The cold surge of 30 June 1995: A mountain-trapped coastal disturbance

[knocker]

Quote

Friday 30 June 1995 was the last of several sunny and hot days over much of Britain.  Temperatures exceeded 30 “C widely over central and southern England, yet by the end of the day they had fallen dramatically by as much as 20degC as a cold surge swept southwards to reach the south coast around midnight. Falls of 10-l5degC in one or two hours were widespread (Galvin 1997; and reports in the Climatological Observers Link (COL) Bulletin, June 1995) as light winds were replaced by brisk northerlies and north-easterlies.  These temperature changes could bring a shock to the system! For example, John Spurgeon (1995) reported how, after cycling to Luton (see Fig. 1 for locations) during the early evening, in shorts and tee shirt when the temperature was still 30°C, he emerged from choir practice into the north-easterlies and a temperature of 14”C! Trevor Smith (1995) drove through the front twice in the Vale of York; first from north to south, experiencing a 9 degC rise, and then from south to north, with a fall of 8 degC. Furthermore, the arrival of cold air led not only to early maxima - at Carlton-in-Cleveland, the temperature rose no higher than the 23°C it had already reached by 0800GMT (Cinderey 1995) - but also to gusts causing damage to three light aircraft, at Louth and Leicester (Pike 1998).

Despite these dramatic changes in temperature and wind, there was little cloud and almost no rain on this surge. How is it possible for such a well marked surge to have no significant weather? To explain the event we first look at it in detail, using only routinely available data, and then compare it with similar events elsewhere in the world.

http://onlinelibrary.wiley.com/doi/10.1002/j.1477-8696.1998.tb06351.x/epdf

[4wd]

We had a field of hay which had dried rapidly during the preceding hot days and were dismayed as the chilly fog rolled in by about 11am.

However the crop was very dry and the previous night had not been dewy.
To the consternation of neighbours it was dry enough to continue with the baler into the afternoon.

Baling hay in fog was a completely unique experience - and it was perfectly OK with no mould at feeding time.

[Summer of 95]

Yes there wasn't any rain, but there was cloud. The 30th was a scorching hot day hitting 30C, I don't remember it getting cold later so it must have hit here after midnight. But the 1st was grey, cloudy but dry and only about 18C, obviously the cool air it had brought. There certainly was cloud! But on the 2nd it cleared again, and was back in the high 20s by the 3rd-4th. It was a one-day blip (there was another one on Aug 12th, when completely unforecast rain fell in the afternoon with a cool wind; again it was hot and sunny in the days before and after).

Them were the days when summers had one-day cool outbreaks rather than one-day hot spells.............

Although thinking about it, there was a similar cool down one weekend during the July 2013 warm spell? All week until Friday it was high 20s and sunny, they had forecast cloud near the east coast for overnight to burn off in the sun, but it covered virtually the whole country by Sat morning and refused to burn off all weekend. It brought a similar temp drop, though not by quite so much (27-19C or thereabouts). Was still a real blip in that hot spell, I think it was about the 20-21st? Reading the analysis of the June 1995 event makes me wonder if a similar mechanism was involved then.

Edited January 18, 2017 by Summer of 95