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Model Output Discussion 17th Dec.2013-12z onwards.


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Again tentative signs of something much more promising possible developing as we move

into the second week of Jan onwards. Anthing beforehand will be just transitory in nature

and any talk of very cold weather setting in at the end of the month or turn of the new

year is just wishful thinking and certainly not based on any meteorological evidence.

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Yuk, that GFS lower resolution output was painful! the PV moves to Hudson Bay and then there may have been some interest but then it decides to move east again!

 

The only remotely interesting feature was that it finished at T384hrs and didn't continue to subject us to more pain! the strat warming is still shown and that's really the only positive I could find to say about this part of the GFS.

 

There are differences between it and the ECM upstream especially around the T168hrs timeframe, overall I think we just need to enjoy Xmas and hope for some changes in the New Year, the PV unfortunately is looking for payback after a few years of not being the star player, its going to need some shifting. Hopefully the strat warming will at least deliver a few punches but not sure if this will be enough to dislodge it, we might need  some more help.

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it also covers the uk sunday monday but in reality delivers nothing at ground level tbh

We need a bit of luck, given the fact we have a major lobe of polar vortex overhead, there is a good chance that we could develop a major disturbance which brings very heavy precipitation which could bring the snow level down to low levels. This is something which won't be picked up until within 3 days or so.

I must be honest given how things were looking 5 days or so back, this is looking a lot more promising, especially those in the west.

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Well the 18z is pretty pony tbh and this pv looks like it wont give up"bit like a woman xmas shopping"and reforms in fi after been put under pressure.Struggling for positives today from the mo but its still only "cough"december and altho this month is all but sorted synoptics wise who nos what next year will bring?Posted Image

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I still think far too many place far to much faith in SW for delivering cold, the last two winters have seen SW events but both of these left large parts of the western part of the UK in no mans land for cold. Remember just because we see a warming that doesn't equate to cold for the UK, I still feel that too many look at the Strat thread as the be all and end all for cold for the UK, yes it's an important player but we need other factors to play ball also.

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The ECM/NAEFs 500hPa means show the same westerly pattern at day 10

http://www.meteociel.fr/modeles/ecmwf/runs/2013122012/EDH1-240.GIF?20-0

http://modeles.meteociel.fr/modeles/gens/naefs/run/naefsnh-1-0-240.png?12

 

so no sign of any real change.

The AO index seems to have peaked for now with many ens members now projecting a gradual fall.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif

 

Certainly no early shredding of the vortex indicated but signs that it maybe passing it's peak strength.

Unfortunately for us it makes little difference as later ens frames show the main centre around Canada and W.Greenland with a smaller area over Siberia

http://modeles.meteociel.fr/modeles/gens/naefs/run/naefsnh-1-0-384.png?12

 

It's hard to see any real cold establishing over the UK until those low heights move further away from our nw.

For now the only consolation the possible marginal snow events as we get those wave developments in the parcels of polar maritime air from the west or north west.

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I still think far too many place far to much faith in SW for delivering cold, the last two winters have seen SW events but both of these left large parts of the western part of the UK in no mans land for cold. Remember just because we see a warming that doesn't equate to cold for the UK, I still feel that too many look at the Strat thread as the be all and end all for cold for the UK, yes it's an important player but we need other factors to play ball also.

Yes its not a guarantee of cold but just that the NH pattern is more condusive to delivering it, a SSW last winter though did deliver a very quick response as the zonal flow reversed, that can happen even whilst waiting for the full effects. Given the state of the PV I think in this instance we are going to need help from the strat.

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Yes its not a guarantee of cold but just that the NH pattern is more condusive to delivering it, a SSW last winter though did deliver a very quick response as the zonal flow reversed, that can happen even whilst waiting for the full effects. Given the state of the PV I think in this instance we are going to need help from the strat.

I think this winter if it's a sustained cold spell you want then yes. I agree, the PV looks unstoppable at this moment in time but things can and do change quite quickly. Now whether that equates to something cold for the UK is another question and one where I think that even with. SSW other factors will override this for any lengthy cold spell this year. What we are seeing now could be as good as it gets and one which if anything makes a good learning curve for future years.
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I'm still not seeing the doom and gloom for January, sorry.

 

We already knew w e were locked in zonal for December, all that has changed is that the more favourable conditions for blocking as we end the month are manifesting themselves in the output - mainly in the ensembles but not exclusively so.

Now this doesn't mean HLB and a strong cold signal should appear in the same timeframe and I wouldn't expect ECM ensembles to show anything other than Ian F describes because within the 15 day timeframe any blocking is very unlikely to establish itself to the extent of bringing a cold spell and even decent blocking that is forming within those ensembles may well show a Westerly flow and moderate or even mild temperatures. Forget ECM32, or at least take its long range output with a pinch of salt, it is just going with the favourite instead of looking at the form guide.

 

The fact is there will be a window of opportunity for blocking to grab a foothold as the jet moves South with low pressure moving into Central Europe out to the mid term and what is considered reasonable reliable timeframe of the output (around 144) at the same time we have pressure rising on the other side of the pole - I will use the latest GFS 06z output to illustrate.

 

Mid term, Southerly jet, low pressure (trough) pushes South into Europe

 

Posted ImagePosted Image

 

From here a lot will depend on how much energy is forced NE over the ridge to our East and how fast and flat the next low pressure system is to our West. Too fast and flat and then the PV and mobile theme will likely override any blocking signal but  a slower pattern behind with the next low not quite so deep will likely keep the pattern amplified - see yesterdays GFS 12z (before it updates today) against the flatter faster ECM this morning.

 

Posted ImagePosted Image

 

Now Nik Sussex has already called fail on yesterdays 12z but it isn't a done deal yet IMO because there is still a signal for a slower pattern behind within GFS ensembles and GEM is still showing this today.

 

Posted Image

 

Even if we take a blended solution the pattern will still be more favourable for blocking going into January proper.

 

We can look at GEM at day 10 and on face value it would show an unsettled Westerly regime but look how much more favourable the pattern is for possible future developments with an almost split vortex. Now this maybe on the optimistic side of the output but ECM is on the pessimistic side IMO and even then it looks like a more amplified pattern would develop again from day 10.

 

 

 

 

Posted Image

 

We already knew we were playing the long game so I'm not sure how the output is so disappointing for January prospects, I just don't see it. I see increased blocking opportunities toward the end of December and through the first week of January (these will unlikely show up as cold runs even where blocking is gaining a foothold) and I do think we have a reasonable shot of a cold spell developing for the second week of Jan with prospects increasing for further blocking from there no matter what EC32 output is.

 

If we end up with a flat zonal pattern at the end of December/ start of January, I will feel very differently but I just don't see that as written in stone at the moment.

I'm not saying it will be cold and snowy second week of January (no hopecasting)- even if we got a decent block set up there is no guarantee we will be on the right side of it. All I am saying is let's not go writing January off on the basis of the current output and the EC32.Even when things look bad we can only realistically write off cold prospects for 14 days max and the output really isn't that bad and the improvements in the output over the last few days seem to have been largely overlooked because the broad theme will remain the same.

 

Granted a lot will depend from developments around the 26th Dec (I pick the 26th arbitrarily because that is when low pressure pushes South into Europe and we are on the edge of reliable output) and it may well turn out we are staring down the barrel again come the end of December but I'm just trying to give an opposite (optimistic) view of how the output may turn more favourable in January.

 

For a total novice like me, this is such a great post - explained clearly with not too much techno-jargon, the balance of optimism and realism I like a lot too.

 

Much to my wife's annoyance I have spent far too much time on here the last couple of months, even though not a lot has been going on from a cold/snowy perspective. However things seem to be slowly falling into place - during the remainder of December perhaps we're going to see the start of something 'juicy'! I really hope so...

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Strat warming needed ASAP

People say its like throwing a grenade into the vortex

The way this vortex is right now , I could see it reforming with no damage done

Posted Image

Consistently showing up on the GFS, and continuing to either maintain its predicted strength or even increase, the forecast of an Asian stratospheric warming is fast becoming a potentially significant feature for our weather in January.

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The ensembles show more promise tonight in deep FI as per the post above. Be very wary of GFS offering up Greenland highs though as this is a common fault with the GEFS and we spent most of last winter chasing these.

Still, at least some eye candy :-)

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The ensembles show more promise tonight in deep FI as per the post above. Be very wary of GFS offering up Greenland highs though as this is a common fault with the GEFS and we spent most of last winter chasing these.

Still, at least some eye candy :-)

 

Indeed. I should point out my posting of that chart was somewhat tongue in cheek. Posted Image

 

I think some people have the idea that pessimism is better and that way you are not disappointed but I guess it all depends how you handle disappointment.

It would be great to get some better output pre Xmas and get a good vibe going in here before we all attend to family and our Xmas dinnersPosted Image .

 

Here are the ensemble graphs for SE England

 

http://www.meteociel.fr/cartes_obs/gens_display.php?x=292&y=121&run=18&runpara=0&type=3&ext=1

 

Some colder runs appearing but of course it is just one run and as the saying goes, one ensemble suit does not a winter make.

Let's hope it is the start of trend and not a crazy GFS pub run out on its Xmas bash. 

Edited by Mucka
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Interestingly enough there is a pattern change which has just started. The forecasted temps over the next week to 10 days look to drop off to about 5-7c in the south and 4-6c further north. Although we have "zonal" conditions forecast the source of the air is from a cooler source now and will continue to do so in the reliable time frame. Predictions of white Christmas for some from the met o, interesting storms and the potential for some colder weather as we get into January via a SSW and southerly jet.......don't forget last week many were adamant that the high was set to stay......keep your eyes peeled some interesting charts to come!!!

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The ECM/NAEFs 500hPa means show the same westerly pattern at day 10

http://www.meteociel.fr/modeles/ecmwf/runs/2013122012/EDH1-240.GIF?20-0

http://modeles.meteociel.fr/modeles/gens/naefs/run/naefsnh-1-0-240.png?12

 

so no sign of any real change.

The AO index seems to have peaked for now with many ens members now projecting a gradual fall.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif

 

Certainly no early shredding of the vortex indicated but signs that it maybe passing it's peak strength.

Unfortunately for us it makes little difference as later ens frames show the main centre around Canada and W.Greenland with a smaller area over Siberia

http://modeles.meteociel.fr/modeles/gens/naefs/run/naefsnh-1-0-384.png?12

 

It's hard to see any real cold establishing over the UK until those low heights move further away from our nw.

For now the only consolation the possible marginal snow events as we get those wave developments in the parcels of polar maritime air from the west or north west.

Even though some charts, such as the GFS 18Z, shows High Pressure over the Pole area, with the Pacific Ridging seemingly linking up with it and helping to buckle the flat Westerly flow across some areas of the Northern Hemisphere (an example at 192 hours)...

 

(edit: fixed problem earlier with attaching wrong chart)

post-10703-0-58732600-1387593727_thumb.p

 

...I would generally agree that the blue and purple 'monster' to our North-West will likely prevent anything particularly cold and/or blocked from occuring for a little while. Although it looks like the ridging from the Pacific and some of the heights over the pole attempts to give the Polar Vortex a bit of a pounding (and could possibly help lead to some amplification downstream, but even then, these ridges could get suppressed), that segment of the Vortex over/to the West of Greenland doesn't look like it wants to take its holiday anywhere else. It does look like that scenario where the Polar Vortex will likely to continue to spit out Lows towards us from the West with varying cool and less-cool periods.

 

Tonight's 8 to 14 day NOAA anomaly chart also seems to suggest Low Pressure over or close by to us with some keen looking heights to the North of Greenland. Along with some possible ridging over the Pacific area and some higher than average heights around the Russia area, this could help create some blocking to our North. But again, I do personally feel doubtful it will be influential or significant enough to provide the UK with very chilly and/or snowy weather (except possibly that chance of some wintriness to precipitation via Polar Maritime flows as phil nw mentioned). Plus, that likeliness of the Polar Vortex staying strong to our North-West along with it throwing energy Eastwards will probably curb chances for the pattern around our area to amplify favorably to provide the cold and snow fans with very chilly weather. Some of the higher than average heights to the North on that chart may, however, help force Low Pressure to take a bit more of a Southerly track at times and probably help keep the UK rather unsettled with maybe some colder air trying to get further South at times.

 

(NOAA 8 to 14 anomaly chart)

post-10703-0-51857300-1387587923_thumb.g

 

Clearly, chance of numerous alterations in regards to the models outlooks can happen, but a continuation of disturbed conditions, particularly to the North-West, with a mixture of cold(ish)/cool and milder days, does look likely for now. And also likely to be very gusty at times with some deep and tight isobar-ed Lows expected to track to the North or North-West of the UK at times next week.

Edited by DiagonalRedLine
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0Z runs maintain the cool/cold theme in the near term,Christmas Eve Christmas Day and Boxing day all look quite chilly id take a stab at temps maybe 4-6 in the north,5-8 in the south with a keen westerly wind.

 

After that im afraid its a pretty familiar tale of a very active Atlantic and little or no Northern latitude blocking right out to the 2nd week of Jan.

maybe Fergie can shed some light on the festive period and whose in with a shout of a white one! :D

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The GFS 00z shows pretty intense stormy weather over the next week, so a heavy pulse of rain and wind might well produce something seasonal.

 

Met office update states,

Christmas Day is likely to be rather cold with sunny spells and showers. Showers will be heavy and wintry at times; especially in the northwest where it will remain very windy. So maybe some suprises

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0Z runs maintain the cool/cold theme in the near term,Christmas Eve Christmas Day and Boxing day all look quite chilly id take a stab at temps maybe 4-6 in the north,5-8 in the south with a keen westerly wind.

 

After that im afraid its a pretty familiar tale of a very active Atlantic and little or no Northern latitude blocking right out to the 2nd week of Jan.

maybe Fergie can shed some light on the festive period and whose in with a shout of a white one! Posted Image

 

I'm not sure about that assessment TBH

The output doesn't go out to the second week of Jan and there are plenty of signs of attempted Northern blocking in the output IMO.though whether it comes to fruition and is favourable for bringing cold to the UK is another matter.

Still, there is nothing to say there is only one way to interpret the output.and GEM is very poor this morning.. 

 

GFS 00z ensembles central England

http://www.meteociel.fr/cartes_obs/gens_display.php?x=256&y=98&run=0&runpara=0&type=3&ext=1.

Edited by Mucka
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I'm not sure about that assessment TBHThe output doesn't go out to the second week of Jan and there are plenty of signs of attempted Northern blocking in the output IMO.though whether it comes to fruition and is favourable for bringing cold to the UK is another matter.Still, there is nothing to say there is only one way to interpret the output.and GEM is very poor this morning..  GFS 00z ensembles central Englandhttp://www.meteociel.fr/cartes_obs/gens_display.php?x=256&y=98&run=0&runpara=0&type=3&ext=1.

Those ensembles look rather cool as it goes, Christmas Day looks cold and there after the mean is offering highs of 5 and lows of 3 for pretty much the rest of the run, with the op at the top end of the pack, so near yet so far..
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ECM looks chilly over Xmas too with a possible snow event for Northern areas on boxing day night/27th if this came off.

 

Posted Image

 

More snow risk?

 

Posted Image

 

Maybe this is a rogue run, looks very differernt and a little odd compared to the other models?

Edited by Mucka
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