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Dave J

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    Exeter, Devon, England
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    Weather - severe and extreme events such as Atlantic depressions, thunderstorms, and heavy snowfalls. I also am interested in Football, (Ipswich Town FC!) and enjoy many other sports too.

    I also have a keen interest in photography which means that I'm often out photographing the weather, much to everyone else's amusement(!)

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  1. The Aberdeen office forecast minimum temperatures for Scotland, due to their local knowledge/expertise...
  2. Some very low maxes today in the SE/ E Anglia: Charlwood, Surrey -2.9C Marham, Norfolk -2.6C Andrewsfield, Essex -2.5C Wattisham, Suffolk -2.5C Kenley, Gtr London -2.4C Farnborough, Hampshire -2.0C London Heathrow AP -1.9C Northolt, Gtr London -1.9C
  3. IT's probably in some way related to the recent cold weather and subsequent thaw. There were balcony railings falling off buildings in Plymouth on the local news yesterday. http://www.thisisplymouth.co.uk/news/Cold-...il/article.html
  4. Yeah it seems to be thickening again, they've gone down to 100m on their latest ob and -2C! EGUW 081650Z 00000KT 0100 FZFG VV/// M02/M02 Q1028 RED NOSIG
  5. Feels quite warm here today despite it being only +4C and cloudy with thick stratus all day. Light winds. I can see a break in the St out over West Dorset heading towards us, so it looks like we'll get another air frost tonight - then some sharper ones to come on Friday and Saturday night as we pick up a drier continental feed. Noticed that Wattisham has been in freezing fog all day! Currently -1C already there: METAR EGUW 081550Z 00000KT 0200 FZFG SCT200 M01/M01 Q1029 RED NOSIG=
  6. Mean temperature for the first 7 days of the month at home in Suffolk was -1.1C! :wacko:
  7. Weather stats from Leavenheath, Suffolk (~60m AMSL) (Departures from mean are from the 1971-2000 mean at Wattisham airfield in Suffolk which is ~10 miles northeast of the site) A cold and dry month, the coldest December for 7 years - and even drier than that December which recorded 17.4mm of rainfall. December 2008 Mean temperature: 3.7C (Lowest since 2001 which recorded a mean of 3.0C) Mean maximum: 5.7C (-1.4C) Mean minimum: 1.6C (-0.3C) Highest maximum: 12.5C (20th December) Lowest maximum: 1.5C (29th December) Lowest minimum: -4.2C (12th December) Highest minimum: 8.5C (22nd December) No. of air frosts: 12 Total rainfall: 12.0mm (23%) Wettest day: 6.8mm (13th December) Days with rain >=1mm: 3 (-8 )
  8. Well it could theoretically snow with an air temperatures as high as 8C, but you would need a dew point of -23C (RH: 11%) and this is extremely unlikely! In reality it's more like around 4C as an absolute limit in the UK (which still requires a dew point of -8C) and is likely to occur in Spring when you get a cold northerly outbreak with strong sunshine able to heat the air at the surface very quickly drying it out - then a heavy shower with a strong downdraft passing over which will lead to very strong evaporative cooling occurring reducing the air temperature to the wet bulb temperature (in this case around 0C) and snow to fall to the surface. Edit - what TWS said basically.
  9. Typical of OON to show off his 4 inches on national television. Sophie Raworth does look very impressed however. Well done and that..
  10. The dew point is effectively a measure of how moist an airmass is, this will vary considerably within a particular airmass particularly over the UK because of the variations between drier inland observation sites and those that are near lakes or by the coast where there are significant moistures sources. Airmasses that originate over the warm Azores (Tm/Tropical maritime) pick up the characteristics of where they are formed and therefore have high moisture content (typically in the summer as high as 15C) whereas those that form over the dry continent of eastern Europe/Russia such as our current Pc/Polar continental airmass, have low moisture content which can be as low as MS10C. Dew points will also fall at night at varying rates as moisture is deposited on surfaces as hoar frost. The dew point can also vary with pressure though this effect is only really noticeable with altitude rather than over distances at the surface, where the variations are an order of magnitude higher. The dew point is the temperature at which evaporation and condensation of water vapour is in equilibrium - it has a very high positive correlation with snowmelt such that the higher the dew point the faster the melting/evaporation of snowcover. This is because the vapour pressure of the snow (frozen water) becomes increasing less than that of air (water vapor) and therefore condensation occurs, which releases latent heat melting the snow (a process which in itself takes latent heat). This is often observed in the form of low stratus and/or fog developing (depending on surface flow) as positive dew points advect over snow fields.
  11. A Tephigram for yesterday will probably illustrate it best. Below is Albemarle's midnight ascent for the night just gone. Ok it's not exactly Lancashire but it's the nearest one we have.. As you can see, at the surface the air temp is 0.2C and dew point -1.2C which you would expect to produce precipitation in the form of snow- however in the profile between approx. 1000ft and 3000ft AMSL there is a wedge of relatively warmer and moist air which acts to melt the snowflakes as they fall through that relatively warmer layer on their way to the surface. The melting snowflakes will fall to the surface as either a mix of raindrops and big snowflakes (that survive the warm layer) or if the cold surface layer is deep and cold enough, result in ice pellets or even the very hazardous and relatively rare freezing rain! There are other complications such as evaporative cooling which can, over time and with little mixing, cause the profile in the lowest few thousand feet to became isothermal along the 0C line and bring the freezing level to the surface - and with it rain changing over to snow! It all adds up to make snow forecasting a total nightmare...
  12. I meant the year, not the month - though it is quite possibly the second coldest recorded CET for a month this millennium. :o
  13. 1996!? It definitely won't be colder than 2001.
  14. They have last nights minimum as -5.6C, coldest CET night since 3 March 2006 (-5.9C).
  15. Kentimetres! I love it. :blush: Speaking of which, Kent was actually the last place that I saw a 'proper' snowfall on 10th April 2006. 10cm of wet and completely unforecasted snow fell close to Tunbridge Wells during the night. ... and that was in the year that became the warmest on record for England and Wales!
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