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Stratosphere watch 2022-23



  • Registered Users Posts: 151 ✭✭Niall145

    Late January 2021 is the only obvious exception, however that was a very localised affair which only delivered snow for North coastal Dublin pretty much (thankfully where I live lol); still the only proper lying snow (lasting more than one day) we've had here since BFTE.

  • Moderators, Science, Health & Environment Moderators Posts: 16,697 Mod ✭✭✭✭Gonzo

    same here in Meath, 2010 is the last time I saw lying snow in January. 2018 is the last time I saw lying snow at any point other than a dusting of 1/2cm, not enough to make a snowball or snowman. This is the 5th winter in a row with barely any snow in Ireland apart from the north-west, some midland areas and high ground.

  • Registered Users Posts: 16,621 ✭✭✭✭nacho libre

    Yes, snow has become rare in January(although I had 4 days of settled snow this January) , and even February is seeing less snow. What I meant was in a cold set with less cold uppers in those months you can get snow, but by Mid March you need the the coldest solutions to get snow to stay on the ground.

  • Registered Users Posts: 1,342 ✭✭✭esposito

    I think our 90s winters were even better than our last 5 winters!

    Obviously Feb 91 (which I don’t remember as too young) but I do remember decent falls of snow in 1996 and 1997and pretty sure it was the month of January.

  • Registered Users Posts: 13,493 ✭✭✭✭sryanbruen

    The SPV is currently weaker than all other years in the ERA5 record!!!

    The zonal mean zonal wind at 10 hPa 60N is today (GFS analysis): -9.8 m/s

    Weakest zonal wind at 10 hPa 60N in ERA5 record for todays date is: -9.1 m/s 2018

    Strongest zonal wind at 10 hPa 60N in ERA5 record for todays date is: 58.0 m/s 2020

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  • Registered Users Posts: 6,867 ✭✭✭pauldry

    We had snow in February in Sligo just 2 years ago. Enough to build 3 snowmen. About 2 inches. But we get snow once or twice nearly every year up here. Donegal even more often.

  • Registered Users Posts: 13,493 ✭✭✭✭sryanbruen

    Re the second spike in warming, I've seen discussion surrounding this that there might have to be a third category of polar vortex evolution rather than just displacing and splitting. Interesting stuff, so pretty unusual.

    This second spike I would say would be an important factor in pushing the effects of this major SSW downward which would give us a likelihood window of second week to third week of March.

  • Registered Users Posts: 16,621 ✭✭✭✭nacho libre

    The latest update from the UKMO is rather disappointing if it's snow you are after. No mention of snow at all. In fact it seems like a more mobile setup after the first week of March. I hope this update is subject to change due to the ssw, but I suspect Glosea has factored this in.

  • Registered Users Posts: 16,621 ✭✭✭✭nacho libre

    It seems there will be a block of sorts but probably not far enough north to advect the very cold air our way, which means any Atlantic systems pushing in will just fall as rain here and in the UK. This really feels like a kick in the teeth , but as has been stated many times SSW do not guarantee us the white gold. However If the ec46 is correct the very end of March could be cold, but that's too late from my perspective. So maybe the problem is we are relying on the 2nd warming to flush it all down into the trop, but we won't see the consequences of that till the end of March.

  • Registered Users Posts: 13,493 ✭✭✭✭sryanbruen

    Reading between the lines, it seems at this current point in time that they are seeing the strat and trop continuing to be in disconnect which has been a theme for much of this winter as Butler says.

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  • Registered Users Posts: 16,621 ✭✭✭✭nacho libre

    Yes, not connecting till late March, if at all. Someone has not told the GFS though. Another garden path scenario in fi. I am not falling for it this time!

  • Registered Users Posts: 1,092 ✭✭✭Packrat

    May I ask politely why serious snow is "white gold" or desirable?

    Severe cold kills people and animals and makes life difficult in general particularly for those of us who take care of either or both.

    No judgment, just trying to understand.

    “The Party told you to reject the evidence of your eyes and ears. It was their final, most essential command”

  • Registered Users Posts: 6,126 ✭✭✭highdef

    It's just personal preferences. In a similar way that I absolutely love hot, calm and sunny conditions with temperatures around 30° being ideal for me. Whilst that could be detrimental to some people, I find it very pleasant.

    I understand that those conditions could prove to be dangerous to some people but it's not unreasonable for me to desire such conditions as I'm currently able to deal with them.

  • Registered Users Posts: 1,035 ✭✭✭compsys

    Well you could say the exact same about extreme warmth.

    Besides, when it snows in Ireland the temperature is still usually above freezing during the day and only a few degrees below at night. That's not severe cold.

    Apart from the odd very unfortunate homeless person on the street (who sadly often also suffer from addiction issues) it's almost unheard of for anyone to die from the cold here. Help and support is available. Despite what the media would have you believe we spend 24 billion euro on social welfare each year - no one goes without the basics.

    Also, this is a weather forum - we're interested in extreme weather and what we want won't change anything.

    Also - sport, alcohol, driving, and flying etc also kill people - should people not have an interest in sport/motoring/aviation etc?

  • Registered Users Posts: 1,092 ✭✭✭Packrat

    Fair answers both, if a touch sociopathic.

    Couldn't agree about sport alcohol aviation etc as they generally only kill or hurt those who participate, and we have severe penalties for those who kill or injure others whilst participating in those activities.

    Probably the best point made was that what people want won't in any way affect the outcome so it's all moot.

    Anyway, I'm derailing the thread so I'll leave it there. Thanks for the replies.

    “The Party told you to reject the evidence of your eyes and ears. It was their final, most essential command”

  • Registered Users Posts: 13,493 ✭✭✭✭sryanbruen

    The U-60N reached -14.8 m/s today according to the GFS, this should be the "peak" of this warming spike and a recovery will take place to westerly by Wednesday but then quickly reverse back to easterly again from the Friday or Saturday. The latest GFS shows the U-60N getting down to -22.1 m/s at its peak on Wednesday, March 1st.

    Here's the latest strat temp charts at 10hPa and 30hPa.

  • Registered Users Posts: 16,621 ✭✭✭✭nacho libre

    So what did it peak at in 2018? With those kind of values, if the trop and strat do connect due to the second warming, mid March onwards could become very cold.

  • Registered Users Posts: 16,621 ✭✭✭✭nacho libre

  • Registered Users Posts: 13,493 ✭✭✭✭sryanbruen

  • Registered Users Posts: 1,852 ✭✭✭Steve F

    I second this but would like to add that if the weather becomes "bad" enough to prevent people from working not every company will pay their workers

    Do people who fall into this category still desire the "white Gold"

    In the current financial climate(see what I did there?) where the cost of living is soaring 3 or 4 days of no pay will be very bad news for lots of families.

    Just the other side of the story

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  • Registered Users Posts: 12,844 ✭✭✭✭average_runner

    There is a bad side to every story. That shouldn't prevent other people looking for joy.

    Hopefully we will have a great summer also, but this will affect other people.

    This is a weather forum where people discuss weather, cost of living go to the economic section

  • Moderators, Home & Garden Moderators, Science, Health & Environment Moderators Posts: 17,681 Mod ✭✭✭✭DOCARCH

    Mod Note: Please stay on topic. Off topic posts will be removed. Not the place for 'good'/'bad' weather debate. This thread is specifically Stratosphere Watch 2022-23. There are other threads for general discussion.

    Post edited by DOCARCH on

  • Registered Users Posts: 13,493 ✭✭✭✭sryanbruen

    The U-60N has reversed back to westerly today at 1.2 m/s and this is related to a spike downward in the stratospheric temperature as illustrated on the graph below.

    However, as has been mentioned, the U-60N will reverse back to easterly again this weekend and will even do so as early as midnight tonight. Although, it is looking like there'll be another temporary westerly period on Sunday before this warming peaks on Tuesday, February 28th down to ~-18 m/s. This reversal could last until the second week of March before the U-60N reverts back to westerly.

    Recent GFS runs have backed off downward propagation, today's NAM forecast is yet to update on stratobserve, the site I usually use, so here is yesterday's forecast. NAM looks to be around neutral on this forecast through the course of March, likely indicative of not much of a signal and the model is struggling to see what will come off of it. This is to be expected with further volatility and changes likely at least for a good week or so. It'd be very useful if there was an ECM equivalent to this.

  • Registered Users Posts: 13,493 ✭✭✭✭sryanbruen

    Here we go, we have lift off. Expected to peak this time tomorrow.

    The SPV is currently weaker than all other years in the ERA5 record for todays date!!!

    The zonal mean zonal wind at 10 hPa 60N is today (GFS analysis): -12.3 m/s

    Weakest zonal wind at 10 hPa 60N in ERA5 record for todays date is: -8.9 m/s 1979

    Strongest zonal wind at 10 hPa 60N in ERA5 record for todays date is: 47.5 m/s 2020

  • Registered Users Posts: 16,621 ✭✭✭✭nacho libre

    A long way off the 2018 peak.

  • Registered Users Posts: 13,493 ✭✭✭✭sryanbruen

    A short review of the February 2023 major SSW event. Provisional GEOS-FP data shows the major SSW peaking at ~-18 m/s U-60N which brought date records for the time of year and was very significant for a displacement event. Displacement events do not tend to get this strong and was more intense than both the January 2019 and January 2021 displacements.

    We seen downward propagation occur during the first to second week of March with the NAO going negative and a transient Greenland block setting up by the 6th ushering in a northerly flow to Ireland. The block quickly weakened and numerous low pressure systems attacked from the southwest during the 8th-11th March bringing outbreaks of snow to many especially but not limited to higher ground. Low pressure successfully undercut by the 12th March and brought in a milder flow from the southwest with only occasional northwesterly cooler interludes. The longevity of the high latitude blocking was what you expect for a displacement event, you'd expect longer from a split type event although as seen in 2018, that can also mean extreme retrogression.

    The GFS in recent days was showing perhaps another push of downward propagation from the major SSW into early April (see the second time series chart below from the 26th). It has backed off this in the very recent runs but we have to wait and see. Could change back or could disappear altogether.

  • Registered Users Posts: 13,493 ✭✭✭✭sryanbruen

    On Thursday, April 20th, the final stratospheric warming (FSW) of the season was declared with the U-60N reversing to easterly and as far as the forecast period goes, there is no sign of reversal back to westerly for 15 consecutive days which marks the dissipation of the 2022-23 stratospheric polar vortex. This is a slightly later than normal FSW which is standard with winters containing mid-winter major stratospheric warming events but is not remarkably so relative to the average date which is April 15th.

    The weak and slow descent nature of this FSW likely means it's radiative rather than dynamic which results in negligible impacts. Late FSW events are usually radiative with one major exception being 2018-19 where the FSW in spring 2019 had the effects of a mid-winter major SSW and May 2019 had record -NAO lasting into the summer of 2019 which was largely dominated by Greenland blocking. The current -NAO episode is purely coincidental rather than being the result of the FSW and is more likely to be a lasting effect related to the major SSW back in February along with favourable MJO.

    From a stratospheric point of view, this was another winter of learning. We started off with a bottom up split in late November/early December which was last seen in the infamous late 2010 period. This meant a split of the polar vortex but from the troposphere to the lower stratosphere rather than the top layers of the strat increasing the risk of -NAO and indeed we got a notable -NAO period coinciding with the coldest December spell since 2010 in the country but due to various things like lack of sufficient instability and warm sea surface temperatures from the very warm spring-autumn period of 2022, there wasn't much snow to be seen for most. The effects of this bottom up split faded very quick by mid-December with the strong stratospheric polar vortex aloft resulting in a prolonged wet, zonal period to mid-January. There were numerous attempts of a SSW forecast by the GFS which had an "upgrade" on 30th November 2022 but its performance correlation throughout the winter showed it as more of a downgrade than anything else. Eventually, we did get a major SSW in late February in the form of a wave-1 displacement which ushered in a brief period of -NAO during March, brief as you'd expect given the nature of displacements. The second half of March had more of a +AO/+NAO setup generally and it was a mild month overall - the very warm Atlantic which reached record heights last September aided this.

    Like 2020-21, another frustrating winter on the whole for winter enthusiasts of so much close shaves but least some managed to get something exciting and wintry out of the December, January and March spells which can't be said for every winter.