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Model output discussion - heading into 2018

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2 hours ago, northwestsnow said:

EC snow lottery charts now show the bulk of the precip missing the midlands!!

Incredible stuff!

Yes incredible alright, even further south on the 18z runs .:blink2:

J84-594.gif

icon-2-81.png

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25 minutes ago, Catacol said:

For those hoping for some cold and seasonal weather heading into January the signals have taken a significant turn for the worse. Negative anomalies in the tropical western pacific forecast to be removed altogether, allowing a big surge in trade winds and removal of AAM from extratropical regions

twc_globe_mjo_vp200.png

 

Vortex profile also now forecast to grow substantially, with the 10 day Berlin chart not making pretty reading - unless westerly influence at mid latitudes is what you are after... 

[ECMWF 240 hour forecast from December 22 2017 12 UTC to January 1 2018 12 UTC: zonal mean zonal wind]

Loss of AAM at 10 days now sees ensemble data remove pretty much all high lat blocking, with high pressure instead forming a neat belt around most of the hemisphere in mid latitudes. As Cohen has reported recently, this is really a setup now pointing at a mild January with cold bottled up in the arctic. 

If blank, model image not available

All of this is then reflected in the excellent GWO tool - for the first time in a good while the spiralling rise in GLAAM has zigged back towards 7.00 on the phase chart... and we are headed now for a period of phase 1-2-3 activity.... low on blocking and high on westerlies in a more "classic" Nina setup.

gwo_fnl.thumb.png.90e3ace906df8340abb5cae10577d566.png

It has been a sudden and somewhat unexpected turnaround. There was no suggestion of a sudden removal of tropical pacific convection strength: indeed the NOAA report of only a week ago saw a slow and steady movement through 7/8.. and ongoing wave 1 activity via favourably positioned blocks had kept the vortex quiet. So what has changed? A very good question. I scan the web and twitter pretty frequently and have not spotted an explanation yet: only observed reality and a prognosis for the next 15 days brought in line with observed data. We know from IF that Glosea suddenly lost its SSW signature... and we can see that the massive surge of heights into the arctic from alaska is now forecast to moderate very quickly and be suppressed. What is driving this? Has Nina simply won the day? Is a warming world making composite data and analysis less accurate? Has extreme arctic sea ice loss got wider ramifications than we are currently aware of? 

We will see what comes out of this analysis as the days/weeks progress because I'm sure some of the big guns out on twitter will have their say in time... but for now it might be a good time to take a break from model watching. Current conditions will take a good 2 weeks to play out - maybe closer to 3 or 4. Winter is not over yet by a long chalk... but we we will need to see factors alter again if the drivers that create the NWP are to produce some better eye candy. For a while the best we can hope for is some mid lat blocking to take the sting out of the atlantic and give some calm, chilly maybe frosty days. MetO forecasts hint at exactly this I think. 

Well that’s added a rather urine flavour of gravy to the festive Turkey. Half of Jan at least written off cold & snow wise? Well at least the NW servers can take a break, as can the coldie members.

Edited by Southender

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maybe snowy, NW Midlands? I expect this to be modeled much further south though, in next few days, M4 southwards to have any possible snow

gfs-0-78.png?18

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2 minutes ago, I remember Atlantic 252 said:

maybe snowy, NW Midlands? I expect this to be modeled much further south though, in next few days, M4 southwards to have any possible snow

gfs-0-78.png?18

Yup showing further north the on the GFs 18z.

gfs-2-84.png

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2 minutes ago, snowray said:

Yup showing further north the on the GFs 18z.

gfs-2-84.png

Ay, I don't expect to get lucky twice, temporary northerly not bad either!

gfs-0-96.png?18

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Not great news Catacol but excellent analysis all the same. That really helped a rank amateur gain an understanding of some of the global factors at play. Many thanks. 

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46 minutes ago, Catacol said:

For those hoping for some cold and seasonal weather heading into January the signals have taken a significant turn for the worse. Negative anomalies in the tropical western pacific forecast to be removed altogether, allowing a big surge in trade winds and removal of AAM from extratropical regions

twc_globe_mjo_vp200.png

 

Vortex profile also now forecast to grow substantially, with the 10 day Berlin chart not making pretty reading - unless westerly influence at mid latitudes is what you are after... 

[ECMWF 240 hour forecast from December 22 2017 12 UTC to January 1 2018 12 UTC: zonal mean zonal wind]

Loss of AAM at 10 days now sees ensemble data remove pretty much all high lat blocking, with high pressure instead forming a neat belt around most of the hemisphere in mid latitudes. As Cohen has reported recently, this is really a setup now pointing at a mild January with cold bottled up in the arctic. 

If blank, model image not available

All of this is then reflected in the excellent GWO tool - for the first time in a good while the spiralling rise in GLAAM has zigged back towards 7.00 on the phase chart... and we are headed now for a period of phase 1-2-3 activity.... low on blocking and high on westerlies in a more "classic" Nina setup.

gwo_fnl.thumb.png.90e3ace906df8340abb5cae10577d566.png

It has been a sudden and somewhat unexpected turnaround. There was no suggestion of a sudden removal of tropical pacific convection strength: indeed the NOAA report of only a week ago saw a slow and steady movement through 7/8.. and ongoing wave 1 activity via favourably positioned blocks had kept the vortex quiet. So what has changed? A very good question. I scan the web and twitter pretty frequently and have not spotted an explanation yet: only observed reality and a prognosis for the next 15 days brought in line with observed data. We know from IF that Glosea suddenly lost its SSW signature... and we can see that the massive surge of heights into the arctic from alaska is now forecast to moderate very quickly and be suppressed. What is driving this? Has Nina simply won the day? Is a warming world making composite data and analysis less accurate? Has extreme arctic sea ice loss got wider ramifications than we are currently aware of? 

We will see what comes out of this analysis as the days/weeks progress because I'm sure some of the big guns out on twitter will have their say in time... but for now it might be a good time to take a break from model watching. Current conditions will take a good 2 weeks to play out - maybe closer to 3 or 4. Winter is not over yet by a long chalk... but we we will need to see factors alter again if the drivers that create the NWP are to produce some better eye candy. For a while the best we can hope for is some mid lat blocking to take the sting out of the atlantic and give some calm, chilly maybe frosty days. MetO forecasts hint at exactly this I think. 

A great post...however...

It really depends what you define as unexpected. It certainly wasn't unexpected as far as myself and a couple of others on here were concerned. A +NAO winter has also been fairly well signposted by the longer range seasonal modelling for some months now. 

It was the same last year where the amplified trop pattern suddenly collapsed, which then precluded any HLB for pretty much the rest of winter (with the caveat that some of the seasonal tools actually saw a winter dominated by HLB).

For a time in early December it looked like we may go on to see a SSW this year, this actually increased my optimism as in my eyes it was essential we saw a late Dec/early Jan SSW as the effects of the amplified trop led state wore off. Alas, it now doesn't look like we will see this and so my faith in January producing anything of note has gone back through the floor.

Edited by CreweCold
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8 minutes ago, Frosty. said:

We coldies are used to things taking a turn for the worse but live in hope that one day things will take a turn for the better!:drinks::santa-emoji:

Way too much time spent perusing the PEAR model!:shok:

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Quite a solemn post from Catacol for coldies but a very good post. Well currently we’re seeing a primarily westerly flow yet we’re looking at a potential snow event(s) Christmas week. We can squeeze transient wintriness I'm sure, however no HLB expected however there’s still interest in GEFS in la la land what makes me curious. Again with the last cold spell the NAO was largely neutral to positive, a decent block is not crucial perhaps so for deep cold.

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1 minute ago, I remember Atlantic 252 said:

Snowfest north, FI yet, but could this thing upgrade? likely not though

h850t850eu.png

The cold in the east is certainly more pronounced and putting up more of a battle with the Atlantic on this afternoon/evenings runs, could be a fair bit of snow around with sliders and battleground events coming up next week.

gfs-1-114.png

gfs-1-132.png

gfs-2-90.png

gfs-2-138.png

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Just now, January Snowstorm said:

Interesting that many of the experts are predicting a mild fest ahead whilst the models continue to upgrade the short term. Many parts could see at least falling snow over next 5 days yet I struggle to remember anyone predicting it.....

I think it was said the other day that this is likely to be the last gasp of the more amplified pattern we saw set up in November through early December.

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1 minute ago, CreweCold said:

I think it was said the other day that this is likely to be the last gasp of the more amplified pattern we saw set up in November through early December.

No. The other day? This has been signalled for a good few days, before that not a peep was said by anyone. Very early this week most were calling it a day not a flake till next year at the earliest most were saying. Even Nick S himself said he was on the verge this has sort of come out the blue, we can get lucky some might have the impression it takes something exceptional to get wintry weather in UK it sometimes feels it. 

There isn’t really any amplification it’s fluid, again conveying it’s not a crucial element for wintry weather anywho.. we have managed these small wedges of +ve heights to N/NW, very hard to foresee. 

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10 minutes ago, snowray said:

The cold in the east is certainly more pronounced and putting up more of a battle with the Atlantic on this afternoon/evenings runs, could be a fair bit of snow around with sliders and battleground events coming up next week.

gfs-1-114.png

gfs-1-132.png

gfs-2-90.png

gfs-2-138.png

Agreed, appears the uppers have upgraded too...I made a post the other day to watch for the 29th. At least some transient snowfall looks like a good possibility to me. 

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Thats a great looking chart there John from the old JMA, I still think that there could be a few surprises coming up.:rolleyes:

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2 minutes ago, Daniel* said:

Agreed, appears the uppers have upgraded too...I made a post the other day to watch for the 29th. At least some transient snowfall looks like a good possibility to me. 

Yes the uppers have also improved a fair bit too, particularly for the south.

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6 minutes ago, Johnp said:

Interesting extended JMA rolling out now, looks rather blocky to the east.

5253DBE9-25D2-4198-8F11-7AA361DE3547.gif

The uk just needs moving several hundred miles further east and then we could be in business:santa-emoji::D:cold-emoji:

Edited by Frosty.

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9 minutes ago, Johnp said:

Interesting extended JMA rolling out now, looks rather blocky to the east.

5253DBE9-25D2-4198-8F11-7AA361DE3547.gif

Quite similar to some of GEFS especially perturbation 8 we coldies need to salvage all what we can. :D I thought the height rises to NE signal would have waned but not quite! 

Edit oops morning - ignore not seen latest. Wait is there something faulty? 00z is all I can get up.

88C8C2FC-70C4-4DA9-9906-1233328B55F1.thumb.png.787ef15cb536996ae4d41fac6323820c.png172E12A1-3065-4018-A4DC-A255C03BD55C.thumb.png.42a452ee056a6dbd6e1819703a4e0158.png

C3BE2477-0577-4C7C-94EE-0A30731D8F8E.thumb.png.ee0cde9cad7e27036613b83104d829d5.png2692C2C9-8293-40EE-B0D9-F7D1C924D7E2.thumb.png.8892c3fc436c2f0979a1fc54f13a88ce.png

Edited by Daniel*
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Just now, Frosty. said:

The uk just needs moving several hundred miles further east and then we could be in business:santa-emoji::D

Or that atlantic trough to dig south more negatively aligned with its parent one thus being in a more favourable undercutting position.

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Been taking it easy for a change but one thing I have noticed is that the MJO in the Pacific, having a few days ago been predicted by all models to decay away by early Friday, has instead remained active and slow-moving.

As per CPC’s expectations of a week or so ago.

An atypical C-Pac SST state for La Niña supports this observed deviation from the models.

So... I’m not entirely convinced about the proposed sudden removal of WPAC tropical convection. It may still wane but perhaps only for a short while? Possibly GP was hinting at this the other day...?

Hmm.

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