Winter/Spring 2013 (Model Output Discussion)

nacho libre

We've seen epic charts like this before, suddenly disappear on future runs in the past. Caution is especially advised when it comes to easterlies in this regard.
i'm 99.9 per cent certain there will be a downgrade in subsequent ecm runs.
in saying that, even with a downgrade of this run, it would still lead to good times for some,and bad times for others:P. if a section of the pv plays ball, by moving to siberia, and there is to be a retrogression to Greenland of any scandi high , hopefully it'll be around the 20th of December:D

M.T. Cranium

Models have reversed roles and the GFS is now mild ramping while the ECM goes nuts at 240h with a very snowy looking map, in poker terms, the ECM has check raised the GFS. Very interesting to see the next step at 00z (ignore the 18z GFS as it cannot be held more reliable in this sort of situation).

The GEM only goes 6 days at the 12z run but is certainly showing potential for very cold air to break through with a 510dm thickness over Norway on day 6. This equates roughly to -12 C 850 mb and -5 C surface type conditions if it advects further west.

I think the betting man's solution here would be a significant shot of cold with better than 2:1 odds for snow some time between 12th and 18th and on that note I would caution friends in particular and readers in general not to bet the ranch on white Christmas bets because you need falling snow on the 25th and I don't like the chances of avoiding either way of losing, cold high pressure or rebound warm fronts, at the timing interval suggested by the heart of this cold spell, especially given the research parameters suggesting a mild spike 26-27 Dec in whatever pattern we reach.

Friday which has been discussed a bit also, rather marginal at low elevations but good potential for accumulating snow in higher parts of north.

maquiladora

nacho libre wrote: »

We've seen epic charts like this before, suddenly disappear on future runs in the past. Caution is especially advised when it comes to easterlies in this regard.

Yep, extreme caution required. GFS and UKMO look a lot less interesting compared to the ECM. Personally I do remember seeing some similar FI charts on the GFS back during the 09/10 winters, though I'm not sure if I remember seeing -12 uppers in the southeast even on those. But I'm sure I haven't seen that before on the ECM.

maquiladora

Deank wrote: »

What time are the ECMs out at later?

ECM ensembles should be out in the next hour or so. Next ECM run will be early tomorrow morning.

Edit: ECM ensemble mean looks good.

force eleven

Villain wrote: »

Calm down calm down, its one run, and not all models are in agreement plus its well into FI. Huge potential but thats all it is for now!

Ten days away is an age in model terms. Four to five days out we will see . If that 240 chart is still there on Sunday evening, then I'll call it. The path to snowmageddon is littered with the corpses of unfinished snowmen...

whitebriar

Larbre34 wrote: »

no, seriously, this is the model thread, anything beyond +72 is irrelevant - ramping and FI polluting all over the place. if those +240s came off it would lead to weather probably not seen in Ireland for centuries which leads to appropriately long odds.

I fear MT may have created a monster this morning

Straight easterlies that cold,if pressure isn't too high would bring snow showers into louth meath and Dublin,the feed would start its sea track at Liverpool bay so long enough.

Light showers or just flurries south of there(ie dry ish Wicklow& north wexford and then snowmageddon again from wexford town Waterford through east cork and points west of those land falls.

I doubt it would be worse than 2010,just a different distribution.

Various features might develop anywhere in the flow changing the areas affected and obviously a frontal attack later hitting a bedded down severe cold pool would see all areas at risk.

naughto

maquiladora wrote: »

ECM ensembles should be out in the next hour or so. Next ECM run will be early tomorrow morning.

Edit: ECM ensemble mean looks good.

can u post it

Nabber

It's nice to get the buzz going again.

But the way the ECM brushes off the low pressure to pass north of GreenLand allowing the high to reach out into the Atlantic. I think this is where a downgrade may come. It might fall inline with the GFS and UKMO and have it drop south of Greenland. Like it so often does.

Long way away to make any plans.

maquiladora

naughto wrote: »

can u post it

nacho libre

The bbc link(http://www.bbc.co.uk/weather/features/20618018) posted on netweather is very interesting, because it shows m.t. cranium's research could still verify around mid december. the nightmare scenario would be, he is right about this time period, but wrong about what happens later in the year. i'd take missing out this time, if we got well below average temperatures in early February.

leahyl

nacho libre wrote: »

The bbc link(http://www.bbc.co.uk/weather/features/20618018|) posted on netweather is very interesting, because it shows m.t. cranium's research could still verify around mid december. the nightmare scenario would be, he is right about this time period, but wrong about what happens later in the year. i'd take missing out this time, if we got well below average temperatures in early February.

Link isn't working Nacho

TheInquisitor

http://www.bbc.co.uk/weather/features/20618018

Deank

leahyl wrote: »

Link isn't working Nacho

http://www.bbc.co.uk/weather/features/20618018

TheMilkyPirate

GFS seems to be joining the party.

maquiladora

18Z looks impressive but the upper air isn't as cold as on the ECM.

Still, it's a long way off and that will change.

mickger844posts

GFS 18z in a similar vain to the ECM 12z but not as extreme. Hopefully no downgrades from the overnight runs.

catch.23

maquiladora wrote: »

18Z looks impressive but the upper air isn't as cold as on the ECM.

Still, it's a long way off and that will change.

For some reason i think I remember someone here saying before that the models (or maybe one model specifically, can't remember) tend to underestimate the severity of the 850hPa temps with an easterly. Is this true or am I imagining it?

(Obviously upper air temps at 240hrs are even less reliable than the rest of the model data, but just out of interest!)

catch.23

mickger844posts wrote: »

GFS 18z in a similar vain to the ECM 12z but not as extreme. Hopefully no downgrades from the overnight runs.

If you're hoping for no downgrades from tonights ECM, you're going to be severely disappointed!!!

derekon

catch.23 wrote: »

If you're hoping for no downgrades from tonights ECM, you're going to be severely disappointed!!!

Why Catch 23 ? Do you know something we don't ? Care to share?

D

odyboody

derekon wrote: »

Why Catch 23 ? Do you know something we don't ? Care to share?

D

Can't be anything but a downgrade, afterall if you gave someone a paint set and said draw the most outrageous chart you can imagine they couldn't come up with better than this afternoons.

catch.23

derekon wrote: »

Why Catch 23 ? Do you know something we don't ? Care to share?

D

Regardless of the fact that this chart is about as extreme as they come, every 240hr chart changes as the time gets closer, hence it will both downgrade (definitely and upgrade (hopefully). The models are not accurate enough for there to be any scenario where a 10 day chart comes to pass with no change in the mean time.

John.Icy

catch.23 wrote: »

For some reason i think I remember someone here saying before that the models (or maybe one model specifically, can't remember) tend to underestimate the severity of the 850hPa temps with an easterly. Is this true or am I imagining it?

(Obviously upper air temps at 240hrs are even less reliable than the rest of the model data, but just out of interest!)

GFS uppers aren't as cold due to the orientation of the high. With ECM we have cold uppers streaming directly towards us as the high over Scandinavia is tilted on a NE to SW axis, which means the uppers are coming directly from a cold source.

With GFS, the high is flatter, so very cold uppers are being diluted over eastern Europe as they are mixing with milder uppers to the south.

maquiladora

I wouldn't worry about the exact details with regard to uppers being +/-2 either way. We're talking about stuff well over 100 hours away. Thats going to change a lot on every run. Overall changes may well end up being a lot bigger than that.

It will be interesting to see how things stand 48 hours from now : still on course for a beasterly, or clutching the straws of another delayed, watered down cold spell?

pistolpetes11

This is a excellent read for you folks

http://www.accuweather.com/en/weather-blogs/weathermatrix/why-are-the-models-so-inaccurate/18097

pistolpetes11

GFS 18Z

http://www.youtube.com/watch?feature=player_detailpage&v=lSNil6im9e0

https://www.youtube.com/watch?v=lSNil6im9e0

pistolpetes11

Ian Ferguson from UK MET office

Final piece of crucial wisdom in MR guidance just issued from Exeter: "...confidence in developments from Monday onwards remains very low....". Having seen their full analysis this caveat sentence is, rest assured, well founded: they're leaning towards EC with latest modifications but let's see where the next few EC runs take us to offer better continuity on some critical nuances Exeter highlight versus UKMO-GM and MOGREPS.

derekon

A stunning midnight ECM just released - severe cold looks like it will arrive in Ireland on Tuesday morning and then push west. Just checked the Icelandic website which mirrors the ECM and this shows the deep blue over Ireland from Monday evening.

This Icelandic website was very accurate during the 2010 freeze.

Given it snow Thursday and the cold looks like it will hit later Monday...........might we now have a wee bit of hope? ie its not ten days away! :D

http://en.vedur.is/weather/forecasts/atlantic/#type=temp

Caff Caff

Looking mighty just a few days out on the oz this morning. A nice progression towards what MT pointed to closing in on the 12th with wintry precip. The GFS seems to be on board too then showing a trend to milder setup as we reach Christmas but we have no idea how long this cold will last. My thoughts are it will not be strong enough just yet but a lovely segway and a taste of what is to come later in the month into Jan as I've thought all along. I didn't see this coming... woooo!! Very exciting models

Caff Caff

derekon wrote: »

A stunning midnight ECM just released - severe cold looks like it will arrive in Ireland on Tuesday morning and then push west. Just checked the Icelandic website which mirrors the ECM and this shows the deep blue over Ireland from Monday evening.

This Icelandic website was very accurate during the 2010 freeze.

Given it snow Thursday and the cold looks like it will hit later Monday...........might we now have a wee bit of hope? ie its not ten days away! :D

http://en.vedur.is/weather/forecasts/atlantic/#type=temp

Nice link. Yea, you can see how by Saturday a cold easterly pushes in and the atlantic fights back with the easterly winning out going into Monday and Tuesday. One, two uniflu!!

Rebelbrowser

MT's take on the models this morning:-

"OUTLOOK ... Much colder air will be massing over the Baltic regions after this weekend and will begin to make a westward push around Tuesday possibly overspreading most of Britain before arriving in Ireland with sub-freezing temperatures and the potential for snow mid-week, and this spell could last several days, a week or even longer -- the latest guidance is not quite as intense as some maps we saw in the past day or so, but still a solid three or four days of wintry weather potential in northeast winds, likely some snow here and there from weak disturbances and the onshore flow of cold air across the Irish Sea. The counties around Dublin, Wicklow and Meath as well as east Ulster would be more at risk but the south coast could see slight amounts and elsewhere the wintry precipitation is likely to be more elevation-based. Current maps have potential for daytime readings of about 0-2 C and overnight lows -7 to -4 C from about Wed 12th to Sat 16th. As speculated yesterday, the cold spell appears likely to relax its grip after that with the blocked Atlantic flow finding ways of pushing back in from the southeast at first, so that near the end of this cold spell, mixed precipitation is likely for a while before a general thaw. The moderately severe cold is about 60% likely on the current guidance, severe cold (days below -2 and nights around -10) about 20% possible. The weakest solution I can envisage is for mixed sleety precip and highs 4-6 C in this period."

Pity Su is not around. Would love to hear his take - usually the voice of reason in these circumstances.

At this stage though some sort of easterly looks inevitable....