Model Output Discussion - cold spell to end Autumn

[frosty ground]

Was it the winter of 2013 that had a small amount of height to our north that deflected the Jet and created the undercut that led to the March 2013 Cold spell?

Wasn't the lead up to that all over the place from the models?

3 minutes ago, Ali1977 said:

See, chocolate fireguard , back comes the cold!! Need another run and ECM support this evening to even think about it being reality 

We need several runs of consistency from all the models.regardless which way they go.

[cheshire snow]

Yes chalk and cheese with the GFS in the space of a few hours.

The truth is the weather makes fools of all of us (even the professionals)

Lots more ups and downs in the next 48hrs IMO

C.S 

[carinthian]

7 minutes ago, carinthian said:

Another run from GFS and this time wants to lock the British Isles in a wedge of frigid air at t192.  Great chart watching, ups and downs continue, but seems the block is not going without a fight with Atlantic upper winds weak in most sectors.

C

The chart below shows how frigid this air mass is on GFS latest run. At t219 has 2m dew point temp of -10c and below for the West Country ! . Anything that hits that from the SW will be snow. 

[Airedalejoe]

1 hour ago, johnholmes said:

Just to cheer you all up, at least those who are looking beyond a week ahead the 500 mb anomalies, well ECMWF-GFS this morning, are not good reading if you want deep cold.

For a couple of days all 3 had gone with the idea of some kind of 500 mb ridge from the Azores well into Greenland, NOAA last evening still does even in the 8-14 day mean chart. Not so the other two this morning although whether the charts shown below are a major shift or just a temporary hiccup will not be known for another 24-48 hours.

Why not enjoy the cold now and for the rest of this week. Some down the eastern side, even on low ground, will see the odd passing sleet/snow shower and high ground is likely to see a temporary covering. Frost for many. Just what is expected in late November early December by some of you?

Links below

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

A voice of sanity! Currently watching large wet snowflakes falling, It's the UK, end of November, it's cold for the time of year, it's how our winters are!

I'd love another this day in 2010 repeat but we'll have to be lucky as severe spells like that don't roll round every 7 or so years.

For me it appears that recently weather patterns seem to become stuck in ruts for our part of the world and the one we're in is high pressure to the west. The current one may not give up quite as easily as advertised this morning and we may get lucky but don't necessarily expect to be skating on frozen rivers))

[Met4Cast]

Given the models eager for blocked weather in the extended I think we can be fairly confident in that outcome, all models suggest it run in, run out.

It's just the evolution in getting there that's a jumbled mess of garbage. Hopefully todays 6z is the start of ending the mess and slowly honing in on the pattern, be nice to see the other models upgrade closer to the 6z this afternoon.

[Scandinavian High.]

Who’s leading the way ukmo.  gfs much better ecm to back track to colder later...

[Nick F]

The meandering southern and northern branches of the split jet stream over N Atlantic sector causing plenty of uncertainty and low confidence with model guidance in the medium range ... because they can’t seem to resolve where to place the ridge between the two branches and where the southern and northern arms meet this side of the Atlantic. 

GFS blows up lows on the northern arm on the 00z then drops them on the 06z in the same timeframe, and along the southern arm it can’t decide how far east to move the lows toward Europe, combine that with cold arctic air being pushed south from the pole by the -AO height pattern developing. It turns into rather a roller coaster of evolutions on each new run!

[Derecho]

Morning, here is my interpretation of the 06z GFS, 00z ECM and 00z UKMO

Only interpretations up to T240 are made

Well we have some wintry weather this week but after that the picture becomes a lot more complicated. We seem to have the ECM developing a disturbance around Greenland which also appears on the GFS 00Z. This disturbance has a huge impact on what happens next… but the GFS 06z and UKMO 00Z don’t have it developing.

GFS                                                         UKMO                                                      ECM


The models are going to struggle awfully with this feature and I will show why. We have warm air marching NW to the W of Greenland which I have mentioned is key. So why is there such a struggle in this area? Well ocean/atmosphere dynamics are complicated and as this SST anomaly map shows we have a lot of cold and warm spots in this area known as eddies.



These SST anomalies will obviously throw a whole extra complication on proceedings, no question about it.

The ECM is the worst case scenario with high pressure being stuck over Spain and the cold air out of reach, therefore robbing us of a northerly late on. We get some cold anticyclonic weather till T216 but milder weather soon follows. The GFS however develops enough WAA to put us under a NW air flow with low pressure in the Central North Atlantic pumping up the block.

GFS                                                          ECM

At T240 we pay the price on the ECM as the cold air rushing out of the arctic only makes it as far south as Shetland later on. GFS meanwhile throws most of us a cold arctic airmass at this time! 

GFS ECM

So the 00z's were a knockback BUT!... we could still get a cold northerly even if that disturbance develops, provided we get a good build of pressure over Greenland then the northerly could still force its way through and shunt the high pressure to the south eastwards. There is also a scenario (unlikely) where the high could drift over Scandi leaving us in colder air.  

Anyway its all up in the air at the moment but here are the ratings

UKMO 8/10 snowflakes – Is this ahead of the curve?
GFS     8.5/10 snowflakes – Doesn’t develop the disturbance so we reap some rewards further in the run, though the coldest air is sluggish to move all the way south
ECM   4.5/10 snowflakes – The worst run, shows lower 500hpa heights getting into the W of Greenland later on

Note that anything below a 4 is when we should start feeling despondent. I don’t see a return to zonality anytime soon given the heights off NE Newfoundland (though ECM looks worse at the end in this respect). There is still a lot of potential here and the GFS and UKMO show that. Remember clean retrogression in the winter is rarely simple so we may see more upgrades as well as downgrades.

Don't give up!

Edited November 28, 2017 by Quicksilver1989

[tight isobar]

Purely for synoptical purpose..

Great greeny high...

And good pacific ridge..ideal ingredients for early december!

Edit:

Not to mention russian warmth also!!!

All aiding waving!!!

Edited November 28, 2017 by tight isobar

[radiohead]

What a change from the 0Z

Edited November 28, 2017 by radiohead

[chionomaniac]

Looks like the GFS 06Z puts us in the freezer from T+168 until the end of the run.

Remember that wave 1 strat disturbances are quite often followed by wave 2 splits lower down, so the chances of something popping up cold wise second third of December will certainly be increased this year. Therefore I would not get too despondent at the volatility of each run.

[radiohead]

Frame it LOL

[chionomaniac]

3 minutes ago, tight isobar said:

Purely for synoptical purpose..

Great greeny high...

And good pacific ridge..ideal ingredients for early december!

Edit:

Not to mention russian warmth also!!!

All aiding waving!!!

Hmm - perhaps it's the cold but it looks a bit droopy to me

[frosty ground]

Very much JFF, but our southern members would love this chart. More so @T0

[carinthian]

7 minutes ago, carinthian said:

The chart below shows how frigid this air mass is on GFS latest run. At t219 has 2m dew point temp of -10c and below for the West Country ! . Anything that hits that from the SW will be snow. 

Ends with blighty almost covered in snow .  Great stuff. The dream lives on for you snow lovers.

C

[Snowman.]

11 minutes ago, frosty ground said:

Was it the winter of 2013 that had a small amount of height to our north that deflected the Jet and created the undercut that led to the March 2013 Cold spell?

Wasn't the lead up to that all over the place from the models?

We need several runs of consistency from all the models.regardless which way they go.

Yes it was and UKMO went against all other models to show it happening. It also accurately predicted the failed easterly.

[I remember Atlantic 252]

4 minutes ago, radiohead said:

Frame it LOL

19th Nov '96!

[Gavin Hannah]

1 minute ago, carinthian said:

Ends with blighty almost covered in snow .  Great stuff. The dream lives on for you snow lovers.

C

 

BIG IF* this came off.... I will be taking some of my remaining holiday (if not snowed in lol) and finding a big hill locally to go have some serious fun!!

 

[Derecho]

1060mb+ high over the far north of Canada 



God netweather would go into meltdown if the later part of the 06z came into fruition 

[weirpig]

Well that was fun  a world away from the previous run   so much volatility at the moment  nothing is really clear.  could it happen?  maybe  and before people start saying its only the GFS 6z.  This morning people were praising the GEM  for first picking up the signals for a failed northerly.   All to play for.  for me continued blocking ( in any form)  is the favourite at the moment.

[ICE COLD]

I have never seen a chart look like that for December . Absolutely crazy . 

[Seasonality]

I deserve a double slap on the wrist for posting this, being 384h and a GFS snow accumulation chart, but just for fun. A snow covered UK.

[Scandinavian High.]

Southern England and south east England if that came of they will have to dig them self’s out snowed in.

Edited November 28, 2017 by abbie123

[Frosty.]

I think it's safe to say the 6z is an upgrade on the 00z..got busy in here all of a sudden from 7 to 119!

[Tim Bland]

And we are back in the game! Just need ECM to get back on track now. Just for fun the end of GFS 06z hs the whole of the uk under up to 15cm of snow !  ❄️⛄️