Spring 2024 - General Discussion
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Variation does and will always happen. For instance, February 2023 was very dry and the May/June 2023 spell was one of the most prolonged for a large number of years for different places (Dublin Airport had its longest absolute drought since 1955 as one example!). However, the trend since September 2022 has been much wetter than average conditions persisting including the wettest October on national record (2022), the wettest March on national record (2023) and the wettest July on national record (2023) all occurring in this time. That is a lot of national monthly records for what is a relatively small climatological timeframe of 10 months between the 3.
Now as you know, our Met doesn't make things easy in being able to access national stats that would prove useful in a discussion like this. The best I have to offer is an Irish rainfall series I one day made for a post on here and interest sakes to compare how wet or dry a month was across the nation and single out backyard bias. It only goes back to 2009 so is not very useful in being able to see effects of CC. When you initially look at this graph, the recent wet period doesn't exactly seem attention grabbing. After all, we've seen numerous spikes significantly greater than what we've seen like November 2009, December 2015 and February 2020 especially being the big outliers above 200mm. These are not necessarily evidence of what has changed though may have been intensified compared to years ago, that can only be hypothesised rather than concrete. One needs to look a bit closer and towards the end, there is a lack of short columns indicating a lack of dry months. This isn't entirely unique in the series - look at the second half of 2019 into early 2020 which was another notable consistently wet period. In fact, I think it's good to note that in the long-term England & Wales precipitation series (which goes back to 1766!) the two wettest 18-month periods on record there are September 2022-February 2024 and August 2019-January 2021. Could be complete coincidence or at least a little eye opening how the top 2 wettest have occurred so close together.
A huge player in the warm sea temperatures in the North Atlantic and subsequently likely this wet period too as an effect is the Hunga-Tonga eruption from January 2022 with all the excess water vapour that emitted.
The AMO is a variation on Atlantic sea temperatures and its existence has been questioned in recent years as a result of things like volcanic eruptions driving its variation rather than it being a natural oscillation. However, for the sake of this, it's the best thing to go by to visualise the sea temperatures over time. If we take the annual rainfall from the first graph below for Ireland from 1850-2015 and picture it overlayed on top of the AMO, we can see the variation making sense with what we've been told. Ireland's wetter years have tended to coincide with a warmer North Atlantic state (positive AMO) whilst drier periods have tended to coincide with a colder North Atlantic state (negative AMO). That's generally speaking the case - there are exceptions as always that may have been skewed by something else.
One other part of CC that may have impacted the recent exceptionally wet period is the frequency of above average heights to our south and southeast allowing those moisture laden southwesterlies to continue to blow for an even higher frequency than you'd expect. Reanalysis confirms this with a very ripe setup for Ireland southwesterly winds.
Anyway, I've done a lot of rambling for one day and will leave it there.
Roll on the next prolonged high pressure 😒
Post edited by sryanbruen onPhotography site - https://www.sryanbruenphoto.com/
Weather photo portfolio - https://sryanbruen.myportfolio.com/weather-1
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Serious analysis and AMO insights SRyan, thank you!
It looks as though our current positive AMO phase could be shorter and with a lower peak than the 1930s/40s phase. Do you think that's the case or have we not peaked yet?
I just Googled it and I'd posted this in June 2022. At that stage we'd had 10 consecutive drier than normal months including the driest autumn on record. So it was inevitable that we were in for a compensatory soaking from late 22. I didn't see it lasting this long though!
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Tomorrow
A cold start tomorrow with some frost and ice as outbreaks of rain spread over Ulster and parts of Leinster through the day, turning to sleet or snow in some places.
Below some patchy snow cover tomorrow over some northern parts on tonight gfs
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