Model output discussion - 16th Nov onwards

[Cheshire Freeze]

Am I the only one sat looking at the GFS tonight thinking that this may be one of those occasions where an easterly just pops up seemingly out of nowhere at a relatively close timeframe? That's some Russian high and follows the general theme of the modelling over the past few days i.e blocking structures getting far enough north to disrupt the PV. As Nick (Bluearmy) has pointed out, that is some anomaly in the GEFS.

Edited November 19, 2015 by CreweCold

[BLAST FROM THE PAST]

I think the Russian HP will play its part but I think to hold the deep trough in our locale with masses of pM air being the main airmass that covers us.  So outlooks for me showing disturbed pattern with NW airflow in general for rest of Nov into Dec with huge Russian High holding to our NE are looking ok to me.  This pattern developing will bring some potent pM air at times with quite stormy conditions to boot.  Good bye benign for next 2 weeks.  So the pattern change to colder and active weather with snow for some for particularly last 3rd of Nov has come very nicely indeed, this could be some winter.

Will post Dec outlook tomorrow, had some catching up to do with my family, I think Dec will hold quite a few surprises.  

In last 6 hours the snow area for SE this weekend has moved about so plenty of nowcasting to come and I think a little pep up of that feature coming down eastern flank is possible.

 

BFTP

Edited November 19, 2015 by BLAST FROM THE PAST

[Singularity]

The signs that the atmosphere will rebound from the near-term tropical interference continue to grow stronger. So it is that a predominantly westerly flow for the UK with alternating tropical and (often return) polar maritime airmasses becomes the favoured path as we end November and stride into December. The original idea of a 'waiting game' winter has gained support once more - but it's not as certain as it would be for a typical El Nino event, so we still can't rule out some surprises next month.

 

In the much shorter term, there's a bit of an argument going on between GFS and the majority of the other models with respect to how amplified the mid-Atlantic ridge is in 4 to 5 days time. This is tied to the level of amplification upstream - across the eastern Pacific and the U.S., occurring in response to the initial sharp negative torque event driven by the increased band of convective activity in the Indian Ocean that's currently ongoing. For whatever reason, the GFS det. makes more of this than the other main det. model runs of note (ECM, UKMO, GEM). At such short range, it has to be said, most people wouldn't tend to side with GFS in a standoff against an army that includes ECM and UKMO. So those interesting developments in the GFS 12z det. run are probably a flight of fancy - and its no surprise to see the 18z det. sporting a flatter outcome with the cut-off low ending up on the far side of the North Sea while the Atlantic powers its way in.

 

 

With the Siberian Block looking exceptionally strong for the foreseeable future, supported by the snow cover advance feedbacks and probably the sea ice extent anomalies as well, yet also plenty of support for deep trough activity in the North Atlantic, I believe we are starting to see the signs posted for a particularly rough ridge in early December that could persist for some time... it will depend on how well that Siberian High is able to mess with the polar vortex. Because it looks to be so large and resilient, it stands a good chance of locking in a segment of the polar vortex close to our NW while it assaults the stratospheric vortex with wave breaks.

 

"No pain, no gain" may become the buzzword of December if things do pan out like that, as if the Siberian High can succeed in breaking down the vortex then it will have plenty of scope to back west through NE Europe. Trouble is, there's a lot that could go wrong - for example if tropical convection doesn't play ball and flares up in the Indian Ocean again. It's even possible that the Siberian Block could align itself poorly for driving the wave breaking we want to see.

 

I know I've discussed the longer range implications of the model output a lot over the past few days, but there have been a number of significant developments so the time has been right. Hopefully the path forward won't writhe about so much over the coming fortnight and this post can remain valid for that time! 

[Mucka]

The UKMO looks much more amplified than ECM to me re mid Atlantic ridge Singularity?

 

 

[damianslaw]

Good posts in the thread this evening - best reading in a long while.

 

General theme is for low heights and trough to maintain a grip on the UK for foreseeable, but nothing too unusual for what is the most unsettled period of the year when westerly airstreams reign supreme.

 

I'm not seeing a return of conditions we have seen for the past month, so things will feel much more normal and seasonal in many respects, lively springs to mind.

[Mucka]

Another nice UKMO if you like chasing the faint chance of an Easterly in FI.

 

 

GFS still similar ideas but sending more energy NE rather than into the continent so not as good.

 

 

Forgetting about no hope phantom Easterlies for a while the latest Euro4 finds an area of snow for Central England in the early hours of Saturday morning.

 

Edited November 20, 2015 by Mucka

[knocker]

This morning's gfs run could be sub-titled "batten down the hatches" Very much the story of.Atlantic depressions running east and impacting the UK. Pretty much a N/S split but with a later tendency to involve all of the UK. Some quite unpleasant conditions from time to time methinks, Just one chart as an example only.

Chart weatherbell

 

Edited November 20, 2015 by knocker

[knocker]

A brief overview of the latest EC32 update

 

To set the tone the anomaly on Sunday 29^th. A familiar picture of LP Siberia/Alaska, HP NE N. North America and low pressure northern Canada/Greenland with associated trough orientated towards the UK. Ergo a westerly mainly Pm regime and temps inclining below average.

 

Moving on a week until the 6^th now a trough over Alaska and a flatter pattern across N. America but the trough to the NW still in situ so the zonal westerly still bringing unsettled weather to the UK with the south favourite for the quieter interludes and temps around average.

 

Moving on another week until the 13^th and frankly there is little change except perhaps the influence of the trough is not quite so marked with HP pushing up from the south and temps could even nudge above average where this occurs.

 

On to the 21^st and not a huge difference with the trough still over Alaska, a sign of ridging Russia but still the zonal westerly dictating things in regard to to the UK weather. Temps remaining around average.

 

Summary

 

Winds from the NW/SW quadrant throughout the period with initially the trough exerting most influence bringing some quite unsettled weather particularly in the north where conditions could be quite wintry on occasions with temps indicative of the Pm air

 

Later the warmer air from the south pushes a little further north so still a north/south split but in general conditions a little quieter with temps around average and perhaps even a little above in the south.

 

Of course this isn’t set in stone and given we are in unchartered territory this year the unexpected could still appear suddenly in the woodshed.

[Polar Maritime]

Morning Knock, Yes the GFS continues this morning to show a cool/unsettled N/W Pm flow into the turn of the Month and into the start of Winter. With some pretty deep depressions showing.

 

[ZONE 51]

Good posts in the thread this evening - best reading in a long while.

 

General theme is for low heights and trough to maintain a grip on the UK for foreseeable, but nothing too unusual for what is the most unsettled period of the year when westerly airstreams reign supreme.

 

I'm not seeing a return of conditions we have seen for the past month, so things will feel much more normal and seasonal in many respects, lively springs to mind.

Possibly a slow progress of increasingly colder air masses and stopping around longer, with milder air gradually cooling each time it arrives, with the atlantic lows rolling in bringing increasingly more northern snowfall. I expect a lot of ppn in the weeks a head being sleet/snow rather then rain only.

 

I feel that the journey into winter is going to be very interesting and with with some surprises from the n/e,

 

A winter of particular interest. 

[Polar Maritime]

NetWx-SR Model on Saturdays Snow probability's.

 

[JoeShmoe]

The EC32 update appears to follow what most respected folks have suggested for the longer term outlook for Dec

Typical early winter fayre really but nothing especially cold

Have a feeling we could be down to I or J on the storm names by Xmas though !

[knocker]

Morning PM. I take it you are girding for some possible white stuff in your area?

[gottolovethisweather]

Yes, agreed. Some nice pleasant reading and well thought out analysis posted up on these last few pages and the signal I take from things is that the Jet might be ramping up again post the weekend's wintry uncertainties and of course, therefore deeper into the start of December.

 

I made reference to the more active Jet profiling predicted for the Pacific region on my last post as copied below, does anyone believe this might be the main reason for those deep depressions reappearing in the mid to long-term outputs again?

 

Here is the link to my original post in its entirety and below that I've reproduced the relevant section regarding the Pacific region comments.

•  
• "It is a bit pointless looking beyond D6 but if I were to look to D10 (0000hrs on Friday 27th November) it currently states the following regarding the NH Jet profile. This appears to show a continuation of things as per where we are now, so a return to Westerly flows and occasional passing depressions but hopefully not as ferocious or worryingly wet as the current ones. The most active part of the Jet appears to be over the Pacific regions by this time. I imagine this will have an impact on our shores come early December but just how it will affect us I will leave to others to ponder."

 

 

It begs the question though in my mind whether this will bear any resemblance to what we've seen so far this Autumn, in fact I'd imagine spells of wintry precipitation will feature more often than otherwise would be the case. The main reason I suspect the colder than average scenarios will be more to the fore is due to the pretty unprecedented (well let's say odd looking) stratospheric feedback signals in addition to much touted NH snow cover situation.

 

Both intriguing and difficult forecasting times ahead, marginality might well be the buzzword for December proper.

Edited November 20, 2015 by gottolovethisweather

[Mair Snaw]

Morning folks... must saying enjoying the slower pace in here so far and agree that some very well written and explained post in this thread which helps for the likes of me still learning there way.. i hope it stays this way for the winter season although i doubt somehow it will... just a quick question from me... i was over in the winters past thread the other day and somebody mentioned December 1981 being a month with a trough sat over the UK with PM air masses getting colder and colder as the month went on... having read some post in here the last few days a few people have mentioned a trough sat near to or over the UK like the EC32 is showing.. now i understand enough to know that no 2 winters are the same but with the colder Atlantic would a trough sat over the UK be possible to produce something like December 81?? just thought i would ask as not to busy in here...

[Frosty.]

Here comes the cold, been waiting ages for this, finally it's almost here and the Ecm 00z shows a short sharp shock this weekend as Arctic air digs south with clear / sunny spells and wintry showers affecting many areas with some areas, especially the hills having a covering of snow, most of the wintry ppn occurs tonight and tomorrow morning with saturday afternoon becoming sunny but also a strong wind chill factor which will make it feel like freezing point or just below and icy patches / widespread frosts overnight / early mornings. Looking further ahead, the southeast continues rather cold well into next week before it joins the rest of the uk in increasingly unsettled conditions with a mix of Tm / rPm / Pm airflows...so i'm expecting further cold shots in the weeks ahead.

Edited November 20, 2015 by Frosty.

[chionomaniac]

The EC32 update appears to follow what most respected folks have suggested for the longer term outlook for Dec

Typical early winter fayre really but nothing especially cold

Have a feeling we could be down to I or J on the storm names by Xmas though !

Yes NAO is positive (ensemble wise) throughout the whole run as would be expected

[snowray]

Everything further west again on the 06z for this Saturday, as things stand, West of London more likely to be snow, east of London more like rain, sleet. All could still change though. North, Midlands, Wales could see a few inches of snow with strong winds generally, gusts 50/60mph.

Edited November 20, 2015 by snowray

[Polar Maritime]

Yes the 6z gives most of central N&E/England/Wales a chance of snow on Saturday with gales, With the Low slightly further West.

Edited November 20, 2015 by Polar Maritime

[Ali1977]

December isn't looking great for a swing to -AO or -NAO, but swings happen. 1946 a prime example, and with SSW looking possible in Jan who's to say this won't happen again. I wouldn't be surprised if the EC32 doesn't start picking up these signals in the next 2 weeks.

[Nick F]

Looking at the 00z ECM/EPS NH Z500 anomaly for days 10-15, two main lobes of the tropospheric Polar Vortex evident over Greenland and Bering Sea/Wern Alaska in that time frame. So we are likely to see a typical El Nino climo as we head into early December, with cold air bottled up over high latitudes and strong westerlies and frequent depressions/storms.

 

However, there is a large +ve height anomaly/upper ridge cresting over central Siberia evident from day 0 to 15 on EPS, the most persistent Z500 signal as we head into early winter, which as many have indicated, is probably a result of early extensive snow cover across Eurasia. With time the anomaly could disturb the circulation of the Polar Vortex through wave activity propagating upwards. When we see the PV disintegrate through perhaps a SSW is uncertain though.

 

Back to the here and now, hope many get to see a flake of snow over the next 24hrs. Bands of rain, sleet and snow spreading down from the north later across central and eastern areas overnight, clearing in the morning. Almost anywhere could see snow falling first thing Saturday before temperatures rise, though settling snow at lower elevations more likely in the north and confined to hills in the south.

 

The wind chill will be a notable thing of this cold snap, GFS shows a band of northerly gales spreading south in the early hours Sat morning, associated with a trough of low pressure sinking south which tightens the isobars, gusts of 50-60mph progged by GFS. On Saturday, Met Office indicate that it will feel like 2-3C across central and southern parts, -1 to -3C further north.

 

A cold day on Sunday, but feeling less so than Sat with winds easing. Less cold next week, as winds turn more northwesterly or westerly, though with low pressure close by, most areas will see spells of wind and rain at times spreading southeast. Perhaps briefly cold enough in the north mid-week and again on Friday for some sleet or snow over higher ground.

Edited November 20, 2015 by Nick F

[TSNWK]

Both MOGREPS (Met office) and ECM ensembles do support the ECM scenario this morning

From a respected poster in the other place... Good news, looking forward to a slightly less stormy and zonal ECM later.

[Liam J]

Both MOGREPS (Met office) and ECM ensembles do support the ECM scenario this morning

From a respected poster in the other place... Good news, looking forward to a slightly less stormy and zonal ECM later.

I may have missed something but that doesn't quite make sense? The 00z ECM did turn zonal and stormy, MOGREPS and ECM ensembles support the ECM so why would it turn less zonal and stormy? 

[mountain shadow]

So after the brief cold snap, the models are pretty much fimed up on zonality with a primarily Pm or Rpm source of air, so average to below average expected with perhaps a notable storm or two. So where do we go from this?

 

Anyone looking for a White Christmas will hope that we see more of this kind of output.. this from the GFS 6z (far FI)...

 

http://max.nwstatic.co.uk/gfsimages/gfs.20151120/06/384/npsh500.png

 

Note the area of upper heights over North Western Russia and how the Low Pressure areas moving through Europe meet them and disrupt.

 

Could those heights push further West and deflect the Atlantic Lows underneath?

[bluearmy]

The gefsp remain more amplified in the longer term than the normal gefs.

I can't disagree that the ecm extended are following a standard Nino expectation for early December but whilst the parallel gefs continue to show this mean ridge to out ne, this could turn out to be an interesting test the gefsp