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Thundery wintry showers

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Thundery wintry showers last won the day on November 12 2012

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About Thundery wintry showers

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    Cumulonimbus Incus

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    East Exeter, Devon
  • Interests
    Weather (of course!), chess, music, computer gaming, social events, football, tenpin bowling, environmental issues
  • Weather Preferences
    Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.

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  1. One facet of this July (noticeable in Exeter over the last few days) has been the large number of supposed "sunshine and showers" type days which have seen remarkably little sun. It hasn't been quite so bad here as the middle third of the month was quite sunny in south Devon, but further north it's really been a cloudfest.
  2. This has been mentioned before, but Heathrow changed from a Campbell-Stokes sunshine recorder in 2005 to a Kipp-Zonen one and the K-Z recorder typically records about 10% less sunshine in the summer months. Allowing for this, August 2007 would be another dry and sunny but cool August (Campbell-Stokes equivalent of approximately 212 hours). August 2005, a sunny month in London by almost any standards, also qualifies relative to the 1971-2000 and 1981-2010 averages, though it was fractionally warmer than the average for 1961-1990. I do agree that dry and sunny but cool Augusts are relatively rare, certainly in comparison with Mays, Junes and Septembers, but the ENSO signals for 2020 have broad similarities with 2005 and 2007, which is one line of evidence that could contribute to us getting another dry, sunny but fairly cool August this year.
  3. I thought June was alright here in Exeter, very wet admittedly but quite warm with close to average sunshine. Two thunderstorms on the 11th and 17th and warm/hot sunny weather on the first two days and 22nd-26th stick out. The first half of July has been quite cool and dry but very dull (it seems to have been a dull first half of July everywhere, even in the dry south), with little in the way of notable weather events either, but sunshine amounts seem to me to have picked up a bit recently, so there is still scope for July to be "saved" if the second half proves to be substantially sunnier than the first half. Next week certainly looks like having more sunshine down here (though maybe not in the north), but the current model outputs for the last week of July suggest that things could cloud over again - it could change nearer the time though.
  4. It's an interesting question, as my experience has been that at most times of the year this holds true, but not so much in high summer. There are a couple of reasons for this that I can think of: The dominant/strong Azores High in high summer, which results in a fair amount of moist tropical maritime air coming into the circulation, rather than clear, showery polar maritime air masses. There's been a lot of frontal activity around so far this month which has prevented clear showery polar maritime air from getting going for long. Sunshine and showers type weather requires instability, which is assisted by relatively cold air masses blowing over relatively warm seas. In the summer months, the sea tends to be cool relative to the land masses, and so we're more likely to get relatively stable air and stratocumulus coming in off the sea. In summer polar maritime air masses can become very unstable as they pass over the land mass due to solar heating, hence East Anglia, Lincolnshire and the south-east tending to be favoured for thundery activity off a showery west to north-westerly in summer due to the large amount of land mass that the air mass passes over before its gets there. But for that to happen you ideally need sunshine to begin with... In summer we tend to get sunshine and showers type weather most often from relatively slack setups, often indeed with a westerly or north-westerly flow, but with a weak jet stream and not much frontal activity - in contrast to what we've had so far this July.
  5. Yes I think 2011/12 goes down as a decent example for much of south-eastern Britain. February was a "month of two halves" and in the SE the cold first half managed to outweigh the mild second half. Also, while June 2020 was rather wet for many, it was a warmer than average month with sunshine just a smidgeon below normal for the UK as a whole, so I don't think comparing with a mild Dec/Jan and cold Feb is a fair comparison. Even if you took the global warming trend out of the equation June would come out no cooler than average. By this measure the likes of 1982/83 and 1993/94 stand out more as potential winter equivalents, both having a near-average December, mild January and cold February (and the average December 1993 hides a regional contrast, it was mild in the SE but cold in Scotland). Perceptions of this summer are being affected by what has admittedly been an unusually dull first half of July.
  6. It has been an exceptionally dull start to July in many parts of the country, and it has also been notably wet in north-west England, though not in the south of England where dull dry weather has reigned. However, there's still a large part of July left, and for all we know the second half could prove to be very sunny and raise sunshine totals above the long-term normal. And yes, Azazel is most likely recalling December 2015 not 2016. That said, over much of Scotland December 2016 was warmer than December 2015.
  7. Having compiled the UK area-average summer index, I get 2007 196, 2012 175. Averaged over the UK, summer 2012 had a mean max temp 0.35C cooler than summer 2007, it had 69 hours less sunshine and it also had 5.6 more wet days. Indeed, 2012 had the highest number of wet days of any summer in the period from 1919 to 2019 inclusive. Of course there will be regional variation around that. By this index 2012 ranks as the worst summer since 1985 and as the 4th worst since 1954, which has the lowest score (161), due to not being quite as cool and/or cloudy as those other summers. Also, if you remove the global warming trend from the data, 2012 comes out with the second lowest index of the whole 101-year period, narrowly ahead of 1954. Since 1980, the summer 2007 score of 196 was exceeded on the low side only by 1980, 1985, 1987, 1988, 1998 and 2012, and equalled by 2008, so by most standards 2007 was still a pretty poor summer for the UK.
  8. I remember June 2013 being dry and quite cool overall (at least for recent years), as part of a generally cool first half of the year which was followed by a much warmer first half. There was an anticyclonic spell early on which I spent in the Vale of York, and it was generally dry and sunny there as I was just to the west of the veil of low cloud that kept coming in off the North Sea and affecting many eastern parts of England. Unusually South Shields also lay just to the west of the low cloud and thus also had a sunny week, but it was a dull spell in East Anglia in particular. Generally both June and July 2013 were warmer and sunnier the further west you were, and July 2013 was exceptionally so. I had a week's holiday near the northern/southern Irish border and it was hot and sunny for almost the entire week with temperatures in the mid to high 20s - somewhat unusual for July, when Ireland tends to be cloudier than in May and June due to increased westerlies. Then I stayed in Dumfries overnight 22/23 July, which was well-timed as the region had a very potent thunderstorm early on the 23rd. Statistically July 2013 was also an outstanding month in Devon with ~300 hours of sunshine, but less exceptional in the east, where north-easterly winds blew at times and brought in some low cloud. August 2013 was pretty normal but I do remember some quite potent thunderstorms in North Yorkshire in late July and again in August. The UK summer index (based on the Met Office values for sunshine, max temp and wet days) for 2013 comes out at 247, which since 1980 has been exceeded in 1983, 1984, 1989, 1995, 2003, 2006 and 2018 - so we can expect a summer as good as 2013 on average once in every five or six years. It would probably rank higher than that in the west and lower in the east.
  9. These figures show that it does vary depending on what part of the country you lived in, even just when considering opposite sides of the south Pennines. One way of doing it would be to apply the Manchester summer index to the UK's areal max temperature, rainfall and rain day stats from the Met Office at https://www.metoffice.gov.uk/research/climate/maps-and-data/uk-and-regional-series. Here I get: 2007: 196 2008: 196 2011: 201 2012: 175 2015: 207 The Met Office provides rain days (>= 1mm rather than >= 0.2mm), which is less ideal, but the index still seems to work well, e.g. in records going back to 1919, the two highest-rated summers are 1976 (288) and 1995 (280), and the lowest by a fair margin is 1954 (161) which I expect would match up well with many people's perceptions. Interestingly 2018 ranks 3rd for the UK with 265. What's coming out from the various stats, though, is that they strongly bear out the original thread title. June 2008 was a decent month for many (especially down here in the south-west, although I wasn't here at the time), and July 2008, despite being wet, generally had sunshine totals that weren't far from normal, and had a warm sunny spell in the last third of the month. It was that August that really dragged the summer down to the level of those of 2007, 2011 and 2015 and even a bit below in some parts of the country.
  10. I saw a couple of very distant flashes of lightning from a cell that sprouted up over Dartmoor, but it was too far away to have any realistic chance of hearing the thunder. I felt a bit cheated when every run of the GFS until today's 12Z showed a band of heavy, almost certainly thundery, showers over Exeter between 0 and 3am, and then on the 12Z it had vanished completely. The 18Z does show some potential again, mainly at 3-6am, but again not as strong as on previous runs. However, rather ironically there are some intensifying cells approaching from the north-western tip of France that have potential to produce something along the lines of the earlier GFS forecasts, should they intensify much further, so at present it's far too early to call this a bust.
  11. This seems to be a facet of our changing climate - in the 1970s and 1980s, it took exceptional synoptics like those of late June 1976 to get temperatures approaching the mid-30s Celsius, and most heatwaves had temperatures predominantly in the mid to high 20s, whereas these days it doesn't seem to take anywhere near as much to get temperatures into the 30s. Climate change projections do quite widely have our heatwaves hotting up at a faster rate than the rise in mean temperature. I think that for this reason it's unlikely that we'll see another summer that fails to hit 30C. Note that 1993, despite its reputation, wasn't a consistently cool summer, there were some hot spells in early and late June in particular but none of them were hot enough to hit 30C. I remember that incursion of unusually hazy continental air around 9 June 1993 which was followed by thunderstorms for some. One of the big attractions of heatwaves has historically been their rarity - like many weather enthusiasts it would seem, I have a history of being excited by extreme temperatures and looking forward to heatwaves just to get the opportunity to experience unusually high temperatures, but as the climate warms these temperatures are becoming less unusual. The highest hourly readings were 27.2C at Exeter Airport today so it probably got to near 28C at some point, which I normally find fine, but today the humidity was rather higher than we have had in many recent spells with those sort of temperatures (e.g. late June/early July 2018), and it is currently a sweltering 28C in my living room. But to my mind it will be well worth it if I get a good display of lightning at around midnight on 25/26 June, as is still being shown on the GFS at just T+24.
  12. 2003 was my favourite year of this decade, mainly due to its high sunshine totals. The summer wasn't as sunny as the spring or autumn, but in Tyneside it had some big thunderstorms, including some on my birthday (22 June). Next up were probably 2006 and 2009, mainly due to the record-breaking hot sunny July in 2006, and the snowy February, thundery summer and snowy late December in 2009. In fourth place is 2005, which I think of as a "very nearly year", in particular the summer would've ranked as one of my all-time favourites had it not been for the extremely dull last third of July. 5th place goes to 2001 - in Tyneside this year had a snowy March, a very sunny May, thundery wintry showers 8/9 November and a snowy end, but the summer and especially September weren't great. My least favourite year of that decade was undoubtedly 2002 - apart from some decent warm sunny weather in late March and April I don't have many positive memories of that year's weather. 2000 and 2004 also lacked positive memories but were saved by snow events - post-Christmas 2000 and the dramatic frontal snow squall on 28 January 2004 which gave thundersnow for some. Also 2004 was a thundery summer, if wet and fairly cloudy. 2007 was another "least favourite" candidate but the April in particular saved it. 2008 was saved by the period from February to mid-April, February for its record-breaking sunny spell from the 8th-19th and late March/early April for late snowfalls and some convective storms, I had a particularly potent thunderstorm in Norwich on 11 April 2008.
  13. I was up in Tyneside in summer 2007 and in June 2012, moved down to North Yorkshire for July/August 2012 and just missed out on the big Tyne and Wear thunderstorm of 28 June 2012. From my recollections 2012 was considerably worse than 2007. The Junes of 2007 and 2012 were both comparably dull and wet in that part of the country, mainly because early June 2007 had a lot of haar near the east coast while much of the rest of the country had some warm sunshine, but June 2007 was nonetheless about a degree warmer than June 2012 even near the coast. July 2012 continued dull and wet, whereas July 2007 at least had close to average sunshine. Late June and early July 2007 were also thundery with 7 thunder-days during the period 20 June-4 July. I rather enjoyed the first half of August 2012, which had a week of sunshine and thundery showers followed by a few days of dry sunny weather, but the second half returned to being dull and wet. August 2007 on the other hand was quite dry and sunny, if rather cool. Indeed I thought summer 2008 was about as bad as 2007 due mainly to that August, which was widely the dullest since 1912.
  14. Had been expecting another day of sunshine and showers and chances of thunder in Exeter, but to my disappointment when I woke up this morning the rain belt was a lot further south than forecast. Not expecting any sun or any thunder today - just a dull wet day.
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