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Winter Model Discussion 12Z 15/1/13 onwards.


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Posted
  • Location: Ramsgate,East Kent.
  • Weather Preferences: BEASTERLYS
  • Location: Ramsgate,East Kent.

Quality charts there Gavin - It's such a fine line at the moment, some special I feel is brewing up come Friday & into the weekend with the Atlantic throwing these lows across the west country before easing over to the East. These types of setups are very good for the West and even the East as the preciptiation generally intensifies once it crosses the midlands / pennines to dump a load over them too. From a IMBY perspective this couldnt be far from great for us in the North West, with always the potential of stalling as the low's meet the block out in the East.

I think one thing for sure is, someone, somewhere is going to get an almighty dumping. I just hope it's in my back garden tease.gif

But surely is will be in long run introducing milder air, and i notice on those snow totals that there is not mch deph if any for the south and south east.

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Posted
  • Location: Penwortham nr Preston, Lancashire
  • Weather Preferences: Severe frosts, warm sunny summers,
  • Location: Penwortham nr Preston, Lancashire

A rare post from me. A question for the knowledgeable:

The Met Office have a snow warning for Friday in the south west:-

http://www.metoffice...ings.html?day=4

but the fax chart for 96 hours does not show this as far as I can tell.

http://www.netweathe...s;type=fax;sess=

Where am I going wrong?

Many thanks,

Mike.

That fax chart is showing an occluded approaching the Southwest, the true warm sector is way down in Southwest France, as the front approaches, the cold air stays for some time (warm air rises), think it was Piers Corbyn who alikend it to water over treacle. Dew points maybe a little on wrong side of marginal according to the GFS around coasts and far far southwest, but this is different to what the fax is showing.

As always the met are giving a heads up too, depending how things change over the next day or two that amber is likely to change, as the Southwest tends to get the most severe snow falls in the uk or nothing at all. so that warning could dissappear or turn red

Edited by Nick JB
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Posted
  • Location: Swansea South West Wales
  • Weather Preferences: Cold and Snow in winter Warm Sunny Summer
  • Location: Swansea South West Wales

That fax chart is showing an occluded approaching the Southwest, the true warm sector is way down in Southwest France, as the front approaches, the cold air stays for some time (warm air rises), think it was Piers Corbyn who alikend it to water over treacle. Dew points maybe a little on wrong side of marginal according to the GFS around coasts and far far southwest, but this is different to what the fax is showing.

As always the met are giving a heads up too, depending how things change over the next day or two that amber is likely to change, as the Southwest tends to get the most severe snow falls in the uk or nothing at all. so that warning could dissappear or turn red

Another point would be that the cloud associated with a frontal system is always ahead of the frontal boundary, so the front on the chart may show to be sitting in the irish sea or south west approaches, but the cloud would be ahead of the boundary along with the precipitation line.

Hope that helps too.

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Posted
  • Location: Near Keele, North Staffs
  • Location: Near Keele, North Staffs

TBH I think we would all be better served if the jet takes the depressions into France as that would allow pressure to the north to build and we would no doubt get a good cold spell out the resultant easterly. Short term pain but a big long term gain! These undercutting situations can be good for initial snowfall but over the years I recall many more dissapointments than big snowfalls. The 06 run is renowned as being unreliable but setting that aside it seems to me that the ensembles have very strong agreement to bring in the Atlantic.

GFS shows a big snowfall later this week, but i'm far from convinced as GFS often overdoes these events. Also, as others have said you can end up with six inches of snow falling and next to nothing settling.

It may all change later this afternoon but a big 12z this afternoon and we need to see further adjustments south given that timeframes are getting a little tight for major changes. I personally think we will get the nudge south but thats based on gut feeling rather than anything else and as of now even the pro's would be hard pressed to be certain.

Jason

Depends where you live Jason, I'm interested in big snow events and I'm not going to get one if what you describe occurs.

Looks like the METO have 'reacted' today to the GFS/ECM output for Friday as the warning differs markedly from the text of their forecast issued in the early hours of this morning.

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Posted
  • Location: Norfolk
  • Location: Norfolk

Depends where you live Jason, I'm interested in big snow events and I'm not going to get one if what you describe occurs.

Looks like the METO have 'reacted' today to the GFS/ECM output for Friday as the warning differs markedly from the text of their forecast issued in the early hours of this morning.

I'd agree with that, their warning talks of break down and the latest fax does seem to show less undercut and more head on, so perhaps the ECM or even the GFS view is more favoured?

Even so, it will come down to forecasting much nearer the time and we will then see whether the cold holds on in the East and North - certainly the latest 6-15 seems to support cold being close to these areas, with the W and SW seeing rain mainly away from the hills

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

I'm cheering for the blue arrows but it could be one hell of a battle once they engage hostilities on friday, the battle could rage throughout the weekend with territory being fought for all the way, the areas which have missed out on snow so far (many areas actually)..should get a good dumping between fri/sun.

post-4783-0-41536000-1358263011_thumb.pn

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Posted
  • Location: Birmingham U.K.
  • Location: Birmingham U.K.

Not sure what you mean? The fax chart at 96hr as drawn is about as classic a "SW frontal snow" chart as you could get. If it happens like that of course, which is highly unlikely! Why do you think it isn't? SE winds, an occluded front heading into cold air and the trough disrupting and sliding under the block up the Channel!

However that chart has since been replaced by the 84hr chart (look at the forecast time, it is the same), which to my eye is much less favourable - it shows more of a straight-on attack rather than an undercut, although the trough is doing its best to disrupt. Also the cold air makes less inroads west, looking at the 528dam line.

Bear in mind that in this set-up, the 528dam line is not too critical.

That fax chart is showing an occluded approaching the Southwest, the true warm sector is way down in Southwest France, as the front approaches, the cold air stays for some time (warm air rises), think it was Piers Corbyn who alikend it to water over treacle. Dew points maybe a little on wrong side of marginal according to the GFS around coasts and far far southwest, but this is different to what the fax is showing.

As always the met are giving a heads up too, depending how things change over the next day or two that amber is likely to change, as the Southwest tends to get the most severe snow falls in the uk or nothing at all. so that warning could dissappear or turn red

Many thanks for those answers chaps. That's cleared up a blank spot for me!

All to play for then!

Kind regards,

Mike

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Posted
  • Location: Royston, Herts 76m asl
  • Location: Royston, Herts 76m asl

Strong hint from Ian F that the meto may ultimately be backing a colder solution:

Wouldn't be a damper if I could share 4-5d modified UKMO-GM output & MOGREPS with them.. ! ;-)

Although he could be referring to snow potential in that region, it being a post in the SW regional thread....it's not clear.

Edited by Weather Boy
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Posted
  • Location: st albans
  • Location: st albans

IF on the sw thread has cryptically posted re MOGREPS/modified UKMO global. i suspect it shows a pretty strong likelihood of a decent snow event(s) for large parts of the country. i suspect we will have to wait for the updated FAXES to get an insight.

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Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire

Well latest NAE moves towards GFS like usual.

Mild incursion well into England by 48hrs.

Such pathetic short term forecasting from the UKM of late.

:rolleyes:

Can you post a chart with your comment? Many of us at work can't view the charts. Thanks.

Think he means this one

13011712_1512.gif

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Posted
  • Location: Carlisle, Cumbria
  • Weather Preferences: Atlantic storms, severe gales, blowing snow and frost :)
  • Location: Carlisle, Cumbria

Well latest NAE moves towards GFS like usual.

Mild incursion well into England by 48hrs.

Such pathetic short term forecasting from the UKM of late.

I'd say the latest NAE is pretty darn chilly for the majority?

post-9615-0-93781800-1358263807_thumb.gipost-9615-0-44213500-1358263769_thumb.gi

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Posted
  • Location: Dublin
  • Location: Dublin

I'd say the latest NAE is pretty darn chilly for the majority?

post-9615-0-93781800-1358263807_thumb.gipost-9615-0-44213500-1358263769_thumb.gi

I'm talking about it progrssively shunting the colder air further east in the short term, by about 50-100 miles between this run.

Yes looks great for many parts but I am looking at it from a reliability view.

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Posted
  • Location: Yateley, NE Hampshire (Berks/Surrey borders)
  • Location: Yateley, NE Hampshire (Berks/Surrey borders)

Chilly maybe but NAE has the 0C isotherm well into wales by T+48!

http://expert-images.weatheronline.co.uk/daten/proficharts/en/nae/2013/01/15/basis12/ukuk/t850/13011712_1512.gif

That is well ahead of even the supposedly progressive GFS 06Z!

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Posted
  • Location: sheffield
  • Weather Preferences: cold ,snow
  • Location: sheffield

seems things are moving at a fair rate of knots here???has something changed suddenly regarding the westward movement of this fronthelp.gif

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Posted
  • Location: Worcestershire
  • Weather Preferences: Forecaster Centaurea Weather
  • Location: Worcestershire

IF on the sw thread has cryptically posted re MOGREPS/modified UKMO global. i suspect it shows a pretty strong likelihood of a decent snow event(s) for large parts of the country. i suspect we will have to wait for the updated FAXES to get an insight.

If UKM GM and ECM follow this...I suspect so Nick..

post-2478-0-34830500-1358264170_thumb.jp

Heavy snow into the SW (with a possible new depression ready to cut beneath the UK a day later)

.. a nice way to start the afternoon's runs...

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Posted
  • Location: Yateley, NE Hampshire (Berks/Surrey borders)
  • Location: Yateley, NE Hampshire (Berks/Surrey borders)

If UKM GM and ECM follow this...I suspect so Nick..

post-2478-0-34830500-1358264170_thumb.jp

Heavy snow into the SW (with a possible new depression ready to cut beneath the UK a day later)

.. a nice way to start the afternoon's runs...

Bloody hell that's a blinder!

FWIW the 850s are 4C lower over Wales on GME at T+48 than on the NAE. Major major model disagreement.

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Posted
  • Location: OSLO, Norway
  • Weather Preferences: Snow, Storms, Heat, Thunderstorms
  • Location: OSLO, Norway

Taken from IF in the Sw and C S england regional thread..

"NB Latest NAE progression across to meridian with PPN Thursday rejected for now and operational version heavily modified - in case anyone looks at raw stuff and starts hyperventilating. However.... Chief awaiting next UKMO-GM to be sure, so we await confirmation on expected evolution. Atlantic push of milder air much faster on new NAE through Thursday, hence much to play for in terms of broader evolution thereafter IF the NAE prog has any validity. At the moment... we lean otherwise."

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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.

GFS 12Z better than 6Z early on as well.

The cold 850's are farther west and better alignment.

Edited by chionomaniac
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Posted
  • Location: OSLO, Norway
  • Weather Preferences: Snow, Storms, Heat, Thunderstorms
  • Location: OSLO, Norway

Even by t60 on the 12z GFS there are differences from the 06z, troughing digging deeper into the atlantic/under the block and heighs stronger over scandi.

gfsnh-0-60.png?12

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Posted
  • Location: Carlisle, Cumbria
  • Weather Preferences: Atlantic storms, severe gales, blowing snow and frost :)
  • Location: Carlisle, Cumbria

If UKM GM and ECM follow this...I suspect so Nick..

post-2478-0-34830500-1358264170_thumb.jp

Heavy snow into the SW (with a possible new depression ready to cut beneath the UK a day later)

.. a nice way to start the afternoon's runs...

GME 850 temps at T72, thats some serious snowfall potential! Probably the full works - blizzards, drifting and a severe windchill factor.

post-9615-0-61814900-1358264725_thumb.pn

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