As of May 2024, we're emerging from a significant El Nino event, which has elevated global temperatures. By examining past years with similar conditions, we can anticipate potential trends for Summer 2024.
As of May 2024, we are currently coming out of a strong, but not exceptional, El Nino event, associated with particularly high sea surface temperatures in the eastern tropical Pacific. A strong El Nino event tends to add about 0.2 to 0.3C to the mean global temperature, and thus the recent El Nino has contributed to the recent period of record breaking global warmth.
As El Nino has some impacts on the Northern Hemisphere climate which can extend into summer, it is worth looking back at previous years when we were coming out of a strong or exceptional El Nino, to potentially gain some further clues as to how Summer 2024 may pan out.
A caveat when considering these years is that they saw stronger El Nino events than the El Nino of 2023/24, but they are worth considering as possible analogues nonetheless. A recurring theme of these three years is that the wettest and most unsettled weather tended to be concentrated early in the summer, followed by drier and more settled weather as the summer progresses.
However, the three summers were rather different in character overall. Summer 1983 was a hot and sunny one overall, with cool and cloudy weather largely confined to June, followed by a record breaking hot July with plenty of dry sunny weather for most but also some notable thunderstorms, and then a very dry August with high pressure dominating the weather.
Summer 1998 was widely regarded as the worst summer of the 1990s, but again the wettest weather was concentrated early in the summer. Most regions had a wet June, July continued cool and cloudy but was wet only in Scotland, and eastern England was quite dry. August 1998 was a north-south split month - it was dry and sunny in the south, but it stayed cool and quite cloudy in the north-west, although even in the north it was generally drier than June and July.
2016 had a very wet June in places, particularly parts of eastern England, followed by a fairly cloudy July and a generally warmer and sunnier than average August. In July and August, rainfall was near normal.
In these years, in stark contrast to the years above with exceptionally strong El Nino events, 1973, 1988 and 1992 generally saw the driest and sunniest conditions during June, with the weather turning cool and changeable during July and August. Although June 1988 was quite cool and cloudy in the east and south of England, due to frequent north-easterly winds, it was a very dry month and much of Scotland had plenty of sunshine. July 1988 was particularly wet and cloudy in most parts of the UK, and August 1992 was also very wet, and very dull in the south, albeit relatively sunny in the north.
But the earlier Junes were not particularly dry or sunny. 1966, too, had a warm June followed by a generally cool and cloudy July and August, but the warmth of June 1966 was caused by southerly winds on the eastern flank of an east Atlantic trough, and it was generally wet and thundery, and very dull in Scotland and Northern Ireland. The main anomaly was 1958, when June joined July and August in being generally cool and cloudy.
It is hard to reach definite conclusions based on this, because the years with exceptional El Nino events have tended to have "back loaded" summers with the driest, sunniest and/or warmest weather concentrated late in the summer, while in years with strong but not exceptional El Nino events, "front loaded" summers have been more common. Because of the relatively limited number of years in the sample, these results could also be statistical quirks, analogous to rolling three dice and getting three 5s and 6s.
What does look likely is a warmer than average summer, because of the recent run of record warm months globally and the sustained warmer than average temperatures here in the UK, assisted by the record warm sea surface temperatures in the eastern North Atlantic. The last substantially colder than average month in the UK was December 2022.
A recurring recent pattern has seen low pressure to the west and south-west of the UK, giving warm and wet weather and frequent southerly winds. But when the weather gets stuck in a rut like this, the rut invariably ends at some point, so there is no guarantee that this pattern will continue through the summer.
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