Weather patterns?

Robwindstorm

Hi guys, just a follow up on some great discussions on the 'General 'page.

Eibhir had some great memories. I remember that April of 84 being glorious followed by a great summer. April 2014 was likewise. I know Bill counteracted this notion with poor Aprils followed by good summers and indeed 2018 had a very cold and wet spring. But I'm wondering off the cuff is there any pattern, with the odd exception, to certain months being the precursor to certain weather types. I must go through my own simple weather diary records and maybe someone like syran would have some more hard facts to test these theories.

Another theory ,as Honesty policy remarked, was summer weather in late spring or very early summer peaking too soon like last year.Does a pattern exist in past years to back up this.

And finally, does a pattern exist of bad European springs like this year, with ourselves, Britain, Spain, Portugal and France experiencing terrible weather, be followed by glorious summers and heatwaves (here's hoping).

Thanks

sryanbruen

I ain't a fan of putting together x = y because it's all statistical noise with little scientific basis to back it up. You can get a combination of x, y and z and it can produce a different outcome if one even differs somewhat or another variable is discovered that may have swung the pendulum in that direction. Now, I'm guilty of doing this myself. On this forum I used to do regular analog updates and had at least some belief in drivers being able to give a vague advance prediction of general trend which may or may not prove useful to contingency planners. I stopped doing them after summer 2019 which was my final long range seasonal forecast as it was so much effort for so little reward as I put it at the time. I'd argue that's even more the case now with too much variables to consider and the massive wildcard of background warming. The recent winter was an absolute disaster.

I'm being a little off topic but it's not just "drivers" that I considered at one point, it's also these monthly weather anomalies or characteristics that I considered into the analogs. People like GavsWeatherVids still do it for their long range updates which I assist in and give the years but I do not approve of this. These "anomalies" are purely statistic and are reflective of one location's weather. Like if a warm April was seen here and you try to correlate that with the weather of a specific month down the line, what if another location had very different weather. What if one variable was very different in other warm Aprils and that swung the pendulum in another way. What if one variable was very different in the months between whether that's an anomaly or driver? A statistic does not affect the weather. It's also relative to current climate and will change over time - a warm April now can be very different to a warm April years back. For example, April 2022 was considered chilly by some at the time and it was near enough the most modern 1991-2020 average but as April is one of the fastest warming months, it is well above older averages.

But anyway, with that mouthful and philosophical opening out of the way, here's some for you from over the years that have been mentioned by me or others:

A warm June = a cold December. This happened in 2010, 2009, 2000, 1996, 1995, 1992, 1976, 1960, 1950, 1940. On the other hand, there's been plenty of warm Junes with mild Decembers following such as 2023, 2018, 2006, 1984, 1975.

A warm September = a mild winter. This is one of the most mentioned because it doesn't have much exceptions. The absolute warmest Septembers - 2023, 2021, 2016, 2006 were all followed by a mild winter. 1985 is a milder September with a cold winter following but is not one of the warmest, 2009 also.

An unsettled September = a cold winter. Plenty of cold winters or winters with significant cold spells coincided with a preceding wet to very wet September such as 1946-47 and 1962-63. However, exceptions include 1978-79 and 2009-10 which were quite dry Septembers especially 2009 which had a prolonged dry period from 8th September, places had little to no measurable rainfall until early October.

A warm April = a cool or unsettled summer. This one stems from the fact 2007 and 2011, the warmest Aprils on record, were succeeded by cool or wet summers. The Aprils of 2009 and 2010 were also relatively mild (though 2010 got frosty at times) and followed by summers that weren't exactly the best rated either. Other warm Aprils followed by poor summers include 2020 and 1987. Warm Aprils that preceded better than average summers include 2014, 2003 and 1984. You could also include 2022 to an extent due to the relativity thing I mentioned above as statistically it was warmer (at least +0.5C above) than most averages.

A cool or wet April = a good summer. Examples of this include 2021 (cold but dry April), 2018 (mild and very wet April) and 2013 (variable rain and cold April). Exceptions? 2012 is a big one, that very wet and cool April began the deluge that would continue into the summer. 2016 wasn't the greatest summer in the world with a lot of cloudy, warm southwesterly winds.

A March dominated by warm, settled conditions = bad omen for the summer. Examples of this include 2012 and 1965 where places had their warmest conditions of the year in March and very poor summers followed. A warm March to be followed by a good summer is a bit uncommon but hasn't not happened. We only have to go back to 2022 for such which had an exceptionally sunny and warm March with a summer that started off quite mixed but got warmer and drier with the best August since 2003/1995 for warm, dry and sunny weather. Other years include 2021, 2003 and 1990 (away from the NW).

There is no scientific reason why if say we have a prolonged period of either very good or very bad weather that it shouldn't last any longer. The reality is with our geographical location and our climate, the normality is westerly winds with sometimes occasional break ups in the pattern via high pressure setting up to our west or east. Anything outside of that is unusual so when we do get periods like spring 2020, climatologically there is always the likelihood of returning to westerly winds because that is our norm. Not due specifically to what a month was characterised by. So when you look at it that way, I can see why psychologically one may think "I'd much rather a great summer than a great spring and the fact we are getting this lovely weather in spring doesn't give me much hopes for the summer". It does feel like we have a quota sometimes and the best example of this I've ever seen is how when you combine Dublin Airport's sunshine totals for spring and summer 2020 and compare it to a normal spring/summer year, you get 101% of average... nearly bang on average but neither season was even close to that! It's as if we spent all our sunshine quota on the spring.. the changes could have been explained to changes in variables though like how we seen a drastic change from May/June 2023 to July. All the high pressure blocking that brought us the warmest June on record retrogressed to Greenland setting up a very wet July.

Robwindstorm

Thanks very much for that syran. As you say it's much harder to predict the weather now than years ago with warmer seas etc.

My old theories of an anticlyonic April =a lovely summer, a Warm settled March =a poor summer and then having two poor summers together (85,86 -2008,2009) probably doesn't hold much water. I hope the latter is not true anyway.

Just also as a matter of interest, I often wondered when I used to look at the old synoptic charts at the back of the Irish independent newspaper, did anyone ever compile these (not the newspaper cuttings) to try and scientifically predict the weather when high-pressure and low-pressure align similarly to past years.

Robwindstorm

Just going through my own records and I can't believe how dry the month of April has been recently. Not always warm particularly in the east with harsh easterlies.

2017 nearly completely dry

2019 dry apart from storm Hannah

2020 Drought

2021 mainly dry

2022 mainly dry

Some of these included a dry 2nd half of march particularly 2020 (covid queuing)

Elmer Blooker

every cold winter is preceded by an anti cyclonic October, the only exception is October 1916 which was wet and cyclonic.
pick any winter that was cold or even severe and you will find that it followed an anti cyclonic October. There’s an old weather lore from the days when there were no weather forecasts that says ‘for every fog in October a snowfall in winter’ I’ll pick a chart from Oct 1894 ..

Oct 1880 too

Gonzo

In recent years we have been having very warm Septembers followed by very unsettled Octobers and in turn we have had very mild winters so this frequent combination of warm Septembers and unsettled often very wet Octobers is not a good sign for winter.

To have some chance towards a winter that might deliver we probably need an average September in terms of temperature followed by a relatively cool but very dry October and then a very wet November.

InAtFullBack

https://www.boards.ie/discussion/comment/121979318#Comment_121979318

I looked back through October 1916 in the re-analysis offering on wz.de and Ireland and the northwest Atlantic Europe region were under a barrage of lows swinging in from the west, southwest and south. Much of this was because these lows were running in to a blocking high east of Finland. This intensified towards the end of October 1916. It was quite a blocking high that kept reforming and spreading it's influence well west throughout the remainder of the winter.

InAtFullBack

https://www.boards.ie/discussion/comment/121979596#Comment_121979596

Strong merit in this I think.

September 2010 was very wet - many of us remember thereafter that winter!

Elmer Blooker

how’s about a few more Jff?

why not get a bit obscure?

an unusually severe Feb followed this ..

sryanbruen

The October fog one interests me (correlation or not) because analogues have shown a lot of dry Octobers or Octobers more often dry than not preceding wintry winters. Naturally, with dry comes high pressure and autumn tends to see an increase in the development of fog due to the relative high humidity.

Looking solely at the Dublin Airport data since 1976 doesn't show much in it outside of individual years. Octobers 1985 and 2012 have the highest number of days with fog in the month of October here according to the data from Tu Tiempo, both of which were followed by relatively wintry winters (1985-86 significantly moreso than 2012-13 whereby the latter Ireland was often on the periphery).

As this is looking at only one station, it doesn't necessarily prove anything because fog can be localised where Dublin Airport doesn't record it but other parts of Dublin may. Just for example, October 2023 has 3 days of fog here (20th, 30th and 31st). However, from my own observations, Dublin also had fog on the 9th via an outbreak of advection fog (more typical of June-September) and radiation fog overnight 24th into the 25th.

The other "issue" with using this analysis as a means of proving anything is the snow/sleet falling day numbers. Like the white Christmas definition, all it takes is one flake to be mixed in so is not a reflection of how snowy a winter is but it's the best data we have available in the public domain so have to make to do with it.