Spring Model Discussion 17/3/13 6PM onwards....

[Tim Bland]

Every fax I've seen in the last week has been an exact replica of the ukmo raw output. I often wonder why they bother because 95% of the time they just redraw the ukmo output.

[-uksnow-]

i see the latest fax supports the notion i presented earlier that the uppers just are not low enough for a frontal snowfall of any significance away from high ground at least. i cant see it, although i take on board what those with superior knowlege are saying.

How have you derived uppers from the fax's?!

[bobbydog]

Every fax I've seen in the last week has been an exact replica of the ukmo raw output. I often wonder why they bother because 95% of the time they just redraw the ukmo output.

well considering its their model and the money it costs, they probably agree with it occasionally........

[-uksnow-]

well considering its their model and the money it costs, they probably agree with it occasionally........

But we paid for it! And i demand a change!

[Cheshire Freeze]

Snow for Midlands

[Tim Bland]

18z GFS goes for a continuation of the cold and snow in the north east while the rest of us look at the charts and drool....I'm sure the mrs said she wanted to go to Edinburgh one day....

[LomondSnowstorm]

i see the latest fax supports the notion i presented earlier that the uppers just are not low enough for a frontal snowfall of any significance away from high ground at least. i cant see it, although i take on board what those with superior knowlege are saying.

Frontal snowfall and the 528 line:

12th March 2006, huge frontal snowfall for Scotland, up to a foot near Glasgow with snow accumulating widely in northwest and central England too, even up to afternoon/evening in the northeast:

February 5th/6th 1996, one of the biggest snowfalls across the spine of the country of the last 20 years:

Great Blizzard of 1891 for Cornwall and Devon:

While the 528 line is often a decent indicator of snowfall, in the case of frontal snowfall this breaks down (much like the pattern) and we're left to other indicators, like the 0C 850hpa line (which is an absolute cut off for snow) or perhaps the 950 hpa temperature if the flow is not purely continental. The fax chart does not necessarily preclude frontal snow simply because of the 528 line being shunted to the north.

[Snowman.]

Surprised at the 18z its 'getting there' we had the same problem in January UKMO v all and it won.

ECM just a steam roller the other day is showed the extreme now its show the worse outcome for coldies.

[Cheshire Freeze]

18z GFS goes for a continuation of the cold and snow in the north east while the rest of us look at the charts and drool....I'm sure the mrs said she wanted to go to Edinburgh one day....

I've still got no idea where the boundary will set up. I don't think it'll be as far north as the ECM and GFS push it though!

[Sawel]

The fax says yes to channel low part 2

updated 120hr fax

Sticks with raw output!

That looks slightly modified to me and it is not a carbon copy of the UKMO +120 hrs chart.

[SnowObsessor90]

The GFS 18z shows an easter washout in FI, It'd be milder yes bit ideal by any means.

Edited March 17, 2013 by SnowObsessor90

[Panayiotis]

That looks slightly modified to me and it is not a carbon copy of the UKMO +120 hrs chart.

Yes it has but only slightly, the splitting of the low is still there and it taking the channel as the route is something we want to see, so its encouraging that the Met have stuck with it, would be interesting what Ian's/Metoffice thoughts are on this *hint**hint*

EDIT:Thanks Ian!

Edited March 17, 2013 by Panayiotis

[Purga]

The fax says yes to channel low part 2

updated 120hr fax

Sticks with raw output!

And by jingo it will be raw..

[Mucka]

ECM London ensembles have the Op on the mild side from the mid term as expected.

Edited March 17, 2013 by Mucka

[Captain Shortwave]

NASA hi res, yet again just showing the T120 to see where it stands in the mid-range

Not UKMO awesomeness I'm afraid

Edited March 17, 2013 by Captain shortwave

[Purga]

Snow for Midlands

Yep - watch for the shift south in tomorrow's exciting episode.

[fergieweather]

Every fax I've seen in the last week has been an exact replica of the ukmo raw output. I often wonder why they bother because 95% of the time they just redraw the ukmo output.

Only at longer range. Issue times for Fax charts are set: sometimes modifications haven't been completed with the GM at the t+96 range onwards until much later evening. Thus the fax issue needs to go with raw GM at times for simplicity. Moreover we have yet to see what mods (if any) Ops Centre are making to 12z GM at 4-5d range. These due imminently.

[fergieweather]

Ok have now received modifications etc re UKMO-GM out into Thurs-Fri. Little to add really: same story as Ops Centre have run with over past 2 days; ie Fri seeing heavy, persistent rain in SW/S; threat of significant snow N Ireland, Wales, N England & Midlands. Rate of advance and northward extent of PPN key uncertainties; GM modified towards deterministic/ensemble middle-ground. No early alerts considered imminent given areal and timing disparities. That's it in a nutshell... so no change from yesterday's Exeter viewpoint.

[Panayiotis]

Majority of models tonight in favour of the low remaining circular and as 'one' (at 120hrs) therefore giving us the warmer SE winds, with a snow to rain event for the south and possibly a major snow event north of Midlands:

SO above is the GFS,ECM,JMA,GEM,NAVGEM,BOM,NASA and CMA models you can see they all have similar charecteristics with the low to the SW giving us the SE winds.

Below however is the UKMO:

Clearly a distinct difference between it and the other models.I think the reason its a snowier scenario for the south is because the 1045mb high is furthest south and nearer Scandi therefore the the low splits and sends some energy under the high towards the channel, the closest models which support the UKMO regarding the high are the GEM and NASA models.

The location and strength of the high to the north will make a big difference and we need the other models to follow the GEM,NASA and UKMO with the high if we want the undercut. The second thing we need to see is the low splitting and sending energy towards the channel, the UKMO is the only one which does this so there is reason to be skeptical.

If the UKMO changes overnight then for the south it will be a snow to rain event however it would be a very snowy event for the north if it favours the other models.

[fergieweather]

Sorry meant to add that EC EPS and extended UK4 both suggestive of v bothersome rainfall totals SW/S England Thurs-Fri; e.g. spot 60mm Dartmoor; 30-50mm more widely. Meanwhile snow signal for S in raw 12z GM considered too pessimistic based on comparable EPS output... so this has been greatly reduced in modified version (some transitory snow but primarily a wet gig), whereas threat of significant snow Midlands north (blizzards possible uplands) has better consensus, including from MOGREPS.

[Guest pjl20101]

The ecm ens have been trending away from a decent slow breakdown for a few runs now. Fewer and fewer runs prolong the cold. The spread on a renewed easterly still showing but more muted on the latest run.

I agree nick and hopefully it shouldn't go the full hog if you like. Think that the op models are definitely contradicting the ensemble output and having a tussle sort of thing. Would be interested to know if the recent higher than usual solar activity currently is having an impact on the current atmosphere state.

[bradymk]

Ok have now received modifications etc re UKMO-GM out into Thurs-Fri. Little to add really: same story as Ops Centre have run with over past 2 days; ie Fri seeing heavy, persistent rain in SW/S; threat of significant snow N Ireland, Wales, N England & Midlands. Rate of advance and northward extent of PPN key uncertainties; GM modified towards deterministic/ensemble middle-ground. No early alerts considered imminent given areal and timing disparities. That's it in a nutshell... so no change from yesterday's Exeter viewpoint.

I would say thats a perfect viewpoint at this stage and looks spot on to me. A long way off though, it will change. I would not be surprised though if something like the UKMO 12z op happens, it does seem to perform well in these situations.

[Mucka]

GFS sticking with a none event, actually pushes the less cold air even furtehr North on the 00z

Not much undercutting from there really with a bit of a stalemate and slack damp E/SE flow developing, the worse of both worlds really.

Fortunately (for coldies) UKMO also sticking to its guns.

Dare say the UKMO would even give the South some good snowfall and the Northern extent of the snow would be the worry for people further North. So all to play for still this morning.

NAVGEM closer to UKMO than GFS

GFS ensembles (Central England)

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=253&ext=1&y=60&run=0&runpara=0

Edited March 18, 2013 by Mucka

[Guest pjl20101]

I've checked the GFS 00Z model charts up to 216 hours on TWO and it looks like yes will get milder but also unsettled with the influence from the Atlantic being very disturbed and I think that is the picture the NOAA site are painting currently.

[shaky]

Much better ecm this morning for coldies!!undercuts back peeps!!