FI Charts ( T120+ onwards) Winter 2023/2024 **READ MOD NOTE IN FIRST

WolfeEire

06z op run is low Res but it's interesting to see the model still flirting with the idea of next week's high linking up with the Greenland system and pulling in a polar airmass.

The prospect isn't entirely without support as the GEFS mean would suggest

Gonzo

GFS 6z getting there towards the end, if only we could go on another few days, where would that high go, we would need it to park itself into position between Greenland and Iceland for several days allowing that bitter northerly down over us and after that try and get an easterly/northeasterly going with cold air locked in. On this particular run the high pressure is a bit too close to the Canadian side for my liking. MT is going for a fairly unsettled period over Christmas itself so perhaps just after Christmas is when we may get our next cold spell and it would want to be much more exciting than the rather pathetic cold spell we just had.

The overall 6z ensembles shows it mostly mild between now and the 22nd of December followed by a rapid cool down into Christmas with a cold spell being edged onto the table perhaps.

Looks significantly dryer from December 15th with high pressure possibly dominating our weather. Those very warm upper air temperatures between the 17th and 21st of December could be very deceptive and instead offer us inversion and very chilly temperatures here at the surface so this run may not be as mild as it looks on the ensemble graph.

WolfeEire

https://www.boards.ie/discussion/comment/121466124#Comment_121466124

Just looking through the perturbations there and there is very strong support for the above northern toppler from a regressing high around 22/23rd.

https://www.meteociel.fr/modeles/gefs_cartes.php?ech=192&mode=1&code=2&ext=0

The mean is moving in that direction too.

Hooter23

Its a long way off yet...but it looks like it might start changing around the middle of december...chance of very cold air from the north or the east too...its changing but we could end up with any kind of weather by the looks of it...we will know in the next few days sure

Gonzo

The one thing we don't want to end up with is close but no cigar with the UK and almost everywhere else in Europe getting plastered. I agree we have quiet a way to go with this one. Another week of unsettled conditions followed by an unknown number of days under possible high pressure and after that everything is up in the air.

Ensembles really starting to dry out from the 15th of December. We still see the chance of a cold spell developing from the 20th of December but with a very wide range of scatter anything from exciting to nothing is on the table.

Hopefully by the end of this weekend we will have a better idea if we're potentially looking at something noteworthy for the final third of December or nothing at all.

Hooter23

If we do get cold from the north it could be much colder than we usually get with potential for polar lows...we used to get this in the past but it does not happen much these days

InAtFullBack

18Z run just out, once this unsettled spell clears next Tuesday it's high pressure building but it sinks SE by the 21st and into a no-mans land with a flabby pressure pattern. A rather dismal output overall and no signs of any real cold, but not overly mild either.

Gonzo

The 18z not much in it tonight but if you thought there was alot of scatter earlier it's even worse now, the milder and colder ensembles are becoming more intense so the gap of uncertainty widens even more.

An enormous spread of options from balmy +10 uppers to plunged into the freezer -10 uppers. Massive uncertainty and anything is possible. Tonights 18z operational in the mildest range of the set so probably won't verify, although high pressure of some description seems nailed on at this stage.

WolfeEire

https://www.boards.ie/discussion/comment/121469358#Comment_121469358

Was just looking at the mean and it is very interesting, at least from the perspective of cutting off the Atlantic and potentially opening up a route for a colder airmass over Ireland in the run up to Christmas. Gfs has been consistent on this for the past 48 hours.

Gonzo

https://www.boards.ie/discussion/comment/121469363#Comment_121469363

Although there is huge uncertainty I do feel at some stage over the next 6 weeks the cold will win out and we most likely will be plunged into the freezer at some stage but what we don't know is will it be a dry and frosty freezer from the north or a snowfest unleashed from the east or north-east. One of them is very likely to happen, or we could get both. I am however looking forward to some high pressure which seems certain at this stage, what I would love would to be on the cold side of the ridge with atmospheric fogs and frost for a few days and then the unstable cold outbreaks after Christmas, wouldn't that be an awesome winter. All to play for right now.

From an early winter model watching perspective this is the most fascinating position we have been in since at least 2018 and before that 2010.

WolfeEire

https://www.boards.ie/discussion/comment/121469383#Comment_121469383

It's all about that high and where it positions itself but right now it's consistently signalled to recede westward or westnorthwestward to link with the Greenland high. With 17 days to go until Christmas Day, I'll take this mean hpa. Was on an American wx forum earlier and the talk is about a mild Christmas period there with a warm Pacific airmass flooding the continent. Pity about them 😛

PokeHerKing

Only 16 days to go folks 🥶

nacho libre

Hopefully the ECM will go the same route as the GFS after day 10. It seems similar enough to the GFS upstream but probably not as quick a route to cold. We just have to hope the sinking high option on some of the Ensembles is not correct. The GFS led the way with the last cold spell, so maybe it'll be the same this time.

WolfeEire

GFS has been performing very strongly in medium to long range output over the course of the autumn. It has not been as good in the 7-day window. I reckon we will see the ensembles over the next few days showing an increasing dip in temperatures for the days leading up to Christmas based on its current output and the 'trend' of a regressing high linking up with the heights over Greenland.

EDIT add-on:

Latest GEFS ENS

WolfeEire

A percentile forecast on likelihood of 850hPAs being minus -5c or below on Dec 22nd below, followed by the various perturbations depicting 06Z GFS run. Cold conditions highly favoured for the couple of days leading up to Christmas. Nothing severe is favoured as of yet but it certainly doesn't look like it will be mild.

Gonzo

GFS 12z has a rather chilly northerly for a day or 2 before Christmas so some seasonal frost and dazzling winter sunshine.

WolfeEire

Thursday 21st December on GFS. It is being somewhat consistent on that Northern toppler for around this time period. Positioning of the high is key should such a scenario develop. Right now, the ensembles are all that matters so will update/edit this post when they are out.

EDIT: Ensembles mean does not follow previous runs re: 20th-22nd in linking up the two highs as well. Next week's high regresses westsouthwestward rather than westward or westnorthwestward and presents more of cool Polar Maritime airmass rather than cold Polar Maritime Airmass potential. The change is very subtle but represents a break from the aforementioned trend of the past 48 hours, irrespective of what the outlier op run above is showing. Will update after the 18z GFS and will taker a look at ECM Ens too when they are out.

Separately, the GEM is favourable toward a more blocked pattern at 240hrs. The ECM positioning of the high is closer to the Azores and there is a distinct lack of heights over Greenland at 240hrs

The GEM ens (top) are a tad cooler than the GEFS (bottom)

On an aside, the latest NAO Index shows a turn toward neutral stage around the 19th/20th. The AO stays negative.

nacho libre

The UKMO forecast is going for a sinking high. They have access to data we don't have so maybe they are seeing that backgrounds drivers won't be good enough for a high latitude block to develop. I suppose another way to look at it might be they won't commit to a cold spell until they are fully confident one will occur, especially given the time of year too. They do dangle the carrot that there might be a colder spell towards the end of December. It would be nice for once if we could get one in the run up to Christmas for once,but if January delivers we'll soon forget about another green Christmas.

WolfeEire

North America in the oven for Christmas.

Dazler97

https://www.boards.ie/discussion/comment/121473081#Comment_121473081

Well that's not something you see every year hopefully that means we'll be in the freezer 🙂 either that or that huge temperature contrast will rampen up the jet stream and send us storms

waterwelly

https://www.boards.ie/discussion/comment/121473468#Comment_121473468

And we know which one it will be 😿

esposito

https://www.boards.ie/discussion/comment/121473081#Comment_121473081

Good. Long may that continue. They’ll probably go into the freezer in late Jan or early Feb which is fine by me.

Dazler97

https://www.boards.ie/discussion/comment/121473614#Comment_121473614

Oh we all know but here's hoping in my fantasy world 🌎

WolfeEire

Plenty of scatter in the run up to Christmas. Turning colder but nothing exceptional on the cards based on latest output. It will change 10m more times. We may rise above the current top monthly air temp of 13.3c later next week based on this but few chances in between or thereafter. It's unlikely that we will exceed the IMT by much for December if at all based on the below. Our current low temp for the month of -5.8c is unlikely to be beaten until later in the month if at all.

It is highly likely that precip levels will finish below normal.

Gonzo

At the moment it does not look like we'll be seeing anything noteworthy in the run up to Christmas. High pressure is likely but it will be a mild ridge most likely with winds from a relatively mild westerly or north-westerly direction coming around the top of the high across us, this is likely to keep us frost free too as there would be alot of cloud around in this scenario.

This spell of high pressure should give us several days without any measurable rain so it will be good for walking and being outdoors.

Once the high moves away we may get a glancing blow of cold for a day or so and after that the models are suggesting the Atlantic returning once again. I think it all hinges on January and February for this winter. All the long range winter forecasts I read suggested that December would be the mildest month of this winter and also the most atlantic dominated but with a dryer trend for the second half of the month. This is turning out to be very accurate so far, I hope they are on to something for January and February.

mcburns07

7-8c and dry for the Christmas period would be absolutely great.

Gonzo

https://www.boards.ie/discussion/comment/121474695#Comment_121474695

a high possibility we will have something like that. It's very unlikely to be a traditional long fetch south-westerly 14C Christmas drizzle.

Gonzo

In terms of warming not much happening on the operational runs but some of the GFS ensemble members are hinting towards a major warming taking place from around Christmas Day onwards, not many are doing it but these are first signs I've seen. Hopefully we will see an increasing number showing this as we progress throughout next week.

ECM also showing hints of a warming end of December/early January.

Gonzo

12z rolling out and looks increasingly mild as the high pressure looks like it will be positioned to the south of the UK and Ireland and we draw up very mild if not warm south-westerlies next weekend with +8 uppers possible.

Moving towards Christmas the high is set to move out into the Atlantic, however there is no northern blocking here to support the high pressure to go far enough north, although cooler air may temporarily move southeastwards across Ireland.

The continent and SE UK goes into the freezer in the lead up to Christmas but Ireland and Scotland stays out in the mild. Of course this is almost 2 weeks away so cannot be taking seriously in any way.

We finish up on Christmas Day in a very mild westerly flow with the high pressure meandering around the Atlantic staying mostly to our south. For us this is a fairly mild run but for the continent it's fairly cold.

sryanbruen

GFS is probably as flat as it looks as it sees the least amount of amplification from the MJO. It goes firmly into the "circle of death" (very scientific 🙃) and stays there.

The ECM has a bit more amplification through phase 5 into 6 but also eventually goes into the COD.

These are not good trends. To get blocking going, you need to see this being amplified through to phases 7-8-1.

The Bureau of Meteorology (BOM) Australian model has been consistently going for a strong MJO progression to phase 8 through the second half of December and then sustains. This would prolong blocking and would also be the key player in forcing a major SSW which would play an important role when the MJO would relax (if this were to verify) and go back through the cycle.

You'd be relying on that BOM verifying but the more time passes, the more it's seemingly on its own with its amplified signal. Therefore, I would not be placing your bets on a cold Christmas to New Year week. This does not preclude polar maritime interludes - Christmas 2004 was such, but it's not great. We would want to see better.