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Model output discussion 8th Feb - Cold for now, but then what?

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11 minutes ago, Nouska said:

Very briefly as I'm not at home for all the desktop links. An animation of the 200 hPa stream function (jet stream level) of the different phases of the MJO. The little phase 'clock' (top right) shows the heights building over eastern Canada and Greenland as the 'hand' passes through phase 8 -1.

wh04_psi200.gif

http://envam1.env.uea.ac.uk/mjo.html

That's a very rough interpretation as it is not a fixed entity - depends on season and amplitude as well as Kelvin waves and tropical cyclone activity.

 

 

Many thanks for that Nouska, ironically I was just on that website like an hour ago. I didn't get to the bottom of the page....many thanks anyway. I guess I just want to learn the physics behind it, but then not many people understand it fully so I might have to wait somewhat longer for the chances to try and get a better grasp on it.   

Fascinating stuff though!

Edited by MattTarrant
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Interestingly for coldies there are quite a few cold looking GEFS 6z perturbations in the extended range with Nly / NEly outbreaks..fingers crossed!:)

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1 minute ago, Matthew Wilson said:

Isnt a SSW a reversal rather than above 0? 

SSW or Sudden Stratospheric Warming, is a rapid warming of the stratosphere. A Major SSW is when mean western-zonal winds reverse.

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1 hour ago, MattStoke said:

Cold spell into the range of the high resolution models.

 

Saturday, which is still beyond them looks the most interesting for many though.

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Looks very light and patchy to me...more the kitten from the east than the beast.

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Can we discuss tweets in the tweet thread please - just because the tweet isn't embedded, doesn't mean it's not a tweet.

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Just now, Paul said:

Can we discuss tweets in the tweet thread please - just because the tweet isn't embedded, doesn't mean it's not a tweet.

A very fair point, and noted.

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1 hour ago, Tamara said:

As usual there are different ways of looking at this.

A few things:

1) We have been able to successfully trace the end of one cold snap in mid January to plot (in advance) the development of the next (albeit its not the 1991 redux one might hope for). That has been possible, through some collective effort and different methodologies converging.  As a practical community exercise that illustrates one of the benefits of being a member of a forum such as this - and far too often it gets obscured and not acknowledged as much as it should. The rollercoaster element might provide the excitement when things look good, but it also can serve to detract the community positives when the solutions on offer do not appeal to the eye of the audience

2) Participating in the regional thread over the coming days will make the most of the snow opportunities there are to come, so it need not be a let down at all. We cannot make it snow. let alone everywhere, and not to desired quantities, but its still possible to make the most of what might come. Otherwise all the chasing since mid January (for those who managed to see snow) has no reward away from the computer. So best head out take pics and enjoy it while it is here and then report back:cold:

3) GP has posted in the technical thread and it makes complete sense as reflected by NWP.  I spoke the other day about the need for the tropical signal (the nucleus for downstream amplification) to work its way through to the extra tropics and only then the full amplification potential downstream can be assessed. Clearly from the downstream pattern that has come into model consensus today, the amplification potential suggested by the Pacific forcing is not apparent to that extent and I had been thinking yesterday evening there must be (again!) a destructive I/O signal not allowing it to fulfil expectations.  In data terms it doesn't seem much at all, but in terms of ripples in a pond stemming from the smallest pebbles, they nevertheless spread far and wide. The timelines I have referred to are clearly set to be at the longest end of the envelope, but then estimations can only be as good as the last data set.

This certainly doesn't debunk the initial thinking, but it does mean we will not get the more seamless movement from one cold evolution (Scandi High) to the next that seemed possible - and it explains why the retrogression signal (which had been responding to in line with expectations) has faded. If anyone thinks it should be due, I will accept any responsibility for heightening any expectations by speaking of converging signals producing "the icing on the cake" but then I will also stick to the fact that this had been quite feasibly reasoned (and believe the fullness of time will show that)

4) The interpretation to take from all this in GSDM terms suggests that the Global Wind Oscillation orbit will be much shallower amplitude than anticipated until the destructive interference from the tropics diminishes. I find it very frustrating that such a compelling tropical and extra tropical amplification signal has been diluted and delayed - having coming so far so well.  Hand in hand with a split vortex solution rather than a displacement, some of those highly appealing ensemble solutions up to yesterday would not have stayed in the virtual world....

5) However there is still the compelling real time signal spoken of in detail previously of rapidly rising angular momentum tendency. The MJO signal might have had an unwanted intervention, but it has not gone away. Lagged by the tropical glitch, rising frictional torque and then mountain torque still cues up the expected amplification - but destined for a cold finale to winter and usher into Spring. Whether the whole audience welcomes that or not is completely subjective of course. 

6) Finally, what we can deduce from all this is yet another proof exercise of what I often repeat. The teleconnections do work, but they do not always evolve to optimise the most desired result. But then that has always been the point - this forum has a natural bias, the science of meteorology has no bias.

 

 

So the destructive Indian Ocean influences scupper long term cold for the UK again.  That Ocean has a lot to answer for this winter lol. 

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Just now, That ECM said:

I get some are disappointed with how long the cold may last but some will have a fun few days.

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I was just thinking exactly that! I think midlands northwards (esp. the towards the east but not exclusively as that little low moves across ) could see some quite meaningful snow.

Rtavn784.gif

 

I like the snowless Bournemouth area on the chart you have posted!

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4 minutes ago, That ECM said:

I get some are disappointed with how long the cold may last but some will have a fun few days.

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With dew points a degree or two above freezing that would be cold rain/sleet for many on low ground.

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1 minute ago, Certain kind of fool said:

I was just thinking exactly that! I think midlands northwards (esp. the towards the east but not exclusively as that little low moves across ) could see some quite meaningful snow.

Rtavn784.gif

 

I like the snowless Bournemouth area on the chart you have posted!

Hey, living here it is to be expected but some are going to see snow looking at the near time output. 

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6 minutes ago, Nick L said:

With dew points a degree or two above freezing that would be cold rain/sleet for many on low ground.

Precip has moved south slightly, and the latest DP look to be around 0 or -1c at 1600 on Sat according to the GFS, this is when the main band comes through. 

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5 minutes ago, Nick L said:

With dew points a degree or two above freezing that would be cold rain/sleet for many on low ground.

Apologies for the dumb question, but it seems weird that here in Leeds in the middle of Feb with the weather coming from the east we are likely to get sleet/rain in - 8 uppers, when back in early November we had falling and lying snow for a day! Why is that? It's too complicated to get my head round.

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Well looking at the GFS, at least it should be sunny (My solar panels will be happy) with the dry air off the continent.

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Sorry I disagree a lot of folk could be seeing snow Saturday manly in the east as the day goes on showers will be turning more sleety.:D

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Edited by abbie123
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Greenland high coming up..?!

UN120-21.thumb.gif.eb9fb2f2685424f0b0c2d9c0f1cda72c.gif

 

 

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Seems that lobe of high pressure which shoots up from the mid Atlantic hangs around south of Iceland a while longer this not allowing the small low over Iberia move as far north and expand so quickly and  join the energy leaving the states thus allowing the winds to stay easterly a short while longer and if the corrections keep the high coming further west that deep low dropping into NE Scandinavia could aid retrogression towards Greenland.

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3 minutes ago, D.V.R said:

Greenland high coming up..?!

UN120-21.thumb.gif.eb9fb2f2685424f0b0c2d9c0f1cda72c.gif

 

 

Unlikely due to Indian Ocean interference. See Tamara's earlier post.

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Just now, mountain shadow said:

Unlikely due to Indian Ocean interference. See Tamara's earlier post.

We'll see, but at 144 there's that shortwave again..

UN144-21.thumb.gif.2979e99758e803ed3751a6819e561e0a.gif

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Looks like it is going to be very pleasant next week, highs in the low to mid teens, plenty of sun. (Sorry :()

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28 minutes ago, Nick L said:

With dew points a degree or two above freezing that would be cold rain/sleet for many on low ground.

That's very misleading on the basis of GFS 12z 

To be honest maximum dew points 1C on that day - along a strip of Lincolnshire/Yorkshire. All precipitation away from immediate coast should fall as snow. It looks like a good day for nationwide snow, perhaps nothing too excessive but it should please many. 

image.thumb.gif.1a4b8644f37d2ba7ac9cd47a5e02a159.gif

Edited by Daniel*
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Spring anyone i wouldn't mind to be honest.

gfs-9-168.png

gfs-9-192.png

Edited by booferking
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The Cfs thinks different I think this pattern maybe more stubborn to clear away and if it does we will get a cold reload before the month is out 

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