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Why has this season been so cold


Gibby

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Posted
  • Location: Kilmersdon Radstock Somerset
  • Weather Preferences: None Really but a snow lover deep down
  • Location: Kilmersdon Radstock Somerset

    I thought I would open this here as I have recently put a blog on my website which I've copied across here for you folks to enjoy and share or disagree with my comments on this seemingly never warming Spring and season past.

    Hi folks. I thought it was time I threw some light on the question that's asked of me on most days in my travels out and about and that is why is it so cold for so long this Spring..well here goes for an explanation.

    For some years now we have seen a repeated pattern in the upper airflow patterns which has meant our normally fast moving ribbon of air high in the atmosphere has been displaced many miles further South than it should be. This has happened in both Summer and Winters recently and was responsible for the snowy pre-Christmas period of 2010 and then the summer last year and now the cold Winter and Spring we have just endured or still enduring. So why is this happening. There are many theories on why it could be happening but no-one really knows the answer. The theories put forward in recent times is that Arctic sea ice melts much more in Summer than used to be the case which cools the waters in the Arctic which outflows into Northern sea areas. This encourages High pressure to form in Northern latitudes and pushes the normal flow of Atlantic driven weather systems on a path much further South either over or to the South of the UK. This means the Jet stream which is normally situated between Scotland and Iceland and he meeting point of the cold polar air masses to it's North and the warmer sub tropical air to it's South is much further South around Spain and even the Canaries at times keeping much of Europe within the Polar Continental air masses such as we have now causing unseasonably low temperatures and still the risk of snow even though it is now April. There is also some talk that long term the Gulf Stream which is an underwater current carrying warm waters NE towards the UK all year round is having less impact on our weather of late with even some Scientists claiming that climate change in years to come could see it weakening or ceasing to flow at all in response to Arctic sea ice melt with the resultant outflow of cold sea water from the Arctic replacing it. This could mean the UK could see more severe winters with regard to ice and snowfall even though these changes could be attributed to global 'warming'. However, all this is highly controversial and on a global scale there are many other factors that could mean something rather different than what I have described above.

    So what is to come. Well there has been signs in recent days that the Jet Stream might be moving North which would mean more of Britain would fall on it's Southern flank and see more traditional Spring weather of April showers and warm sunshine but there are also opposing signs from the output this morning that this movement North may be muted, short-lived or not happen at all so that more cold weather could be experienced in the weeks and months to come. Should that be the case then the late Spring and Summer could be another chilly and wet affair but this is sheer trepidation at this juncture and as we all know the weather alone will make up it's mind without consulting us for permission so it's a case of watch my daily forecasts and reports for hints at where the weather is going and if I see a sign of an impending heatwave I will be the first to let you know but as it stands it looks unlikely anytime soon.

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    Posted
  • Location: Fazendas de,Almeirim, Portugal
  • Location: Fazendas de,Almeirim, Portugal

    Thanks for including this - very well written and I think everything mentioned is entirely relevantsmile.png Reasons behind these changes I know were outlined in depth by many also in the recent mini ice age thread which covered (related) similar important ground to this topic .

    I mentioned changes in ENSO phasing with La Nina dominating and changing temperature profiles of the Pacific - influencing the path of the jet stream and with further implications for the sea temp profile of the AMO (Atlantic Multidecadal Oscillation). Also a weak and ever weakening trend in solar activity and cycles and associated with this, a re-distribution of ozone in the stratosphere which is more conduisive to upper atmospheric warming and hence the increased observance of blocking over the arctic and northern latitudes you describe and outline so wellsmile.png

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    It's the same thing we've been seeing for years now, patterns getting stuck for long periods, more northern blocking, a disrupted jetstream. I think it's mainly down to a weaker more meandering jetstream because the temperature contrast between the poles and tropics has reduced because the Arctic has warmed so much more than the tropics, that seems likely to be the main suspect. Seems to make perfect sense to me. Low solar activity may have an influence as well.

    This sort of spell is not a one off, something is definitely up the past few years IMO, whether it's something temporary or more permanent who knows, I'm leaning to the idea that we are entering a long term change in the climate we've been used to with more extreme blocked weather patterns becoming more frequent and more well, extreme. So more droughts, more floods, more cold, more snow, more heatwaves possibly. We'll see.

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    Posted
  • Location: Wigan
  • Location: Wigan

    It's the same thing we've been seeing for years now, patterns getting stuck for long periods, more northern blocking, a disrupted jetstream. I think it's mainly down to a weaker more meandering jetstream because the temperature contrast between the poles and tropics has reduced because the Arctic has warmed so much more than the tropics, that seems likely to be the main suspect. Seems to make perfect sense to me. Low solar activity may have an influence as well.

    This sort of spell is not a one off, something is definitely up the past few years IMO, whether it's something temporary or more permanent who knows, I'm leaning to the idea that we are entering a long term change in the climate we've been used to with more extreme blocked weather patterns becoming more frequent and more well, extreme. So more droughts, more floods, more cold, more snow, more heatwaves possibly. We'll see.

    The heatwaves have been thin on the ground, its seems we locked into long lasting cold, but not heat, why is this? Have we just been unlucky

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    The heatwaves have been thin on the ground, its seems we locked into long lasting cold, but not heat, why is this? Have we just been unlucky

    We did have some exceptional heat in 2003 and 2006. Perhaps we have just been unlucky since or there's something that happens during the summer that for some reason makes getting heat here difficult. We do seem to be overdue a hot dry summer and if we do get one it could be quite exceptional if the pattern gets stuck again but in a different way.

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    Posted
  • Location: on a canal , probably near Northampton...
  • Weather Preferences: extremes n snow
  • Location: on a canal , probably near Northampton...

    we were also in drought conditions from probably summer 2010 to april 2012 in most of the majorly populated English regions, so the general public with short memories or new houses get caught out and report more often severe weather events involving water.

    .

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    Posted
  • Location: Derbyshire Peak District 290 mts. Wind speed 340 mts
  • Weather Preferences: Rain/snow, fog, gales and cold in every season
  • Location: Derbyshire Peak District 290 mts. Wind speed 340 mts

    A nice concise summary there, Gibby.

    The only changes I would make would be to substitute the words 'enduring' for 'enjoying' but each to their own eh!

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    Posted
  • Location: Clayton-Le-Woods, Chorley 59m asl.
  • Weather Preferences: very cold frosty days, blizzards, very hot weather, floods, storms
  • Location: Clayton-Le-Woods, Chorley 59m asl.

    2 words why this season is so cold: Global Warming/Climate Change.

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    Guest pjl20101

    Three situations haven't helped towards our spring so far the SSW event in January, the Russian meteorite and the Asian mountain torque. Good job the UKMO GloSea4 can pick up on SSW events and has done very well picking up the cooler than average signal for spring so far. Think the model deserves a pat on the back so far.

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    Three situations haven't helped towards our spring so far the SSW event in January, the Russian meteorite and the Asian mountain torque. Good job the UKMO GloSea4 can pick up on SSW events and has done very well picking up the cooler than average signal for spring so far. Think the model deserves a pat on the back so far.

    Why would the Russian meteorite have any bearing on our spring weather?

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    Posted
  • Location: South Yorkshire
  • Location: South Yorkshire

    2 words why this season is so cold: Global Warming....

    I honestly can't work out if this is meant tongue-in-cheek. If we were enduring numerous heatwaves would they be caused by global cooling?

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    Posted
  • Location: Clayton-Le-Woods, Chorley 59m asl.
  • Weather Preferences: very cold frosty days, blizzards, very hot weather, floods, storms
  • Location: Clayton-Le-Woods, Chorley 59m asl.

    I honestly can't work out if this is meant tongue-in-cheek. If we were enduring numerous heatwaves would they be caused by global cooling?

    Yes and no. The gulf stream is slowing down and it caused by global warming. In the future the gulf stream will be grind to the halt so we get severe winters. It is called Shutdown of thermohaline circulation.

    http://en.wikipedia....ine_circulation

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    Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl

    It`s impossible to hone in on one particular influence on these Atmospheric changes as there`s so many pieces to the jigsaw.

    There`s certainly been a change to the NH profile since the start of this century with more blocking further north and long periods of a southerly tracking jet.The Arctic cold that used to be bottled up around a strong vortex in Winter now displaces into mid-latitudes on a more regular basis.

    I did a reanalysis of the 500hPa NH patterns comparing the 2 periods 1988-2000 and 2001 -2012 just for the Winter quarter and posted this in a previous thread.This time i have done another measure this is for complete years for the same 2 periods -the first period if we remember was often refered to as the Mod...n Wi...er era and we can see why.

    post-2026-0-46927300-1365346676_thumb.pnpost-2026-0-03127200-1365346685_thumb.pn

    A remarkable switch around since we now have a mirror image of the 90`s decade as we can see those yellows(positive Hts.)around the Arctic pushing the the weaker jet stream further south.

    If i was pressed to name one reason then i would think Arctic warming has to be a big factor pushing the thermal boundaries and therefore the jet stream further south.

    Why the Arctic has warmed is another question but the lowering Summer Ice levels and the influence on sea temperatures cannot be ignored.

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    Posted
  • Location: Windermere 120m asl
  • Location: Windermere 120m asl

    There has been a definate shift in the position of the jetstream over the past 5 or 6 years - it has been displaced much further south compared to the much of the period between 1988-2006, and it is notable how this shift in its position particularly during summer has also coincided with rapid loss of arctic sea ice and consequently a much weaker polar vortex as the cold from the arctic has been allowed to move south into the middle latittudes changing sea surface temperatures.

    However, there are probably many factors at play as to why we have seen a switch to colder drier winters and cool wet summers in recent years. Sunspot activity as been very low, and there are some who believe weak solar activity has a major influence on conditions.

    We didn't see major arctic sea ice loss during the cold 1977-1987 period which saw a number of very cold winters and by recent standards much colder summers - the likes of summer 78 and 85 were very chilly.

    It could be a temporary cyclical pattern. Last year started very differently, and we saw significant warmth in late winter/early soring period. The cold early winter of 2010/2011 quickly transferred into a very mild period culiminating in the record warmth of April 2011. So whilst our winters and summers have seen similiar patterns in recent years, our springs and autumns have been notable for the lack of marked diversity from one year to the next. Indeed our springs since 2007 have all returned at least one very notable warm period, i.e. April 2007, first half May 2008, March/April 2009 in general, May 2010, April 2011 and March 2013, but also very contrasting fayre during the remaining spring periods.

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    Posted
  • Location: Carmarthenshire
  • Location: Carmarthenshire

    There has been a definate shift in the position of the jetstream over the past 5 or 6 years - it has been displaced much further south compared to the much of the period between 1988-2006, and it is notable how this shift in its position particularly during summer has also coincided with rapid loss of arctic sea ice and consequently a much weaker polar vortex as the cold from the arctic has been allowed to move south into the middle latittudes changing sea surface temperatures.

    I wonder what people would be saying about the current period if it came straight after 1987? Historically the period 1988 - 2006 stands out as being one of anomalous warm, dry summers and a lack of cold winters, which probably makes the post-2007 period all the more notable.

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    Posted
  • Location: Exile from Argyll
  • Location: Exile from Argyll

    Yes and no. The gulf stream is slowing down and it caused by global warming. In the future the gulf stream will be grind to the halt so we get severe winters. It is called Shutdown of thermohaline circulation.

    http://en.wikipedia....ine_circulation

    The Gulf stream, whether it is idle or turbo-charged, will have little impact on the UK weather if prevailing winds change to a northerly/easterly direction as has happened in recent weeks.

    All looks fairly normal as far as speed is concerned.

    http://bulletin.mercator-ocean.fr/html/produits/psy3v3/ocean/regions/bull_ocean_nat_fr.jsp?nom=psy3v3_20130403_23103

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    This season is very cold, but last year spring was a very warm, few complaints there, the fact that last spring was very warm and this one was very cold, shows how mother nature balances climate, we should not complain. The last time I remember a spring that was as late as this one was in 1986, and march was normal that year. So despite global warming or climate change as it is now called to make it more palatable to the general pubic, the weather will always, vary from season to season, from year to year. The run off warm months and years, from 1988-2006, we have to forget about this period, its history now, and not let the issue of climate change affect our views that we should not have very cold seasons again, and remember in future we will have warm seasons and cold season, I for one, I am not complaining after such a record breaking warm spring last year, it is all about balance. Gender Male, Location Battersea London.

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    Indeed our springs since 2007 have all returned at least one very notable warm period, i.e. April 2007, first half May 2008, March/April 2009 in general, May 2010, April 2011 and March 2013, but also very contrasting fayre during the remaining spring periods.

    do you really mean to include March 2013 as having a very warm period or is it me mis- reading what you have posted?

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    Posted
  • Location: Dulwich Hill, Sydney, Australia
  • Weather Preferences: Hot and dry or cold and snowy, but please not mild and rainy!
  • Location: Dulwich Hill, Sydney, Australia

    do you really mean to include March 2013 as having a very warm period or is it me mis- reading what you have posted?

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    Posted
  • Location: Dulwich Hill, Sydney, Australia
  • Weather Preferences: Hot and dry or cold and snowy, but please not mild and rainy!
  • Location: Dulwich Hill, Sydney, Australia

    No idea why it won't include my text for the previous post, but I guess its a typo and he mean March 2012 which was quite warm.

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    Posted
  • Location: Whitefield, Manchester @ 100m
  • Location: Whitefield, Manchester @ 100m

    Yes and no. The gulf stream is slowing down and it caused by global warming. In the future the gulf stream will be grind to the halt so we get severe winters. It is called Shutdown of thermohaline circulation.

    http://en.wikipedia....ine_circulation

     

    First rule of making scientific declarations as fact - back up with some evidence.

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