Mid-Winter: Forecast and Model Discussion commentary

[That ECM]

 I remember Atlantic 252 sure?

[HarvSlugger]

GFS is actually looking better at 72 hours now

 

[MJB]

Snow moving in 

[Jacob]

At 78h the low wiedly stops heading north on the GFS 12z. Good sign?

[V for Very Cold]

For a complete amateur like me, could posters help me with 2 things

i) post images to explain what they are talking about 

ii) explain trends rather than snapshots and instant judgements of a particular frame?

 

thank you in advance

Edited January 1 by V for Very Cold

[MJB]

 HarvSlugger Love your enthusiasm Harv BUT GFS is more consistent than you   

[Neilsouth]

 clark3r I have no confidence in any of the models at the moment I'm afraid

[Ali1977]

That’ll do nicely ️️ before the rain starts 

Edited January 1 by Ali1977

[TSNWK]

Looks a bit north / but more slidey 

[Paul]

I think when it comes to some of the more emotional and strong reactions to individual runs, maybe a bit of perspective can help. Take the GFS, including it's ensembles it's essentially being run 88 times a day. With that in mind, is it really worth getting too hung up on the variance between the operationals run to run?

[HarvSlugger]

 MJB im learning!

I will never speak at the start of a run

[I remember Atlantic 252]

iffy at 90

[Mcconnor8]

GFS more slidey, better than 6z imo.

[Neilsouth]

 Jacob The slower the low moves into the south and the later it does will benefit far more of us! Really don't want it pushing through quickly during the day when temps and dewpoints are higher

[wellington boot]

 Mike Poole Yes, that was what i wondered, whether anyone had a historical perspective, as well as a more sophisticated understanding of it's progression and behaviour. 

Some further reading has answered some of my questions I think. I was reminded that it doesn't simply relate to a particular period of a phenomenon that persists through 360 degrees - it only exists at all between the Western Indian Ocean and the western Pacific. Hence to extent that effects are observed, they build over the warm Indian Ocean and then fade away over the colder waters of the Pacific. Notwithstanding your comment that the correlation isn't perfect, amplitude through phases 7/8, which does appear consistently to drive colder conditions in the UK and across Europe, is much less likely to occur, because phases 7 and 8 are at the end of the MJO cycle, where that pulse of convective energy does typically die away over cooling Pacific waters.

Thinking about it, it clearly ties in interestingly with considerations around ENSO, which on its own is often described as weakly affecting conditions in the European sector. I can see how ENSO and MJO will interact and how that might explain the real but indirect and therefore weak/inconsistent impact of ENSO on our weather.

[TSNWK]

 Mcconnor8 0 850 further north by about 50 miles though.

[Mike Poole]

 Mcconnor8 There’s something else at work here other than just north south position of Azores low and Greenland heights, something seems to affect the orientation of the low as it approaches the UK, meaning this run looked worse than it actually was.

[Mr Marky Marky]

Damn

 

@icecold I just did

Edited January 1 by Mr Marky Marky

[Mcconnor8]

 Mike Poole Yep it looked further North at T48 but the low elongates more and moves further South later on.

[ICE COLD]

Don’t look at the UKMO

[WYorksWeather]

Best not to jump to conclusions too early in a run - by day 4 GFS is slightly further north and east with the mild air but it really is the subtlest of shifts, not much to worry about. 12z on the left, 6z on the right.

These sort of changes at this range are really nothing to worry about. The start of the run didn't look great, but in the end that's what, a 20-30 mile shift? To put that in perspective, that's about one or two model grids given the GFS resolution!

Let's see what happens later in the run.

[Mcconnor8]

So we have ICON looking the best, GFS looking slightly better than before, and UKMO/Arpege looking poor.

[Ice Day]

Not an ideal UK at 96 compared to the GFS with the rounder low.  That said, the 120/144 will likely still be reasonable.

 

[smith25]

 Mcconnor8 what's the AI models now?

[Penicuikblizzard]

 Mcconnor8 ukmo isn’t poor for the north