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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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    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. Yes, it could have been, as the hourly temperature readings from Exeter Airport suggest a rapid temperature drop to 3.1C, which is just about low enough for the odd bit of half-melted snow to survive on its way down: http://www.weathercast.co.uk/world-weather/weather-stations/obsid/3844.html
  2. In the long run I think yes, but I think it will be a slow and erratic process, as it would seem that for every X amount of warming in the Arctic, our northerlies only warm by a very small fraction of that amount. I reckon we'd probably need at least another 2 to 3C of global warming, even taking into account the Arctic amplification, to make it close to impossible to get widespread lowland snow from a northerly, and probably close to 5C of global warming to nuke those rare but intense "Beasts from the East". After all as you mention in your next post we managed to get widespread snow (even including an instance of lying snow here in Exeter) in late January/early February this year, from air masses that weren't originating from the east, or even from particularly far north. I can foresee Britain continuing to get widespread lowland snow from northerlies throughout the next half-century, but with the frequency of northerlies that are cold enough gradually becoming fewer and further between, and increasingly outnumbered by the northerlies that just bring rain. The same goes for easterlies too, as while the coldest easterlies tend to be colder than the coldest northerlies, the majority of our easterlies are also pretty marginal for snow. There is a chance that we might not warm by enough to make it impossible to get widespread lowland snow off a northerly, because the amount of warming that we'd need for that would be likely to have destructive knock-on effects in various parts of the world, notably including the Arctic itself, hopefully spurring humans into action to try and avoid dangerous levels of climate change.
  3. Yes, I think the Arctic climate encountered a step-change in 2005 when the main driver of warming in the region shifted to being warm sea surface temperatures and lack of sea ice. Between 1990 and 2004, much, though not all, of the Arctic warming could be explained synoptically, and the same was also true of our relatively mild and snow free winters in the UK, as when we did get northerlies they weren't significantly less potent than they were earlier in the 20th century. There was a paper on this subject by Erik Kolstad (Marine cold-air outbreaks, Climate Dynamics) which showed no significant decline in the potency of northerlies between 1961 and 2000. It would be interesting to see an updated scientific analysis of marine cold-air outbreaks for the period 2005 onwards, as I expect that it would give very different results. I have a suspicion that the Arctic might have passed another "tipping point" into a warmer base climate state in 2016 driven even more strongly by SSTs and sea ice than in 2005-2015, although we'll need at least a couple of years more data to be able to have as much confidence in this as with the 2005 shift. Although the greatest warming from 2005 onwards has occurred in the "Arctic Rim" at 70-80N, which is most sensitive to sea ice changes, these climatic shifts are also evident in the ERA reanalysis for the Arctic north of 80N: http://ocean.dmi.dk/arctic/meant80n_anomaly.uk.php
  4. Yes, and all of this is happening despite relatively favourable synoptics for sea ice growth for a large part of the autumn so far. I think the exceptionally high sea surface temperatures on the Eurasian side of the Arctic, extending across towards Alaska, may be largely to blame, following record breaking temperatures there during late July and August after an unusually early melt-out. I recall looking at the 1995 Arctic melt season (which at the time saw one of the two lowest minimum extents on record, the other being 1990) and sea ice was slow to form on the Eurasian side of the Arctic because of persistent strong southerly winds in that region in late September. However, as soon as the southerlies abated, the ice quickly reformed and by 20 October a large majority of that region had iced over. Things have clearly changed a lot up there since then!
  5. Copernicus (using the ERA5 reanalysis) has September 2019 as nominally the warmest September on record, just ahead of 2016, and has 2019 on course to be the 2nd or 3rd warmest year globally. Surface air temperature for September 2019 | Copernicus CLIMATE.COPERNICUS.EU
  6. I tend not to look forward to winter because of the lack of daylight. I don't think I suffer strong enough "light withdrawal symptoms" to officially qualify as having Seasonal Affective Disorder but I seem to have a mild version of that kind of thing. On average it doesn't have a big effect on my quality of life but I tend to find it easier to be in high spirits in spring and summer than in autumn and winter, all other things being equal. One marked instance of where all other things weren't equal was in 2010, when I found the darkest months of November/December/January more enjoyable than many of the lighter months, for reasons that many of you may be able to guess.
  7. At one time (back in the early 2000s) I was one of those who dismissed January 1987 as chiefly a south-east event, mainly because I had access to weather stats for Lancaster and they just had a centimetre from it, and because the archive charts show very high pressure across the north. But my present-day impression is that most areas had a fair amount of snow, with sheltered western areas tending to be the exception, as the air mass was so cold that it was able to generate plenty of North Sea convection all the way up to eastern Scotland despite the very high pressure. Another area that was heavily hit was, unusually, southern Cornwall, with massive falls in places like Penzance, as the air mass was so cold that even the far south-west peninsula was cold enough for snow, and it presumably got hit by snow streamers running along the English Channel.
  8. I was in South Tyneside during that February 2012 spell and remember an ice storm on 4 February and some freezing rain on 9 February, but I was just to the north of the freezing rain/snow boundary. The ice melted quickly on the 5th, but I remember travelling down to Birmingham by train around the 6th/7th and finding that there was a fair amount of lying snow from Durham southwards, though not in Birmingham itself. I saw pictures from the University of East Anglia suggesting that the Norwich area had fairly deep snow which stuck around for a while. I also remember January 2012 having an anticyclonic spell in the middle of the month with some stunning sunsets, reminiscent of the anticyclonic spell of 8-20 February 2008. Otherwise nothing else sticks out as particularly noteworthy. The winter of 2011/12 was also notable for insane warmth in the Russian and Norwegian Arctic with seasonal temperature anomalies locally in excess of 15C.
  9. It depends on what dataset you're using, as NSIDC still has the 2019 sea ice extent above 4 million square km: https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/ NSIDC also has 2019's sea ice minimum as the second lowest, though only very marginally ahead of 2007 and 2016. My initial thoughts were that, yes, it was surprising that August ended up as the Arctic's warmest August on record at 925hPa, but when I think deeper about it, it's not really that surprising. Temperatures over the main ice pack were often close to the long-term average, especially late in the month, which restricted the decline of the sea ice extent, but the 850hPa temperatures over the Eurasian side of the Arctic - where all of the sea ice melted out by midmonth - were often exceptionally high. Barring favourable synoptics there's a good chance that the refreeze north of the Eurasian continental mass will be unusually slow this year.
  10. Here's some old classics from a NW or WNW direction, these brought plenty of snow to much of the North West: https://www.wetterzentrale.de/maps/archive/1955/era/ERA_1_1955011712_1.png https://www.wetterzentrale.de/maps/archive/1958/era/ERA_1_1958011912_1.png https://www.wetterzentrale.de/maps/archive/1973/era/ERA_1_1973021400_1.png https://www.wetterzentrale.de/maps/archive/1978/era/ERA_1_1978011000_1.png https://www.wetterzentrale.de/maps/archive/1981/era/ERA_1_1981011500_1.png https://www.wetterzentrale.de/maps/archive/1982/era/ERA_1_1982121700_1.png https://www.wetterzentrale.de/maps/archive/1995/era/ERA_1_1995030200_1.png This one, although brief, was pretty well timed: https://www.wetterzentrale.de/maps/archive/2004/era/ERA_1_2004122512_1.png This westerly brought severe snowstorms to many parts of Scotland and Northern Ireland, I don't think snow generally lay for long at low levels across the north of England though: https://www.wetterzentrale.de/maps/archive/1993/era/ERA_1_1993011112_1.png I was in Lancaster in the early 2000s so became pretty familiar with the search for these setups. However, my luck was out during that spell - the only decent snowfall that Lancaster had during my time there was on Christmas Day 2004 (from the second-to-last north-westerly linked above), while I was away! Actually, come to think of it, Lancaster had falling and lying snow from a west-north-westerly as recently as... this year, and it stuck around for a few days, so even in the current warmer climate it is possible. I remember Lancaster University tweeting about it:
  11. It could very easily have been Jan 1984 - that was an unusually snowy "westerly" month from the north Midlands northwards. The WNW'ly type delivered widely around the 15th in particular and then there was a frontal snow event around the 21st-23rd which had similarities with that of early February 1996. https://www.wetterzentrale.de/maps/archive/1984/cfsr/CFSR_1_1984011506_1.png I remember the snow from a westerly on the evening of 11 February 2014 - I was up in North Yorkshire at the time and remember a dusting that evening, but it had largely gone by the next morning as milder air moved in. It was the only lying snow of the entire 2013/14 season, which stuck out as the most snowless season that north-east England has had in the past century. Yes, one can draw parallels between 2013/14 and 1987/88 as the winter of 1987/88 similarly marked the end of the cold winters of 1985-1987 (and the more generally snowy period of 1978-87). However the winter of 1987/88 was followed immediately by more exceptionally mild winters in 1988/89 and 1989/90, whereas 2013/14 was followed by the closer to average winter of 2014/15, which I recall had fairly widespread snowfall from westerlies around 14 and 29 January.
  12. Some interesting stationary waves at around 3:05 - is that what you meant? I have often been intrigued by those, how the clouds seem to be moving and yet staying still at the same time. They were quite common when I was living up in Tyne and Wear, but less common down here in Devon.
  13. Yes, it was. The last third of December 1987 was generally dull, drizzly and mild with a persistent tropical maritime SW'ly, but on Christmas Day we had an incursion of returning polar maritime air which was still fairly mild and brought plenty of sunshine: https://www.wetterzentrale.de/maps/archive/1987/era/ERA_1_1987122512_1.png It wasn't as mild as some of the tropical maritime air that we had either side of Christmas Day but it would probably have felt warmer in the sunshine. I don't remember the day specifically, just remember browsing some climate stats some years ago and seeing a long run of sunless days in late December 1987 interspersed with ~6 hours of bright sunshine on Christmas Day.
  14. It's hard to understand why there is a patch of ice around Spitzbergen as that region has consistently had above-average temperatures through the summer - perhaps ice has been transported down from the north? Certainly the ice patch is reflected by the fact that the capital Longyearbyen had its first lying snow of the season a few days ago, which is unusually early for recent years (in most recent years it hasn't snowed and lay there until October, although last year there was a bout of lying snow near the end of September). Over the past year it's especially been over the other side of the Arctic, especially around and northward of the Bering Sea, that we've seen exceptionally high temperatures and seen ice struggling to take hold even in winter, in a region that has historically tended to be at least partially ice covered all year round. The fact that we're unlikely to record our lowest annual minimum is a reflection of how extreme August 2012 was for its rapid melting, assisted by an intense low early in the month. It's still possible that 2019 could record the lowest annual mean sea ice extent if the refreeze is sluggish during the rest of autumn.
  15. Examining the global temperature stats from the main centres, it would appear that 1979 was when global warming got underway after the slight drop in global temperature between the 1940s and 1970s. 1980 and 1981 were both very close to being the warmest on record at the time, and from then onwards it kept warming up. I don't think Britain's climate showed any evidence of warming until around 1988-89. Winter 1979/80 was indeed fairly mild but there were several very cold and snowy winters after that, notably 1981/82, 1984/85, 1985/86, also January 1984 in the north, and the exceptional easterly in January 1987. There were also several cool summers during this period. The shift to milder winters started with the winter of 1987/88, while the shift to warmer summers started in 1989. I think we will run into cycles of cold winters again. I remember Philip Eden remarking on a 22-23 year cycle of cold winters around 1895, 1917, 1940, 1963, 1986, and 2008-2013 was a bit delayed relative to the earlier recurring cycle but not by a lot. If this cycle keeps up we might well run into some more cold winters around 2032-2035. But as the global temperatures continue to rise, each batch of cold winters will typically be less cold and less snowy than the previous one.
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