Longest run of consecutive wet months?

[Summer8906]

With February certain to become the 8th consecutive wet month across most of England and Wales I'm wondering what the longest consecutive run on record (particularly in the post-war period) is?

I can only recall one other comparable run since the late 70s: September 2000-April 2001 was I believe a run of 8 consecutive wet months (though winter 2000/01 was considerably less miserable than the current winter as there were also a number of sunny anticyclonic interludes).

1960/61 is the other famous example. The second half of 1960 seemed to be an unremitting rainfest:  a truly horrendous period to have lived through weather-wise by all accounts. Mirroring this year, Jan and Feb were also above average albeit slightly drier. The run however ended in March which was mercifully very dry, so 60/61 was another run of eight. (April was wet again, but May and June were dry).

I doubt March will be as dry as 1961 this year, and based on models there is a risk of it being a 9th consecutive wet month as some models (not all, I should stress) suggest a very wet start to the month. Met Office also suggesting a wet first half of the month, with a promise of a drier second half (but they have been promising drier in the 16-30 day timeframe for weeks now, and it's never happened...)

So when, I wonder, was the last time we had 9 wet months on the trot?

Also wonder whether we are on course for the wettest mid-year to mid-year (July to June) on record?

 

Edited February 22 by Summer8906

[Metwatch]

Similar to the ones you mentioned here:

 

[mike57]

I was around in 1960, but too young to remember it. First major weather memory is the smog and daytime darkness in Dec 1962.

[A Face like Thunder]

I started at grammar school in 1960 and yes, it was wet up until March 1961. However dirty shoes = 25 lines, those were the days. 40 years on, 2000/1 was very similar, although I recall the worst of the autumn 2000 flooding ended at the start of December.   

[Summer8906]

 Metwatch Ah sorry, I missed those. Thanks.

[LetItSnow!]

February 2001 had an extremely wet opening to the month and was on course to be another exceptionally wet one, but some anticyclonic weather in the middle section of the month stopped it from tipping into the exceptional category, though it still has an EWP average of 105.3mm. I think further localised flooding in the south occured early in the month. While January 2001 was a break in the north it was another very wet one in the south, strange month in some ways. April 2001 gets forgotten for how wet it was as well, coming after the extreme rainfall in April 2000. Nowhere near as extreme as that but it has an EWP of exactly 100mm. Remarkable period that I have heard is absolutely remarkable and unprecedented for its extremeness so the fact we could rival that just 22 years later is quite extreme.

[BruenSryan]

 Summer8906 The wettest July-June periods on record:

UK: July 2006-June 2007 1344.4mm (records since 1836)

England & Wales: July 2000-June 2001 1258.3mm (records since 1776)

[Summer8906]

 BruenSryan thanks - wonder how we're comparing so far for July 2023-June 2024 thus far, particularly if we factor in the possibility of 2 more slow-moving heavy rain events in the south before the month's end?

 

[Summer8906]

2 hours ago, LetItSnow! said:

February 2001 had an extremely wet opening to the month and was on course to be another exceptionally wet one, but some anticyclonic weather in the middle section of the month stopped it from tipping into the exceptional category, though it still has an EWP average of 105.3mm. I think further localised flooding in the south occured early in the month. While January 2001 was a break in the north it was another very wet one in the south, strange month in some ways. April 2001 gets forgotten for how wet it was as well, coming after the extreme rainfall in April 2000. Nowhere near as extreme as that but it has an EWP of exactly 100mm. Remarkable period that I have heard is absolutely remarkable and unprecedented for its extremeness so the fact we could rival that just 22 years later is quite extreme

I remember Jan and Feb 2001 well - Jan 2001 was perhaps a colder version of Jan 2024 in that it too started with 5 wet days, though these were colder than the same period in 2024. Then there was a two-week cold spell until the 20th (one day later than this year) before the breakdown arrived on the 21st. The rest of the month was unsettled and somewhat milder than normal but not drastically, but the weekend of the 27th/28th produced another short settled interlude with temps back down to average.

The first 10 days of Feb 2001 were extremely wet but then it became dry and sunny with cold nights, before turning cold and unsettled at the month end. However the first 10 days were extremely wet; all three months of that winter were notable for extremely wet periods alternating with much drier, colder ones.

More interesting than winter 23/24 and its 11 weeks of dull, wet, mild southwesterlies, that's for sure.

[LetItSnow!]

 Summer8906 The month of my birth... 23 years ago exactly on this day!  I was told of snow falling on my birthday but I'm thinking hail was far more likely! That or the gas and air was making my mother see things. Can't imagine weather watching was her biggest concern.

[Summer8906]

 LetItSnow! Happy birthday!

Makes me feel old though, I was already more than 10 years into adulthood by then...

There was light snow, enough for a slight covering, down here, even in Hampshire, land of mild, wet and dull winters, on the final Sunday in Feb. The Sat was a cold northerly and very sunny, I vividly remember this as the foot and mouth outbreak had just occurred; I did a walk but had to stick to the roads while out walking as the countryside had been locked down and the footpaths closed. (It was fortuitous that the foot-and-mouth "lockdown" took place during a dull, cold and wet early spring as it didn't feel so much like we were missing anything...)

So could easily have snowed on this day.

 

Edited February 22 by Summer8906

[A Face like Thunder]

 Summer8906 I've been having a look at Brazell's London rainfall stats for the period 1900-64. 7 out of the 8 months from July 1960 to Feb 1961 were wetter than average, with the eighth month - Dec 1960 - coming in at 96% of average, so yes, a truly horrendous period, which I remember from Oct 1960 (231% of average) when we arrived back in the UK after 3 years in the Tropics..

Looking at the stats, there was only one period of 8 consecutive wetter than average months and that was March to October 1917. Other consecutive periods were 7 (Apr to Oct 1924) and 6 (May to Oct 1903 and Apr to Sept 1946).

Other notable periods of above average rainfall, but not consecutive months, were 1927 - 1928 (8 out of 10), 1937 (10 out of 12), 1941 (8 out of 9) and 1952 (7 out of 8).

Compare these with the 15 consecutive less-than-average rainfall months from Oct 1920 to Dec 1921, and we have some idea of how variable our weather can be!  

[Summer8906]

 A Face like Thunder Interesting. Dec 1960 was wet by EWR but obviously drier in London.

So if March does provide a 9th consecutive wet month, it looks like we will have achieved a historic streak. Obviously you're talking about London rather than England and Wales as a whole, but possible I guess we'll have had the first such streak since before 1900.

[hillbilly]

Wettest period i can find here at the local met office[Bradford] is 10 months,June 1927- March 1928 averaging 109mm over the period.

10 month from September 1968 average 97mm

9 month from June 2019

8 month 1944-1945

8 month 1946-1947 but also has 11 out of 12 months in the same period

8 month 1960-61

8 months from June 2012

7 months from October 2015

 

 

 

[Summer8906]

Bumping this now as I'm starting to look at the Monthly Weather Report to provide full documentary evidence on EWP.

I'm also expanding it to cover dry months too.

Started by looking at the period 1974-77, which is notable for extremes of both kind (dry and wet).

For wet months, we had a run of 6 from June to November 1974, though July 1974 was slightly dry in the South East/Central Southern region.

We then had another run of 7 months from September 1976 to March 1977.

So neither will challenge the likely 10 months now, from July 2023 to April 2024.

On the other hand, the period did feature a remarkable 11-month dry period from October 1975 to August 1976.

From the 70s onwards, this is the longest run of consecutive dry or wet months I can find. What a period to have been into the weather! I was alive then but sadly can't remember it.

Furthermore, from May 1975 to August 1976, only September 1975 was wet.

Will continue searching further back, for anything to challenge the current likely-10-month wet spell, or any other remarkable dry spells.

Edited March 29 by Summer8906

[LetItSnow!]

 Summer8906 I haven't finished scrolling through the data but for the overall UKP series, there was a 13-month period from January 1872 to January 1873 where every month was above average, most notably so, though different decadal average may mean some teeter around average.

January 1872 140.2

February 1872 88.2

March 1872 84.9

April 1872 69.1

May 1872 66.2

June 1872 100.0

July 1872 122.9

August 1872 80.8

September 1872 104.1

October 1872 149.5

November 1872 140.7

December 1872 138.3

January 1873 109.1

1873 and 1874 proved to be dry years meaning that the rest of 2024 or at least 2025 and 2026 are likely to be less wet, though in the warmer, wetter era perhaps less likely to swing to notably dry, but it is possible.

Also for extra information, that was just before the extremely wet period I spoke about before that lasted from 1875 to 1883 which actually averaged a little wetter than the past ten years which have been unusually wet. It shows that just because you have one period of extreme rainfall it doesn't mean it won't keep swinging that way. You could argue that the atmosphere swinging to an unusual extreme for the time shows than swinging to an unusual extreme of the other type, aka for us, dry, could happen - or it could compoud the likelihood for a similar spell to persist into the rest of the 2020s and early 2030s but even more excessively wet due to extra moisture.

The ultimate answer is that no one knows. We know the forces at play but we don't know how they'll play. It's sort of like sports really; you might know who's playing but you don't neccesarily know who's going to win.

Coming from someone aversed to sport that is.

[WYorksWeather]

 LetItSnow! I think one of the things that is hardest to disentangle about these statistics in terms of a 'flip', is to what extent there is a genuine cyclical pattern, vs. reversion to the mean.

In short, after a summer like 2022, the odds are that our view of 2023 is coloured a bit. I'm not saying it wasn't poor, but that comparison makes it seem worse. Similarly, I have a feeling that a slightly better than average summer this year would feel a lot better, even if it wasn't as good as 2022 or 2018, because of what preceded it.

In other words, whether there is a cyclical pattern at all is debatable unless you do some pretty robust analysis on the data. After such an exceptionally wet period beginning in July 2023, then it's almost certain that we will have a much drier period that follows it, but a prolonged flip to dry is not necessarily likely.

To say otherwise would imply the gambler's fallacy, in the absence of a statistically robust cyclical mechanism, which is present e.g. in the Pacific for El Nino, but is at the very least much less clear for Europe.

[LetItSnow!]

 WYorksWeather I mean, yeah. I was only looking at the raw figures though, not talking about my perceptions. I didn't categorise summer 2023 as poor as I don't like humid, oppresive heat so it never bothered me. I'm happier when it rains than when it doesn't.

[WYorksWeather]

 LetItSnow! Yeah I meant in terms of figures as well though - in the sense that I'm not sure whether for example a prolonged wet period is followed by a prolonged dry period more often than pure chance would dictate.

I do disagree with you on preferences, but of course this forum is for everyone! Not a fan of extreme heat though, so definitely agree with you on that.

[LetItSnow!]

 WYorksWeather Well, I don't really think the weather (or indeed the universe) really has a balance that could make sense to (relatively) pea-brained humans. The Earth's time-scale is incredibly large, way larger than our existence let alone our records. What we percieve as an unusual frequency may not be unusual if we had a larger scale of monthly records we could analyse over tens of thousands, even hundreds of thousands of years. Then there's the fact that we tend to search for patterns to make sense and of course the planet doesn't have a brain like we do. What we think is random tends to probably be far more organised than we realise. There are only global drivers and I suppose chance that steer the weather. Perhaps their was a particular thing going on that promoted excessive wet weather between 1875 and 1883 despite lower global temperatures. Likewise, there may come a time when there may be something that promotes persistent high pressure over a similar time frame may promote high pressure over and around our shores despite warmer global temperatures and a predisposition for wetter weather. 

[pinball wizard]

As interesting and noteworthy as this wet spell is, my interest is in what happens next. At some point this spell of wet weather will end, what I'm intrigued by is how long before a similar or even wetter spell appears. Irrespective of one's beliefs regarding climate change and it's causes, many predicted that a warmer atmosphere would result in higher rainfall. With our proximity to the Atlantic and island location I'm really fascinated by potential climatic changes. 

With no scientific basis whatsoever I've a hunch that we may have a dry hot summer, I hope I'm wrong about the hot bit as I'm useless once it gets above 18c at night for any length of time, but I've a feeling that we'll have a 'good' summer and then a return to monsoon season from October. Be interesting to see how things pan out.

 

[WYorksWeather]

 LetItSnow! Yep, it's definitely one where putting my data analysis hat on, we just don't have a long enough time window.

It may be that there are semi-predictable trends for e.g. UK rainfall that operate with an average period of several decades or a century or more. Currently, they'd be indistinguishable from noise, whereas with say a 1,000 year or 10,000 year record, they would appear as obvious to us as e.g. the ENSO cycle.

In terms of the variation in trends, there are really three types of factors. The first type are forced changes - e.g. the fall in temperature due to SO2 from a volcanic eruption, the rise in temperature from CO2 emissions, variations in solar activity etc. The second type are autocorrelations - so named for the fact that a dataset correlates with itself over time - these are the cycles or patterns that the human brain looks for, and can of course be regular, like seasonal changes, or irregular, along the lines of the NAO, ENSO, PDO, etc. The final type is of course random noise.

Breaking it down, we know that 1.) would be expected to lead to wetter winters, but possibly not wetter summers, so maybe a boost in probability for this event overall. 2.) is the most uncertain one - we don't have enough data to be sure. Finally, how much of the occurrence we ascribe to 3.) will probably vary depending on what we observe over the next 10-15 years.

Until proven otherwise, I think I ascribe most of the cause to 3.), though possibly with a bit of a helping hand from 1.). I'm uncertain how much to ascribe to 1.) to be fair - it depends on whether there is a further CC related impact beyond just warmer air holding more water that has caused this event. It may be that the overall weakening of the jet stream will lead to increased interannual variability in both temperature and rainfall (a lot has been said, anecdotally, that patterns are tending to 'stick' over the UK for longer than they used to). But again, the data analysis hat says that we don't have enough information.

 

[WYorksWeather]

 pinball wizard That would be the sort of Mediterranean hypothesis - that climate zones are shifting. If we do see more years with winters like this past one, and summers similar to 2018 or 2022, then we are moving towards a more Mediterranean climate. Again though, we don't have enough data to really evaluate whether our summers are getting drier. At the moment, our winters are getting wetter, but summers aren't showing much change. If the expanding Hadley Cell does push the Azores High further north and east on average, we would eventually expect that to override the warmer air holds more water forcing in summer, locking us into dry and hot summers, and then when the Azores High retreats in winter, locking us into the Atlantic-driven pattern so wet and mild, but rarely retreating far enough to allow us proper cold winters.

Again, that is the theory - warmer and drier summers, milder and wetter winters. But a lot of this is predictions of changes that are only in their early stages - the scientific understanding on rainfall could still change by 2050, as it is much more complicated than temperature predictions, which are very easy for the most part.

[Summer8906]

 LetItSnow! Thanks, will continue to look at the MWR to find out if some of the "usual suspects" (e.g. 1954, 1958, 1965-68) produced 10 or more consecutive wet months.

[Summer8906]

 WYorksWeather If anything I would say our summers are getting cloudier and more SW-ly than previously, and probably a little damper. 2018 and 2022 along with August 2016 seem to be very much the exception, rather than the rule. In the past few years we've had the very poor 2021 and 2023, and the below-par 2015, 2017, 2019 and 2020.

The one more positive pattern we were getting was dry and sunny springs, but that has now failed for two years on the trot - 2023 and 2024 being the first time we've had two poor springs back to back for quite a while.

Edited April 2 by Summer8906