Dry Julys of late 20th century in the S and SE

[Summer8906]

The "months different to what you remember" thread prompted me to dig up some stats on July in the later 20th century, prompted by a discussion on July 1979.

It's remarkable just how many dry Julys there were in the last 30 years of the 20th century in the S and SE, even in the cooler 70s and 80s. Wet Julys were very much the exception rather than the rule. Even though not all were warm and sunny, all Julys from 1975 to 1990 were, according to the Monthly Weather Report drier than normal in central southern and southeast England , with the exception of 1978, 1980 and 1988. These were then followed by further dry Julys in 1994-97, 1999 and 2000. (Actually I think even the cool and dull July 1998 was dry in the S and SE, though MWR stops at the end of 1993 so cannot verify).

July 1971 and 1972, and to a lesser extent 1974, were also dry in the southeast. I suspect this will have heavily influenced the 1971-2000 July stats, which are probably significantly lower for rainfall in the S and SE than any other 30 year period. Would be interesting to see if they are significantly lower than 1961-90 or 1981-2010, and more particularly 1951-80 or 1991-2020. Would also be interesting to see if a graph of July rainfall shows a marked dip during the 70s, 80s and 90s.

Or is it just that the decades prior to the 70s were unusually wet, making these 30 years "seem" dry according to the rolling 30-year averages?

So for those of us who grew up in the latter years of the 20th century, the change to wetter Julys in the 21st century has come as a bit of a shock and months like July 2007 really did seem like an extreme aberration!

Edited April 10, 2023 by Summer8906

[cheeky_monkey]

was there a change to wetter July's in the 21st Century? i never noticed it TBH 

[Earthshine]

Was going to say I don't think July's in recent years have been particularly wet either!

[Metwatch]

These graphs may be helpful, July rainfall in the south / south east region (very similar areas covered for both datasets.) 

Second graph shows July monthly rainfall anomalies, relative to the 61-90 average. 

Edited April 11, 2023 by Metwatch

[Summer8906]

19 minutes ago, cheeky_monkey said:

was there a change to wetter July's in the 21st Century? i never noticed it TBH 

We seem to have had quite a few wetter ones recently, for example 2002, 2004(? - out of the country but apparently pretty unsettled), 2007-09, 2011, 2012, 2017 and 2021. Think 2005 was also wetter than average overall despite a mid-month warm spell.

 

 

[Summer8906]

15 minutes ago, Metwatch said:

These graphs may be helpful, July rainfall in the south / south east region (very similar areas covered for both datasets.) 

Second graph shows July monthly rainfall anomalies, relative to the 61-90 average. 

Interesting, there does seem to be an indication of somewhat drier Julys between 1970 and 2000 though it's not very pronounced. There does seem to be a notable peak around 2010, not entirely unexpected, with the 00s having quite a few wetter-than-average anomalies. I do notice some years (e.g. 1974, 1987) flip from dry to wet when compared against longer-term means than the 30-year mean though.

Edited April 11, 2023 by Summer8906

[cheeky_monkey]

5 minutes ago, Summer8906 said:

Interesting, there does seem to be an indication of somewhat drier Julys between 1970 and 2000 though it's not very pronounced. There does seem to be a notable peak around 2010, not entirely unexpected.

in fact it look like there was a general slow trend towards drier Julys between 1940 and 2000 then it looks like they start to get wetter again after 2000

[Summer8906]

13 hours ago, cheeky_monkey said:

in fact it look like there was a general slow trend towards drier Julys between 1940 and 2000 then it looks like they start to get wetter again after 2000

Going a bit OT but it's also notable how some Julys in well known fine summers were actually wetter than average (or at least the 1961-90 average). July 1933 and 1959 for example. Would never have guessed that July 1961 and 1963, neither especially known for fine weather, were drier than 1959. And one of the driest on record is July 1885, drier in fact than just about every July in famous hot summers, and a month which never seems to come up in historical discussions.

Presumably 1933 and 1959 both had lengthy spells of thundery weather over a wide area, whereas by contrast 1961 and 1963 had a lot of dry but cool, cloudy weather, not unlike 1979.

Edited April 12, 2023 by Summer8906

[A Face like Thunder]

Interesting Summer 8906, thanks. Brazell (London weather stats) confirms your point about the Julys of 1959, 1961 and 1963. We were out of the country in 1959, but always understood that this was the 'best summer' between 1949 and 1975. Brazell's stats for July 1959 rainfall were 'Total 1.57 ins of rain in the month which was 64% of average, there were 22 dry days and the wettest day of the month was 28th with 0.42ins of rain'. So, excluding 28th, there were 8 dry days with rainfall amounting to 1.15 ins or 0.14 ins average per 'wet' day, which is probably about right for a good summer month. The point about 1959 however was it was consistently dry during the summer and autumn, something which 1961 and 1963 never achieved.