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06z model discussion - rain, snow, rain, or rain, snow, snow?


Paul

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Posted
  • Location: Near Eastbourne East Sussex
  • Location: Near Eastbourne East Sussex

OHH The depression is starting to hit me now...It looks like my area the south coast is going to miss out...BBC weather yesterday were showing loads of little snow symbals for me bu i now see they have changed their minds and are going for rain.

Anyway perhaps time for me to look further afield...Ok I'm not too hot on the charts.

Any of you kind souls see anything interesting beyond saturday and the predicted end of this possible Snowy (for some) but ridiculously short snowy spell....

Will we ever see a sustained cold and snowy spell like we used to get in the late 70's and early/mid 80's or do we have to put up with a bit of leading edge snow from the westerlies hitting cold air these days?

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Posted
  • Location: Nr. Tunbridge Wells (150m/450ft asl)
  • Location: Nr. Tunbridge Wells (150m/450ft asl)

The question, simply, is what effect will the mass of cold air (and believe me the cold air is significant - parts of the midlands were getting down around -8/-9 last night, we were down at -5 in oxford) on the front as it moves northwards. Simple as that. It's the first question, and it will have a bearing on all meterological developments thereafter.

Meanwhile, take a look at my metoffice chart for oxford. It gives two three hour periods of heavy snow early tomorrow, before some light snow on thursday afternoon, with temps never above 1C. Then tomorrow night, while the temps is supposedly down at -4C, it gives us rain. How screwy is that?

http://www.metoffice.gov.uk/weather/uk/se/...st_weather.html

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Posted
  • Location: Gloucestershire
  • Location: Gloucestershire
No mate you're going to get rain to, you'll be lucky to get snow for an hour. I think it will push further north quicker then expected leaving the rain for most us, my opinion.

BB for the last 2 days you have continually talked about how poor this is going to be in Bristol, you're probably correct. Please remember though you are 20 mins from the cotswold escarpment and hights up to nearlt 1000 ft. Regional variations occur up here to just a few miles so why not visit?

You do live at just a few feet above sea level so I don't think the 'M4' analogy has much to do with the weather you receive when height will be our best bet. Bristol is never going to see much in the way of snow unless everything is perfect, that's life unfortunately.

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Posted
  • Location: Peterborough N.Cambridgeshire
  • Location: Peterborough N.Cambridgeshire
No mate you're going to get rain to, you'll be lucky to get snow for an hour. I think it will push further north quicker then expected leaving the rain for most us, my opinion.

Don't think so based on the models.

Look at these links and follow the temps around your location and then along the S coast.

http://www.wetterzentrale.de/pics/Rtavn2417.png

http://www.wetterzentrale.de/pics/Rtavn3017.png

http://www.wetterzentrale.de/pics/Rtavn302.png

Look at your max temp of 5C compared to N of the M4. Now like I said yesterday it is a bit vague saying N of the M4 because areas just S of the M4 towards the E i.e W London could also see snowfall although only for a few hrs.

For your location you either need a potent NW,ly or a cold E,ly and a LP tracking to the S. Unfortunately NW,lys are rarely cold enough and the other synoptics are very rare indeed. This is why your location and JS location is probably the most snow free zone in the UK because you are always feeling the effects of the Atlantic ocean.

Edited by THE EYE IN THE SKY
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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

The heaviest most disruptive snow will be through wales and the midlands with up to 4 inches blowing about in a freshening easterly wind. London and the south east will get around 2 inches. Manchester across to Leeds maybe an inch but this appears to be the northern limit of any organised snow and it will be fizzling out later on thursday. The longer term could see milder air making more inroads northwards into scotland but there is still a chance that the far north will stay in the cold airmass and that the wintry conditions may spread back south westwards into next week after a milder end to the week. I'm hopeful that the scandi high will continue to have an influence on our weather for a while to come and that any milder incursions are brief. :wallbash:

Dewpoints are lower up here today after ½ inch of overnight snow so i'm looking forward to several cold days ahead with a decent cover of snow and sharp frosts.

Edited by Frosty039
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Posted
  • Location: Redhill, Surrey
  • Weather Preferences: Southerly tracking LPs, heavy snow. Also 25c and calm
  • Location: Redhill, Surrey
No mate you're going to get rain to, you'll be lucky to get snow for an hour. I think it will push further north quicker then expected leaving the rain for most us, my opinion.

Timing, if the fron tdoesn't get to us until the early hours then snow will be had for more than folk expect. If it arrives early then a different scenario will occur. But the SW suffers with AGW so rain it is :wallbash:

BFTP

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Posted
  • Location: Rochester, Kent
  • Location: Rochester, Kent

Don't see it turning to rain, to be honest - at least for tomorrow morning, based on the 6z output.

Consider the two 850hPa charts covering the period:

post-5986-1170843173_thumb.pngpost-5986-1170843179_thumb.png

For the first part of Thursday we can see that the -5C line covers the whole country with the exception of Cornwall. Clearly the further N, and E of this line the better chance you have of snow. All things considered, though, it will not need to be -7C at 850hPa to cause snow. Anyway, take some time to consider the 1000hPa-850hPa heights. Snow is progged as this front pushes through nearly everywhere. This implies that the 1270m critical maximum height for snow must cover the whole country. Remember that heights are linearly correlated with the mean temperature for the slice of the atmosphere concerned.

Now have a look at the 2nd chart. Yes, the -5C has receded - but that's some 1300m up in the atmopshere, and the temperature at that point is still sub-zero. Looking at the height for this chart also puts virtually the whole country behind the 125dam line.

That is cold enough for snow; and this reflects the mean temperature that the precipitation will be falling through. ie it is difficult to claim that the snow will turn to rain before it reaches the ground based on these two charts.

[edit] this applies to inland areas only; localised RH changes near coasts raise humidity and cause the evaporation rate to slow, hence heat is not lost through evaporation so the surrounding environment becomes much more critical - so if you live near a coast you should use the 2mT charts as well [/edt]

Edited by VillagePlank
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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

It's still up in the air- even the GFS suggests that, while there may be a snow to rain event across central areas on Thursday, in Scotland and high ground of N England it might stay as snow throughout- and then after a moderately cold Friday there's still a chance of some wintriness on the leading edge of Saturday's front, chiefly on high ground.

Then there's the UKMO and ECMWF which suggest a snow to rain event only for the south tomorrow, snow in the north, and a snow to rain event on Saturday.

I have to say that I can't agree that the GFS has been the most accurate model at handling this; if anything it appears to have been the UKMO, although it did overcook Saturday a bit two days ago. GFS overdid the northern blocking two days ago and was too progressive yesterday; it may yet prove to be too progressive even today, though odds favour at least a temporary return of milder weather by Sunday.

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Posted
  • Location: Melbourne, Victoria
  • Location: Melbourne, Victoria

good post plank and its nice to see some science being used.

my feeling is this is very positive, the charts show (i think) rain for the south coast and 10/15 miles inland, further up from there, snow will be the order of the day. last night was colder at my location than forecast and we should see similar tonight, though clearly the increasing cloud cover with the front approaching could put a limit on the cold.

i see several hours of snow for all areas except the southern strip.

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Posted
  • Location: West Sussex
  • Location: West Sussex

Can anyone tell me how they think the south downs will do? i.e. Cissbury & Chanctonbury Ring?

I live only a couple of miles from the coast so will I even see wet snow/ sleet/ or nothing but rain?

I am doubtful of seeing anything on the ground other than puddles... hopefully someone can better this??

HELP?!

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Posted
  • Location: Rochester, Kent
  • Location: Rochester, Kent
Then there's the UKMO and ECMWF which suggest a snow to rain event only for the south tomorrow, snow in the north, and a snow to rain event on Saturday.

I disagree.

At least for the first 2/3rds of tomorrow. Any area that gets snow cover before dawn (seems fairly likely to be widespread south of the country) is likely to keep a particularly cold surface layer as some of the incoming radiation from the sun is reflected, and some is used to melt the snow - which leaves proportional less to heat up the surface. This means the ground does not heat up at the rate the models suggest that it will meaning the 850 heights will keep low - which is the 'reasoning' behind the 2nd 850 chart I posted above, I think.

[edit]As BFTP suggests, this could all actually be about timing, and orientation of the front. I am basing what I am saying entirely upon the GFS 6z output so one must consider the accuracy of the model[/edit]

Edited by VillagePlank
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Posted
  • Location: Colchester
  • Location: Colchester

A very exciting 24-36 hours ahead.Going to be very interesting to see whether the models or meto fax charts have the best call on this.My hunch is to go with Meto because all this cold air hanging around ( -5.6 c at 7.00 am here today).Looking ahead to the next week what is the latest model output suggesting about height rises over scandinavia and greenland

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Posted
  • Location: Rossland BC Canada
  • Location: Rossland BC Canada

I don't think the GFS has a very good handle on the next 24-36 hours and with the current depth of cold air in all parts of the UK and Ireland except a few coastal locations in the far south, the more likely outcome is for low pressure to form southwest of Ireland, move east through the Channel and for the arctic front to remain about where it is now for most of the next 48 hours.

That should lead to widespread snowfalls of 8 to 15 cms in southern England and most of Wales except perhaps the southwest tip.

Ireland could also see some snow in central and northern districts, say 5-10 cms for some.

I agree it is more likely to rain in places like Plymouth and most of Cornwall, but this looks like a situation where warm fronts just won't make northward progress until low pressure breaks through north of Ireland.

With that amount of snow and a fairly strong east wind by Thursday, the word blizzard might be heard before this is over -- blizzard by UK standards, that is.

I can understand the spread of forecast ideas here, but the current depth of the cold air is the key for this observer, and I don't see anywhere for milder air to go but up and over.

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Posted
  • Location: Birmingham U.K.
  • Location: Birmingham U.K.
I'll be very suprised if it just turns mild - there is a big mass of very cold air over the UK. Atlantic air hitting this will easily turn to snow- esp away from the south.

Couldn't agree more, Bottesford. That cold block will take some shifting imo.

Fingers x'd!!!! :wallbash:

Regards and stay safe,

Mike.

Edited by Winston
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Posted
  • Location: Beverley, East Yorkshire. 52m, 170ft
  • Location: Beverley, East Yorkshire. 52m, 170ft
Does anyone have any latest sat images off the system coming in ??

This excellent link was posted on here yesterday

http://oiswww.eumetsat.org/SDDI/cgi/listIm...201000#controls

gobbyash

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Posted
  • Location: Birmingham U.K.
  • Location: Birmingham U.K.
I can understand the spread of forecast ideas here, but the current depth of the cold air is the key for this observer, and I don't see anywhere for milder air to go but up and over.

I quite agree Roger. That cold pool seems very dense. Interesting times ahead!

Regards,

Mike.

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Posted
  • Location: Lytham St Annes, near Blackpool.
  • Weather Preferences: Cold/snowy. Summer: Warm/gentle breeze. Anytime: thunderstorms/gales.
  • Location: Lytham St Annes, near Blackpool.

Just looked at the n-w extra charts for tomorrow. Acc to those, I'm looking at 6-9 hours of snow tomorrow. So many people are saying it just won't get that far, so I don't know whether to get excited ot not. Guess it'll be a case of radar watching, as it will be for many. I'm just imagining the Malvern Hills (where I used to live) near Worcester. Some nice sledging for a while tomorrow there I would have thought.

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Posted
  • Location: Fleet, NW Hampshire: 80M ASL
  • Location: Fleet, NW Hampshire: 80M ASL
Couldn't agree more, Bottesford. That cold block will take some shifting imo.

Fingers x'd!!!! :wallbash:

Regards and stay safe,

Mike.

Absolutely. That cold isn't going to shift easily without a fight, trust me. 40 yrs of weather watching has taught me that. More happy faces than sad tomorrow.

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Posted
  • Location: Nr. Tunbridge Wells (150m/450ft asl)
  • Location: Nr. Tunbridge Wells (150m/450ft asl)
I don't think the GFS has a very good handle on the next 24-36 hours and with the current depth of cold air in all parts of the UK and Ireland except a few coastal locations in the far south, the more likely outcome is for low pressure to form southwest of Ireland, move east through the Channel and for the arctic front to remain about where it is now for most of the next 48 hours.

That should lead to widespread snowfalls of 8 to 15 cms in southern England and most of Wales except perhaps the southwest tip.

Ireland could also see some snow in central and northern districts, say 5-10 cms for some.

I agree it is more likely to rain in places like Plymouth and most of Cornwall, but this looks like a situation where warm fronts just won't make northward progress until low pressure breaks through north of Ireland.

With that amount of snow and a fairly strong east wind by Thursday, the word blizzard might be heard before this is over -- blizzard by UK standards, that is.

I can understand the spread of forecast ideas here, but the current depth of the cold air is the key for this observer, and I don't see anywhere for milder air to go but up and over.

That's a brave step, rojer j smith! Defying all the models and the metoffice and co. And you're unlikely to be ramping from canada too!

Nonetheless, i will be very envious of leicester (and other places like it) if this metoffice forecast comes off. Its pretty special frankly.

http://www.metoffice.gov.uk/weather/uk/em/...st_weather.html

Edited by wellington boot
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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

Well... put it this way, the less far north the snow gets on Thursday, the more chance there is of snow showers returning to north-eastern districts on Friday, and the more chance there is of an even bigger snow event for most on Saturday.

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Posted
  • Location: .
  • Location: .
I got to a globally warmed -7C last night, glad I don't live in the AGW bubble in the SW. So now a GFS model has shown a breakdown and an all over the place picture with a less cold longterm solution WIB has decided it is very accurate. Nonsense as usual especially as he ignores the thoughts of the METO. :wallbash:

There is very cold air over the UK now [bar AGW SW] and temps will remain very low today with further dipping tonight...just in time for the front to move in and bring drizzle to the SW and snow for the rest of us. Temps now even colder in Scandinavia with certain places getting close to -40C and this cold air is not going to get shunted East. Watch for the models to pick up a strong pressure rise up there. They have hinted at it but will start to enhance it soon for the latter half of Feb. It is cold out there and no amount of mild ramp can stop that...enjoy. Lincolnshire, East Anglia and Midlands look like getting a major dumping and much of Wales from the Brecons northwards.

BFTP

Listen Fred,

1. There is no need to refer to me (goes for others too). I'm just a middle-aged ex-beardie (Piers take note) who started a new job this week in Royal Mail and who just happens to think AGW is one of the dictating factors in UK weather Plc. I'm really not important enough for you or other to spoil this thread over.

2. I'm not convinced that the really cold air will hold before the arrival of the ppn. Temps in the south-west really have been higher (which is actually a big reason I sometimes overdo things by the way). For instance it didn't get to freezing here last night, and we had light rain yesterday pm. It's now 5C and climbing.

3. If I think this is marginal it's really based on experience of winters past where the cold air ahead of this kind of set-up for snow was usually much much colder, and would draw in a very cold easterly. That isn't present with this, so the best we can hope for is front-edge snow for a time.

4. Yes it is cold out there. But I do think you and a couple of others (and it is only a couple) would do better not to leap on every cold snap as a sign of the end of AGW. That doesn't help you or anyone. AGW is here but, and it's a significant but, this does not mean we may not sometimes have cold snaps. This is at least the third in an otherwise mild winter.

5. If you do get snow, do enjoy it. I don't want to see rain tomorrow. When I get back off my shift tonight I'd love to have white flakes falling. I'm just a big sceptic about this set-up I'm afraid.

6. I continue NOT to buy into the stalling argument. I think that could be a recipe for rising temps before the ppn - if the front holds to our west and takes longer to arrive. If it stalls over the Midlands/north tomorrow then that might be a different story.

Edited by West is Best
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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 think four inches is as deep as anyone can expect tomorrow because the snow will be moving north east and fizzling out after the initial heavy falls in the south west turn to rain as it becomes slowly milder with a slushy afternoon in southern england. People in yorkshire northwards will be disappointed with just light snow flurries as the heavy stuff pulls east across the east midlands into lincolnshire before dying out. A fine friday but another brief snowy spell on saturday before mild air pumps north and east across all areas.

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