE GUIDANCE IS A LONGWAVE TROUGH REACHING THE WEST COAST BY FRI...WITH MORE HEAVY PRECIPITATION LIKELY FOR CALIFORNIA.

That infamous ensemble member does that!

An increase in amplitude, phasing , significant low developing near the se around day 7!

Although the models want to reform the PV they don't really drive the energy east but more ne initially. So this is where we have the earlier timeframe domino effect because where any high sets up will determine the start point position if things happen upstream which are a bit more favourable.

I think at this time the ridge holding further north is possible so cold surface flow hanging on a while longer, we might not see the depth of cold that the blue member has unless we get very lucky. Although I was rather taken by the NAVGEM 06hrs run which is possible within the overall model trends.

 

Edited by nick sussex

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Still looking very tricky to work out what is happening early next week with regards temps, never mind a potential snow event. What is v interesting is some solutions in the GEFS at 240, many look like having the potential to create a block to the north, or over the UK. The problem with the GEFS at that range is that the models can't even decide what's happening at 48 hrs. A bit like a golf shot, slightly off line at 48 yards is out of bounds at 240 yards - for you golfers.

With what the METO have said lately I expect over the next few runs more and more blocked patterns will show within the Ens

Anyway, what does look like happening at some point Monday is snowfall - where it falls TBC.

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37 minutes ago, bluearmy said:

Chris1986 ,  perhaps you need to let Alex go now. he will shortly become an ex hurricane (he may already have undergone that change) and be absorbed into the Atlantic trough over the next 24/36 hours.    Those NOAA charts showing a white H do NOT indicate him still being a hurricane. 

gfsp 00z shows a more snowy occlusion heading east early next week than the gfs op did.

Modelling still looks messy and unconvincing. 

 

 

I probably do need to let it go but it's interesting so all in good time haha, supposedly he is weakening over the azores but will still maintain hurricane force winds - cut and paste from hurricane advisory forcast :- 

Most of the coldest cloud shield has now shifted into the western semicircle, a signal that extratropical transition is likely beginning. With Alex now moving over 16C sea-surface temperatures, and with colder water still ahead of the cyclone, transition to an extratropical cyclone should be complete within the next 12 hours. However, global models suggest that there will be enough baroclinic forcing to maintain hurricane-force winds after transition occurs despite the cold waters of the north Atlantic.

Either way I like a spanner for now, just makes it even more interesting :) 

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It does now look as though there is some cross model consensus for some kind of attack from the Atlantic on Monday, although the track and angle of the attack is still up for grabs based on which model has the track correct.

I would however suggest that anywhere from the Midlands northwards should be safe from any milder incursion on Monday, and certainly the Atlantic could yet get pushed back or dive South.  However, the UKMO 3-5 day outlook for Sunday to Tuesday for most regions makes no mention at all of any incursion from the Atlantic with only reference to some 'snow showers'.

I am not sure whether they are playing catch up or whether they are basing their outlook on other data sources?  Quite amazing though either way and you would imagine that something has to give sooner rather than later surely?!

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5 minutes ago, Kentish Snowman said:

It does now look as though there is some cross model consensus for some kind of attack from the Atlantic on Monday, although the track and angle of the attack is still up for grabs based on which model has the track correct.

I would however suggest that anywhere from the Midlands northwards should be safe from any milder incursion on Monday, and certainly the Atlantic could yet get pushed back or dive South.  However, the UKMO 3-5 day outlook for Sunday to Tuesday for most regions makes no mention at all of any incursion from the Atlantic with only reference to some 'snow showers'.

I am not sure whether they are playing catch up or whether they are basing their outlook on other data sources?  Quite amazing though either way and you would imagine that something has to give sooner rather than later surely?!

I think going back to Steves comments re  Feb 1996, which was traumatic if you lived in London like I was is the difficulty in determining how far east things will get.

I remember watching the BBC forecasts showing the precip and with each update it slowing up, sum total a few flakes blowing in the wind whilst the BBC was displaying snowy images to the west!

These set ups are notoriously difficult to forecast accurately. So brave of Steve to make that forecast but I'll be keeping quiet! lol

 

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Funny, but I want everything to shunt another 400 miles west! Never going to happen. It really is knife edge stuff for you guys across the water though. Could be high risk, high reward!

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Tamara I will write a reply later - the fact that you took the time to reply to me

 

Nick phase 2 looks to be a slider bymut perhaps at a slightly more northery location -

not sure yet -

S

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