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Thundery wintry showers

Long range forecast team
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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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    Male
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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
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    Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.

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  1. CET 5.8C, EWP 103mm. I reckon that mild and wet weather early and late in December will outweigh a cold spell in the middle.
  2. Historically this early in the season cold weather via northerlies has been a lot more common than from easterlies in late November and early December, although there have of course been exceptions like 18 November 1985, 20-23 November 1993 and 5-7 December 1995. Sub -10C 850hPa air is somewhat rare from either north or east at this time of year although sub -8C is not that unusual. This is partly because the continent and North Sea still have a fair amount of cooling to do, and partly because blocked easterly types with a persistent Scandinavian high are less likely to happen at this time of year. The late Nov/early Dec 2010 instance saw the cold come from a mix of north and east winds but the easterly spell was brought about by a Greenland high ridging across to Scandinavia, and the coldest day in the CET area (28 November) arose after five days of northerlies, just as the easterly was starting to kick in. In many recent years the warmth of the Arctic has meant that it was a struggle to get northerlies that were cold enough to bring lowland snowfall, but the Atlantic side of the Arctic has cooled down quite a lot this November and is currently relatively cold for recent years. Of course there are regional differences - an easterly type is on average somewhat more reliable at bringing cold and potentially snowy weather to most of central and southern England, whereas over much of Scotland and north-east England it is the other way round - but taking the country as a whole the equation tends to be more in favour of northerlies early and late in the season with easterlies causing a higher percentage of significant cold snowy spells in January, February and early March.
  3. Thundery wintry showers

    Aren’t Windows updates a pain?

    I haven't had many problems with Windows 10 updates on my desktop but they have often been a pain on my laptop, probably partly because it is relatively rarely used and was upgraded from Windows 7. Windows will force-feed the laptop updates at an inconvenient time and if you close the lid overnight or when travelling on a train or a plane (the latter two being bad times to update due to internet connection issues, the first being bad due to disrupting sleep) it will automatically switch back on after a short while to stop you from circumventing the automatic update. Not good if it then gets very hot. Also, on the laptop, updates tend to reset a lot of my preferences back to the Microsoft defaults (this has happened somewhat less often on my desktop computer) and this isn't just the bi-annual feature updates - it happens quite often after minor system updates also. Examples include resetting my picture viewer back to Photos, my music player back to Groove Music, re-enabling Automatic Folder Type Discovery and then resetting my preferred Details folder views back to the defaults. Although updates generally play nicely with the settings on my desktop, here was one time on my desktop where an update to Office 2016 reset the Developer tab in Excel back to the default of disabled, so for a while I was left wondering where it had disappeared to. If you have Windows 10 Pro you have a fair amount of customisability with updates, but if you have Windows 10 Home you generally have no choice but to update as and when Microsoft deems suitable, with the exception of the bi-annual feature updates which can be deferred. I am not against forced security patches, but I am against forced system and feature patches. It's often said that getting the latest feature updates "gives the best user experience", but a lot of the time new features are thrust on users when they are still buggy and incomplete and degrade the user experience, and they only become improvements after a while of ironing out bugs in subsequent mini-updates. Most cases of updates tinkering with default settings are probably unintentional, but there are exceptions, such as when I disabled OneDrive and one of the feature updates re-enabled it, reset all of my OneDrive settings back to their defaults and then introduced an ad for OneDrive that popped up every time I opened Windows Explorer. Generally the cynic in me thinks that Microsoft will feel they don't have to put as much effort into leaving people's settings alone now that updates are compulsory. In the past they had more pressure on them to make sure that updates were right or else people would disable them altogether and leave their systems insecure. And when it does go wrong, well, it serves as a neat little nudge towards the Microsoft defaults which could help increase user compliance with the defaults as the path of least resistance, and the more people comply with the defaults, optimising defaults for the vendor's revenue streams becomes a more effective policy. Microsoft still hasn't managed to get most Windows 10 users to use Edge, though.
  4. It got pretty close in Exeter but not quite close enough - there was a period of light rain with a temperature of 3C.
  5. Thundery wintry showers

    Winter 2018/19

    In the early days of Netweather it was Joe teddy beari, and then changed to Joe laminate floori! There was also a new town called Sprunehorpe.
  6. Thundery wintry showers

    Winter 2018/19

    The global warming trend is a gradual thing, but in individual locations such as the British Isles there is a lot of natural variability superimposed on it, and step-changes can and do happen for no apparent reason. The step-change to milder winters around 1988 was particularly marked for the month of February, which had a CET average of 2.7C over the period 1978-87, and then an average of 5.3C in the period 1988-2002. January also saw a step-change but it was less extreme. On the other hand the very mild December of 1988 proved to be a one-off, and the Decembers of the 1990s were slightly cooler than those of the 1970s and 1980s - even the warmish December of 1994 was cooler than four of the Februarys of the 1990s. The step-change in February was significantly down to a change in synoptics with a marked increase in the frequency of "westerly" Februarys. I read a copy of the RMetS Weather Log for February 1988 several years ago and recall that the Weather Log noted that the near-absence of easterlies that month was unusual for recent Februarys, and then the Februarys of 1989 and 1990 were even more "westerly". Meanwhile, the cooler Decembers owed a lot to a higher frequency of northerlies and easterlies.
  7. Thundery wintry showers

    Guide To ... Uk Winter Setups

    A revised version of the earlier "Winter Snow Setups/Non-Snow Setups" topics, this goes through the range of winter setups we can get. As in summer, the main determining factors in what sort of winter weather we get are the positioning and strength of the jet stream. A strong jet stream means that depressions will frequently move from west to east, giving a "zonal" pattern over the UK. Because the Atlantic is relatively warm and moist, assisted by the warm North Atlantic Drift, zonal types often tend to be mild- but not always. A weak jet means lows track less frequently from west to east and blocking highs can form more readily. Whether we get cold wintry weather depends on the positioning of the high. Zonal, northerly tracking jet When low pressure systems track well to the north of Scotland, we usually end up with high pressure close by to the south, and a mild moist tropical maritime airmass covering the north. It is usually dry and mild in the south with a fair amount of sunshine, but cloudier and wetter in the north and west. Bartlett/Euro High An extension of the northerly tracking jet scenario, this setup sees the Azores High displaced over to Europe, keeping Britain in a persistent tropical maritime south-westerly regime. This setup brings Britain's warmest winter temperatures. This setup is often associated with large rainfall totals in the Scottish Highlands. Broadly speaking it tends to be dry and sunny wherever the high covers, northern and western Scotland tend to be dull and wet, and intervening areas often end up fairly dry but cloudy. Zonal, jet tracking over and to the north of Scotland This is the most common "zonal" winter pattern with low pressure systems regularly moving from west to east, bands of rain moving east at intervals, with brighter showery polar maritime air in between the rain belts. If the lows track from SW to NE then southern and eastern areas often spend a lot of time in "warm sector" mild moist tropical maritime air. It tends to be wet everywhere, sunny in the east and dull in the west. If the lows track more from NW to SE much of Britain spends a lot of time in polar maritime air, giving sunshine and showers. It tends to be wet but sunny in most regions, especially sunny in the east and especially wet in the west. On rare occasions, if there is an influx of Arctic air or cold pools from Canada/Alaska into the mid-Atlantic, we get so-called "cold zonality" with widespread snowfalls, especially in northern and western regions. An extreme case of this occurred in January 1984. Zonal, jet tracking right over Britain This pattern tends to be very wet as the lows track straight over the British Isles. Temperatures tend to be close to normal but with a bias towards milder conditions in the south, and cold polar incursions often reaching the north, giving snow for Scotland and northern England. Zonal, southerly tracking jet This pattern is not very common but when it does happen it can usher in prolonged spells of cold snowy weather for the British Isles. Low pressure stays to the south, sometimes bringing fronts into southern areas which can bring snow as the milder air meets cold polar air to the north. Otherwise, high pressure oscillates between Greenland and Scandinavia bringing repeated bursts of northerly and easterly winds. Blocked, high pressure over Britain When a winter anticyclone settles over Britain the weather tends to be dry, but the weak winter sun is ineffective at burning away low cloud. Thus sunshine amounts can vary considerably depending on how much cloud is trapped within the high- in general an input of moist tropical maritime air, or an easterly drift from the moist North Sea, may result in days on end of "anticyclonic gloom" with low cloud and mist and no chance of any sunshine. Alternatively, a clear anticyclone may bring frosty foggy nights and sunny days, as happened in December 2001 (below). Blocked, high pressure to the east When high pressure is well out to the east, this allows Atlantic lows to come towards the British Isles but they stall to the west, which tends to give rise to mild, rather cloudy southerly regimes. The equivalent of the summertime "tropical continental" southerly type which dominated the month of July 2006 rarely occurs in winter, but it does crop up occasionally. Depending on the amount of cloud circulating around the high's western periphery, a prolonged spell of anticyclonic gloom may ensue (as happened in February 1993 and early December 2004), or it may be warm and sunny by day but with cool nights, as happened in February 2008 (below). Unfortunately, with highs both over and to the east of Britain there is no synoptic way of determining how cloudy the highs will be- satellite imagery, atmospheric profiles etc. are your best bet for guidance. Blocked, strong Azores or mid-Atlantic high This kind of blocked pattern results in mostly mild weather as north-westerly winds suck up mild air from the Azores and around the high's periphery to the UK. Sometimes as a low moves out into Scandinavia it may introduce a brief burst of cold northerly or north-westerly winds with some snow showers, but these blasts usually tend to be short-lived. Blocked, Scandinavian high The Scandinavian High is often regarded as the "holy grail" by many cold/snow lovers, because it directs cold continental air across from the east. However, the Scandinavian High is really more of a building block towards an easterly- if the high is kept too far east the continental air may well stay away to the east. If an easterly does reach Britain then it will pick up moisture over the North Sea, and the resulting weather is largely dependent on the upper air temperatures, and the 850hPa temperature is often used as a guide. If the upper air is relatively mild (typically above -5C), the air will be stable and the moisture will give rise to layers of stratocumulus and persistent dull dry weather. However, if the upper air is cold (typically below -5C, preferably -10C or below) then the air will be unstable, and will give rise to heavy, often prolonged showers, especially but not exclusively for eastern areas. This setup brings much of England and Wales its coldest weather, and can produce significant snowfalls as happened in February 1991 (below). Northerly type Northerlies are another major source of snow events, brought about by high pressure to the west, and low pressure over Scandinavia or the North Sea. However, northerlies too have a major "stumbling block" if it's widespread snow you're after. Unless there is a southerly tracking jet stream, or a strong anticyclone over Greenland (preferably both), we tend to get brief "topplers" with just 36-48 hours of northerly winds, a few wintry showers for exposed coasts, and then milder weather pushes in. However, if a block can hold to our north-west for long enough for the northerly to sustain for upwards of a few days, then we will often see troughs form in the airflow bringing snow showers well inland. A large area of high pressure over Greenland, extending towards Iceland, will usually keep the British Isles affected by repeated bursts of polar air from the north. The "polar low", a low that forms in cold northerly airstreams and tracks south, is a particularly prominent source of snowfalls in a northerly regime. Although it is usually northern and eastern areas that see the most snow in a northerly regime, western areas can see the largest amount when pressure is low to the north, resulting in the Arctic air being sent south through the east Atlantic and around to Britain from the west or north-west (similar to the "cold zonality" described earlier, but via a northerly regime). Continuing the Christmas theme, this brought many western areas a white Christmas in 2004. Frontal battlegrounds Finally, when pressure is high to the north or east bringing cold polar and/or continental air towards Britain, and this cold air meets Atlantic systems coming in from the south-west, causing the systems to stall, this can lead to prolonged outbreaks of snow. For example many western areas were heavily hit during early February 1996 from this kind of setup.
  8. I thought I detected some sleet mixed in with the heavier rain showers in Exeter at around 6pm, and it may have been genuine as Exeter Airport measured 3.4C with a dew point of 1.8C at the time - if so, remarkable to get a bit of wintriness in October in Exeter of all places! It's definitely 100% rain now though with the temperature creeping above 5C.
  9. Thundery wintry showers

    Winter 2018/19

    I'll be formulating thoughts on the UK winter during mid to late November, but for now I can hazard a guess as to the mean global temperatures for Winter 2018/19: November - warm December - warm January - warm February - warm March - warm
  10. Thundery wintry showers

    November 2018 C.E.T. forecasts and optional EWP contest

    A fairly cold (by recent standards) and cyclonic November, CET 6.3C, rainfall 122mm. I expect it to be colder than average early and late in the month with a milder interlude in the middle.
  11. Thundery wintry showers

    Winter 2018/19

    The northerly blast of 26/27 October 2012 brought my old home town of South Shields its first October snowfall since 1992. I was living in the Vale of York near Thirsk at the time, just far east enough to catch the showers, and it was briefly cold enough for a dusting of snow there that night, but I don't think October snowfall is as rare in that part of the country - it certainly snowed around Thirsk on 30 October 2000 and probably in late October 2008 as well. The one that is currently forecast looks about as cold as the 2012 one and less cold than the 2008 one, but as others have said, this one will probably last a day or two longer than the 2012 northerly. I am still envisaging a cold cyclonic November as per the N-W autumn forecast, possibly with some further northerlies, but don't have many ideas yet on how winter 2018/19 will pan out.
  12. Thundery wintry showers

    Best and worst winters

    Records go back to 1993. Best: 1. 2010/11 2. 2009/10 3. 1993/94 4. 2000/01 5. 2017/18 Worst: 1. 2015/16 2. 1997/98 3. 1992/93 4. 2013/14 5. 2004/05 I have taken the Novembers and Marches into account as well as the traditional winter quarter, for as many of us saw this year, they can occasionally produce very notable wintry spells. It's also a Tyne and Wear-centric stance as that's where I spent the majority of the winters, but as far as I'm aware my top 5 were also pretty good in the Exeter area. 2010/11 edged out 2009/10 as a consequence of the very memorable November (the whole month had a lot of interest, though of course especially the last week) as well as the record-breaking December. 2017/18 only just edged out 2008/09. Lack of sunshine was the main factor that prevented the winters of 1995/96 and 2012/13 from entering my top 5, and also contributed somewhat to the low ranking of 1992/93. On the other side of the coin, high sunshine totals saved the largely snowless winters of 1999/00, 2006/07 and 2007/08.
  13. Thundery wintry showers

    Least favourite weather events

    Those relentlessly dull "easterly" months when I was living in Tyneside, with temperatures hovering around 3-5C, a big wind chill effect and stratocumulus trapped underneath a cap. December 2002 takes the wooden spoon award from this point of view. January and March 1996 were similar and were even more exceptionally dull than December 2002 but their snow events saved them from taking the wooden spoon award.
  14. Thundery wintry showers

    The decline in thunder days.

    Some parts maybe, but certainly not the Munich area for instance (I follow a few of the webcams there, there were some spectacular looking storms there in late May in particular). It's not unusual for a summer like this year's to be largely devoid of thundery activity though. There weren't many thunderstorms about during the summers of 1976, 1989 and 1990, and while 1995 had a thundery July, June and August of that year had somewhat less thundery activity than usual. Continuing a pattern seen in several recent years, parts of north-east England have had above average thundery activity this summer. At my parents' location up in North Yorkshire there were 9 days with thunder during the summer quarter, which is close to the long-term annual average for that area of the country. Here in Exeter, in contrast, there were none at all. 2007, 2009 and 2011 were other marked examples of summers when the north-east often seemed to be favoured.
  15. Thundery wintry showers

    Model output discussion - summer rolls on

    The ECMWF 12Z looks very scary for Tuesday, sending the low into mainland Britain without losing much of its intensity:
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