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Paul

Model output discussion - 16th Nov onwards

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The GFS 18hrs run has moved towards the ECM 12hrs run with that troughing digging south into the Atlantic, its not as amplified though.

 

The ECM ensembles are lukewarm about advecting colder air in towards De Bilt. So this looks like an operational run versus ensembles scenario at the moment.

 

We'll see tomorrow whether theres any legs in this, the ECM would still need to amplify that trough further even if it sticks to its trend.

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Despite the lacklustre 18z GFS op, worth watching how the  ridging over Canada and northern U.S behaves over the coming days, 12z (0.25) EPS mean shows this +ve height anomaly drifting N/NE towards Greenland out to day 15 as far as they go. This may perhaps allow a higher chance of the arctic flood gates opening towards mid-month, as the GFS has been hinting at in FI on recent ops.

 

I can't see the Polar Vortex completely falling part in December, very unlikely IMO, as it is very strong ... stronger than climo average for late Nov. Though it will at least get pulled/wobbled around by the ridges being forced by El Nino, such as the one over Canada. Also the strong Aleutian low modelled will certainly allow increased wave activity towards the pole in combo with the ridge to the east. So the pressure is on for the PV to remain intact as we head into January.

 

But of course that leaves us in a waiting game through much of December, probably, for any sustained cold and wintry spell. Brief arctic cold snaps certainly possible as the trop vortex gets stretched around again.

 

EDIT, updated EPS weeklies now out and the control shows the Canadian ridge drifting NE across the far north Atlantic from day 20, while a trough drops down over mainland Europe.

Edited by Nick F

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Thanks Nick F :)

Tentative signs that the Euro high may well give way,hopefully some momentum in the coming days for something along those lines..

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As said by Nick GFS is a lot more robust but attempts to follow the ECM passage.

 

gfsnh-0-234.png?18

 

ECH1-240.GIF?30-0

 

Give those mobile users some insight. 

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Thanks Nick F :)

Tentative signs that the Euro high may well give way,hopefully some momentum in the coming days for something along those lines..

 

Certainly the signs are from the 12z  EPS and GEFS mean to dampen the Euro high anomaly by day 10-15 as the ridge over Canada shifts NE, it's a big +ve Euro high anomaly over the next few days for sure and one we want to go away to get any countrywide cold from the strong PV as it is.

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GFS 00z is shockingly bad if you are looking for any sign of blocking setting up mid Dec.

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A brief overview of the latest EC32 update

 

Starting on the 10th December with a familiar story. Low pressure over the Aleutians and Greenland with troughs NE Atlantic and eastern Europe. Flattish across N. America and HP to the SE of the UK.  Thus pretty much a Scotland/England split with the HP being quite influential further south and temps above average in the latter.

 

In the next week up to the 17th little change except the trough moves east over the UK doing away with any ridging so a more zonal unsettled flow for all of the UK and temps around average.

 

From there to the 24th no significant change except perhaps the HP again pushing up a little from the south thus backing the general flow a tad.

 

From then on until January the first, this being the broad brush output, no strong signal for anything except a zonal westerly with temps around average.

 

Summary

 

After a spell around the 11th -14th when HP builds briefly from the west/south west the rest of the run can be described as zonal with an interplay between the Pm and Tm air and tending towards a N/S split over the UK with much of the wintry stuff being confined to the north. Temps around average but dip below in the north during the transition NE tracking depressions and perhaps above further south with the more balmy interludes.

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A brief overview of the latest EC32 update

Starting on the 10th December with a familiar story. Low pressure over the Aleutians and Greenland with troughs NE Atlantic and eastern Europe. Flattish across N. America and HP to the SE of the UK. Thus pretty much a Scotland/England split with the HP being quite influential further south and temps above average in the latter.

In the next week up to the 17th little change except the trough moves east over the UK doing away with any ridging so a more zonal unsettled flow for all of the UK and temps around average.

From there to the 24th no significant change except perhaps the HP again pushing up a little from the south thus backing the general flow a tad.

From then on until January the first, this being the broad brush output, no strong signal for anything except a zonal westerly with temps around average.

Summary

After a spell around the 11th -14th when HP builds briefly from the west/south west the rest of the run can be described as zonal with an interplay between the Pm and Tm air and tending towards a N/S split over the UK with much of the wintry stuff being confined to the north. Temps around average but dip below in the north during the transition NE tracking depressions and perhaps above further south with the more balmy interludes.

Not the best update for anyone hoping for a pattern change, hard to see that being too far away from correct over the next few weeks, further on there is always a chance. GFS has dropped its Greenland high signal again too.

As the METO have suggested, this year we may have to wait for some SSW, this could still deliver some very cold periods in Jan/Feb.

It would be great to see some cold weather coming for the Xmas week though...

Edited by Ali1977

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The change in the extended ens over the past day or two is to keep at least a chunk of vortex on the Canadian side. would have been nice to have it located only on the Asian side but seems that a step too far for the time being.

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ECM1-144.GIF?01-12

UW144-21.GIF?01-06

ukmo and ecm 144hrs identical 

 

gfs-0-144.png?0

gfs having none of it 

 

gens-0-1-144.png

gefs messy very much the same not really showing the same possibilities the ecm and ukmo show this morning.

 

but the gem pretty much at 144hrs inline with ukmo and ecm

gem-0-144.png?00

ecm 216 well all i can see is continued flattening of any heights that try to block.

 

and the 240 shows this well.

ECM1-240.GIF?01-12

Edited by emotional rollercoaster

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This morning's GFS has the nasty looking low on Sunday tracking to the NW of Scotland. Would briefly bring some strong winds to the Hebrides but as mentioned yesterday need keep a beady on it.

Chart weatherbell

 

post-12275-0-13807000-1448953078_thumb.p

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Some of the charts posted at the moment have the look of the super zonal periods of the 90s

Whilst it is too early to make a judgement on the second half of December , it looks highly likely the first half will be remembered as mild, wet and potentially stormy

I imagine a couple more named storms will be christened in the next few weeks

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certainly different 09 

 

Rrea00120091201.gif

Rrea00119971201.gif

dec 1st 1997 would think by these charts winter 97/98 would of been a cold one.

i certainly dont think scotland wont go without this winter.

 

its about time the vortex took a good beating 3 years in a row its run the show been awhile since a decent ssw event maybe we will be lucky later in december but i wont hold my breath.

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GFS lost its atlantic blocking pattern in FI on the 18z & 0z as predicted.

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The ecm is still running this low very quickly through Scotland with gusts around 70kts in northern England.

 

post-12275-0-86276300-1448955984_thumb.p

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The ec32 mean, week three and four, certainly allows for some polar incursions

Around mid month and again between xmas and new year being the favoured periods

im sure Ian will advise re the clusters later

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First day of winter..lol..it feels more like spring! knockers daffs will be loving this.:)

post-4783-0-09726200-1448957703_thumb.pn

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Whilst waiting for something colder and looking through the latest set of GEFS ensembles my attention is being drawn to the chances of a notably severe windstorm in the 5 -10 day period. There are several near misses and 3 -4 direct hits. (example attached) so maybe a 20% chance of something particularly severe at the moment.

post-23399-0-90986200-1448958184_thumb.p

post-23399-0-90986200-1448958184_thumb.p

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Overall today the theme from yesterday continues with the digging trough in the west Atlantic but not as amplified, this leads to less pressure build north.

The ECM at T240hrs does suggest some changes upstream with more amplitude developing into the central USA this could develop a more nw/se jet track into Europe.

The PV at this stage has split into several lobes and so prospects for at least more PM incursions increase especially if more amplitude upstream verifies.

I think the trend is likely to see less milder interludes and more cooler/colder days as we head towards mid month, as for anything substantial its a wait and see for the timebeing.

If the nw/se jet track does happen this normally comes in tow with pressure rises towards Svalbard , the issue of course is whether the jet relents sufficiently to allow that to have a bigger say.

 

 

Edited by nick sussex

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31 minutes ago, nick sussex said:

Overall today the theme from yesterday continues with the digging trough in the west Atlantic but not as amplified, this leads to less pressure build north.

The ECM at T240hrs does suggest some changes upstream with more amplitude developing into the central USA this could develop a more nw/se jet track into Europe.

The PV at this stage has split into several lobes and so prospects for at least more PM incursions increase especially if more amplitude upstream verifies.

I think the trend is likely to see less milder interludes and more cooler/colder days as we head towards mid month, as for anything substantial its a wait and see for the timebeing.

If the nw/se jet track does happen this normally comes in tow with pressure rises towards Svalbard , the issue of course is whether the jet relents sufficiently to allow that to have a bigger say.

 

 

Very good assessment. Developments upstream will be the key to the jet speed and profile. Until we get something to disrupt matters its more of the same for next 10 days. Of course the feeling often is that early winter in El Nino years can be dominated by an active jet and ostensibly mild conditions with the colder weather towards winters end. It will be good to test this theory now that we have this mild start.

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5 hours ago, mountain shadow said:


Steve, mid to long term modelling has improved so much over the last few years that sudden unexpected cold spells are extremely unlikely to happen.

I think that's why it's less fun on here.


So, even here on the 1st of December we can write off any cold spell as a result of Northerly blocking. 

 

Mountain in all honesty how can you say "So, even here on the 1st of December we can write off any cold spell as a result of Northerly blocking." Are you saying there is zero chance of Northern blocking for the entirety of Winter of the very first day of it? Absolute bonkers. Posts like that is why it's less fun here

Edited by -Bomber-

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Little to show yet on anomaly charts of any marked change in next two weeks

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2 minutes ago, johnholmes said:

Little to show yet on anomaly charts of any marked change in next two weeks

 

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29 minutes ago, -Bomber- said:

Mountain in all honesty how can you say "So, even here on the 1st of December we can write off any cold spell as a result of Northerly blocking." Are you saying there is zero chance of Northern blocking for the entirety of Winter of the very first day of it? Absolute bonkers. Posts like that is why it's less fun here

Well, the models aren't showing it, so it is a fair point. I don't think he meant to say that there is no chance of any northerly blocking for the next 3 months, but more that there isn't anything to make it seem likely the next two weeks or so.

 

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