FI Charts ( T120+ onwards) Winter 2022/2023 **READ MOD NOTE IN FIRST POST**
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22-11-2022 7:31pm#1
Mod Note
This thread is for posting/discussing/analyzing FI CHARTS ONLY i.e. Charts in the unreliable time frame, generally +T120 onward for Winter 2022/2023.
If your post does not specifically relate to an FI chart then it doesn't belong here - Off topic posts will be moved
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Ok, I've had enough of this Autumn and with a week of it still to go, I thought it would be a good idea to open the Winter FI thread extra early, as the GFS short range models are already showing us an insight into the first week of December at this stage.
After what seemed like over a year of relatively dry and high pressure dominated weather, the autumn brought a significant pattern change to something much wetter since September 2nd. We are still currently in this very unsettled Atlantic dominated pattern but it does look like a change could possibly be happening just in time for the gates of winter of swing open!
The models are currently playing around with high pressure for the 1st week of December but what they are not sure of is the high pressures position. The positioning of the high pressure at this time of the year is critical to how cold or mild it could be. If the high sits right over us expect plenty of frost and maybe fog. If the high sits to our east, expect mild southerlies or south-westerlies. If the high is just off our west expect a cool north-westerly flow from the Atlantic. If the high pulls out to the mid Atlantic expect maybe a cold northerly shot. If the high positions itself between Iceland and Scandinavia, expect some sort of very cold north easterly etc.
The GFS 12z just rolled out and is showing a rather chilly 1st week to December as heights try to rise towards Greenland. We begin winter December 1st with a rather chilly easterly wind from the Irish/North Sea. This should be a much dryer scenario than what we are currently in. There maybe some showers on Irish sea coasts but at this stage unlikely to be wintry.
We generally keep this easterly going through the 1st week of December but it is not a proper cold easterly, a rather cool and slightly unsettled easterly so eastern and northern areas would expect showery outbreaks of rain at times, It would feel very raw in this setup but unlikely to be cold enough for snow away from high ground as we are not drawing in a properly cold easterly.
We finish up with heights trying to rise over Greenland and Iceland.
This particular run doesn't really get high pressure sitting over us, so less in the way of frost and fog with this one compared to some of the earlier GFS runs I seen over the past few days. There is an overall cooling trend for the first week of December but nothing properly cold either. Overall it looks like we should get a respite from the Atlantic for at least a week, although it may not be completely dry. There is alot of uncertainty to the first week of December as the positioning of the high and the overall strength of it will be key to how dry we get, if it will become chilly and frosty or could we potentially open the doors to something colder from the north or the east. Alot to play for but it does look like we will begin winter on a slightly more seasonal note than usual.
Once we get the next week out of the way, things should start to become a bit dryer, but not completely dry either. Expect this outlook to change quite a bit over the coming week especially with the positioning of the high pressure. After a very mild to warm and highly unsettled November, these charts make a welcome change and I wouldn't be surprised if the first week to 10 days of December end up fairly chilly and more seasonal.
Post edited by Gonzo on23
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The 12z run continues with that theme:
Note, the GFS isn't wonderful with Irish temperature predictions, so I'd shave a degree or so off those daytime maxes shown - especially away from coasts.
Also, the SSW over East Russia continues to show up on the charts!
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We still have a long way to go on this one. Every GFS run is completely different to the last and there is alot of scatter with an almost equal number of mild vs cool to cold runs.
The 6z builds a strong area of high pressure over us which would lead to several days of seasonal frost and fog and rather chilly daytime temperatures. This then pulls out into the Atlantic and at the very end of the run tries to pull down a direct Arctic Express which just about reaches north-eastern Scotland. We can't go any further than this but would like to see this high go further north and slightly more to the west.
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Nice charts from the ECM tonight. For snow at lower levels surface temperatures still a bit high as are sea temperatures but promising to see cooler weather coming from an Easterly direction, also nice to see on tonight's run much less rainfall accumulations ( most of the projected rainfall to fall by next Weds ). Could see some dustings on mountain tops at the end of the run with a set up like that especially the likes of Wicklow.
Interesting to see the Jet coming from the NE.
Chance even colder weather may come from the East ??
Post edited by Meteorite58 on31 -
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Some substantial blocking on several runs, cross model and especially within the ensembles.
Interesting times ahead. Plenty of runs still look a bit boring with high pressure just too close, but becoming more seasonal regardless. I suppose you will put up with some days of high pressure being too close to us for any action to kick off *IF* the high eventually goes walkabouts to a more favourable orientation and position. No major cold pool lurking so we either need something prolonged to give the cold a chance to start spilling into Europe or else we'd need to look at two bites of the cherry and the first spell will set the scene for a reload that will get going much quicker. Cold spells at the start of real Winter can be a real pain when the cold is far away, not often on this island we get the perfect synoptics lasting 7+ days so all the pieces of the puzzle fall into place. 2010 is a great example. Blocking and wind from the East started ~20th November but the peak of the snow that period was what, the 28th Nov - 3rd Dec?
GEM a very nice evolution in FI. Substantial blocking to our North.
By +240 you finally have the deep cold starting to spread from Russia/Eastern Europe. Patience needed.
Considering it's Day 8, the GEM and GFS are really quite similar, though the GFS does not play out anywhere near as favourably owing to better setup on the GEM. Still, a trend you say? My interest is growing but I feel like we had a phantom cold spell only last December (IIRC?) so staying firmly grounded for now.
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ECM at Day 10 another variation of huge blocking to our North. Cold pooling to our East is better here than the GEM, closer...just need things to go our way at that stage with alignment to unleash the beast.
Let's see where we are Sunday evening when todays Day 8-10 charts become Day 6-8.
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Personally I don't know what to make of it all. There's been a clear signal for a decent number of days now for ridging over Scandinavia to start influencing our weather by early December and give relief from the zonal Atlantic flow which has dominated this autumn since the pattern of the late summer broke on September 2nd. There's a lack of cold residue aloft over the continent to advect westward in an easterly flow. This has been common for many easterly attempts we've seen especially of late it seems - most notably February 2017 and January 2021. This has resulted in retrogression of the anticyclone to Greenland being more vital than ever to allow a trigger low to drop into Scandinavia and give the sufficient cold airmasses that would be required to guarantee sea level snow to an island like Ireland. However, would the blocking pattern be able to sustain itself for that long to feed in these airmasses?
Sea surface temperatures (SSTs) around Ireland are currently 11-13C with warmest being in the deeper waters of the Irish Sea. These values are around 1-3 degrees above average for this point in the year, particularly in the Irish Sea. Warm SSTs are like a double edged sword. They can enhance instability and lead to higher lake effect rates, therefore more showers. However, if the sufficiently cold airmass is not able to be advected in the first place, then these showers, unless necessary cooling takes place from intense showers, will generally be of cold rain.
The other thing I am wary about is the state of the stratosphere. The upper stratosphere has had a temporary displacement of the stratospheric polar vortex (SPV) towards Siberia. This in theory would allow for some height rises towards Greenland albeit unlikely a massive omega block that would deliver a severe cold period. Then the upper stratosphere is set to go very cold again over the North Pole with the SPV returning to its home, remember the stratospheric polar vortex naturally is still strengthening until the New Year period when climatologically it peaks in a typical winter. At the same time, we have a very blocked troposphere - at least according to all the modelling of the past week - which leads to a bottom up split of the polar vortex in the lower stratosphere closer to the trop. Apparently, this last happened in the famous late 2010 period to this extent that's been projected by some runs (KEY WORDS being SOME, not all or most!). It must be stressed that is merely a reflection of how lacking such wave reflection from the trop to the lower strat has been since then and blocking highs won't just magically develop in the same way and end up in the same places ideal for cold air advection. If the blocked troposphere disappears, so does any hope realistically speaking for cold lovers of returning to a blocked setup as the strong stratospheric polar vortex aloft higher up would link with the troposphere and give a very zonal pattern which would be difficult to get out of. This is what happened in February 2011.
Earlier this week, I did this very crude set of diagrams to show the classic evolution of a cold spell that is featured in many past winters. We start off with what we have now basically - higher pressure to our E/NE whilst the Atlantic low gets blocked off to our west. Warm air advection between the two weather systems takes place from Iberia or Africa to the Arctic. This inflates the ridge of high pressure on the eastern side and forces the area of low pressure to our west to undercut. At this stage, airmasses being advected westward via easterly winds and the Scandinavian anticyclone are not typically all that cold - to differing degrees from year to year - though rather chilly in nature as it is a continental flow. However, as the high retrogrades to Greenland, it allows colder air to feed into Scandinavia and northeast Europe. Favourable positioning of low pressure systems to our SE will allow cold air advection towards Ireland. A classic negative North Atlantic Oscillation (NAO) signature. This is what happened in both winter 2009-10 and November 2010. In the case of November 2010, the air was sourced straight from the Urals from an extreme northeast direction that is highly rare.
We have been taunted time and time again with "potential" from blocked patterns in so many years. Let's not kid ourselves. I would probably have to use more than two hands to count the many times alone. The whole "short term pain, long term gain" has been said to death as of this point and I expect to see it used more again with the lack of cold residue over the continent and waiting for the block to retrogress westward to allow the cold air to feed in from either the Arctic or Siberia. I don't like the sound of putting up with these raw chilly, cloudy easterlies. I will leave model commentary to other posters and will not be much word from me on the matter until a clearer picture is being painted by everything coming together.
To end this post on a positive note, least we have something to discuss rather than just the rain, rain, rain which this autumn has overstayed its welcome on.
Enjoy the rest of your weekend and thank you for reading my waffle as always.
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GFS 12z has dropped the northerly idea from this morning and going for an easterly instead through the 2nd week of December.
Showers of a wintry nature blowing up over the Irish Sea and peppering much of Leinster. Donegal and parts of the south coast getting in on the action too perhaps.
By this stage inland parts of the country struggling to get much above -1C during the afternoon with bitterly cold long fetch easterlies screeching in from a long distance into Russia via the Siberian Express. The east coast is the warmest part of the country in this setup with the warmer than average sea surface temperatures keeping coastal parts of Leinster up to around 3 or 4C.
This is indeed a Beast from the East for the middle portion of December. Try not to get too excited because this is along way off and the next run could be more like earlier runs where we don't get properly cold or unsettled. If we are seeing charts like this maintained a week from now i'll start to get excited.
Post edited by Gonzo on13 -
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A further swing to the cold side from the GFS with the milder runs becoming less and less for now. We need alot of luck for this to be maintained as this is over 2 weeks away. Everything has to fall into place perfectly and even if it does all it takes is one low pressure from the Atlantic to spoil the fun much like it did in the build up to Christmas last winter. At the same time this is the first time we've had any sort of wintry charts to look at since things went horribly wrong just before Christmas last year.
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After a few wobbles in the charts ECM showing Lots of cold nights showing up now with frost in places, low rainfall totals, daytime temperatures towards next weekend in low single digits, light winds in general look to back from SE to E to NE to N from about Weds onwards becoming more N'ly towards the end of the run. Looks promising to settle and cool down for a bit. Will see how long the the Russian High keeps the cold aimed at us and helps to block out the Atlantic.
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