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phil nw.

Model Output Discussions 12z 30/11/16

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58 minutes ago, Singularity said:

The higher height tendency toward Iceland/Scandinavia  in the face of the Atlantic troughs has the look of a low-magnitude stratospheric-forced high latitude ridge, which I believe is what we saw in Jan 2013 to produce 'something from nothing'?

Worth keeping an eye on as a means to score a bonus cold shot ahead of whatever we may achieve in the second half of the month - but not (hopefully yet...) worth betting on.

Can you explain this please as January 2013 was a full blown SSW; nothing low magnitude about it.

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13 minutes ago, Singularity said:

wave_2_ecm.png

This, helpfully posted in the stratosphere thread by Frank_WX, is what could be driving the ridge building Iceland-Greenland that I discussed earlier.

Models are known to really struggle to capture regional downwelling of mid-stratosphere anomalies, with a known erroneous bias toward blocking it at the tropopause (base of stratosphere). GFS can be particularly bad at that, hence the Jan 2013 debacle.

Not saying it'll play out that way this time, but my interest in the potential is increasing.

I am not sure how reliable the Strat. outputs are in the later frames but a look at the GFS  op run sees a definite increase in Atlantic ridging towards Scandinavia in week 2-at the lower levels ie 30hPa and lower.This ties in with the 500hPa ht anomalies.No sign of this on the Pacific side

NH_HGT_50mb_384.gifgensnh-21-5-384.png

It will be interesting to see if we get any consistency from this in future runs.

 

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Well the EPS 10-15 anomaly really gives little indication of any significant change. It's dominated by the vortex lobe in Northern Canada with a fairly flat pattern over the States and still the jet tracking NE although one arm does branch over Africa  The trough in the western Atlantic has gone and positive anomalies, albeit quite weak, dominate the Atlantic but the ridge lies SW (orientated NE) of the UK so the westerly upper flow remains with temps around average NOAA is not dissimilar apart from the ridging in the eastern Atlantic

814day.03.gif

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21 minutes ago, Gael_Force said:

Can you explain this please as January 2013 was a full blown SSW; nothing low magnitude about it.

SSW was on 7th January with propagation down to the troposphere not until around 14 days later which is later than the weaker regional response I am referring to.

SSWC_uwndTemp_JRA55_20130107.png

Rrea00120130111.gif  Rrea00120130112.gif Rrea00120130113.gif

 

Though now that I look, the SSW did give us something similar so I can see how the two events could easily get mixed up! By some cruel irony for those in the southwest the low decided to sit in about the worst possible position on that occasion while the fronts were occluding out. By the time the low sank sufficiently south to let cold easterlies in, there was little precipitation left. The response was also strangely short-lived in the Atlantic sector. A horrible proof that even a SSW with a blocking response in the right place can still fail to deliver the good son a regional scale. The lack of far-southern snow was to prove a harbinger of the times to come in March, when the far south missed out on lying snow while areas further north saw one or more notable deposits.

Rrea00120130120.gif Rrea00120130122.gif Rrea00120130123.gif

 

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Next week we see much milder air moving in sending temps into the low teens for most areas by Wednesday - temps dropping back by the weekend but we remain in a westerly flow

ECMAVGEU12_72_2.pngECMAVGEU12_120_2.pngECMAVGEU12_168_2.png

ECMAVGEU12_216_2.pngECMAVGEU12_240_2.png

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5 minutes ago, Singularity said:

Though now that I look, the SSW did give us something similar so I can see how the two events could easily get mixed up! By some cruel irony for those in the southwest the low decided to sit in about the worst possible position on that occasion while the fronts were occluding out. By the time the low sank sufficiently south to let cold easterlies in, there was little precipitation left. The response was also strangely short-lived in the Atlantic sector. A horrible proof that even a SSW with a blocking response in the right place can still fail to deliver the good son a regional scale. The lack of far-southern snow was to prove a harbinger of the times to come in March, when the far south missed out on lying snow while areas further north saw one or more notable deposits.

Rrea00120130120.gif Rrea00120130122.gif Rrea00120130123.gif

 

I'm guessing you mean the far southwest? The above charts brought far-from-cruel weather here in Bristol with snow on a number of occasions after the largest dump on the 18th. Temperatures were nothing impressive but consistently the right side of marginal.

 

In terms of the models for the coming week, I'll refrain from saying that more average weather is on the way as that would be misleading. 11-14C is pretty exceptional for the winter months. What's being shown is a very long drawn southwesterly for at least 2-3 days starting on Wednesday. After that is anyone's guess and I am assured that whatever follows, the southwesterly will be quite shortlived. For something more average for this time of year, you want to be seeing something like this i.e. temperatures more in the 5-9C range:

archives-2014-12-10-0-0.png

That would of course require a much stronger jet which is something that remains fairly weak throughout the reliable timeframe and only really kicks up a notch into GFS FI (no change there then). I think we're in one of those patterns where it's either really mild or really cold, largely given the meridional nature of the jet. We've been on the winter side of it recently, and are about to be on the autumn side of it again. 

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22 minutes ago, fergieweather said:

Worth noting EC 12z deterministic and control sit in a cluster of.... just 5. Trend heads to slightly below average temperatures post-13th-ish onwards.

Hi Ian, 

Any hint on whether that sits from Atlantic/Polar maritime or something more blocked?

Cheers

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19 minutes ago, knocker said:

Well the EPS 10-15 anomaly really gives little indication of any significant change. It's dominated by the vortex lobe in Northern Canada with a fairly flat pattern over the States and still the jet tracking NE although one arm does branch over Africa  The trough in the western Atlantic has gone and positive anomalies, albeit quite weak, dominate the Atlantic but the ridge lies SW (orientated NE) of the UK so the westerly upper flow remains with temps around average NOAA is not dissimilar apart from the ridging in the eastern Atlantic

814day.03.gif

Can't disagree really, but just a thought, maybe that little positive anomaly towards Greenland doesn't tell us if it is a negative anomaly at the beginning of the period and an even more positive one towards the end - slight straw clutching really but without being able to see more ensemble input it's impossible to be sure!

Very large spread on ensembles towards D10:

EEH1-216.GIF?03-0

and

http://modeles.meteociel.fr/modeles/gens/ecmwf/graphe_ens3.php?mode=2&x=306&y=141&run=12&ville=Londres&runpara=0

 

Edited by Man With Beard

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1 minute ago, Man With Beard said:

Can't disagree really, but just a thought, maybe that little positive anomaly towards Greenland doesn't tell us if it is a negative anomaly at the beginning of the period and an even more positive one towards the end - slight straw clutching really but without being able to see more ensemble input it's impossible to be sure!

 

Yep, I think you'd need to see the stamps to see the bigger picture 

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39 minutes ago, fergieweather said:

Worth noting EC 12z deterministic and control sit in a cluster of.... just 5. Trend heads to slightly below average temperatures post-13th-ish onwards.

Most coldies would take the eventual evolution of the control though! 

The  mobile couple days evident on the 00z mean anomolys have now dropped away on the 12z with higher mslp evident around the uk through the 10-15 day period. I find the mean uppers below 0 of interest given the mean dam 552 never really gets further south of N England. That supports the higher than average mslp predicted and I would have expected uppers to be showing a bit higher than that. 

Low anomolys evident n Africa into the med towards the end of the run. Maybe we will be able to advect some colder conditions into Europe after all?  Generally unconvincing though given the blocky look and lowish uppers, suspect the London graph will be chilly later. 

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gem-0-132.png?12  gem-0-168.png?12  gem-0-216.png?12

I know GEM is not a well respected model but it does at least serve a purpose tonight in that it illustrates what could happen if the two lows in the mid-Atlantic days 5-6 were to not undergo a merger. The western feature sets the jet stream on a much more northerly course ahead of the trough disruption which itself happens further west - so we see a mid-latitude block by day 9. 

Just another option on the table - it seems feasible enough given that lows have a habit of not combining together when originally they had been assumed to do so by the models.

If we could just combine that route with the height rises Iceland-Scandinavia... is it too much to ask for? :drunk:

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27 minutes ago, Singularity said:

SSW was on 7th January with propagation down to the troposphere not until around 14 days later which is later than the weaker regional response I am referring to.

I know this should be in the stratosphere thread but it's not very busy at the moment so hope it's OK. :)

This particular SSW seems to have had a strong response right through the layers in double quick time.

      Z500 last ten days of 2012          Z500 first ten days of 2013

psnh_jun_hist_z500_201236.gifpsnh_jun_hist_z500_201301.gif

The 30mb gif that covers the period.    fadf0571a22e86c85832ec97e16875f9.gif

Images courtesy of JMA and other atmospheric levels to show the rapid propagation here.

  http://ds.data.jma.go.jp/gmd/tcc/tcc/products/clisys/figures/db_hist_pen_tcc.html

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14 minutes ago, Nouska said:

I know this should be in the stratosphere thread but it's not very busy at the moment so hope it's OK. :)

This particular SSW seems to have had a strong response right through the layers in double quick time.

      Z500 last ten days of 2012          Z500 first ten days of 2013

psnh_jun_hist_z500_201236.gifpsnh_jun_hist_z500_201301.gif

The 30mb gif that covers the period.    fadf0571a22e86c85832ec97e16875f9.gif

Images courtesy of JMA and other atmospheric levels to show the rapid propagation here.

  http://ds.data.jma.go.jp/gmd/tcc/tcc/products/clisys/figures/db_hist_pen_tcc.html

The misalignment with the plot I showed is perplexing... and I'm sure I remember the Jan 13th event being considered a bonus that cropped up at relatively short notice although ECM did a much better job with it than GFS (as Steve Murr loves to point out when relevant).

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lots of mild air incoming on the Gfs 18z with temps occasionally into the low teens celsius across the south, not mild all the time, there is the odd cooler day here and there but its the first proper mild spell of the winter. There will be some rain and stronger winds at times but fine and sunny spells too, especially to the lee of high ground.

hgt500-1000.png

ukmaxtemp.png

hgt500-1000 (1).png

ukmaxtemp (1).png

hgt500-1000 (2).png

ukmaxtemp (2).png

ukprec.png

hgt500-1000 (3).png

ukmaxtemp (3).png

ukmaxtemp (4).png

hgt500-1000 (4).png

Edited by Frosty.

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Decent FI, and again I'm sure it'll be a good ENS run...just a shame that it's FI, but we have to start somewhere. 

IMG_3687.PNG

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the GFS has been very bullish for a few days now for a sustained spell of wet and windy weather with mild temps after the driest november since 1929 i think flooding should not be a issue sice the ground is relatively dry so far what we dont want to see is weeks and weeks of it then it will become a problem once again there is still a 50% chance we could get a colder spell to end the month

Edited by igloo

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2 minutes ago, igloo said:

the GFS has been very bullish for a few days now for a sustained spell of wet and windy weather with mild temps after the dryest november since 1929 i think flooding should not be a issue sice the ground is relatively dry so far what we dont want to see is weeks and weeks of it then it will become a problem once again there is still a 50% chance we could get a colder spell to end the month

The GFS has a strong tendency to be completely wrong after +96h though

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Well at least we would get some more snow before xmas, the Gfs 18z saves the coldest weather until last!

hgt500-1000.png

ukmaxtemp.png

prectypeuktopo.png

Edited by Frosty.

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So it looks like we have high pressure  to the west of uk  on the 18z -, And on 12z  run over the uk is this change  to colder weather later on December .:D my runs needed.IMG_1234.PNG

IMG_1235.PNG

Edited by abbie123

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Today

Dry with sunny intervals in most areas and little wind. The exception may well be the south west where there will be more cloud and wind.

1hourprecip_d02_10.png1hourprecip_d02_18.pngtemperature_d02_28.png

The GFS this morning can be quite reasonable summed up as very fluid and unsettled which the anomaly illustrates..

gefs_z500a_5d_nh_41.png

A bit more detail for the next ten days.

At the beginning of the week a large upper trough dominates the Atlantic and as the HP over the UK slips away SE the surface fronts associated with the former bring wind and rain to the north late Tuesday. From here it is once again all about the interplay between the cold and warm air as troughs, fueled by the continued upstream energy input, track east combating occasional ridging from the Azores  The troughs win the battle so by 12z Saturday we have this position

gfs_uv250_natl_27.pnggfs_6hr_precip_eur3_27.png

And thus it continues and really the 500mb chart at T240 says it all

gfs_z500a_natl_41.png

So in a nutshell the weather for the next ten days. Unsettled with systems regularly tracking across the UK bringing rain and windy interludes. more likely effecting the west and north west. And given the direction of the upper flow the temps will be above average.

Taking a glance way further down the line the GEFS still indicating the positive anomaly Iceland area and the det. switching to a much more meridional pattern which does seem to be the most apparent route to the HP to the N scenario.

Edited by knocker

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By the lack of replies in this thread I take it ec was really bad, I think it still shows potential for a Greenland high at 168h

ECH1-168.GIF?04-12

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