The Weather Outlook

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Retron
29 December 2024 16:03:20
The 12z GFS continues to ramp up the winds... widely in the high 60s or 70s. Atrocious once more, and it's getting that much closer now. I'd give anything for the ICON solution instead!

EDIT: And the MetO raw is up to 59 now, which is the highest it's shown here for several years. Not good!

https://www.theweatheroutlook.com/charts/gfs/12_78_windvector_gust.png 

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Leysdown, north Kent
Brian Gaze
29 December 2024 16:03:46
GFS still showing >70mph gusts on New Year's Day in the south.

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Brian Gaze

Berkhamsted

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Brian Gaze
29 December 2024 16:08:09
Arpege 12Z not as bad.

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Brian Gaze

Berkhamsted

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Retron
29 December 2024 16:15:47

Arpege 12Z not as bad.

Originally Posted by: Brian Gaze 

It's lower than whatever the MetO raw uses, and I'd be happy enough with that - IME bad things start to happen above 60, and above 70 is when the really expensive stuff starts happening (e.g. roof tiles falling on cars).

I'm not sure what it is about GFS that means it prefers to ramp up wind speeds. So far this autumn/winter it's been 3-1 to GFS vs MetO, or in other words three times the MetO raw has gradually crept up to whatever GFS was showing all along. The exception was the last storm, where the lower MetO values ended up being the correct ones (and GFS downgraded at the last minute).

EDIT: And wind aside, the 12z GFS goes on to develop a massive dump of snow in the south, as a low stalls and gets shredded. Just goes to show how small changes upstream make the difference between a quick collapse and an old-school battleground. I'd still feel happier though if it would just downgrade the wind!


Leysdown, north Kent
ballamar
29 December 2024 16:23:03
GFS OP run buries the south next weekend! All change again and as someone used to say JFF
doctormog
29 December 2024 16:25:33

GFS OP run buries the south next weekend! All change again and as someone used to say JFF

Originally Posted by: ballamar 

This GFS op run is broadly similar (at this stage) to the 00z op run.


ballamar
29 December 2024 16:29:28

This GFS op run is broadly similar (at this stage) to the 00z op run.

Originally Posted by: doctormog 

Yep pointless looking at detail but consistency of the pattern will be important - the key is still the low midweek and the track of this will define much of what comes after. 

On that point it looks nasty midweek especially with a lot of travelling taking place.

Ally Pally Snowman
29 December 2024 16:34:06
GFS 12z is back with a bang. An absolute beauty.  One day a run like this will actually happen. 
Bishop's Stortford 85m ASL.
Retron
29 December 2024 16:36:56

GFS 12z is back with a bang. An absolute beauty.  One day a run like this will actually happen. 

Originally Posted by: Ally Pally Snowman 

Yes, once the snow comes down it hangs around, and just look at those minima over the snowfields... a classic run in the end.

https://www.theweatheroutlook.com/charts/gfs/12_225_uksnowdepth.png 

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https://www.theweatheroutlook.com/charts/gfs/12_228_uk2mtmpmin.png 

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Leysdown, north Kent
Chunky Pea
29 December 2024 16:38:02

It's lower than whatever the MetO raw uses, and I'd be happy enough with that - IME bad things start to happen above 60, and above 70 is when the really expensive stuff starts happening (e.g. roof tiles falling on cars).

I'm not sure what it is about GFS that means it prefers to ramp up wind speeds. So far this autumn/winter it's been 3-1 to GFS vs MetO, or in other words three times the MetO raw has gradually crept up to whatever GFS was showing all along. The exception was the last storm, where the lower MetO values ended up being the correct ones (and GFS downgraded at the last minute).

EDIT: And wind aside, the 12z GFS goes on to develop a massive dump of snow in the south, as a low stalls and gets shredded. Just goes to show how small changes upstream make the difference between a quick collapse and an old-school battleground. I'd still feel happier though if it would just downgrade the wind!

Originally Posted by: Retron 

I find the GFS is usually in and around the mark for winds and wind speed. Regarding storm tracks, the UKMO is typically the best model to watch in my opinion. And if the ECMWF is your thing, the Estonian Met Office have some nice hourly maps with a number of parameters available, including mean wind and gust speed in a clean and easy to read format. 

https://www.ilmateenistus.ee/ilm/prognoosid/mudelprognoosid/euroopa/?lang=en#layers/tuul106g,presmslp 


Patrick,

East Galway, Ireland.

Gandalf The White
29 December 2024 16:57:33

This GFS op run is broadly similar (at this stage) to the 00z op run.

Originally Posted by: doctormog 

Yes, and as I think you intimated earlier, and as has been noted before, the 00z and 12z are the two more reliable runs of the four, in that order.

It’s all still very messy in terms of precision about what might fall from the sky, how much and where, as is to be expected so far ahead.


Location: South Cambridgeshire

130 metres ASL

52.0N 0.1E



Gandalf The White
29 December 2024 17:03:34
It seems a long while since we could say the main arm of the jet stream was aiming for North Africa

https://www.meteociel.fr/modeles/gfse_cartes.php?ech=204&code=code&mode=5&mode3h=0&runpara=0&carte=1 


Location: South Cambridgeshire

130 metres ASL

52.0N 0.1E



Brian Gaze
29 December 2024 17:08:03

Yes, and as I think you intimated earlier, and as has been noted before, the 00z and 12z are the two more reliable runs of the four, in that order.

It’s all still very messy in terms of precision about what might fall from the sky, how much and where, as is to be expected so far ahead.

Originally Posted by: Gandalf The White 

There's really not much difference.

The anomaly coefficients at t+5 days:

00Z, 12Z: 0.893

06Z, 18Z: 0.890

See:

https://www.emc.ncep.noaa.gov/users/verification/global/gfs/prod/atmos/long_term/images/evs.global_det.gfs_4cycles.acc.hgt_p500.past10years_monthly.timeseriesdiff_init00z06z12z18z_f120.g004_nhem.png 


Brian Gaze

Berkhamsted

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Gandalf The White
29 December 2024 17:11:47

There's really not much difference.

The anomaly coefficients at t+5 days:

00Z, 12Z: 0.893

06Z, 18Z: 0.890

See:

https://www.emc.ncep.noaa.gov/users/verification/global/gfs/prod/atmos/long_term/images/evs.global_det.gfs_4cycles.acc.hgt_p500.past10years_monthly.timeseriesdiff_init00z06z12z18z_f120.g004_nhem.png 

Originally Posted by: Brian Gaze 

Thanks, but I was talking about the period beyond 5 days, where the 06z threw up a very difffent evolution - for whatever reason.

IIRC the 00z and 12z are populated with the most up to date data?


Location: South Cambridgeshire

130 metres ASL

52.0N 0.1E



Jiries
29 December 2024 17:13:27

Look at France miss out the cold and here so cold!  Hope to see lot snow events from Wed and to the  weekend.

Brian Gaze
29 December 2024 17:16:12

Thanks, but I was talking about the period beyond 5 days, where the 06z threw up a very difffent evolution - for whatever reason.

IIRC the 00z and 12z are populated with the most up to date data?

Originally Posted by: Gandalf The White 

At t+10 days the 12Z is marginally more accurate than the others. That said, there isn't a neck in it and I would think the latest run would be better at t+240 than the previous one at t+246.

https://www.emc.ncep.noaa.gov/users/verification/global/gfs/prod/atmos/long_term/images/evs.global_det.gfs_4cycles.acc.hgt_p500.past10years_monthly.timeseriesdiff_init00z06z12z18z_f240.g004_nhem.png 


Brian Gaze

Berkhamsted

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"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan

Ally Pally Snowman
29 December 2024 17:17:02

Look at France miss out the cold and here so cold!  Hope to see lot snow events from Wed and to the  weekend.

Originally Posted by: Jiries 

We can but dream Jiries. 


Bishop's Stortford 85m ASL.
Brian Gaze
29 December 2024 17:18:43
The CMC run raises questions.

Edit: GEFS look very mixed.

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Brian Gaze

Berkhamsted

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Rob K
29 December 2024 17:29:58
12Z GFS op run would deliver the coldest day for much of England since 1987, maxima of -6C in the south… about as likely as me scooping the Euromillions this week (and I haven’t bought a ticket).
Yateley, NE Hampshire, 73m asl

"But who wants to be foretold the weather? It is bad enough when it comes, without our having the misery of knowing about it beforehand." — Jerome K. Jerome

Rob K
29 December 2024 17:33:23

Edit: GEFS look very mixed.

Originally Posted by: Brian Gaze 

Comparing the 12Z to 6Z GEFS out to 192, the initial cold is prolonged a bit but we still have a very pronounced split by day 7. Maybe a few more on the mild side than the 6Z had, but the op run is (no surprise) in the cold set. 


Yateley, NE Hampshire, 73m asl

"But who wants to be foretold the weather? It is bad enough when it comes, without our having the misery of knowing about it beforehand." — Jerome K. Jerome

Retron
29 December 2024 17:35:53

12Z GFS op run would deliver the coldest day for much of England since 1987, maxima of -6C in the south… about as likely as me scooping the Euromillions this week (and I haven’t bought a ticket).

Originally Posted by: Rob K 

Well, there's a 10x higher than normal chance of winning a million of you *did* have a ticket, as it's a special superdraw for New Year's Eve.

That said, assuming you have a ticket, you're still more likely to win that million than have the 12z GFS op come off, I reckon! 😂

On a more serious note, despite the damaging winds still shown on the op, the ensembles have ever so slightly toned things down. Long may that trend continue.


Leysdown, north Kent
Taylor1740
29 December 2024 17:39:34
Ensembles are the key rather than opp runs and unfortunately they are trending in the wrong direction for cold weather fans.
NW Leeds - 150m amsl
idj20
29 December 2024 17:40:27
Almost like old times in here, it's 2009 all over again but thankfully without the working in tomato greenhouses part. 😂

GFS continue to ramp up wind speeds across Kent on Wednesday evening, touching 80 mph gusts, albeit briefly (mercifully). UKMO and the lesser known GEM appears to be showing toned down versions and the ICON is showing it even completely bypassing to our south, so it's still not set in stone and can expect some downgrades. Wonder what the mighty ECM might come up with.

As for the "good stuff" beyond, I might start snow-hoping once we get Wednesday's rough stuff out of the way but I suspect it'll all have evaporated to nothingness by then. 🤣


Home location: Folkestone Harbour.

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