winter model output Winter Model Output Discussion -12Z 07/02/13 onwards

[Weathizard]

quote me if i am wrong but doesn't the NAO jump on board after the AO gets down to lower latatudes,just a thought?

Well I thought the NAO/AO are representative of what the models are showing currently, ie if we had a massive 1050 Greenland high it would be strongly negative and a zonal flow would be positive. This is what I was told a while back I think.

What is more relevant to our weather though I wonder could any experts correlate what is more important with regards to cold? (Ie is a negative AO better than NAO?)

[johnholmes]

Ah, sorry: see v good explanation by scrolling down at http://weatherfaqs.org.uk/node/152

It's very commonly used in all rain-snow modifications at UKMO and any other main Met ops centres internationally.

good to see the empirical methods are still in use, reminds me of similar night duties 40 years ago!

oh and the link Ian posts is possibly the best on the web for factual information about meteorology. It should be as it was originally prepared by a senior forecaster in UK Met

Edited February 7, 2013 by johnholmes

[Ryan Dutch Weatherman]

Well I thought the NAO/AO are representative of what the models are showing currently, ie if we had a massive 1050 Greenland high it would be strongly negative and a zonal flow would be positive. This is what I was told a while back I think.

What is more relevant to our weather though I wonder could any experts correlate what is more important with regards to cold? (Ie is a negative AO better than NAO?)

It must me the combination, also wenn the blok is too far west , brittain nor west Europe wil get meridionaal south , only -negative NAO doesnt alway means cold /or winter.

Greater chanse with combi.

[john pike]

120 fax chart

[Tom Montalbano]

HI Ian-

Using Boyden @ 50% for Sun / Monday still only gives us 1293 DAM available @ 850-1000 HPA

WUnderground has GFS thicknesses at-84

http://expert-images...021100_0712.gif

Whats the UKMO thickness overnight Sun into Mon>?- sub 1290 DAM?

Steve

Steve/Ian,

IF the FAX at t120 comes to fruition, what do you think would be the outcome for the SE. I know a bit of an IMBY poser!

Regards,

Tom.

[Panayiotis]

120 fax chart

Ah it shows the shortwave to the north of Norway, I dont like that feature! As others have said it stops the retrogression of the high. Edited February 7, 2013 by Panayiotis

[Allseasons-Si]

Well I thought the NAO/AO are representative of what the models are showing currently, ie if we had a massive 1050 Greenland high it would be strongly negative and a zonal flow would be positive. This is what I was told a while back I think.

What is more relevant to our weather though I wonder could any experts correlate what is more important with regards to cold? (Ie is a negative AO better than NAO?)

It must me the combination, also wenn the blok is too far west , brittain nor west Europe wil get meridionaal south , only -negative NAO doesnt alway means cold /or winter.

Greater chanse with combi.

We need them both neg for stronger signal i think

the AO going in the right direction,just need NAO to jump on board.

[Ryan Dutch Weatherman]

It means snow also for the SA on your chart i see 120 , end 96 ok .

Nice Charts/

That is Bracknell.

[TEITS]

Rather late viewing the latest models.

Looking at the fax charts im rather bemused, unless my eyes are playing tricks due to being late. At +72 the fax chart has been modified with the LP further SW compared to the UKMO raw and yet +96/+120 they are exactly the same as the UKMO!!

Personally the jump between +72 & +96 looks rather odd on the fax charts and at +96 I would of expected the LP to be further S than indicated.

[Allseasons-Si]

Ah it shows the shortwave to the north of Norway, I dont like that feature! As others have said it stops the retrogression of the high.

NO,i dont like it either,the 18z gfs romoved it so theres a bonus,we shall see

[Ryan Dutch Weatherman]

We need them both neg for stronger signal i think

the AO going in the right direction,just need NAO to jump on board.

That is it , that was the problem this year with the NAO.

Wenn the Nao in januari was much stronger in januari we could have been seen something like 47 for brittain.

But lets look now to feature.

[fergieweather]

Incidentally, 12z EC keeps the higher WBPT's lingering for longer across southern England, but crucially it's EPS demonstrate how the deterministic sits at one extreme, with most members cooling the airmass quicker. Both EC-EPS and MOGREPS snow probs agree on strong signal for Midlands/Cotswolds re Sun-Mon heaviest snow; only part of UK not within sub-200m WBFL by noon Monday is far SE, where rain/sleet more likely. Elsewhere, the southward retreat of ppn possibly out of phase with WBFL reduction means a steady lessening of snowfall anyway through Monday, aside from showers into the NE... this phasing issue critical to just how widespread & disruptive snow could prove, e.g. for Mon AM rush-hour. Peak totals remain clearly signalled for Midlands, as noted, and parts of upland S-central England (e.g. on M4 corridor) but we'll await 00z with interest, not least as the over-deepened 12z EC is considered an extreme solution in it's development, with UKMO-GM not far behind (it's deeper solution reduced in Exeter modifications).

Edited February 7, 2013 by fergieweather

[Ryan Dutch Weatherman]

That is it , that was the problem this year with the NAO.

Wenn the Nao in januari was much - nagtive in januari we could have been seen something like 47 for brittain.

But lets look now to feature.

NO,i dont like it either,the 18z gfs romoved it so theres a bonus,we shall see

I dont see that as a major problems , it can confused the models some little bit.

[Tom Montalbano]

Rather late viewing the latest models.

Looking at the fax charts im rather bemused, unless my eyes are playing tricks due to being late. At +72 the fax chart has been modified with the LP further SW compared to the UKMO raw and yet +96/+120 they are exactly the same as the UKMO!!

Personally the jump between +72 & +96 looks rather odd on the fax charts and at +96 I would of expected the LP to be further S than indicated.

Dave,

That's a very good point you make, even after that modification on the t72 FAX, the jump to t96 takes the low due east up the Channel. I must admit I was half expecting a track further S.E. entering France on the Central Nth. coast! Still time for some correction but I'm not going to doubt the METO!

Regards,

Tom

Edited February 8, 2013 by TomSE20

[Allseasons-Si]

I dont see that as a major problems , it can confused the models some little bit.

it is a major problem as it stops the flow from the east RDW,which is why i commented earlier about it(for a uk imby),,if that shortwave/low isn't there in later runs,i would be a happier man but the latest fax 120 is not good as it stands.

[Ryan Dutch Weatherman]

http://www.emsc-csem.org/Earthquake/earthquake.php?id=303931#.URQ-95IWcDw.twitter

[SMU]

Incidentally, 12z EC keeps the higher WBPT's lingering for longer across southern England, but crucially it's EPS demonstrate how the deterministic sits at one extreme, with most members cooling the airmass quicker. Both EC-EPS and MOGREPS snow probs agree on strong signal for Midlands/Cotswolds re Sun-Mon heaviest snow; only part of UK not within sub-200m WBFL by noon Monday is far SE, where rain/sleet more likely. Elsewhere, the southward retreat of ppn possibly out of phase with WBFL reduction means a steady lessening of snowfall anyway through Monday, aside from showers into the NE... this phasing issue critical to just how widespread & disruptive snow could prove, e.g. for Mon AM rush-hour. Peak totals remain clearly signalled for Midlands, as noted, and parts of upland S-central England (e.g. on M4 corridor) but we'll await 00z with interest, not least as the over-deepened 12z EC is considered an extreme solution in it's development, with UKMO-GM not far behind (it's deeper solution reduced in Exeter modifications).

HI Ian--

- just on my repsonse- I am guessing from the 12z suite the consensus was sub 1290 DAM post T84 ( 00z Monday ) across central areas spreading south-

Its funny we get less data than you however using the ECM KNMI link

http://www.knmi.nl/e...agse/index.html

Which shows the operational & control were windy & excessive snowfall outliers for mon-

Plus the MEAN -

We could deduce that the consensus was further south west with the track.

The GEM being at the western end. The indepth UKMO data shows that the thicknesses start to look good late sun into mon for the midlands & that penetrating south post this-

However my concern is that the 18z GFS ( very poor for guidence ) was deep like the ECM op & adjusted NE like the ECM op- mainly squeezing out the snow to rain - & keeping most of us on the fringes-

heres the GFS 18z thicknesses at 84-

http://expert-images...021106_0718.gif

now circa 1295 DAM & very wet for the south!

S

Edited February 8, 2013 by Steve Murr

[MKN]

Ps it's also why the GFS ppn type discrimination charts are broadly pants.

Which were bang on the money wrt the end of the last cold spell on the Friday night. Right off gfs and be prepared to be dissapointed imo

[TEITS]

A quick map i've put together which is based on all the output today including ensemble means.

This is for Monday 0Z because I feel during Sunday night into Monday morning is the point when rain will turn to snow. I have also highlighted the position of the LP as I currently see it.

[Captain Shortwave]

unfortunatly it wasnt strong enough to do any damage.....

S

There will be front page headlines, a dozen people have had their novelty teacups broken. Mass panic prevails over ones ability to drink our beloved beverage.

On other new the gfs ensemble were a little underwhelming to be honest. With the snow likely to miss where I am. I will simply wish for it to fall on areas which haven't been effected so far this winter so good luck to you all

[TEITS]

Which were bang on the money wrt the end of the last cold spell on the Friday night. Right off gfs and be prepared to be dissapointed imo

Yes I do agree with you.

I have known a few occasions in the past few years when the NAE/Met O/BBC have forecasted heavy snow and the GFS disagreed and was proved right. The GFS may have its faults but I do rate this model within the +48/+72hr timeframe.

[Ryan Dutch Weatherman]

Cptec 12z , The Brazilian model is finished yet.

[Nath]

A quick map i've put together which is based on all the output today including ensemble means.

This is for Monday 0Z because I feel during Sunday night into Monday morning is the point when rain will turn to snow. I have also highlighted the position of the LP as I currently see it.

That line cuts my house in half LOL

If I were a betting man (Which I am lol) I would bet heavily on the low being a fair bit further south than showing on some models this evening, and wouldnt put it past being a decent snow event all the way down to the south coast. Still think the models are a tad overzealous with that low.

[Timmytour]

Just a gut feel about the sunday/monday thing..... I think after tomorrow the adjustments the models make in the position of the low will be smaller and smaller, but will generally tend to stay adjusting in the same direction...that being northwards. At the moment i would think that would put a lot of england at the risk of missing out on any meaningful snow...BUT..... a couple of days before such an event there always seem to be a big almost erratic leap.

So my guess is tomorrow will show a big shift south bringing the south coast into play....followed by a series of smaller shifts north which will not threaten north of the M4 but will put at risk those areas nearest to the south coast for the monday at least....but then they might get lucky on the tuesday.

I'm warming to the idea of this turning out to be a bigger event for most of the country then perhaps the models as they currently stand are showing

Edited February 8, 2013 by Timmytour

[Bonjangle]

A quick map i've put together which is based on all the output today including ensemble means.

This is for Monday 0Z because I feel during Sunday night into Monday morning is the point when rain will turn to snow. I have also highlighted the position of the LP as I currently see it.

TEITS -You following the M4 corridor?

You have now missed me out by 3 miles , damit i am going to bed sulking at your silly prediction as all models will change tommorow and also saturday , i thought you had better knowledge than that.