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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
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    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. Mild v cold winter weather

    Looking at the synoptic charts the mild sunny Christmas Day was most likely 1987. The spell around Christmas 1987 was mild and dull but Christmas Day itself was sunny, thanks to a not-particularly-cold polar maritime incursion. Other less likely possibilities are 1983 (similar setup, but more likely to be showery) and 1988, though 1988 had a tropical maritime air mass and so would probably have been cloudy. Personally I'd much rather it be mild and sunny than mild and cloudy, especially if it results in an emphasis on high daytime maxima (rather than minima). It's not common to get very mild weather combined with bright sunshine, but the early part of the February 2008 anticyclonic spell managed it (as did the very beginning of the December 2001 anticyclonic spell if I remember rightly, though it soon turned colder) and it also happened widely on 13 February 1998.
  2. February 2005 - return of the easterly!

    Yes, there was an easterly in late Feb 06 which was tamer than the Feb 05 one. I remember a frontal rain/sleet event in Leeds (possibly corresponding to your wet snow event) and a couple of days of snow showers when the snow failed to settle.
  3. Will This Winter be like 1947 / 1963 ?

    I don't believe that it's impossible for Britain to have a severe winter, but it's becoming less and less likely with time as the global temperature continues to rise and the Arctic Amplification continues to accelerate. It would still be possible IMHO if at least two out of the three main winter months had similar synoptic setups to December 2010 and/or March 2013. Given that March 2013's cold came mainly from the east, at a time of year when the land masses warm up significantly, I would expect larger negative temperature anomalies were those synoptics to be repeated in one of the three main winter months. This year the cooling north of 80N (see link below) and the freeze-up of the Barents/Kara region are progressing at a similar rate to 2009, and we managed a pretty severe spell from 17 December 2009 to 9 January 2010, which picked up air mass sources from both north and east. http://ocean.dmi.dk/arctic/meant80n.uk.php I think it's extremely unlikely that we'll get anything remotely approaching 1963 or 1947 but I don't think we're yet at the stage where it's impossible. Perhaps the insane warmth of the Arctic in late 2016 would have ruled out the possibility for the 2016/17 winter, but at present, though still anomalously warm up there, it's nowhere near as extreme as last year.
  4. The decline in thunder days.

    One of Philip Eden's books had stats for average thunder frequency over England and Wales by month going back to the 1910s. July and August became drier, sunnier and less thundery after the 1980s and June followed suit in the 2000s, and it would appear that the subsequent cloudier and wetter summers weren't accompanied by a similar recovery in thunderstorms. This does hide some regional variation though- around Newcastle there was an increase in thunderstorms around 2003-2012, while in Kent and Sussex there has been a further decline since the 1990s. This year in Exeter there was a big overnight thunderstorm on 19 July, the biggest that I've experienced since the Norwich thunderstorm of 18 July 2012, but apart from that, only the odd distant rumble.
  5. Where have the long fetch northerlies gone?

    I think the main reason for less UK snow during the winters of 1988-2004 was the synoptic setups, with a greater emphasis on a positive North Atlantic Oscillation, more westerlies, and less northerlies and easterlies. Rising global temperatures also contributed, but the region of the Arctic from Svalbard into the Russian Arctic, which is where our northerlies often originate from, only warmed slightly. North Sea areas (e.g. Aberdeen, Newcastle, Norwich) tended to pick up one or two snow events even in mild winters due to snow showers off northerlies, probably the starkest example being the last of those winters, in 2003/04. Since then, we've still been getting the northerlies but they just haven't been as cold, because our source region of the Arctic has warmed massively, with some winter months seeing widespread anomalies of 10-15C. There was a straight northerly on New Year's Eve/Day 2016/17 which brought only rain and sleet showers to eastern areas, and another one back on 14/15 February 2016 which gave most areas only wet snow and the odd dusting. Historically shortwaves in northerly airstrreams sometimes produced frontal snow, and indeed inland areas often relied a lot on them because of the tendency for showers to often be concentrated around coasts, but in recent years it often hasn't been cold enough. 2010 was a very interesting case because although the Arctic was anomalously warm on average, the warmth was strongly concentrated in the Canadian Arctic and our source regions saw much closer to average temperatures (and as one of Reef's graphs showed early in this thread, this area of close to average temperatures extended to the general region north of 80N). The northerly of 18 December 2010 picked up a scoop of cold air from continental Greenland as well as pulling in air from Svalbard and the Russian Arctic, where temperatures were close to the long-term average, and this led to a northerly of rare potency for recent years. That combination of relatively low temperatures in our cold air source regions, plus favourable synotics to bring it to the British Isles, and anomalous warmth in the Canadian Arctic, was also a feature of the winters of 1947, 1963 and 1979. This year, our cold air source regions haven't been as anomalously warm so far as they were last year, although that's not saying much.
  6. Arctic Sea Ice Discussion 2017 - The Melt Season

    I thought calling the minimum was premature back then, but it seems unlikely to be beaten now, as the Arctic sea ice extent has continued to slowly increase despite the storm. It may have helped that the storm has a fair amount of cold air in its circulation.
  7. I recall that when we've had northerlies and little troughs running down the western flank of the northerly flow with embedded pools of warmer air, the GFS has tended to outperform the UKMO and ECMWF, as the latter two models tended to underestimate the extent of the warmer air and so forecast snow instead of rain or sleet. The other main advantage of the GFS model is of course much of the data being freely available. But the ECMWF has been the best-performing model overall since at least 2006. There was a time when the UKMO model didn't do significantly better than the GFS, particularly at day 6, but I recall that it gained ground several years ago and these days tends to be a little behind the ECM overall at days 4-6 but a fair way ahead of the GFS.
  8. August 1998 and August 2007

    I remember Augusts 1998 and 2007 mainly for their lack of notable weather events. August 1998 was a north-south split month, and from the Midlands southwards it was generally dry and sunny with fairly warm days and chilly nights, but further north it was breezy and sunshine was mostly near or slightly below normal with below-average daytime temperatures, although even in the north most places were drier than average. I was in South Tyneside that month and there were numerous sunny and fairly warm days in the first two-thirds, when the winds were mainly westerly, but in the last third the wind veered northerly and it turned cool and cloudy with a few days having maxima of 13 or 14C. In August 2007 there was a rather different regional distribution, with east Wales, the Midlands and north-east England coming out driest and sunniest relative to normal, whereas northern Scotland and to a lesser extent East Anglia had a cloudy month. Correspondingly in South Tyneside the month was predominantly dry and sunny with average temperatures. August 2000 was a pretty significant turnaround from earlier in the summer in South Tyneside, the second half was quite memorable, often sunny with sporadic heavy downpours, although we had sea fog on the 21st while most other regions had thunderstorms. The month must have been pretty memorable in Northern Ireland (again especially the second half), where Aldergrove reported well above average rainfall and sunshine, and 7 days with thunder. It was also a very sunny month in parts of East Anglia. However, some areas such as Manchester only had close to average sunshine. July 2000 was a west-east split month, dry and sunny in western Scotland (the Glasgow area fared particularly well if I remember rightly) but very dull and rather cold in the east. Lowestoft had only 50% of average sunshine, and parts of Norfolk had mean temperatures 1.5 to 2C below the 1961-1990 normal according to RMetS Weather Log.
  9. Strangely the lightning detector on the radar suggests that the lightning fizzled as it approached Exeter, but in fact there's been a lot of lightning around here, especially just to the south, during the past two hours, not so much to the north. Probably the most spectacular thunderstorm that I've seen since the 18 July 2012 one in Norwich.
  10. Summer 2017 Discussion

    Here in Exeter this has been a month of very marked contrasts- we had that exceptional hot and sunny spell from the 17th to 21st, with maxima between 27 and 30C for five consecutive days which is somewhat unusual for Devon, but the early part of the month was dull and wet, and since the 22nd it's been mainly dull with the odd spot of drizzle. Funnily enough June 1976 had below average sunshine over much of western and northern Scotland despite the near-nationwide hot sunny spell at the end, but I think we'd be hard pushed to find a summer month for London that had a similarly large temperature deviation but below average sunshine. It's an oddity that we'll probably see more of as our climate warms. Looking further back, the Junes of 1966 and 1982 were warm (but not as warm as this June) but dull and wet for most, although in the case of 1966, Heathrow was one of the few locations in the UK that had slightly above average sunshine. Those two Junes were also rather different in character to this one, with frequent cyclonic/southerly regimes and a high frequency of thunder.
  11. Summer 2017 Discussion

    When I was little I believed that I hated hot weather, and everybody seemed to be going on about how 30C was bliss, and nowadays I welcome heat in brief doses and lots of people say this is selfish because of the misery and inconvenience that it causes. You just can't win sometimes! I generally find low 20s most comfortable (high teens are also fine if it's sunny and not too windy) but welcome short spells of high 20s and even low 30s mainly for variety and novelty value. I must admit that this recent heatwave got a bit too much for me after the first few days, the main problem being the duration, which was the longest in June since the very famous one in 1976. As for the upcoming spell of weather, I don't think it will be a washout, with fronts moving across the country relatively infrequently, but it may well turn out persistently cloudy for many. Probably a bit dreich in the north at times but with comfortable temperatures in the south.
  12. June 2017 C.E.T. Forecasts

    1966 has often intrigued me, as June was the warmest month of that year, but it was also the dullest June on record in Scotland by a fair margin. It was also an unusually thundery month in many places. Frequent cyclonic/southerly regimes appear to have been the culprit, and given the surprising lack of sunshine, there were probably a lot of slow-moving fronts over Scotland. As for the current month, it seems very difficult to get a run of significantly below-average temperatures at the moment with plenty of anomalous warmth around the extratropical Northern Hemisphere, propagating up to the 850hPa level. The GFS ensembles are consistently going 1-2C above the long-term normal out into Fantasy Island range.
  13. Arctic Sea Ice Discussion 2017 - The Melt Season

    Interesting, albeit scary, to see that the sea ice volume anomaly increased during May despite a relatively slow reduction in the sea ice extent. NSIDC shows the melt rate accelerating somewhat over the last couple of days, fuelled by relatively warm air masses over the Barents/Kara region as well as notably warm air over the Chukchi, Beaufort and East Siberian seas. http://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/ Forecasts from the GFS and ECMWF look rather concerning with high pressure remaining persistent over the region with the thickest sea ice, and also maintaining relatively warm air masses over the Barents/Kara and Chukchi/Beaufort/East Siberian seas. Even the cold air close to the North Pole looks like being mixed out in about a week's time, so we could well see 2017 catch up with 2016 in two or three weeks' time.
  14. Arctic Sea Ice Discussion 2017 - The Melt Season

    It's surprising that, according to NSIDC, the rate of sea ice melt hasn't sped up during the past week despite the emergence of a dipole anomaly, although the strength of the dipole and the input of warm air masses into the Arctic Ocean have both been rather weaker than previously projected by the GFS and ECMWF models. Some relativvely warm air from central Eurasia may introduce some melting around the Barents/Kara area in the next week, where the sea ice extent is currently high for recent years, but at the same time we may see a let-up in the warm anomalies around the Chukchi and Beaufort seas. I agree, we're currently in an interesting position given the low health of the ice but rather larger extent than this time last year.
  15. Both Exeter and my parents' in North Yorkshire got proper big thunderstorms today.  Staying up at my parents' this weekend, but due to an ill-timed trip to South Shields, I contrived to miss the whole lot!

    1. Daniel*


      That's most unfortunate zilch here in SE London