06z model discussions

[Rustynailer]

I'm going to go against the grain and say that the 06Z is not a good run for cold/snow lovers into FI; although the synoptics look enticing, apart from a 36-hour easterly around 19 February it is generally too warm for wintry precipitation, and the easterlies and near-average temperatures would almost certainly bring dry cloudy weather.

The Euro models remain the highest-potential bets into FI.

This 06z run doesnt match the ensembles ether, i am clearly under -10 air at the time

Russ

[PersianPaladin]

Do you expect a lot of shower development in eastern areas ahead of the main frontal band?????

UKMO charts do not show many showers getting inland; unless you live within 5-6 miles of the east coast.

This is in contrast to late December 2005 when I got 10cm of snow from showers coming in off the north sea.

[January Snowstorm]

but I don't mind as there are people more deserved than me who haven't seen a single flake

this winter, so I hope it is those people who benefit the most from this cold spell.

Brian.

Yes folk like js who lives in Costa del Cork

[kold weather]

Hi Ian, to be honest the ECM is ultra close to what the 06z shows in terms of upper patterns, i strongly suspect the 0z ECM would be nearly the same even out to 300hrs if it ran that far and it also handles the upper trough very similarly as well as the weak high developing near Icealand which leads to this on the 06z run:

http://www.wetterzentrale.de/pics/Rtavn3121.png

Its not that cold but as I said in the technical thread, if it comes off i don't think it would be, but rather a second pluse would be the one to watch in any such set-up.

The ensembles seem to be very split, some go for a mild SW zonal flow and re-set the AO (which may I add is utter nosense I believe, fresh pluse of warming will assure that much...) and others have a intresting, though on the face of it not that cold set-up, with a supressed jet stream it'd be intresting, with some not that cold at 850hpa but the set-ups with these sorts of set-ups often are cold at the surface, as the next few days may wlel prove.

06z shifts Thursdays possible snow line further north again however the 06z was the furtherest north yesterday as well so that may not mean much, though to be fair the models relaly don't matter too much from now on in.

Edited February 6, 2007 by kold weather

[PersianPaladin]

Heavy snow ? 10-15cm !!

Eeee when I were a lad that were nowt but a heavy frost

Aye.

[runboy]

Kold, you say the models show the snow line further north-does the line cut right across the country, west to east, or is it like a sausage shape that only goes as far east as say Northamptonshire.

If the latter than eaither way with me being so far east that snow line can go as far north as it wants, I won't get any!

[Joneseye]

Kold, you say the models show the snow line further north-does the line cut right across the country, west to east, or is it like a sausage shape that only goes as far east as say Northamptonshire.

If the latter than eaither way with me being so far east that snow line can go as far north as it wants, I won't get any!

I think this may illustrate the point KW is trying to make. Note the timings at the top!

[TEITS]

I noticed on the NW update from John Holmes that mentions the possiblities of the snow reaching N England. Well im not so sure it will and if anything I believe the N extent shall be lincs currently which isn't far from me.

Looking at the latest UKMO model there certainly is the chance that the snowfall could be prolonged due to the front not moving very quickly.

http://moe.met.fsu.edu/tcgengifs//ukm/2007020606//slp8.png

The zone at the moment that is most likely to see heavy snowfall is stretching from N Wales across W Midlands/E Midlands, N parts of E Anglia (Norfolk,Cambs etc). What I believe will happen is instead of the snow turning to rain in these areas it shall remain as snow and then simply die away as the centre of the LP drifts into N france.

I have drawn a map to show you what I mean.

[VillagePlank]

One of the more interesting aspects of that which the MetO have published today is the notion that 'London' is specfically mentioned. Almost as if they know their charts don't say so, but they still are issuing a warning for the place, anyway.

Peculiar.

[JohnAcc]

I noticed on the NW update from John Holmes that mentions the possiblities of the snow reaching N England. Well im not so sure it will and if anything I believe the N extent shall be lincs currently which isn't far from me.

Looking at the latest UKMO model there certainly is the chance that the snowfall could be prolonged due to the front not moving very quickly.

http://moe.met.fsu.edu/tcgengifs//ukm/2007020606//slp8.png

The zone at the moment that is most likely to see heavy snowfall is stretching from N Wales across W Midlands/E Midlands, N parts of E Anglia (Norfolk,Cambs etc). What I believe will happen is instead of the snow turning to rain in these areas it shall remain as snow and then simply die away as the centre of the LP drifts into N france.

I have drawn a map to show you what I mean.

He TEITS,

I hope your right. I'm based in the West Midlands and it would feel so cruel at T+48 for this to go pear shaped. However, I'm fully aware that there is every chance of this!

Rgds, John

[runboy]

Thanks Joneseye. So it that case moving further north would help me in Norwich.

TEITS-I like your map, looks good for you and me! And I still promise you that snowman in your honour!

[grab my graupel]

I have drawn a map to show you what I mean.

Good afternoon Dave,

Yes I am inclined to agree with you.

I have to go a little off topic to illustrate your point.

I have watched both the Sky and the BBC forecasts today, and where the BBC forecast

shows the precipitation head further North, Sky are adamant that what you are saying will happen.

Going by recent model runs also, I feel that the chances of my area seeing snow are diminishing,

and are reliant upon maybe a rogue shower cropping up.

So Iam going to be concentrating on radar watching soon.

Brian

Edited February 6, 2007 by grab my graupels

[SMU]

My take on things before the 12's- PS TEITS like the map-

With refernce to the Shortwaves tracking in on Weds eve/Thursday Night-

These shortwaves & their interaction with the main depression off to the West of ireland is almost impossible to button down-

Simply put, the Max Northerly extent of the Snow will be realised if the Shortwave fully phases with that atlantic depression & is pulled rapidly North with little easterly jog-

The max Southerly extent is obviously where the shortwave totally missed a phasing event & just carries sailing on by-

This will then see the best scenario develop for the Southern areas-

These 2 developments are highlighted perfectly for me within the METO 00z & 06Z run- ( look at the 'tilt' of the lows here-

firstly look at the 00z-

http://moe.met.fsu.edu/tcgengifs//ukm/2007020600//slp10.png

One System that has formed will push northwards- Notice how the tilt of the low has that NE orientation- looking at it you expect the natural progression to be slightly more NE-

More importantly though is the fact that one stronger circulation can advect more warmer air into the block ahead of the frontal band-

Now look at the 06z-

http://moe.met.fsu.edu/tcgengifs//ukm/2007020606//slp8.png

The tilt look more SE not NE & we have a smaller shortwave developing which will have less ability to advect warmer air into the Front-

In essence the 06z IMHO wold be a slight upgrade for snow potential WRT temperatures along the frontal Boundry-

Its a pity the 06z doesnt go out past 60 because the next chart would have been key-

Also again worthy of note if it was missed from this morning is the Second bout of PPN coming through -

I highlighted the fact that rather than the WHOLE system moving North it could stall out to the west of ireland & send anotyher shortwave around the base into the Colder air-

The 06z Does develop this feature- As for snow out of this it would be down to the flow returning from the NE at the time & highlights perhaps a region in a similar sort of area to the first band-

here it is- although this again COULD slide EAST-

http://www.wetterzentrale.de/pics/Rmgfs781.gif

In terms of the longer range output- I think 99% of people believed the synoptic pattern wouldnt develop to such an extent where by at t 48 we are discussing a posible large scale snow event-

Its very understandable this- many many let downs in the past, Last minute model changes never delivering cold, features not occuring at the right time, rain instead of snow-

we have ALL been there - However we must realise now that in part we are over that 'major' error in terms of any cold/snow being missed & we are into the 'finer' tuning stages of the run in-

The evoltion though POST thurs & friday is far from set in stone- Taking this at face value we are in a rather unique situation & to my mind have only been here a handful of times in the last 20 years - What we should have learned is that the model bias & lack of raw data from regions that have the greatest impact on this evolution gives enough weakness & margin of error to still expect the models to back track away from the 'progressive' type scenario current displayed to one of continued southerly tracking Shortwaves & blocked conditions-

I draw you to this mornings GEM - Usual disclaimers apply here because its NOT one of the big models however I 'think' in the mid term its feel for the flow perhaps is better than the ECM & GFS-

I know thats a big statement - however in this heightened period of model error- historic examples ( Although few & far between) lead me to believe the Cold - deeply manifested to the NE wont be a pushover & may well over come the drive from the atlantic escpecially given that the PV is WAY AWAY to the west...

http://www.wetterzentrale.de/pics/Rgem1081.gif

The 108 Chart shows how the atlantic hasnt driven East & the small shortwave energy is sliding SE away from the main vortex- Ring any bells-??

All the GEM is doing is continually splitting the Vortex - where as the main models keep bringing it together & surging it east-

If you believe the PV can be split once-

http://moe.met.fsu.edu/tcgengifs//ukm/2007020606//slp8.png 06Z

There is no reason why it wont continue that way - that would be my take on the evolution past 96-

If this to occur what you will see is both the GFS & UKMO etc limiting the extent of the northern energy & starting to pull it South again- This would occur in the 96-120 range-

If it does this archive chart here:

http://www.wetterzentrale.de/archive/ra/19...00119790207.gif looks very similar to the current prognosis- which went to here-

http://www.wetterzentrale.de/archive/ra/19...00119790211.gif

& finally here-

http://www.wetterzentrale.de/archive/ra/19...00119790214.gif

http://www.wetterzentrale.de/archive/ra/19...00119790215.gif

I dont think this milder weather is all said & done- I would say & hope that the amalgamation of the atlantic into one single vortex again is model bias rather than model integrity-

Lets hope so eh.....

S

[The Weather Yoda]

One of the more interesting aspects of that which the MetO have published today is the notion that 'London' is specfically mentioned. Almost as if they know their charts don't say so, but they still are issuing a warning for the place, anyway.

Peculiar.

Having seen the weather at lunch time I think the meto are thinking that most places will see some leading edge snow as the front moves in, but in the south this will very quickly turn to rain. However, it may still cause a few problems before it turns to slush.

With regard to the 6z this did indeed show the snow line further north than previous models, but as someone has already mentioned it is still further south than yesterdays 6z. Tens of miles are going to make all the difference in this situation and with 36 hours to go there is still time for the line to go further south or north. Just look at the event a couple of weeks ago when the snow suddenly switched direction hours before it arrived and Nick et al got a nice covering.

Nothing is for certain until you see it happening through your window...

[VillagePlank]

Interesting to note that RH levels are quite low for a situation where intense precipitation is predicted to occur. This can mean - note the 'can' and the ommisson of 'will' - that in some lower RH areas (like S/E, and London) that the rising DP as the front moves across will not force the precipitation back to snow; rather it will be the mix of air, itself; if this is in the case, and you've lying snow, you might not even see any rain even where progged behind the front.

It's not well known, but it can snow with a surface temp of 8C as long as RH is lower than 20% (Fouriers Law, and Hicks Law)

So for the time shown on the chart - even though the temp maxes are at 3C for the time (unlikely, but then that's GFS) RH is 70% which still gives a 50% chance of snow if it precipitates due to the notion falling snow cannot melt because evaporation is so fast in low humidity environments that the cooling produced by evaporation is greater than the warming caused by the environment.

Edited February 6, 2007 by VillagePlank

[kold weather]

Yes thats my call as well Eye, heaviest snow in a line between Brum and also Norfolk, snow lighter further north you go, snow turning to rain further south. Fax charts are very similar to what tyou show as is a couple of high resolution models as well.

IF this set-up does occur further south then is expected then this will also slow down the change back to rain for southern area. In fact I've note din the past in these sorts of fronts with warm air advecting its way in that sometimes the warm fronts, at least the frist one is nearly always of snow the whole through, then fizzles out before a stronger one comes in and turns the precip back to rain.

Steve, i'll pray for that Feb 79 set-up, intrestingly the GEM has been quite firm in wanting to bring in a easterly at some point. other models don't but they are close and if they are over-doing the LP out to our west at 120hrs (and lets be honest, they normally do!) then the GEM set-up may not be too wrong and as tyou say I'm not sure the models are too good when these polar vortexes split and if its happens oce, the weather has a habit of doing something several times after that as well.

Finally its intresting that possibly our snowiest set-up for a while has come with 850hpa barely at -5C by the time it arrives, goes to prove that you don't always need deep cold to get cold and this weeks cold will really hurt the CET i suspect.

Edited February 6, 2007 by kold weather

[PersianPaladin]

I hope the snow stays to the south; I don't want my heavy rogue wintry showers to be killed off by patchy snow drizzle.

Edited February 6, 2007 by PersianPaladin

[mezzacyclone]

It's magnificent posts like the above of yours SM that prevent me from doing my job and pulling my brain cells away into the interesting part of my crust like a super magnet?

and to think how we stated our sorrow at missing 70's - 80's classic setups like the one we are grasping now only the other week?

(Yearly allowance off topic post hereby used)

[PersianPaladin]

Some of these 80's\70's comparisons make me laugh.

Honestly, with the amount of uncertainty at the moment; the lack of significant cold pooling into our shores and the marginality of the event for most - you would think it would be anything BUT resembling such past synoptics.

Marginal....localised....temporary.....these are not words that fall into past synoptics.

Edited February 6, 2007 by PersianPaladin

[James M]

I hope the snow stays to the south; I don't want my heavy rogue wintry showers to be killed off by patchy snow drizzle.

Well at least you would have a chance of snow from showers whereas I if the PPN doesnt reach this far north then Im stuck with nothing, though I suppose I shouldn't be greedy as Ive had a fair share of decent fall in the past few years and the south haven't.

Edited February 6, 2007 by James M

[smhouston]

hmm,so basically,this event has gone from a non event, to a possibly a majority of the country even, to now a only south england event? woo,sounds great

[Paul]

Will be locking this one soon and opening a 12z discussion.

New discussion now open here:

http://www.netweather.tv/forum/index.php?showtopic=36226