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The annual Christmas day count down from T+384


johnholmes

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

    The annual Christmas count down from T+384

    Yes its that time again folks, another roller coaster, stomach churning ride on the GFS express into Santa land.

    Will it won't it?

    Today is the first run actually into Christmas Day using the 'normal' GFS output. The CFS has been doing it for months.

    No doubt GFS will produce nearly as many possible situations as CFS has and still is doing.

    Anyway, I'll leave Paul M to keep his CFS output going for Christmas on NW Extra. Here we will watch GFS and then introduce ECMWF to the fun at T+240, then the Met O gets on the ride from T+144.

    Normally the charts I will show will be those from NW Extra but this evening(2239) they still have not come in for T+384 so just GFS is being shown.

    So what of the DAY 1?

    00z showed a mild picture with some rain approaching the south and west.

    06Z had a rather less mild view with possibly some frost in places at first.

    12z has obviously been on the mulled wine and shows a mouth watering version, see below

    post-847-1197239706_thumb.jpg

    The high started over Europe, ex initial Scandinavian development from tomorrow 10/12/07

    with the 850mb temperature chart now and below it the ppn chart

    post-847-1197239744_thumb.jpg

    post-847-1197239770_thumb.jpg

    and the surface 12z temperature chart(often 2+ degrees too cold)

    post-847-1197239829_thumb.jpg

    So day 1 and only 3 variations in the 3 runs I've seen so far!

    Little point in any in depth discussion from me as its the very first day. We watch and wait through the coming days to see if any kind of pattern emerges. This may make it possible, if a trend emerges, to give a 'punt' for a white or green day.

    Day 2 T+360

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    Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

    http://www.wetterzentrale.de/pics/MT8_London_ens.png

    Good idea and lots of ensemble agreement tonight, so i will predict an upper air value between 9C and -6C, with a median of 2C, as this comes closer, i will narrow my prediction down, however for London, the signs are not too good in regards to very cold weather (sub-zero at least at night).

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    Posted
  • Location: New York City
  • Location: New York City

    Any chance of getting this thread locked so that one doesn't have to trawl through pages of comments to get to main posts from John? There is a casual discussion in the winter area.

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    Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

    Personally i feel that this thread should stay open.

    Also, based on the GFS6z ensembles, i am narrowing down the range of upper air temperatures to between 7C and -6C, with a median of 1C, supporing near average temperatures, temperature wise.

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    Mods/techies,

    I think we should have a seasonal feel to this thread. Any chance of a snowy background with Santa making an appearance as we get closer to the day? :lol: :lol:

    I wholeheartedly agree!festive backrounds and keep the thread open.It'll sort the candycanes from the humbugs :D

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

    I would prefer the thread is kept open BUT that admin/mods are happy to delete threads which are one liners, belittle any other poster etc. The same as any other thread.

    Most updates will be done using the 12z data with passing comment on the other runs if I've seen them.

    Comparison with the other models as they come on line and possible comments re ensemble data, using Derbyshire as about mid England.

    Obviously I will try to make comment on the 'weather' for the whole UK that I think each days run suggests, albeit a brief one until nearer the time.

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

    Day 2 or T+360 12z

    Here is the msl-jetstream Extra chart.

    post-847-1197307676_thumb.jpg

    The 00 and 06z versions were, respectively cold at 00z with a high over Russia and 12z temperatures showing from 0-+9C countrywide, south to north.

    The 06z had HP over the Balkans with a s-sw flow over the country=T12 of 9-13C with rain in the west and north.

    12z shows a different idea and who knows when we can begin to think(note the word) we are spotting a trend developing?

    1000-500mb with hope for some lucky ones

    post-847-1197307437_thumb.jpg

    now the 850mb temperatures

    post-847-1197307470_thumb.jpg

    with the precip chart

    post-847-1197307494_thumb.jpg

    IF this turned out to be near the actual then we have snow falling on higher ground from the nw flow and perhaps some from the returning warm front to the sw but then milder again

    Day 3 may show something different again, far too early to think in terms of trend spotting but interesting to see how GFS deals with events this far out. Its starting from T+144 with general agreement from the 3 main models regarding the high currently(10/12/07) developing.

    sorry the last chart is just a repeat so please ignore

    jh

    just a brief comment on the 18z= yest another view?

    this time lp off n Scotland with HP Azores=windy wly in far nw, ppn for many especially in north; temps from(T18)2-5 most, 10+ in far sw), ppn with -5 850mb temp could be wet snow or even snow with some elevation.

    Anyway 7 runs and almost as many variants so far, although more cold than mild so far.

    post-847-1197307339_thumb.jpg

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

    Day 3 or T+324 hours

    again for 12z with brief comments about the other runs

    Today we have a cold nw flow with some ppn showing in the usual places in this type of airflow. This would give some a genuine White day with snow or sleet/soft hail falling on the day.

    The 1000-500mb chart shows

    post-847-1197407040_thumb.jpg

    now the precipitation and msl chart

    post-847-1197407098_thumb.jpg

    with the zero isotherm to follow

    post-847-1197407127_thumb.jpg

    finally the 850mb temperatures

    post-847-1197407367_thumb.jpg

    just 3 days at 12z to look at and we now have 3 all suggesting not mild; 2 with a pretty similar set up, that is a coldish unstable nw flow.

    Is this it?

    Far too early to get more than mildly interested this far out but interesting as we have 6 out of 10 runs thus far that show a cold situation rather than 2 mild and 2 others average or ?

    18z to follow as a brief comment; 00 and 06z both showed coldish set ups with the 06z rather similar to the 12z.

    = very different, now has HP over Denmark with winds from se in south east and fresh sl'y in nw, temps now in range 2 to 6 for most but above 10 in far sw, some rain in west and nw and ? over the se/e anglia area.

    so another variant.

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    Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

    http://www.wetterzentrale.de/pics/MT8_London_ens.png

    Good ensemble agreement, the range is narrowed down to between 2C and -5C, with a median of -2C, so xmas day is looking below average.

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

    Day 4 at +312

    12z and its showing this on the 1000-500mb chart for 12z

    post-847-1197498366_thumb.png

    the rainfall and msl chart shows this

    post-847-1197498414_thumb.jpg

    with the zero isotherm here

    post-847-1197498440_thumb.jpg

    and the 850mb temperatures here

    post-847-1197498476_thumb.jpg

    so what does this mean?

    well we have yet another possible weather pattern, now about the 5th or 6th variant in 14 runs so far, not yet got to Xmas Day on the 18z tonight.

    This one shows a developing low to the sw of Eire swinging wind and rain into the country during the day. At 12z it suggests temperatures are 5-7C north of the front and 10 south of it, up to 12C in fact for the far south and sw.

    So no White there, other than snow on the mountains in the north truning to rain.

    Three more days before we can start to do a comparison with ECMWF for the same time.

    The prediction beyond Christmas has all sorts of possibilities, rain gales, snow, all but the kitchen sink it would seem.

    The other runs, 00,06 and now 18z all have rather different ideas from each other. No real suggestion of any trends as yet.

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

    well its Day 5 or T+288 hours

    12z

    Has deepish low between nw Scotland and Iceland with wnw flow into country ahead of ridge in from west; strongish winds near low.

    ppn shows some heavy falls just clearing Channel coast, presumably a cold front with the usual spread of showers in airstream shown on msl/rainfall. -5c in nw and loc as far as Borders, and <0C rest country. T12 shows range 2-5C apart from sw where double figures. So on that basis some snow on the day for upland areas, see the charts below.

    remember though its the 5th 12z run, so a long way to go; however for cold/snow lovers its the 4th one I've rated cold or below average. Out of the 17 runs now its shown this tendency on 12, mostly with a west or nw type of flow, NOT easterly.

    remember that the low to the nw started out life to our sw, hence the core of relatively warm air near it. Only that tongue shown on the 1000-850mb chart has colder air in it. So just that area is most likely, ON THIS CHART predict, to have any white stuff, and even then only above 1500ft or more.

    msl-ppn

    post-847-1197565394_thumb.jpg

    1000-850mb thickness

    post-847-1197565423_thumb.jpg

    zero C isotherm

    post-847-1197565456_thumb.jpg

    comments on the other 3 runs once the 18z is in the Extra area.

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

    what the comments or Extra

    the comments on 00,06 and 18z will come out once I've seen the 18z and mulled it over?

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

    I don't think its going to last quite that long although its still not certain how it will nd.

    Could be a chance of some leading edge snow in the run up to Xmas.

    sorry about no updates last evening for 00, 06 and 18.

    In a rush again now so will add them this afternoon.

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

    well got a few mins before I go out so here with update on other runs

    00z=deep low N Sea with wnw flow over UK; 850mb=<zero for many; ppn=for e/ne and loc elsewhere;T12=3-8 but >10C south wales-east Anglia

    06z=low well to wsw with sw flow for most then ridge later from west; rain from sw with 850mb=<zero all early but only Scotland later;T12=3-6 north of frontal zone, 10-13 south of it

    18Z=low sw of Iceland=sly over UK; ppn areas in west mainly; 850=<zero C for most; T12=4-5C except sw=10+

    I would say so far out of 19 runs, we have below normal or even cold=14; mild=5; most of the air flows show a westerly, between nw and sw; no easterly has so far shown up.

    Just to spice up this thread I'll attempt a stab at a Christmas forecast on here during tomorrow!

    should be fun

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks
    Be careful John-some will take it as gospel!!

    yes very true but never mind

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

    a brief summary of the 00 and 06Z before the 12z comes out

    00z=HP to sw also Europe with LP near Iceland=slackish w'ly; 850=<zero C all; ppn= for w/sw and loc patchy light eastern side; T12=3-5(>10 in sw)

    06z=(at 18z)deepish LP to sw(see 00z!!) =sly; 850=>zero all except central+n Scotland; ppn=fairly widespread; T12>10 apart from n/c Scotland

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

    Day 6(T+288)

    detailed comments to follow later this evening, along with 18z picture,

    but White Christmas for some, more by Boxing Day perhaps???

    post-847-1197654057_thumb.jpg

    my apologies for this being done so late

    Its certainly a different forecast to any so far, and has little support from other runs, both before and after(see Day 7 comments)

    below is the 1000-500mb chart

    post-847-1197709914_thumb.jpg

    and now the msl and precip chart

    post-847-1197710016_thumb.jpg

    and the 1000-850mb chart

    post-847-1197710052_thumb.jpg

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

    Day 7 and its now T+240

    This means we have ECMWF twice a day, the 00z and 12z(when its in) to compare with the GFS output.

    My forecast will have to be delayed as I've got a lot on tonight(yet another party!) and a family lunch tomorrow at a superb restaurant in the Derbyshire Peak. 16 survivors from the 40 or so around twenty years ago!

    Anyway on to a look at the output for 12z today with GFS.

    A more likely happening than the one it posted just 24 hours ago.

    The high, even on Christmas Day is now progged not to have gone that far away, close enough anyway(even if over Poland) to be exerting some influence over the UK. Just what the eventual outcome will be is still quite wide open. I suppose the most likely one, and the one seen in the majority of runs over the past few days is some kind of southerly or south westerly flow. As yet its not certain though by any means.

    below is the 1000-500mb chart

    post-847-1197738391_thumb.jpg

    now the 1000-850mb

    post-847-1197738422_thumb.jpg

    with the msl-ppn chart

    post-847-1197738449_thumb.jpg

    and finally the zero C isotherm chart

    post-847-1197738478_thumb.jpg

    just looking at the 00 and 06z runs:-

    the 00z with LP off nw Scotland had a breezy w-sw flow with most of the ppn in the north west but not exclusively, the 850mb was <0C for most and T values of 3-6 for many but >10 in the sw.

    at 06z HP was to the east with LP just ne of Iceland=slack Sly; and ppn for many northwestern areas, some mod+ and not totally dry elsewhere;

    T06 showed values of 11-12 in the sw and s Wales, otherwise 8+ and similar by 18z

    Comparing the 00z GFS to that by ECMWF; ECMWF had the main low near Iceland with a marked trough from the nw into the UK, so w-nw flow behind it and Sly ahead of it.

    Thus it was the marked trough which was the main difference, both had lows to our nw admittedly not in very similar positions.

    I'll update comparisons with the 12z ECMWF later tonight or tomorrow morning.

    From now on with two outputs at 00 and 12z I'll drop cover of the 06 and 18z GFS runs.

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

    Day 8 or T+216 and now with the ECMWF for comparison

    The 12z GFS had LPjust north of NI at 995mb giving a mainly s'ly flow over the country. 850mb temps>zero C for all but the far west but most parts fell <zero C by evening . ppn showed most rain for the west with spits and spots at 12z elsewhere. T12 temperatures showed 3-8C with> 10C for s Wales and sw and southern areas of England.

    ECMWF had LP to the nw of Scotland at 975mb with a ssw flow for all.

    A quick look at the two charts below shows, whilst they each suggested wind flow from a southerly point with either average or above average temperatures the positions of the main centres was not very close.

    No doubt a continued uncertainty with them both as to the actual events.

    GFS

    post-847-1197844214_thumb.jpg

    ECMWF

    post-847-1197844263_thumb.jpg

    I really do promise to put my first Xmas Day forecast out tomorrow; family matters and DIY problems at home have caused the time slippage.

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

    Xmas Day first full forecast

    We now have data for the past 8 days from T+384 down to T+216

    Using the 12z for each day we have 3 ‘cold’, 2 ‘mild’ and 3 either ‘average’ or going from one definition to another. So nothing conclusive. The ‘cold’ cluster was mostly at the beginning with a tendency with the more recent runs to favour a less cold even mild weather type. In no case was there any suggestion of major blocking either north or east of the country. The cold set ups were w-nw flows with low pressure somewhere to our north east and the milder ones had low pressure to our west or south west.

    Having spent quite a lot of time studying the charts, 00, 06, 18, as well as the 12z runs, I am led to the following suggestion AT THE MOMENT for Christmas Day

    No real white Christmas for perhaps 95% of people in the UK. There MAY be some snow either falling or lying for a very few communities in the Scottish mountains with possibly some snow patches showing, if the tops are clear, on some other mountain tops, Lakes, N Wales(possible) and N Ireland but little else.

    The day looks like being one with low pressure dominating and somewhere between south west and north west of the country. Currently it looks like rain at times for more western and northern areas with districts to the lee of the main mountains probably being dry for quite a large part of daylight.

    Temperatures levels, around mid afternoon, look like being around normal for most, with winds blowing from between south and west. Depending on the timing of any rain from these lows then parts of the east may have a touch of frost early. The freezing levels look too high, even if precipitation is around for any snow below about 3,000ft in the country.

    That is how I see it this morning, as a summation of all the charts from T+384 down to T+216 for 12z.

    I will update this forecast on Friday 21st and continue with the daily synoptic review of the main models at the same time.

    The final update will be done on Sunday 23 December.

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