Model Output Discussion 18th Nov.2013-12z onwards.

[nick sussex]

Putting aside the finer detail the ECM 12hrs run is close to its 00hrs run. The PV although not as strong as some we've seen is reluctant to leave Greenland, if the PV was less robust I think we would have seen a split but its certainly putting up a fight.

 

The 00hrs ECM ensemble mean was  better as it suggested moving the PV at least away from the western part of Greenland and also didn't push the high into central Europe, we certainly don't want to see the pattern set up too far west if we see more amplification in the USA.

 

The output is overall a bit frustrating, you can see how the pieces could fit together but we're still missing a few important features, its really down to that Pacific ridge to blow a hole over Greenland so that we can at least take advantage if the pattern in the USA plays ball.

[legritter]

ECM still teasing us towards the very end run ,but at 9/10 days its going to be a long road .But i feel we are looking now at a more mobile pattern come later this week .looks like there could be some very cold air in far north and n/west Atlantic and hopefully some sign of a possible attack on the polar vortex .Its been a frustrating time but atleast cold, hopefully the white stuff will come at a more favoured time ,IN WINTER .13weeks of it plus march as a bonus ,

[Ali1977]

My guess is by Tue the models will show some very cold air coming 5th is of Dec. This high pressure over and around the uk is proving hard to forecast beyond 10 days, lots of west then east then west. Wonder if, or where the Met think it will go.

[Scorcher]

What a great summer chart this would be, certainly not ideal if it's cold and snow you're looking for though.

 

Edited November 24, 2013 by Scorcher

[Summer Sun]

Looking at the ensembles December 3rd onwards has a lot of scatter on show so its still anyone's guess as to which way it will go

 

 

All options remain open

Edited November 24, 2013 by Summer Sun

[Frosty.]

I read a comment earlier which said the Gem had dropped the pattern it was showing..well all that's happened is the pattern change has been delayed by a few days with a stronger anticyclonic signal causing the hold up, same goes for the ecm 12z, indeed, the gem and ecm are similar with what would follow the delay, turning much colder with increasingly wintry weather on a nw-se aligned jet, I don't mind waiting a few days, we have all winter ahead of us. Anything wintry before Dec 1st is always a bonus but I believe a very wintry spell will hit the uk during the first half of December,

[Catacol]

My favourite chart of this GFS 12z run, though it is FI

 

That's a Dec 81 chart for sure. Not sure we can get as much troughing dropping south from the north as happened then, but we will see.

[Catacol]

I don't agree - for me there is nothing to suggest HLB, for sure the chances of brief NWerley incursions, but I don't see anything in the output that deviates from the METO outlooks for early December.

 

Agree this time Ian. That's a first!

 

Also dont agree with the earlier post stating that the vortex cannot stand up to the repeated ridging out of the aleutians for long. That simply doesnt stand up. I can throw pebbles at a double glazed window all day long and it wont break. But if I then use a concrete block? Ah... different outcome! Aleutian ridging is good because it is keeping the pattern amplified as IanF posted earlier... but it wont cause a break up of the vortex itself. For that we need a major warming and at the moment there isnt one on the cards.

Edited November 24, 2013 by Catacol_Highlander

[Methuselah]

That's a Dec 81 chart for sure. Not sure we can get as much troughing dropping south from the north as happened then, but we will see.

Indeed, CH. And that proves that anything can come from anything?

[Bristawl Si]

Some on here are mentioning Dec 81. My recall of that month down here was a lot of snow and a couple of decent blizzards. Are the charts really hinting that scenario?

[Summer Sun]

Here is the Latest from Gibby on the 12z models

 

The UK has High pressure over the Eastern Atlantic with a slack Northerly flow over the UK bringing a mix of sunshine and cloud with frost and fog patches at night or cloudy, benign conditions with very little rain. Through the week the weather will become somewhat milder for a time as the High to the West flattens and moves gently South with a milder feed rounding the Northerly periphery of the High and down across Britain. By the end of the week a trough slips SE over the UK, most likely on Friday with a weakening band of rain moving down across all areas with colder and brighter weather following with wintry showers in the NW to start next weekend.

 

GFS then shows milder air quickly returning next weekend and the start of the new week as SW winds round a declining High pressure with a front moving SE once more early in the week with some further rainfall but very little in the South. Again this is followed by a return to colder and dry weather as an intense High pressure area comes down across the UK to be replaced by an Atlantic ridge opens the door to a Northerly flow  with snow showers especially in the North and East and frosts by night.

 

UKMO closes it's run with High pressure out to the WSW with milder air again rounding the High replacing the day or two of colder weather which will occur early next weekend.

 

GEM tonight shows High pressure declining SE with some very mild Southerly air moving up across Britain supported by Low pressure having formed to the SW. The weather would remain largely dry with just light drizzle and mist near Southern and Western coasts and hills.

 

NAVGEM shows High pressure next weekend relaxing South with milder air rounding the High across the North and later areas further South.

 

ECM follows a GEM route of High pressure declining away SE over Europe with a very mild Southerly flow sucked up over the UK with largely dry conditions before a complex frontal system moves erratically ESE across the UK by midweek or soon after.

 

The GFS Ensembles show that from the mid run period things diversify between members in a huge spread North and South of the UK. The weather slowly becomes more unsettled too with some rain likely for all in the second week.

 

The Jet Stream shows that the flow is maintained to the North of the UK for some time to come turning South down the North Sea later in the week. Then in Week 2 there is some indication that the Northern arm weakens and resets over the Atlantic towards the UK.

 

In Summary the weather remains in very static mode for the first week with quiet benign conditions and only patchy frost and overnight fog as cloud remains stubbornly persistent for many. In Week 2 things become rather more difficult to call as there is some sign of our High declining with more unsettled weather with some rain at times. despite a few options of a colder Northerly flow is shown from GFS right at the end of it's run there is little support for anything particularly wintry likely within the next two weeks as things stand currently.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[Grimsby Snow Lover]

Some on here are mentioning Dec 81. My recall of that month down here was a lot of snow and a couple of decent blizzards. Are the charts really hinting that scenario?

I flicked through the archives and to my very untrained eye I would say not. This is only one example but clearly shows a much weaker PV over Greenland. I wouldn't say there was strong HLB, but it looks more blocked than current charts are showing.http://www.wetterzentrale.de/pics/archive/ra/1981/Rrea00119811128.gifOnly in the far reaches of FI does the PV look weaker, but no way near the same extend as in Dec 1981.http://www.wetterzentrale.de/pics/Rtavn3721.pngReally hope I have read the charts wrong and the similarities are there as I want snow and cold as much as the next coldie on here.

[MR EXTREMES]

Putting aside the finer detail the ECM 12hrs run is close to its 00hrs run. The PV although not as strong as some we've seen is reluctant to leave Greenland, if the PV was less robust I think we would have seen a split but its certainly putting up a fight.The 00hrs ECM ensemble mean was better as it suggested moving the PV at least away from the western part of Greenland and also didn't push the high into central Europe, we certainly don't want to see the pattern set up too far west if we see more amplification in the USA.The output is overall a bit frustrating, you can see how the pieces could fit together but we're still missing a few important features, its really down to that Pacific ridge to blow a hole over Greenland so that we can at least take advantage if the pattern in the USA plays ball.

Intellicast Nick or anyone but better for Nick it gives dew points radar percip type wind temp and so on also does an interesting blog for weather in the state's etc etc.Sorry mods just an idea I don't know how accurate it is but it does seem to get data from noaa.It saying dew points for Portsmouth are plus 2 would that be about right. Android app Edited November 24, 2013 by emotional rollercoaster

[Dancerwithwings]

Steve Murr quoted this earlier today in one of his posts "Shades of December 81 still ringing in my mind" And boy i remember it !... We got buried.

Sunday/Monday 14th December 1981

 

Edited November 24, 2013 by Dancerwithwings

[The Northern Ramper]

1981-82: Another one my parents go on about! Mid December, South West and Southern England seeing 12 inches. North East England getting 7 inches, with 6 foot drifts. 2 days later (20th December) Northern England got 7 inches, and 6 foot drifts. Mid January, there was general snow, with a cover of 1-2 feet in parts. Snowy, and very cold.

[phil nw.]

Can we talk about 1981 etc in one of the other Winter threads please folks.

 

Let's get back to todays models eh?

 

Thanks.

[Mucka]

I read a comment earlier which said the Gem had dropped the pattern it was showing..well all that's happened is the pattern change has been delayed by a few days with a stronger anticyclonic signal causing the hold up, same goes for the ecm 12z, indeed, the gem and ecm are similar with what would follow the delay, turning much colder with increasingly wintry weather on a nw-se aligned jet, I don't mind waiting a few days, we have all winter ahead of us. Anything wintry before Dec 1st is always a bonus but I believe a very wintry spell will hit the uk during the first half of December,

 

I couldn't find the comment you were referring to, about it "dropping the pattern" but when we are talking about timing we are usually talking about a small period of time and specific details not days and a general pattern. I get what you mean so maybe this is just semantics but what if this next pattern is "delayed" and so on and we eventually get something similar to that which was modelled to happen a couple of weeks before, is it the same pattern but delayed or a new pattern that resembles it?

It is probably fairer to say the general conditions (the synoptic) for a deep European trough to form and strong mid Atlantic ridging have not been dropped from the output.

 

Edited November 24, 2013 by Mucka

[Ali1977]

Better ridging into greenland

[BlueHedgehog074]

The UKMO, ECMWF and GFS seem to agree to a generally settled week with High Pressure over us or just to our South-West feeding in a slack flow mostly from a North-Westerly direction. It looks like it will start cool/cold at the beginning of the week, with a chance of frost overnight in some places (though the frost probably most likely where clear skies occur). An example for Tuesday at 3am from the GFS 12Z Minimum Temperature charts:

 

Temperatures look as though they could drop around, or below, freezing in places:

 

Milder and less-cold conditions then look likely on Wednesday and Thursday as milder air spreads in from the West and North-West. Wednesday, in particular, could possibly see temperatures into double figures in Southern areas of the UK:

 

 

(Some milder 850 hPa temperatures looks to spill over the UK, too)

 

Right at the end of the week and into the early weekend, it looks we will see a more disturbed North-Westerly flow, as Low Pressure swings down from the North-West and submerges the UK in colder air:

 

 

Some showers, or longer spells of precipitation, looks likely on Friday as the result of this, most especially over the North of the UK. And some of it could fall as sleet and snow over high ground. Additionally, a possibility of some weak fronts and areas of precipitation spilling over the top of the High Pressure system this week that could affect some North-Eastern areas. But otherwise still a generally quiet week overall weather-wise.

 

After that, there seems to be a possibility of the High Pressure to the South-West gradually transferring to our East, which could then start drawing in milder air from the South or South-West (although the positioning of the High to our East could mean Southern and Eastern areas could see a cooler South-Easterly feed should this verify).

 

Both the 12Z GFS and 12Z ECMWF showing similar outlooks at 192 hours with those areas of High Pressure to our East (although ECMWF's pressure patterns do generally look more amplified over the Western Atlantic area).

 

 

Even though this could feasibly lead to a European block with a High to our East (but not guaranteed), that pronounced ridging to the other side of the world on those two Northern Hemisphere charts could still help lead to a more favourable blocking pattern for cold over the UK, especially if it can help move some of the Vortex over/near Greenland further Eastwards. The 8 to 14 day NOAA anomaly chart seems keen for higher than average heights over Western America to show a fair deal of amplification (I think it showed something similar in that area 2 or 3 days ago if I remember), with some troughing and areas of lower than average heights to the North-east of the UK, which could help lead to some cool/cold North-Westerly and Northerly flows. Does also look like on this chart that High pressure could stay close by to us to our West. The chart doesn't really seem keen for a European High Pressure block to occur to the East of us. But I suppose even if there was, this could get flattened quickly. 

 

NOAA 8 to 14 day anomaly chart (23rd November update from yesterday, but wouldn't be terribly surprised if tonight's one ends up similar).

 

Edit: Tonight's NOAA 8 to 14 day anomaly chart. Not much has changed really, except for a chance for the areas of higher anomalies to our West/South-West could link up with the ridging from Western/North-Western America.

 

Whilst some of the charts do show a fair deal of amplification, it's always possible we could end up being on the wrong side of an amplified High Pressure system and/or block. Or that chance of Northerly flows being pushed too far East. I guess it will depend on the possible displacement of the Polar Vortex, too, and seeing how much disruption that gets done do it. 

 

With this potential being a while away, that usual idea of keeping an eye on how the models, ensembles and anomaly charts develop these ideas could be useful, as well as keeping an eye on the tricks that Polar Vortex may have up its sleeve (despite some Polar Vortex disruption looking possible. But whether it will be enough is not completely certain. Plus, I suppose if we do see an area of the Vortex unwilling to depart from the North-West of us, we could just see a less cold Westerly flow, or a mild South-Westerly one).

 

I also made this maze game underneath for you to have a go at (if you want to), highlighting possible solutions that could happen in 10 or so days time. Which ever exit you come out of is the solution most likely to happen. ;-)

 

 

Game Rules:

 

1. No cheating allowed. This includes: not going over the blue lines (maze walls), and going around the outside of the maze.

 

2. You are allowed up to 5 seconds to plan your route out ahead.

 

3. Once you've reached an exit, it's game over.

 

4. Should you reach more than four 'dead ends', it's also game over.

 

5. Good luck with what ever solution you get.

 

6. This is not a 100% guarantee of what you will get.

 

(click image for playable-sized version of the Model Maze)

Edited November 24, 2013 by DiagonalRedLine

[Snowman.]

MUCH further west compared to the 18z.

 

[bradymk]

MUCH further west compared to the 18z.

 

It's because the GFS has completely failed in the modelling off the low in Eastern US and is now moving in line with the other models. It wanted to bring the low out to the sea which was why GFS had pattern further east than the others.

[nick sussex]

Better ridging into greenland

Sadly that low is sending too much energy eastwards and has the wrong tilt to develop a northerly ahead of it. A brief nw PM flow is possible but the more important part of the output is later on to see whether the ridge in the Pacific can do some damage to the PV, the main chunk is over Siberia but there won't be any decent cold for the UK with the current NH pattern unless those low heights get removed from the north.

Edited November 24, 2013 by nick sussex

[Mair Snaw]

MUCH further west compared to the 18z.

 

That is the 18z!!!

[Mucka]

 

(click image for playable-sized version of the Model Maze)

Model Labyrinth.png

 

Drizzle and cloudy Easterlies for me along with either a new pair of eyes or a pair of spectacles that resemble mini telescopes.

Think I will pass on being able to see again until this GFS run is over. 

[Snowman.]

That is the 18z!!!

oops