Switch Around

[Weather-history]

With the arrival of some Spring warmth, we mustn't get complacent at this time of the year as there can be drastic changes. It can easily can go from warm Spring sunshine to Winter frosts and snow in a space of a couple of days, I call it "Switch Around". Spring is the season when such drastic changes are at their greatest.

Here's a selection of past "Switch Arounds"

With high pressure over the near continent and a gentle southerly flow, the start of May 1997 was very warm and sunny with temperatures soaring as high as 27C in the south. The heatwave however was short lived and by the 3rd, the weather was becoming unsettled from the west as low pressure moved in. By the 5th, it was wet across many parts as the low transferred into Scandinavia but more significantly it pulled down a very cold Arctic northerly flow across the UK and by the 6th, everywhere was much colder with maxima below 10C and showers of snow was reported in the north and even in the south sleet was recorded. At night time, there were sharpish frosts for the time of the year with minima as low as -4C

From temperatures into the mid 20s to maxima below 10C in a space of a couple of days, one of the most dramatic switch arounds of recent times.

2nd May 1997

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6th May 1997

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Mid May 1995

High pressure was over Scandinavia at the start of May 1995 and this led to a warm continental southerly flow across the UK and increasingly high maxima. Temperatures soared into the high 20s under brilliant sunshine, with Cheltenham recording 28.6C on the 6th. On the 7th, a low was moving into the North Sea and this pulled down cooler air along its western flank and this set up last for a week as increasingly cooler northerly winds flowed across the UK. By the 12th, the air was sufficently cold enough to produce wintry showers even in the south and in the north there were sharpish frosts for the time of the year with minima as low as -5C.

A switch around of heatwave to frosts and wintry showers within a fortnight.

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Mid April 1995

The UK had a gloriously sunny and warm Good Friday (14th April) 1995 with maxima close to 20C, thanks to high pressure. Very gradually over the Easter break, the high pressure slowly retreated into the Atlantic as low pressure pushed into Scandinavia and this allowed a cloudier cooler northwesterly flow to push down across the UK. On Easter Monday, several fronts brought rain to many parts and behind these fronts Arctic air was pulled down across the UK. The weather became considerably colder with maxima often below 10C and there were wintry showers of snow/sleet and hail in many places and frosts at night. A complete switch around to the warm and sunny weather of just 5 days before.

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March 1990 was a very mild month and ended with high pressure over the Low Countries drawing up warm continental air across the UK with maxima reaching as high as 20C. A change in the weather occurred on the 2nd as a low developed to the east of Scotland and this pulled down a cold Arctic flow across the UK. This brought snow showers and even snow cover to places and there were damaging frosts with minima as low as -9C in places. Indeed, minima were lower than recorded than anything that was recorded during the previous winter.

1st April 1990

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4th April 1990

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The last two days of March 1989 was pleasantly warm with some sun and maxima close to 20C. A major change in the weather type was taking place by the 1st of April as high pressure from the Arctic was slipping south into Scandinavia dragging with it very cold Arctic air. A cold SEly flow developed on the 2nd and as the low near the southwest of the UK slipped into the continent this became an easterly and snow showers fell across many parts. Maxima that were in the high teens a couple of days before were now around just 4 to 5C. The low over the continent began to push back northwards and when it engaged the colder air over the UK, the rain turned to snow in places. Some places in the south actually had their first snowcover of the season. The rest of April 1989 was generally unsettled and fairly cold.

1st April 1989

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3rd April 1989

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The last few days of April 1987 were warm and mostly dry but there was a thundery breakdown in the last two days of the month. The start of May marked a transistion from fairly warm weather to much colder weather as a low pressure to the NW of Scotland moved into the North Sea and pulled down NWly winds across the UK. Maxima were well below average and snow was reported in showers in the north. May 1987 turned out to be a colder month than April 1987, a rare event.

30th April 1987: The last day of one of the warmest Aprils on record

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2nd May 1987: We had snow down to sea level here in Manchester.

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19th April 1985

Across southern England on the 19th of April 1985, many areas had some sunshine and it was pleasantly warm with maxima in the high teens. Across Scotland, a low pressure was moving into Scandinavia an associated cold front swept southwards bringing with it a significant temperature drop so by the 20th, southern parts of England bearly had maxima above 10C as a cold NNEly flooded southwards. The next week saw repeated surges of Arctic air flooding southwards culminating on the 27th, with snow shpwers in places and night frosts

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Mid April 1976

High pressure was ridging towards the UK on the 15th and the weather became generally dry and settled although fronts plagued the north of Scotland. The high then drifted into the North Sea and this allowed a continental easterly flow to develop across the UK and temperatures rose higher in the brilliant sunshine and warmer airmass to highs of 21C. On the western flank of the high, colder air was plunging south from the Arctic over Scandinavia and as the high moved further north the colder air pushed SEwards towards the UK behind a cold front that was sweeping across the UK. By the 23rd, it was colder everywhere with frosts at night, and in the SE, there were wintry showers in the NEly breeze. Maxima were below 10C, when they were reaching 21C only a few days before.

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24 April 1971

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28 April 1971

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14 May 1969

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19 May 1969

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Mid April 1969

High pressure was ridging towards the UK on the 15th and the weather became generally dry and settled although fronts plagued the north of Scotland. The high then drifted into the North Sea and this allowed a continental easterly flow to develop across the UK and temperatures rose higher in the brilliant sunshine and warmer airmass to highs of 21C. On the western flank of the high, colder air was plunging south from the Arctic over Scandinavia and as the high moved further north the colder air pushed SEwards towards the UK behind a cold front that was sweeping across the UK. By the 23rd, it was colder everywhere with frosts at night, and in the SE, there were wintry showers in the NEly breeze. Maxima were below 10C, when they were reaching 21C only a few days before.

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One of the most famous ones

This was one of the most dramatic changes in weather of recent times. The last few days of March 1968 were very warm and reasonably sunny in the south. Warm southerly winds were flooding the country and maxima were reaching the low 20s and on the 29th, a maxima of 25C was recorded in Norfolk, the highest maxima ever recorded for March equaling the record set in 1965.

The 1st of April 1968 marked the change in the weather. High pressure was ridging southwards from Greenland into the central northern Atlantic. A low pressure developed in the North Sea and a very cold northerly set up between the low and the ridge formed over the UK. By the 2nd, everywhere was cold with maxima in the low single digits and there were snowfalls and snow cover in a number of areas. At night time, there was some very severe frosts for early April with minima as low as -10C recorded in some areas.

The change was dramatic and maxima that were in the low 20s during late March, were only around 3-6C during early April.

29th March 1968 25C in parts of the SE

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3rd April 1968: Very cold with snowfalls in places

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Around the 12th of May, southerly winds were pumping up tropical air across the Uk, which gave rise a little heatwave. In the glorious sunshine, temperatures soared into the low 20s but this was not a foretaster to a good summer and was infact one of a very few hot spells during 1965. By the 16th, trouble was brewing to the west of the UK as a low pressure developed and moved across the country. As it pulled away into the near continent, cold NNE winds flowed down the western flank of the low and maxima that were into the 20s, a week before now barely made it into double figures. Wintry showers fell especially over the hills in the north. There was another blast of NE winds at the end of the month and under the leaden skies temperatures barely reached double figures, an omen for the coming summer.

14th May 1965: Warmest day of the year

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19th May 1965:

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Edited March 25, 2006 by Mr_Data

[johnholmes]

tks for those interesting changes Mr D. It sure is possible to have very big switches. Remember June 1975, snow stopped cricket in Buxton and a week later it was in the high 20's C

John

[yamkin]

With the cold air not that far away, we may be in for colder conditions.

[Thundery wintry showers]

Very good examples.

I often wonder what this forum would be like if we had another switch like that this year- everyone saying "accept it, snow potential is over..." and three days later, you guessed it, it's snowing!

I remember the 1995 and 1997 examples very well- the 1997 example was a particularly large shock as I remember March and April of that year being exceptionally warm and almost completely snowless across the country. I remember being almost incredulous on the 6th May when it started snowing. I also wonder how people coped with the yo-yoing temperatures in 1995- unfortunately I didn't pay much attention to that sort of thing back then.

[Weather-history]

Here's another example that hit Scotland the hardest.

11th May 1993: Glasgow 18C

http://www.wetterzentrale.de/archive/ra/19...00219930511.gif

14th May 1993: Glasgow 5C

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[johnholmes]

try again

June 1975,, one of the biggest 'turn rounds' in many many years.

on 1st max at Finningley was 11.0C and the county cricket match at Buxton got stopped due to snow

and by the 6th the max at Finningley was 25.6C, and similar values in many parts of the country.

John

Edited March 26, 2006 by johnholmes

[Scribbler]

You’ve taken me back a few years!

As a teenager I used to play village cricket for Blackheath, not far south of Guildford in Surrey.

Somewhere around 1959, 1960 or 1961 our Sunday afternoon match in June was interrupted by a genuine blizzard. It snowed real snow for an hour or more until there was sufficient lying snow to cover a cricket ball – I know because we lost one until it melted later that day! We threw snowballs and made several snowmen and the match was abandoned.

The following weekend we played cricket again and cooked in the hot sun – we all commented on the change.

I don’t remember if it was warm beforehand – but looking at the historical records I can’t find a particularly cold June around then - although I stand to be corrected if my dates are wrong.

A ‘switch around’ of the first order.

[acbrixton]

Mr Data many thanks for this: salutary and illuminating!

Regards

ACB

[Summer of 95]

Very good examples.

I often wonder what this forum would be like if we had another switch like that this year- everyone saying "accept it, snow potential is over..." and three days later, you guessed it, it's snowing!

I remember the 1995 and 1997 examples very well- the 1997 example was a particularly large shock as I remember March and April of that year being exceptionally warm and almost completely snowless across the country. I remember being almost incredulous on the 6th May when it started snowing. I also wonder how people coped with the yo-yoing temperatures in 1995- unfortunately I didn't pay much attention to that sort of thing back then.

I remember May 1995 very well, an amazing month really with all its extremes.

From the 2nd-7th the temperature climbed above 21C every day, hottest were the 4th to 6th when it hit 25. Monday 8th was the VE day holiday and the contrast was a real shock- overcast, barely 10C with a nagging north wind. The next 10 days were the coldest period I can ever recall at that time of year, colder than at any time in May 1996. On several days the temp remained in single figures; on the Friday and Saturday night there were airfrosts (on Saturday 13th frost still covered the lawn at 9am, nearly 4 hours after sunrise) and the crowning glory was on Wednesday 17th when it snowed in Shrewsbury and Oswestry for around 3 hours in the morning (didn't settle there but did above about 250m); the afternoon max was around 4 or 5C. From about the 20th onwards it got a bit milder but was still not warm, and often dull. The last few days at the end was one of the very few really unsettled periods between March and September.

May 1995 was one of only 2 months I can remember which had both snow and 25C; other was April 2003.