Model Output Discussions 12z 01/09/2016

[Ali1977]

10 minutes ago, MattHugo said:

Given general model guidance and the overal signals from the EPS then, for now at least, it is the milder more W or SW'ly type that is 'most likely'. Clearly in meteorology there is always scope for another option, so certainly a few more model runs required to determine whether the more anticyclonic, colder regime is indeed maintained across the UK throughout most of next week, or whether a milder flow arrives from the W or SW. The spread becomes evident from next Tue/Wed but note for Reading at least the 00Z EC HRES (Deterministic) whilst at the bottom end of the spread isn't, overall, an outlier in terms of 850mb temps, but certainly some difference between CTR and HRES.

Compared with the likes of the GEM and the GFS mind from 00Z then it certainly is an outlier...

http://meteocentre.com/models/compar_models.php?map=eur&lang=en&size=large&run=00&stn=PNM&&range=long&type=sidebyside&hh=240

My money is on the block being removed circa Tue/Wed of next week...as things stand!

Matt.

Thanks for the input Matt, nice to see that graphic pop up every now and then.

 

Looking at the 12z I think it is stepping a little closer to the ECM, heights slightly better over Scandy with colder air entrenched than the 06z, which in turn is dragging colder air into the UK...up to Next Mon anyway.

[SMU]

GFS on the cusp of working it out -

 

anyone forecasting the blocking to be moved out the way may want to rethink...

[Kieran]

Much better heights into Scandanavia at 108 hours than on the 6z:

6z : 

 

12z: 

 

[northwestsnow]

Nope, looks like GFS still wants an Atlantic victory although it did seem to have a good think about the alternative ..

[SMU]

What the GFS is doing @ 144 is because it has no clue where to seperate the energy thats going North away from a smaller area of PVA going south it just spreads it evenly across the piste

hence at 144 a fan of shortwaves ( about 4 ) scattered across the UK

Watch the ECM / UKMO show better resolution & show clarity where the energy is-

S

[SMU]

& there you go UKMO 144

1 shortwave sliding through Ireland & the SW

boom

s

[beng]

2 minutes ago, Steve Murr said:

What the GFS is doing @ 144 is because it has no clue where to seperate the energy thats going North away from a smaller area of PVA going south it just spreads it evenly across the piste

hence at 144 a fan of shortwaves ( about 4 ) scattered across the UK

Watch the ECM / UKMO show better resolution & show clarity where the energy is-

S

We've seen this before with GFS - notably as mentioned above in Jan 2013 - I'm amazed that they can't do something about it in this day and age, especially when ECM/UKMO - in fact almost all the other models seem to handle it better.

[Mucka]

GFS always looked hugely over progressive with westerlies sweeping across Europe and into Russia.

Even over the last 24h this is quite a backtrack 

Whether we can back things far enough West to keep on the cold side of any block remains to be seen but by next week the advance of snow cover West should be right into central Europe which will be amazing for early Nov.

UKMO consistent.

Still plenty of PV energy around Greenland though so we will need some better upstream amplification to maintain blocking though to mid month but a Scandinavian high should help with that as it stalls the Atlantic

[Mucka]

GEM also smelling the coffee

[booferking]

5 minutes ago, Steve Murr said:

& there you go UKMO 144

1 shortwave sliding through Ireland & the SW

boom

s

Any idea what the uppers would be incoming from this chart please?

[terrier]

So the gfs moves slightly towards the ecm. But which ever way we look at it the boys at Exeter seem to think westerly pattern will move in early next week. So few cold crisp days then back to our default pattern. Hopefully we will see some more sustainable cold as we head deeper into November. 

[Ali1977]

Whilst the GFS and GEM are stepping towards the ECM, and the UKMO sticks to its guns, they still have the block too far East to be able to hold firm against the forces coming in from Greenland - I think it'll be close but no cigar, although definitely a decent cold spell for early Nov.    And as Terrier says, the block isn't favoured to hold on by the METO - is it now time to enjoy the cold knowing it will be here till Tuesday, and then look for the next one which will possibly be the start of a much better set up.

Edited November 3, 2016 by Ali1977

[feb1991blizzard]

1 minute ago, terrier said:

So the gfs moves slightly towards the ecm. But which ever way we look at it the boys at Exeter seem to think westerly pattern will move in early next week. So few cold crisp days then back to our default pattern. Hopefully we will see some more sustainable cold as we head deeper into November. 

I don't mind a return to the Atlantic if its A) Brief and B) a bit like the one that would soon follow that chart below and brings a NW wind in with wintry showers.    A is a certainty and B is a possibility.

[Severe Siberian icy blast]

1 minute ago, terrier said:

So the gfs moves slightly towards the ecm. But which ever way we look at it the boys at Exeter seem to think westerly pattern will move in early next week. So few cold crisp days then back to our default pattern. Hopefully we will see some more sustainable cold as we head deeper into November. 

Terrier that isn't what's been said at all is it. It's a 60/40% based on this mornings runs. Also they said if it breaks then it's anticyclonic with temp average at best. 

Then this default mobile pattern really isn't default is it because we haven't had rain for 2 months. In fact October was the most negative month ao/NAO for many years.  

Anyway back to the models. This evening there's a notable swing toward the ecm of this morning so looking good for a longer spell. . . . To be continued 

[Ali1977]

What has been created interestingly enough by the slightly better blocking pattern is a big Siberian high, this has potential to link with some WAA from the Canadian side at some point does it not? PV is obliterated over Greenland on this run, very different at day 10.

Edited November 3, 2016 by Ali1977

[gottolovethisweather]

While we're all chasing around attempting to decide which model is right with its timing as to when the inevitable Westerly breakdown comes (at least to most extremities of the UK), it is worth everyone NOT taking their eye off the prospective forecast conditions beforehand. As predicted for a while now, Saturday through Monday, maybe Tuesday will be the chilliest spell with wintry type showers (including hail and perhaps thunder) penetrating quite a way inland as far south as Southern and Eastern counties. In fact, some BBC forecasters have suggested it will feel raw in the wind, no bad for the first week of November. 

 

Edited November 3, 2016 by gottolovethisweather

[Yarmy]

15 minutes ago, booferking said:

Any idea what the uppers would be incoming from this chart please?

Hard to say, but -5 (at 850hPa) perhaps touching the east coast? You can use the cheat sheet here (posted by Nouska above) to estimate from the SLP and heights:

[Summer Sun]

This afternoon's GFS delays the milder air till Friday

Blink and you'll miss it

GEM manages to keep the milder / less cold air in place longer

Before that Saturday to Monday will feel like 1c to 3c with the wind chill factored in

[Eskimo]

The PV still in tatters even at the end of the run on the GFS. 

[fergieweather]

11 minutes ago, terrier said:

So the gfs moves slightly towards the ecm. But which ever way we look at it the boys at Exeter seem to think westerly pattern will move in early next week. So few cold crisp days then back to our default pattern. Hopefully we will see some more sustainable cold as we head deeper into November. 

Ah, caution here: whilst assessment from the 00z suites suggested a 60% favour for the westerly pattern, it is by no means clear-cut and this is exemplified by EC individual members for the period post-Tuesday. Moreover, even if such a pattern is indeed the outcome, it's longevity is questionable (e.g. GloSea indicative of blocking returning later in the month). 

The key point here is that in such a period of clear model volatility, with a bit of a knife-edge between the westerly/mobile solutions versus the more blocky ones, it's not sufficient to simply rely on ENS means. They will be skewed (in any model - not just GFS) by the more 'energetic' members (=the westerly ones) and may not offer reliable route ahead *if used or cited in isolation*.

Inspection of individual stamps is essential and I'd be surprised if no GFS stamps offer a notion of either a much slower / less vigorous return to mobility (colder, slack conditions here holding on for longer) and / or something de facto blocked (as per 40% of EC 00z members, but we wait to see how this shifts in the 12z).

 

[Spah1]

I thought UKMO 12Z only came out at 5pm? Am I missing some thing. 

Edited November 3, 2016 by Spah1

[Mapantz]

A noticeable windchill developing in to the second half of the weekend, and then in to the start of next week - as wind speed increases. 

[Johnp]

1 minute ago, Spah1 said:

I thought UKMO 12Z only came out at 5pm? Am I missing some thing. 

The clocks going back? 

[bluearmy]

2 minutes ago, Spah1 said:

I thought UKMO 12Z only came out at 5pm? Am I missing some thing. 

Yeah - you forgot to put your clock back on Saturday night !

[Spah1]

4 minutes ago, bluearmy said:

Yeah - you forgot to put your clock back on Saturday night !

Nope that's not it. 

Edited November 3, 2016 by Spah1