Winter 2022-23 - General Discussion

We have only began meteorological autumn. It is the 11th of September when I am writing this post. Often times this time of year, the thoughts turn towards winter. There has already been a lot of talk on other forums such as Netweather. With energy prices exponentially on the rise, the likelihood of whether 2022-23 will be a cold winter will hold greater than normal chance to be discussed I am sure. As a weather enthusiast and weather photographer, I long for extreme weather events whether be it windstorms, snowfalls, severe frost. However, when writing my winter thoughts, I try and leave bias aside.

Ireland's last genuine cold winter was back in 2010-11 when we had the coldest December on record and likely the coldest month in Ireland since January 1881. 2017-18 and 2020-21 were cold by modern winter climate whilst 2012-13 and 2014-15 were average. Most winters, as to be expected in a temperate oceanic climate like Ireland has, have been mild since 2010-11. We've had some exceptional mild ones, 2018-19 was our all-time mildest on record. 2021-22, 2016-17 and 2011-12 were also up with the mildest. These four exceptionally mild winters were noted also for their anticyclonic nature which is unusual for having such a mild winter though not unprecedented - 1974-75 and 1988-89 also were exceptionally mild and had a lot of ridging from the Azores more akin to summer. On the other side, we've also had notable stormy winters in 2013-14, 2015-16 and 2019-20; to a lesser extent 2014-15 too.

2021-22, the most recent winter season, had a lot going for it from a cold perspective. The exceptional mild autumn pattern of 2021 raised some eyebrows however. The early significant stratospheric warming through October, history has told us this doesn't necessarily translate to a weak stratospheric polar vortex through the succeeding winter and in fact the opposite as PV disruption events cut off wave activity and late autumn is a cooling time of year so this only allowed radiative cooling to intensify and lead to a strong stratospheric polar vortex through the winter which never receded. This was even more the case in the infamous mild and dry winter of 2016-17 which started off with an exceptionally weak SPV through November 2016 but quickly became stronger through December. There was a cold end to November 2021 that brought lowland snowfall to parts of the UK but Ireland was on the periphery and there was a cool start to December. It was looking positive for cold lovers at this point as unlike 2020-21, Siberia was greatly colder this time around and NE Europe had a lot of cold residue with one of their coldest starts to December in a long time. There was a milder spell mid-December with anticyclonic gloom then pre-Christmas there was famously a lot of talk about the first white Christmas since 2010 (or 2004/09 if you want to be technical) with Greenland blocking possibly getting going. In fact, the NAO did indeed go negative for a short period from the 20th to 24th December 2021. This was the first time we've seen -NAO at this time of year since 2010. However, something went very wrong in the atmosphere that remains a mystery and the blocking went kaput with low pressure successfully undercutting it from the south which would result in a deluge Christmas. At this time there was a massive spike in sunspot numbers on the sun, the biggest so far seen in solar cycle 25 up to that point which has been used as a blame for Christmas 2021 going wrong for coldies. I don't buy that direct attribution however and that it was pure coincidence. Then after that we seen the mildest New Year on record with record-breaking mild southwesterly winds drawing up tropical maritime air from notably warm seas. At this point, it seemed like all bets were off for cold and snow with only the long range GFS showing cold, blocked charts most of the time. La Niña favoured a mild, zonal February and that was indeed what we got. So was 2021-22 the biggest fail ever for a winter season? I don't think so. I think 2018-19 was bigger. In 2018-19, there was a big model consensus for a -NAO dominated winter which was theorised to because of expecting a massive sudden stratospheric warming event in Dec/Jan which did happen but the effects did not project onto the NAO and the Met Office did consistently hint at cold conditions which apart from late January just never happened. In 2021-22, there wasn't that same seasonal model consensus and the Met Office forecast was strongly for a mild winter.

With that generic introduction and recent history perspective out of the way, here's what I think based on current modelling and teleconnections or drivers.

For 2022-23, these are how the usual teleconnections/drivers look from an early view:

• QBO is in its mature westerly phase. This is said to decrease the likelihood of a major mid-winter sudden stratospheric warming occurring and lead to an intensified North Atlantic jet stream. Therefore, increase the chance of a mild winter.
• The North Atlantic Ocean is in an unprecedented warm state. The sea surface temperatures are off the scale near Newfoundland. Warm sea temperature anomalies around here historically do not correlate well with a cold winter in western Europe. Back to at least 1951, the North Atlantic hasn't been warmer than it is now. A general warm North Atlantic in winter time is more conducive to a weakened North Atlantic jet stream with less of a contrast between the tropics and the arctic. However, any westerly winds will be greatly milder than normal and polar maritime northwesterlies will be highly modified compared to usual. The warm SST anomalies also allow Atlantic tropical cyclones to hold tropical status for longer further north.
• The ENSO region in the central Pacific Ocean is in a developing La Niña phase. The modelling suggests this will reach moderate status by November. Currently it is in weak status with the recent week returning an anomaly of -0.8C in region 3.4. La Niña is said to favour front-loaded winters in Europe with negative NAO early on through November, perhaps December and positive NAO later with a mild February. This is especially true for stronger events, less so for weak events. This will be the third consecutive La Niña winter in a row, 2020-21 and 2021-22 both had moderate La Niña events too. The La Niña is currently more central based than eastern based - whether the event is central Pacific based (CP) or east Pacific based (EP) has been shown to have significantly different effects. An east based La Niña is more conducive to a cold winter than central based. There are also mixed events which are far rarer and the sample size is too small to come to any conclusion or to theorise.
• The 2022 Atlantic hurricane season has been notably calm to date and is highly unusual for La Niña. The Saharan dust layer this year has been strong and has been the prime reason for calm activity. August 2022 was the first August without a single named Atlantic tropical storm since 1997 and is the first known occurrence that has occurred during a developing La Niña, the other occasions were El Niño or ENSO neutral. September has so far seen a few named storms but the season remains firmly inactive on what is expected as of this point in the year. Active hurricane seasons are said to increase the chances of a cold winter but this theory like most others has mixed results at best and there are plenty exceptions - the last inactive hurricane season was back in 2015 and each hurricane season since has been active yet there has been no genuine cold winter in that time. 2009 was an inactive season and was succeeded by the coldest winter since 1978-79.
• The Indian Ocean Dipole is in its negative phase. Therefore, there is little chance of a repeat performance of 2019-20 when autumn 2019 had an anomalously positive IOD phase and this resulted in little wave activity to disturb the stratospheric polar vortex from intensifying. 2019-20 was therefore infamously called the 'Polar Vortex of Doom' winter with Europe having one of its mildest on record and for Ireland, a very wet stormy one and notably so in February 2020. However, that is irrelevant to this year because the opposite has happened.
• Solar cycle 25 is nearing its solar maximum phase which is expected to occur around 2024-25. The solar minimum occurred in December 2019. Solar maximum winters are associated with mild, zonal winters whilst cold winters are said to happen around or just after minimum. 2020-21 had a vast amount of high latitude blocking but it was never in the best position to send severe cold weather directly towards Ireland and was a near miss. Apart from that, the winters around solar minimum of 24/25 have been mild to very mild. This is a big contrast to what happened in the prior solar minimum. Blocking position is of vital importance! Ireland is one tiny part of a big world.

As you'd expect from posting early, the drivers are mixed and don't provide much to base thoughts off of. On the whole, I would lean towards a mild winter and not because of the fact that mild winters are just our norm anyway. The record mild North Atlantic even though it could lead to a weakened jet stream means any westerlies we would get would be significantly milder than they are already. Another Azores or Euro high dominated winter like 2021-22 would be exceptionally mild again and would completely overthrow any colder shots from the north or the east in the overall seasonal means. Would need a genuine strong Griceland block in my opinion to lessen the impacts of the mild Atlantic. If we are to see any cold weather, it would be early on in the season to go along with what you'd expect with a La Niña.

See how these thoughts evolve over time. Will they age poorly? How much will they change?

Thank you for reading.