Model Output Discussion - Colder but how cold and for how long?

[MJB]

8 minutes ago, tight isobar said:

These warnings will wax n wane over the nxt few days- as to be expected in such a flow- tiny increments will change possible warning zones/ areas.  Seen this MANY times ..

Unless there are systems/fronts  and other that what's currently being discussed, there won't be any , you won't see any warnings suddenly crop up, I think this week is virtually sorted now 

[alexisj9]

1 minute ago, steveinsussex said:

Eh? There has been no mention about rain this week ! If these mild sectors are now popping up then it’s new

Not new as such, just as we get closer the models firm up, in this case on what was already there, all lows have a warm sector, so it's always been there.

[MattH]

Just a quick post but the reason for the quick transition to the westerly type is, in my opinion, linked to the recent weakening of the strat vortex and how, within the lower layers of the strat/top of the trop are likely to behave following the consolidation of the vortex in the coming days. We can see this very well in the below four plots...

 

 

The lobe of the vortex that has been bringing the extreme cold to N America is ejected eastwards over the N Atlantic and clearly to a locale where it then helps to drive the charts and patterns we are seeing for next weekend onwards, as the PV plots highlight very well and the vortex is then a more uniform system. Personally, the MJO through recent phases may also be helping the westerly push, but it is the above which is the key driver for the rapid breakdown of any HLB. 

Does this signal the end of winter after just a week of cold? - does it heck and don't let anyone tell you otherwise in this instance. 

The reasons for the potential/expected/likely return of blocking have been well documented by Tamara, Catacol et al in recent posts and it is likely to be a relatively short wait before further winter synoptics return by late Jan or early Feb onwards. 

All that aside as I mentioned the other day, for those who like the cold enjoy the week ahead.

Kind regards. Matt. 

 

 

 

 

[kold weather]

The METO not mentioning  the southern region isn't that surprising, pretty much all the models they use mainly are in the 'southern' camp, UKV is south, ECM Op is relatively  south, probably about 80-85% of the ECM ensembles are south or just clip with a tiny amount and UKMO GM is south.

I'm sure they are keeping a watching brief just incase, especially as at the moment its a bit of a low risk high impact situation but the weight of all the global model output is still pretty strongly towards it remaining in the channel, if only by a little. History would suggest thats the most likely outcome as well.

The fact there are small margins is why though it will still be watched, probably more than its probable 10-20% risk would normally warrant.

Edited January 14 by kold weather

[offerman]

4 hours ago, Midlands Ice Age said:

Can I make this clear.. this is not quite the intended gist of my post.

They do not automatically increase just 'errors'. They increase the total amount of data (Including errors), this has the result that it increases the volatility of the output data (a larger envelope if you like). The overall effect will be more of a more chaotic output.

We are already seeing this with the models overreacting to some sorts of signals, particularly in a 'stuck' pattern where a small difference here and there can produce a totally opposite outcome.  We also see overblown lows very frequently.......   My gut  'feeling' is that this will happen more frequently if we just add in more computing power.

We will at the moment benefit more by sorting out the software glitches, than by spending many millions on hardware. Its the balance really which is important moving forward.

Midlands Ice Age   ( i don't only post at midnight?)

 

Hi MIA 

thanks for your post again and brilliant. It is as the last ones you put out as well and thanks for the corrections. I think you made an interest in point about overblown Lows  as well and that’s a classic example of why can’t they update the algorithms /systems with data that would then output are more realistic option .

it will be great when we see the day when they can put in place, what you have suggested, and correct the software. 

[Spah1]

1 hour ago, steveinsussex said:

Eh? There has been no mention about rain this week ! If these mild sectors are now popping up then it’s new

We have been talking about it raining in the North West for 4 days. Stupid mild sector in the low. 

[Tamara]

1 hour ago, Windysun1 said:

So basically you cannot forecast with any great accuracy with these signals as there are too many variables?

No, totally the opposite as the post quite clearly explains. It is using the combination of the GSDM data that was discussed which is most inclusive. The MJO composites need to be used in conjunction with those parameters and other daily proxies.

[clark3r]

Icon has low further south affecting northern France and missing south uk

[wightwootton]

5 minutes ago, clark3r said:

Icon has low further south affecting northern France and missing south uk

Though, the cold is now extended to next Sunday!!!

[johncam]

9 minutes ago, clark3r said:

Icon has low further south affecting northern France and missing south uk

Did also note the -8 850's don't get that far south either 

[Anthony Burden]

Afternoon all,great write up from Matt H all models showing this very cold blast with still a possibility of snow in the south that has lingered on and off for a while. Then what looks like a milder spell that may well be short lived,with northern blocking perhaps showing up in the charts not so far away.The impact  of the blocking being assisted by the SSW.

[tight isobar]

I’m rallying this 12z gfs run..

[tight isobar]

Bummer .. still not completely shutting this 1 down just yet.. this is the crux of northward transfer!!.. I’ll still await ens.. nxt suites I think…@north west waver spoiler -

Edited January 14 by tight isobar

[Zero Visibility]

 

Not good unfortunately.

[Day_9]

The fact that the wheels come off so quickly is just more reason to not to pin your hopes on anything that a model shows as a possibility- particularly beyond a 4/5 day timeframe.

the global atmosphere is a chaotic system with so many variables that it is impossible to give anything other than broad outlines of possibilities.

Because severe cold and snow is so rare for a small Atlantic island, any hint of that as a potential outcome gets people understandably very excited….. and the fall from that elation is long and painful.

Many years of lurking on here tell me that the number of times snowmageddon forecast out at 240 actually verifies is probably in single percentage points.

 

[Day_9]

The ensembles show my earlier point almost every time.  Good clustering (consensus) up to 5, sometimes 6 days.  After that anyones guess.  
 

in this latest case I would say after the cold spell, the signal is for seasonally average with the possibility of milder or colder outbreaks ahead…..

[January Snowstorm]

Just wanted to say very well done to John Holmes who marked our cards a few days back that Westerly winds were imminent while the rest of us were drooling over charts. How right he was!!

All change for end of week as the Atlantic takes over again. Positives are the musings from the Strat that things still look favoured for further blocking. For me and going by experience it's at least 2 weeks back from chart below

[iowpompeylee]

The silence says it all…………. The low is dropping south….. all I can hope is for it to clip the Isle of Wight

[Drifter]

Siri, draw me the ugliest winter chart imaginable.  

[blizzard81]

It's just got to be said I'm afraid - you just can't possibly sugar coat the output today. It's awful. 

[Isleofwightsnowgal74]

5 minutes ago, iowpompeylee said:

The silence says it all…………. The low is dropping south….. all I can hope is for it to clip the Isle of Wight

Still time for change I guess?! Can someone say which models are showing what now and at what point does it become ‘nailed on’? Thankyou 

[TSNWK]

4 minutes ago, blizzard81 said:

It's just got to be said I'm afraid - you just can't possibly sugar coat the output today. It's awful. 

Where did the shuffling heights go?

[festivalking]

7 minutes ago, Isleofwightsnowgal74 said:

Still time for change I guess?! Can someone say which models are showing what now and at what point does it become ‘nailed on’? Thankyou 

ECM GFS ICON UKMO, they all say the front is in the channel. Cross model support I'd say its pretty certain. Yes there is a chance but we're just 48 hours from it now

Edited January 14 by festivalking

[James Maidstone]

43 minutes ago, Zero Visibility said:

 

Not good unfortunately.

Still talking about a 60 mile shift northwards for this run to bring the South into the game, marginal adjustments, unfortunately with UKMO, Icon and ECM all singing from the same hymn sheet, the odds are not in our favour.

[ANYWEATHER]

16 minutes ago, blizzard81 said:

It's just got to be said I'm afraid - you just can't possibly sugar coat the output today. It's awful. 

Yes, with high pressure forecast to build over mainland Europe ,it leaves the UK in Yuk Yuk territory. None descript weather with cloud laden south westerlies, wind ,rain especially for Northern Britain and mild ,perhaps very mild.