Model Outooks: Winter 2008/2009

M.T. Cranium

Model trends past day five at present have low confidence due to difficult initial conditions over North America where pattern change is underway. Large scale retrogression appears to be developing across western regions and the east Pacific, with a very cold Siberian air mass making gradual progress into northwest Canada. This will have the effect of lengthening out the hemispheric waves but also, the energy centres being tracked from today to about the 13th have only moderate resolution at best, there is still a lot of discussion about where the current developing low (in the northern Gulf of Mexico) is actually heading for the next 48h. This is the strong low that is shown on the GFS exiting Newfoundland on the 12th-13th and heading for somewhere around the Faeroes to Iceland. Some recent runs have shown this feature becoming very intense (00z GFS had it to 947 mbs).

The earlier feature that crosses Ireland on the 12th and the UK early 13th is probably almost in the bag now, but its future evolution downsteam is not that certain either.

I think the model tendency at the moment is too mild past about the 18th and that there won't be an endless progression of Atlantic fronts as suggested, but more of a developing trough over the eastern Atlantic and possibly faster movement west of the Siberian high shown coming in from around Novaya Zemlya next week. This could be a bigger factor than shown after about ten days.

So I would remain optimistic about the chances for some snow and cold weather late December and some parts of January.

TheGreenGiant

just out of curiosity folks, what would we be looking for in models or charts that would bring a fall of snow? Like would we need a good easterly wind around the end of December or a northerly depression coming down from Iceland? Would be good to know what to look out for, especially since this year so far has been much colder compared to the mind winter we had last year.

A good decent Northerly/Northwesterly with polar air would do the trick nicely in late december or january for your area [not so much mine as we're too sheltered].
A prolonged Easterly either from a cold continent-it's not cold at the moment so the Easterly would have to have a very very deep fetch from way behind the Urals somewhere and would have to go on more than a week... [very unlikely but not impossible]
If you had a deep and cold snowy near continent recently cooled down by a few potent northerlies-then you wouldnt need a long fetch and maybe a few days of an Easterly would cool us down enough for the white stuff.

A Northeasterly with a direct feed from lapland providing it's very cold...which it could be as theres an artic high near it at the moment with some very cold air embedded.
Thats actually in my opinion an easier outcome from current synoptics [chart analysis] as all you need is a high to pivot correctly in the atlantic stretching towards Iceland to allow air to stream from that source.

A Scandinavian High preferably a thin one located over northern Scandi and greater than 1050 mb is what you need for your Easterly.
The current artic high located over Russia might do that so watch the charts in the reliable time frame [5 days out or less] to see if it is inching westwards.
Watch for the other things mentioned in that timeframe too.

TheGreenGiant

Thanks for that Black Briar, hopefully we get a better fall of snow than what we got last year:cool::D

Snowaddict

Just to add some optimism regarding potential wintry synoptics. If one runs through the average 850hpa temp charts for the 06Z run there is a definate consensus amongst all of the models of an easterly influence strengthening around the Xmas period. The first chart is the average chart for Xmas day.


This is a far cry from the operational run, and indeed is very encouraging IMO. It shows a strengthening of an easterly influence, travelling ever westwards from Northern Scandi and North Eastern Europe towards Western Europe (UK and Ireland), while at the same time the cold pool gradually intensifies.




Just take a look at P number 18, and if you run through the sequence you can see where it is going.



And Perturbation Number 15....



Perturbation 14.... (Don't write off a white Xmas just yet)



Perturbation Number 8.....



And finally, Perturbation Number 2.



In conclusion, we need to take all the perturbations into account.
There is substantial agreement on approx 60% of the members on the latest run of an easterly development towards the Xmas period.
Keep watching, because although the outlook is open to substantial change, it is very encouraging IMO, and there is the potential, and at the moment thats all it is, but there is the potential as others have said for very wintry conditions for the end of December / January.

Regards,
SA

TheGreenGiant

good stuff SnowAddict, those charts look pretty darn good, lets just hope that they come off in time for the Christmas period, but very encouraging indeed:D

Snowaddict

TheGreenGiant wrote: »

good stuff SnowAddict, those charts look pretty darn good, lets just hope that they come off in time for the Christmas period, but very encouraging indeed:D

Exactly, lets hope so.
I have no doubt that they will revert to milder options again and will continue to change between several setups, but I do feel that this could be the year in terms of a true easterly type setup, we have not seen one for so so long in Ireland. Possibly in the last third of this month or early January.

Lets hope something good comes from them, and its definately one to watch.

Rgds,
SA.

Lol lads
14 days hence those charts are-so very very very low resolution ie highly highly unreliable.
The slightest change in the near time of the position of a feature renders such out put useless
They are also a minority of the variants.

They are a tiny possibility.

You'll always find pertubations like that somewhere in GFS.

*important point to note* The GFS is píss poor at resolving potential Easterlies.It's an NWP biased in favour of Atlantic influences.
It's the ECM's that you need to watch for optimism regarding Easterlies and the UKMO.

arctictree

Some nice looking charts now on the GFS 12z now for Saturday/Sunday. They seem on the wrong side of marginal at the moment so hoping for an upgrade in the next couple of runs. The 18z for Sunday is interesting in that there is 'Potential' for an easterly to develop off a scandi high and a euro low:



Unfortunately, the Atlantic wins out over the next few runs and nudges all that east. Still quite far out so there is the potential for change.

Snowaddict

Once again, as on the 06Z run, several of the perturbations are going for the development of an easterly, some as early as the 19/20 December.

This is a bit early IMO, however I do feel that we will eventually see an easterly out of this and if things continue to trend as present, there is significant potential for a wintry outbreak to develop across the Ireland within the next 30 days IMO and going on the ensembles.

The following perturbations go for an easterly development over the UK and Ireland around the run up to or Xmas / St Stephen's Day period.

Indeed, quite a few of them:


http://91.121.94.83/modeles/gens/run/gens-16-0-324.png?12


http://91.121.94.83/modeles/gens/run/gens-20-0-360.png?12


http://91.121.94.83/modeles/gens/run/gens-17-0-384.png?12

(Very interesting)

http://91.121.94.83/modeles/gens/run/gens-15-0-324.png?12
(Very interesting)

http://91.121.94.83/modeles/gens/run/gens-10-0-360.png?12


http://91.121.94.83/modeles/gens/run/gens-9-0-300.png?12


http://91.121.94.83/modeles/gens/run/gens-7-0-384.png?12
(Very interesting)

http://91.121.94.83/modeles/gens/run/gens-6-0-384.png?12


http://91.121.94.83/modeles/gens/run/gens-3-0-360.png?12


Thats 9/20 or 45% of the perturbations showing cold to very cold air over Ireland and UK from time periods ranging from the 20th to the 26th of December.


These are open to change, however with 45% of them showing 850hpA's of between -4 and (-12 in once case) across various parts of the British Isles, the outlook does seem positive.


Of course this may all change and may not come to fruition, however it is encouraging.
Regards,
SA.


PS: I also think, going on the 12Z run, that Sat/Sunday could have potential, however as Artictree said above, we are currently on the wrong side of marginal. But its still a bit off, and GFS 12Z was certainly an upgrade in terms of staying cool to cold over the next few days as least, with only brief milder interludes (mainly on Friday for a time).

Well I suppose it's more encouraging than if it wasn't there.
But thats about it for the moment.
When I see Easterlies peering in ECMWF and the UKMO,I sit up.
Not much point in an Easterly right now though or even late next week as it would actually Warm us up!

That said,it's not an impossibility.

Deep Easterly

ECM 12z still showing big pressure rises to the north east. However, we seem to continue to stay in a cool, showery NW stream throughout most of the run. If anything, it looks a little cooler during the early days on next week that was shown previously:


Possibly enough to whiten high ground significantly at least. The above chart still showing plenty of potential for that easterly over East Europe to make inroads towards us. Depends of course on direction lows to the north will take beyond this charts. More importantly, if that Azores could just feck off away south and west, then chances would increase hugely of something bigger and better happening down the line.

Snowaddict

ECM tonight at T+168 screams potential. It is very close to an easterly with a trigger low thrown in for good measure.

Now I'm not saying that this will materialise, there is every chance that the raging atlantic will break in.

However, in the last 36hrs, things have certainly stacked up more in favour of the development of a wintry outbreak.

Although, prudence would lead me to say the chances are about 30 to 35% (maybe over optimistic) for an easterly / cold outbreak, if things keep trending this way.

This does need to be watched however because as I stated, I do feel that within the next 20 - 30 days there is significant potential for a wintry outbreak.

SA.

LEIN

It seems Weathercheck's optimism has rubbed off onto Snowaddict.

Hope your right SA an Easterly wind with lots of wintry potential is long over due around these parts.

Bring it on!!

patneve

I'd love a nice blast from the east:rolleyes::rolleyes::rolleyes::rolleyes:The one of Jan '08 didn't deliver in Dublin city, although areas North of Dublin had a bit of a snow fest...

Snowaddict

Damo9090 wrote: »

It seems Weathercheck's optimism has rubbed off onto Snowaddict.

Hope your right SA an Easterly wind with lots of wintry potential is long over due around these parts.

Bring it on!!

Indeed .

Seriously though, the outlook is interesting.

Even if we don't get an easterly, its going to quite cool / cold over the next few days at least.

Snowaddict

Snowaddict wrote: »

ECM tonight at T+168 screams potential. It is very close to an easterly with a trigger low thrown in for good measure.

Now I'm not saying that this will materialise,

Of course it wont materialise-T-168 is 7 days which is low resolution and even at that you are saying that out at that low resolution theres only a chance that something you want and I want might happen AFTER we get to that t-168 map which is far from set in stone anyway..

Put it to you this way not only is there only a chance at t-168...theres only a chance that that t-168 would happen at all as it itself is FI...never mind what you would be depending on following on from it.

To be honest with you thats Humpty dumpty forecasting and it's only going to disappoint you

Snowaddict

Deleted User wrote: »

Of course it wont materialise-T-168 is 7 days which is low resolution and even at that you are saying that out at that low resolution theres only a chance that something you want and I want might happen AFTER we get to that t-168 map which is far from set in stone anyway..

Put it to you this way not only is there only a chance at t-168...theres only a chance that that t-168 would happen at all as it itself is FI...never mind what you would be depending on following on from it.

To be honest with you thats Humpty dumpty forecasting and it's only going to disappoint you

Yes, your quite right there. Anyway, the outlook is not bad though all things considered.

SA.

chalkie

Snowaddict wrote: »

Yes, your quite right there. Anyway, the outlook is not bad though all things considered.

SA.

Hi SA.

It's certainly generating enough debate (friendly and otherwise) on various forums! I think a more realistic assessment was made earlier this evening by Will Hand on the uk.sci.weather newsgroup, albeit before the 12z ECM came out. He said;

"Well what a situation. All quite complex. As I have already said in another thread an eastern block will just fail to develop with a bifurcating jet and relaxing upper trough on Thursday into Friday. On Friday a warm front attempts to come in against the cold air perhaps giving some sleet. However, warmer air from Atlantic soon surges east and cloud and rain, preceeded by some snow in northeast should come in later on Friday, but it could be slower. It all gets very interesting on Saturday as deep cold air pushes in behind a slow moving cold front with warm air rapidly occluding out.
Probably rain on low ground but needs watching and possibly wintry on back edge, then on Sunday signs of even more slowing and a cut-off low forming as upper trough digs down into Spain. Then we will have an awful rain/sleet/snow mix. At least it won't be mild! After that I'm really not sure, I don't believe GFS, OTOH it looks feasible with a temporary easterly and vortex over France, though less cold before more zonality later. If I had to make a choice I'd say we will end up with a low just to the north of Scotland by mid-week and a rather cold westerly with rain and hill snow, but confidence is very low. It also looks like the Siberian high may extend across the Arctic, which would push Atlantic lows further south. I await the 12Z ECMWF and JMA with interest."

Will has made some good calls in the past in similar borderline situations. Of course he's been wrong too but given his experience and background I'd give him more credence than some of the guys.

I lurk on Netweather a fair bit and Glacier P's posts are of interest...to say the least. It's clear someone like GP has an extensive familiarity with teleconnections (and a specialised vocabulary to go with it!).
Occasionally I can follow what he says but a lot of the time the cold spell is tomorrow's jam"...i.e. the teleconnection signal for cold is at 10+days. He seems to be standing by retrogression and if his utterings come to pass we may continue to see shifts in the next three to four runs. I'd like to see him proven right but before xmas!

For me, I'll wait for another two ECM runs out to T+168 (MAX) before I'll make my own conclusions. Right now I think, SA, your call of 30% for Easterly isn't too far off the mark. Let's hope it improves but history tells us....;)

Joe

mike65

Here comes the westerlies and there is no chance of snow. You read it here first!

Snowbie

Danno wrote:

Here is an idea, every day from now until the big day, someone details each model run for the big day and posts it in here... no discussion allowed use the http://www.boards.ie/vbulletin/showt...p?t=2055433432 thread to comment instead.

For newbies... http://www.wetterzentrale.de/topkarten/fsavneur.html is where the model output comes from.

Perhaps we could use this template...

Model Output by GFS: Thursday December 11th 1800: Ireland is under high pressure, 1030mb. Upper air temperatures are between +2c and -2c. Nearest 528dam line is 400 miles north. A light rain/drizzle band covers the country. Air temperatures range from 8c to 11c. Snow Chance: 0%

Model Output by ENS: Thursday December 11th 1200: Ireland is under influence from Low pressure anchored off South Greenland. Upper air temperatures range from +1c to -3c. Snow Chance: 0%

Addition 1: I state GFS or ENS in the model as closer to the time we can add in details from UKMO, JMA, ECM etc... when they start showing output for 25/12/2008

Addition 2: Could MT Cranium take care of reporting on the 00z model outputs as he, well, will probably be the only regular boards weather forum member that will be online at 4am Irish time! (barring some seriously good charts)

Good idea Danno, obviously i would contribute but my time be taken up more over the next few weeks so i will give my input when i can. Hope we can get a few to cover most runs.

I would concentrate on 18Z GFS majority of the time, i'm sure Patrick will do ECM runs, UKMO?
Will we take the avg conditions 00-24Z for the 25th like from your template where possible?

Danno

Take a look at http://www.boards.ie/vbulletin/showthread.php?t=2055439442 but please don't post any comments on there.

Use this thread to discuss the big day in question.

I have made a change to the page by bringing in scope to detail other model runs. ENS and GFS are the only 2 that will output data for 25/12/2008 for the next four or five days... but after that it gets more interesting as more and more model runs begin to cover 25/12 and of course the accuracy begins to increase. It will be fun to look back over the thread on Stephens' Day and comment on which model was the best/worst etc...

Deep Easterly

Sounds great Danno, do we just post charts in the new thread? and/or give a brief rundown of what they are showing? My first impression from the ECM is that that model seems very cautiously going for a stormy period around Christmas, with up and down temps. Very very early to say for sure though.

nacho libre

mike65 wrote: »

Here comes the westerlies and there is no chance of snow. You read it here first!

sorry mike65 but there will be snow on high ground. there probably won't be snow on lower ground but sooner or later there will be. so enjoy your westerlies while you can;)

Danno

Deep Easterly wrote: »

Sounds great Danno, do we just post charts in the new thread? and/or give a brief rundown of what they are showing? My first impression from the ECM is that that model seems very cautiously going for a stormy period around Christmas, with up and down temps. Very very early to say for sure though.

I don't know about posting charts as if they are linked, then they will change four times a day, besides, a text run down would be better for the poor oul hoor on dial-up!

LEIN

mike65 wrote: »

Here comes the westerlies and there is no chance of snow. You read it here first!

Lads time for a ban i thinks. :P:pac:

Pangea

I heard there mite be a chance of snow this weekend , given very cold.

Danno

Anyone see Evelyns forecasts at 7pm and 9.30pm... looking very promising, especially that precip predictive chart. http://www.rte.ie/news/2008/1212/6news_av.html?2462567,null,230 <<< have a peek! :P

nacho libre

well it seems the showers will be confined to coastal counties. Hopefully, some will pentrate futher inland,though. i think later tonight or tomorrow morning maybe our best bet.

Danno

Looking at the NW Hi Res 12z Output and Coastal Munster looks like getting plastered with snow. Other risk areas include West Mayo, Galway, Clare, West Offaly, West Laois, NW Kilkenny. Amounts diminish away from the west coast, but it seems to be an organised trough with plenty of potential.

Any rish to the east coast appears to come from todays weather front stalling over the UK and reversing back in to the cold air over Ireland.