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Model Output Discussions 12z 01/06/2017

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20 minutes ago, knocker said:

I'm not absolutely sure what you mean by this. Are you suggesting that experienced senior forecasters at Exeter do not have the background or qualifications in atmospheric physics to understand teleconnections? Connections which at best remain theoretical for pressure distribution in the eastern Atlantic unless one can take all signals into account and even then.............. Any enlightenment would be appreciated

I cannot answer for Singularity but I take it that he refers to the lack of a proven connection in the literature rather than a lack of understanding among the scientific community. I've not seen any teleconnection graphics on any of the big science sites that point to a strong link between Pacific placed convection and UK summer weather. There is a tentative suggestion that Indian Ocean activity may have more influence.

As an aside and purely just a thought - the last time we saw such a UK centred cut off low - solar activity was rapidly declining and looked very similar to this:-

ql_musiyymm.gif

Another summer where long range models showed vast swathes of positive heights but failed to pick up the tiny and persistent trough that blighted UK summer.

 

Edited by Nouska
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14 minutes ago, knocker said:

I'm not absolutely sure what you mean by this. Are you suggesting that experienced senior forecasters at Exeter do not have the background or qualifications in atmospheric physics to understand teleconnections? Connections which at best remain theoretical for pressure distribution in the eastern Atlantic unless one can take all signals into account and even then.............. Any enlightenment would be appreciated

I suspect the met office go with the EC / mogreps ..we know EC  was pretty solid in its path to a settled outcome perhaps mogreps the same, either way those nice updates are going to change radically, probably today or tomorrow..

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8 minutes ago, Nouska said:

I cannot answer for Singularity but I take it that he refers to the lack of a proven connection in the literature rather than a lack of understanding among the scientific community. I've not seen any teleconnection graphics on any of the big science sites that point to a strong link between Pacific placed convection and UK summer weather. There is a tentative suggestion that IO activity may have more influence.

As an aside and purely just a thought - the last time we saw such a UK centred cut off low - solar activity was rapidly declining and looked very similar to this:-

ql_musiyymm.gif

Another summer where long range models showed vast swathes of positive heights but failed to pick up the tiny and persistent trough that blighted UK summer.

 

Ah you may well be correct and not my interpretation of "The lack of strong theoretical grounding" Interesting description of the Canadian vortex lobe though that has been, and continues to be, so influential in the Atlantic :)

Edited by knocker
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15 minutes ago, Nouska said:

I cannot answer for Singularity but I take it that he refers to the lack of a proven connection in the literature rather than a lack of understanding among the scientific community. I've not seen any teleconnection graphics on any of the big science sites that point to a strong link between Pacific placed convection and UK summer weather. There is a tentative suggestion that IO activity may have more influence.

As an aside and purely just a thought - the last time we saw such a UK centred cut off low - solar activity was rapidly declining and looked very similar to this:-

ql_musiyymm.gif

Another summer where long range models showed vast swathes of positive heights but failed to pick up the tiny and persistent trough that blighted UK summer.

 

Yes this is what I meant - thanks for the interpretation Nouska.

Essentially, there is a mechanism known to exist, but studies disagree on the extent of influence on extra tropical patterns. This may be due to the role of AAM cycles, with studies tending to look at the overall picture rather than against the cycle. We look to be poorly placed in the cycle on this occasion which adds to the level of influence being seen on this occasion.

So it becomes difficult to gain enough certainty to apply a significant modification to longer-range model guidance.

In this light it's a shame that work on the Global Dynamic Synoptic Model (GDSM) was abandoned some years ago, as it made some promising steps toward better understanding of the role of the AAM cycles in connection with other forcing.

 

Also in my last post I should have clarified that I meant 'significant' in the scientific sense I.e. there is enough variability in results that the impact of the C-Pac signal befomes muddled unless the picture is broken down further. This being where I believe further research is much needed to facilitate more confident application of signals from such events; in particular weighing up against other sources of tropical forcing.

Edited by Singularity
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36 minutes ago, knocker said:

I'm not absolutely sure what you mean by this. Are you suggesting that experienced senior forecasters at Exeter do not have the background or qualifications in atmospheric physics to understand teleconnections? Connections which at best remain theoretical for pressure distribution in the eastern Atlantic unless one can take all signals into account and even then.............. Any enlightenment would be appreciated

I am sure S will reply but my take on his comment is that he meant that there is no strong theoretical grounding, and UK senior forecasters I would assume would know this, not that they have a lack of same?

 

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1 minute ago, johnholmes said:

I am sure S will reply but my take on his comment is that he meant that there is no strong theoretical grounding, and UK senior forecasters I would assume would know this, not that they have a lack of same?

 

Yes it's been clarified John.

Anyway a quick look at this morning's anomalies albeit they haven't been a great deal of help recently

The GEFS 8-13 does indicate a new alignment of the low pressure over n. Canada and with positive anomalies to the west of the UK and a trough to the east. Thus the upper flow light in the NNW vicinity still portending unsettled weather with temps no great shakes. This meridional pattern in the eastern Atlantic tending more zonal as the period progresses thus the upper flow backing to around WNW so no sign of any protracted warm spell with temps around average. NOAA would appear to be in the same ball park.

gefs_z500a_5d_nh_53.thumb.png.4c1b03f99bfca3f06fc85d16e55d3f57.png814day_03.thumb.gif.13f76921436229c0565c03c0cf69ac2b.gifgefs_z500a_5d_nh_61.thumb.png.d7f7f6eb62f6466f452cd92facace0ee.png

Cannot post the 8-13 EPS but it's very much in the same ball park as the GEFs, perhaps makes rather  more of the trough over NE North America and tad less amplified in the Atlantic. And it finishes the run at the end of the month with HP to the south west and LP to the north west and upper flow just north of west and temps around average.

Using just this it's very difficult to see any sustained settled spell with temps above average and not fairly mundane fayre with the usual N/S bias.

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Regarding Solar activity from what I've noticed the most settled summers tend to come around solar minimum or in the middle of a solar cycle. Once again though this only increases the chances nothing more.

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1 hour ago, northwestsnow said:

I suspect the met office go with the EC / mogreps ..we know EC  was pretty solid in its path to a settled outcome perhaps mogreps the same, either way those nice updates are going to change radically, probably today or tomorrow..

Going for a north-south split with a broadly westerly upper flow, best in the south, most unsettled further north is the general idea from the end of the coming week so it sounds like waxing and waning of the azores high / ridge  versus generally lower heights to the nw / n and occasional troughs over the uk.

Edited by Frosty.
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3 hours ago, MP-R said:

Such a frustrating problem in this country. Why are we such a trough magnet?! Makes you wonder why, if there's no oomph to push the trough out, why there IS enough to push it in.

My own hope is that the constant flip flopping of the models means there's no certainty of a trough dominated outlook after the next two days' summery blip versus a more settled one. FI looking very La Niña-esque on some runs.

Complete coincidence gets the trough in and fails to get it out. There's still a tiny bit of momentum from the Atlantic towards us right now - that gets it in. But just at the point the trough hits the UK, the Azores High ridges on one side, forming a loop over to heights on the other side - that stops the trough getting out. 300 miles west or south and we're in a week long heatwave!! 300 miles in any other direction is still good too!!

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On the face of it, the longer term signal still sounds generally summery for southern uk, especially southern and south-east england, not so good for the north but this doesn't preclude at least some fine and warm spells further north too.

Edited by Frosty.
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I think models are a bit over the top with this cool pool sitting over the UK for a few days next week. It'll either drift east or southeast, sitting right over the UK looks like an exaggeration, we've seen things like this before ,  It would be an amazing model prediction if it did come off this way since it was picked up ten days out. Funny how models can never pick up a ridge at this range and keep it going, its always the troughs never the ridges.  

Edited by 40*C
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Enough about the longer term for a minute, the next two or three days look very summery with increasing warmth and plenty of sunshine across the board on mon / tues with wednesday looking warm and humid, especially further south with sunny periods but with thunderstorms breaking out and spreading north across the uk.

DE27yKRUAAAQlHm.jpg

DE2stTUVwAA7puc.jpg

DE2uBlMW0AEvYOJ.jpg

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Regarding the slow movement of the depression at the end of the week. My simplistic take on this is as the amplification takes place during the week  the current more or less zonal flow becomes meridional and that completely slows down any west-east pattern movement Thus in one foul swoop the amplificatin creates the cut off low and then restricts it's movement. Three charts of the 500mb wind field does illustrate this

gfs_uv500_natl_16.thumb.png.118be8ecea21df8aed5a1d2c7cc18c58.pnggfs_uv500_natl_22.thumb.png.8d86b73b5116ac9969f195cc2c813d50.pnggfs_uv500_natl_34.thumb.png.c7581cc2e613dd44c6696d38b180588e.png

Edited by knocker
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1 hour ago, Man With Beard said:

Complete coincidence gets the trough in and fails to get it out. There's still a tiny bit of momentum from the Atlantic towards us right now - that gets it in. But just at the point the trough hits the UK, the Azores High ridges on one side, forming a loop over to heights on the other side - that stops the trough getting out. 300 miles west or south and we're in a week long heatwave!! 300 miles in any other direction is still good too!!

Indeed, that's also very frustrating haha. You'd think that when its forcing mechanism is cut off, it'd fill quickly or at least sink into the void to the southeast.

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The GEFS 6z mean is not backing down from a trough dominated outlook although later there are signs that the south would improve as the azores high / ridge becomes more influential again..but the idea of a very slow moving trough over or very close to the uk for a considerable period is still alive and well. 

21_120_500mb.png

21_168_500mb.png

21_216_500mb.png

21_240_500mb.png

21_288_500mb.png

21_312_500mb.png

21_366_500mb.png

Edited by Frosty.
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1 hour ago, knocker said:

Regarding the slow movement of the depression at the end of the week. My simplistic take on this is as the amplification takes place during the week  the current more or less zonal flow becomes meridional and that completely slows down any west-east pattern movement Thus in one foul swoop the amplificatin creates the cut off low and then restricts it's movement. Three charts of the 500mb wind field does illustrate this

gfs_uv500_natl_16.thumb.png.118be8ecea21df8aed5a1d2c7cc18c58.pnggfs_uv500_natl_22.thumb.png.8d86b73b5116ac9969f195cc2c813d50.pnggfs_uv500_natl_34.thumb.png.c7581cc2e613dd44c6696d38b180588e.png

is there any chance this so far non existent low will not happen?.... lol..

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1 hour ago, mushymanrob said:

is there any chance this so far non existent low will not happen?.... lol..

Well you nwever know mushy. The first low sfirts around N Scotland and perhaps the Azores will ridge?

gfs_ptype_slp_eur3_18.thumb.png.85b543d00b5c2b77bc6cfac2c89ffceb.png

but see that little fella to to SSW of Greenland above, well that shoots around to curtail that  :shok: Where's the blocking ridge when you need it?

gfs_ptype_slp_eur3_29.thumb.png.06e50715f111e700a58a8f90cde50588.png

Edited by knocker
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UKMO has the trough keeping more to the NW and with the fresher Atlantic air after the cold front on Thursday it could stay quite sunny in the east. Nothing to complain about from this run really unless your after the Low centre

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12z has just rolled out - and its just as vile as the last run so not going to bother posting the charts.

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39 minutes ago, 40*C said:

12z has just rolled out - and its just as vile as the last run so not going to bother posting the charts.

I can confirm there is a very slow moving trough hanging around for days and days just like the 6z although the south does improve slightly beyond T+270 hours.:) 

Edited by Frosty.

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Rukm1441.gif Rtavn1441.gif Rgem1441.gif

As to be expected when it's a cut-off low we're dealing with, there's quite a bit of variation at 6 days range in terms of the position and intensity of the system.

UKMO has remained steadfast with a position more to the NW as an increasingly slack feature. Showers fairly few and far between for the southeast where it could still feel quite warm in the afternoons. Progressively cooler and more showery as you head NW from there - but never terribly so.

GFS has adjusted the position of the original low NW since the 00z which is of some interest, but also added a secondary feature swinging in which lacks much support from other sources at this time. Not a good thing to happen as this not only brings a spell of more persistent rain and suppressed temps, but 'tops up' the trough with cooler, more unstable air - so helping it to then hang around well into next week. 

GEM remains the odd duck with the low making more eastward progress - but at the expense of it being deeper on Thu-Fri due to the stronger jet stream required to achieve this. So cooler with a greater number of showers during that time, but slowly trending drier through the weekend, albeit with some fairly cool air in place so struggling to feel very summer-like except perhaps in the far SE.

 

So yes - a variety of some note. UKMO offers hope that the weekend could continue to feel reasonable enough away from the NW, but GFS conjures up some unwelcome secondary shenanigans while GEM would rather have a considerable bash at the positive monthly mean temperature anomalies.

If the ECM 12z could side with UKMO, I'd at least feel a little more positive than has been the case for several days now.

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Things must be really bad when this is considered ok..can we just rewind to when it looked like a lovely prolonged spell of high pressure.:D

UKMOPEU12_144_1.png

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One thing's for sure the GEFS anomaly doesn't look promising

gefs_z500a_5d_nh_53.thumb.png.ab605ed3f3f633c70a1250647b6fa24e.png

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9 minutes ago, Frosty. said:

Things must be really bad when this is considered ok..can we just rewind to when it looked like a lovely prolonged spell of high pressure.:D

UKMOPEU12_144_1.png

We seem to have reached the nadir and are now starting to see very slight improvements to conditions this coming weekend. Notably UKMO which keeps the trough further to the NW and fills it out nicely, so areas to the S and E in particular might actually get away with a reasonable weekend. Awaiting further runs with interest.

Edited by stainesbloke
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8 minutes ago, stainesbloke said:

We seem to have reached the nadir and are now starting to see very slight improvements to conditions this coming weekend. Notably UKMO which keeps the trough further to the NW and fills it out nicely, so the S and E in Par might actually get away with a reasonable weekend. Awaiting further runs with interest.

I agree, the south and south-east would do ok from that set-up but the north and north-west would be progressively cooler and more showery..on the plus side, in the sunny spells it would feel pleasant anywhere but now I'm scraping the bottom of the barrel for good things to say about the current output generally..BUT..The next 3 days look summery so it's not all bad!:D

Edited by Frosty.
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