Spring Model Discussion 18Z 6/3/13 onwards....

[bluearmy]

Please explain the similarities between the last easterly and this much briefer affair.

As ever, we will not have much clue re precip monday onwards till saturday at the earliest.

[Methuselah]

Latest CFS run, and the cold just keeps on coming until the start of April! I'm sure that model is Anti-mild!

http://www.meteociel...&carte=0&run=10

Hasn't the CFS had us under a BFTE all winter? Or was that last year?

[snowmadchrisuk]

I think you will find Monday will be a largely cloudy or overcast day with little convection nor frontal activity affecting the South of the UK at least. There will be though a strong and cold NE wind though with big windchill factors rather than disruptive snowfall.

They mean snow is unlikely to settle at a rate of more than 2cm elc , but it doesn't mean it won't be falling on Monday and apart from that the rest of the week does look fairly dry on the hole , on current charts anyway.

[SE Blizzards]

Hasn't the CFS had us under a BFTE all winter? Or was that last year?

I have only been viewing that particular model over the last 12 months or so. I know it's not regarded highly in many peoples opinion but i do recall it suggesting a cold spell of weather in March for quite some time now. I guess it has to be right sooner or later.

[Gibby]

Please explain the similarities between the last easterly and this much briefer affair.

As ever, we will not have much clue re precip monday onwards till saturday at the earliest.

Yes that is quite true and who knows what's shown by the models could look very different by then. The similarities you mention are few. In the last Easterly we had a slow moving High pressure area to the NE with static pressure pattern and an inversion close to the surface capping convection chances for most away from the East Coast. This of course gave us those endless grey cold days with no precipitation of note. This time we have rapidly rising pressure over Monday in the NE feed as High pressure slips South to the West opening the door to a slack Northerly flow with clear skies and the chance of some scattered snow showers through several days as things stand tonight.

[Dave Kightley]

Great runs for nearly next week esp.. Time of day will depend on snow later in the week i suspect.. It snows in april for e.g. memory 1998/1999 had snow falling rush hour after early rain the South west... Just memory not fact or anything

[bluearmy]

this is an omega block in the mid atlantic/greenland area. it becomes a west based -NAO in the 14 day chart. can we stay the right side of the cold? well surely some of the uk will.

[Captain Shortwave]

ECM ensembles have the cold (-8 uppers) hanging on at least in the Eastern part of the UK and Scotland until day 8. Looks like an Atlantic vs Scandinavian trough battle coming after that.

Before then it's time to play your convective snow shower cards right.

[bluearmy]

ECM ensembles have the cold (-8 uppers) hanging on at least in the Eastern part of the UK and Scotland until day 8. Looks like an Atlantic vs Scandinavian trough battle coming after that.

Before then it's time to play your convective snow shower cards right.

spreads take the atlantic energy across the south of the uk days 9 and 10. could be knife edge stuff if that verifies - will it be cold enough where the precip meets the embedded cold ?

[Bradowl]

Please explain the similarities between the last easterly and this much briefer affair.

As ever, we will not have much clue re precip monday onwards till saturday at the earliest.

A few times in late 70s and early 80s we had a very similar set up to what we've got now and back then Snow wasn't forecast right up until showers had started developing over north sea.

Forecast on radio 4 at five to six back then........ Tomorrow will be very cold but mostly dry with just a few isolated Snow showers near eastern coasts.

By end of following day we had well over 6 inches of Snow.

[Captain Shortwave]

spreads take the atlantic energy across the south of the uk days 9 and 10. could be knife edge stuff if that verifies - will it be cold enough where the precip meets the embedded cold ?

aye, it's for mother nature to know and for us to find out. Lets see what the northerly does after our initial cold blast. Small shortwave features might work in our favour.... or not of course.

[chris pawsey]

A few times in late 70s and early 80s we had a very similar set up to what we've got now and back then Snow wasn't forecast right up until showers had started developing over north sea.

Forecast on radio 4 at five to six back then........ Tomorrow will be very cold but mostly dry with just a few isolated Snow showers near eastern coasts.

By end of following day we had well over 6 inches of Snow.

[SMU]

I have to disagree with the comments tonight- from the people comapring this upcoming potential to the last one, Especially Gibbys one Scattered snow showers- I would say thats well wide of the mark based on the current output.

The previous cold spell had all the ingredients of convective snowfall at about T72 - but on the very best runs that potential at best was reserved for the very corner of Kent & suffolk. Also the penetration of showers was capped because the flow from the east stopped over the UK & faded to the south.

When the models got to T 48 the convection had been reduced to pretty much nothing apart from the Channel- which saw one continuous streamer.

The problem is here is what is the expectation from posters- People should be clear what they are posting- with the thought process behind it- as theres a lot of confusion.

Some people are playing the snow chances down due to previous let downs & the historic corrections south that the models seem to take in easterlies, however some are saying it wont be showery just because.... the last one wasnt.

If we take the UKMO / GFS blend at face value tonight there is significantly more instability in the timeframes of 84-102 tonight than there was in the last cold spell which should produce higher cloud tops & stronger PPN rates.

How can people compare this

http://www.meteociel.fr/ukmo/runs/2013030712/UW96-21.GIF?07-18

to this

http://modeles.meteociel.fr/modeles/gfs/archives/gfs-2013022300-0-6.png

Its almost laughable.

There will a sharp transition to cold sunday PM with back edge snow prevelent over the south, then a clearence before the snow showers pile into the SE & E.( & before this the NE)

On inspection it appears that the window which presents itself for England is around 18-24 hours. In this I would expect to see a covering the further east you go with the hot spot being EA & Suffolk & kent. Maybe the best case scenario - 5-10cm. with the consensus being 1-2 cm especially over the hills.

Of course people could say well whats the point of forecasting PPN- well if the models dont change then based on experience thats where its going to turn up.

I expect an embedded trough in the flow sometime Monday- Im sure it will pop up on the fax at some point.

If we have learnt anything the models do correct south- so possibly if I was in the NE it would be nervous times for where the line of convection starts as there will be a sharp cut off to stable descending air- Probably Scotland Maybe Northern Scotland.!

All in all- an exciting weekend, overnight sunday & AM Monday looks to see the biggest potential for accumulating snow- which looks to melt sometime tuesday....

Maybe just maybe enough for a sledge run or 2...-

I dont percieve this post to be ramping- just a general assessment of what the models show now.

Frontal wise- GFS going for around 10cm for the NE & Scotland.

http://www2.wetter3.de/Animation_12_UTC/114_35.gif

Nothing presented via convection.

[Summer Sun]

ECM full ensemble shows a definite trend upwards now towards the end of the ensemble

A milder end to March may be on the cards

Edited March 7, 2013 by Gavin.

[Mair Snaw]

Great runs for nearly next week esp.. Time of day will depend on snow later in the week i suspect.. It snows in april for e.g. memory 1998/1999 had snow falling rush hour after early rain the South west... Just memory not fact or anything

Same here last April 4th 30cm of snow from early evening into the night, caused mayhem in my village and surrounding areas...and that was from this chart

http://www.wetterzentrale.de/archive/2012/avn/Rhavn00120120404.png

Edited March 7, 2013 by bigsnow

[Paul]

Just for the sake of clarity, a few people disagreeing with someone's opinion does not equate to giving anyone stick - this is a discussion forum, differences of opinion are normal.. If those differences of opinion go ott and become disrespectful please use the report button to let the team know so we can deal with it, so posts into the thread can then stick to being about the model output.

[Cloud 10]

spreads take the atlantic energy across the south of the uk days 9 and 10. could be knife edge stuff if that verifies - will it be cold enough where the precip meets the embedded cold ?

The JMA at 192 hrs might not be far away.

[virtualsphere]

1999 i think when i was in year 5.I remember rain during the day and smow had settled by the time i got home..Were late in the season..

Yes, April 1999 saw a large (temporary) snowfall in my area. We were coming back from Scotland, and had driven all day, and just 30 minutes from home it started snowing heavily and sticking, and we struggled to make it back.

It's actually quite a contrasting set-up to what the models are currently predicting for next week. In 1999, the cold air came from the north:

Note the mid-Atlantic high, and low pressure over Scandinavia.

What we're seeing the models show for next week (using Steve M's UKMO chart as an example) is for the cold to come from the east, with the block positioned further north and ridging down into the Atlantic from Greenland:

[Cloud 10]

GFS 18z going for snow for central and southern areas on Sunday.

[Mucka]

GFS continues to upgrade snow risk for North on its ppn charts for as early as Saturday. Can't see it happening but better to see it modelled than not.

Shame GFS is notoriously bad at prdeicting ppn type.

[Geordiesnow]

Slight change in the orientation of the flow from an ENE'ly to a stright easterly, this results in the front being further North and the colder air heading more WSW/ly than SW'ly so for southern areas, it would take longer for it to turn colder.

On face value, I would prefer the 12Z run for the fact the flow looks more unstable therefore a more widespread and higher chance of a sunshine and shower set up.

[chionomaniac]

A big northwards adjustment with the precip positioning ( and lower 850's) by T+84 on this run. Makes it interesting because there will be a snow line lying across the country somewhere come Sunday night. Probably.

In fact quite a snow fest north of the M4 ( and probably further south) by Monday evening.

Edited March 7, 2013 by chionomaniac

[DEYS(Kent)]

Very subtle changes but significant for the far south....

[Snowman.]

Further NE just a tad on this run.

Brings a much Higher risk of some heavy snow for the South.

Even better with a big blob in the south.

compared to

Edited March 7, 2013 by SN0WM4N

[Man With Beard]

Am I the only one looking south rather than east? There was a whole lot of snow over Northern France for Sunday night on the 06Z and 12Z - every GFS run seems to bring it further north and now it hits the south coast on Monday morning.

edit: ok I see the new posts!

Edited March 7, 2013 by rjbw