Jump to content
Cold?
Local
Radar
Snow?

Model Output Discussion - 10th Jan Onwards


Recommended Posts

Spotted a post you think may be an issue? Please help the team by reporting it.
  • Replies 2.6k
  • Created
  • Last Reply

Top Posters In This Topic

Posted
  • Location: Near Romford Essex.
  • Location: Near Romford Essex.

    The GFS northerly does look impressive and I remember 2003, thunder snow, total white out conditions and horizontal snow....if that makes sense.

    28th of January 2004Posted Image

    Link to post
    Share on other sites
    Posted
  • Location: Raynes Park, London SW20
  • Location: Raynes Park, London SW20

    Well putting aside the GFS lower resolution I'm much more interested in tonights UKMO which is not so straightforward as first might seem, the high is actually strengthening between 120 and 144hrs.

     

    Low pressure over Italy and still disrupting energy over the UK, the Azores high is a bit of a spoiler but that output is the best for a few days after the constant edging east of the pattern.

     

    Hi Nick,

     

    Do you think the Azores high will link up with the Scandi high reinforcing the easterly over the south of the country? Or will that low just pile in - very hard to read if that low will go NE or SE....

    Link to post
    Share on other sites
    Posted
  • Location: Leeds
  • Location: Leeds

    I am expecting nothing for the next couple of weeks as every bit of potential never seems to get past +120h, if that Azores high would budge sw so low pressure has an easier time undercutting it would be game on with that cold pool building to our east.

    • Like 1
    Link to post
    Share on other sites
    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    Hi Nick,

     

    Do you think the Azores high will link up with the Scandi high reinforcing the easterly over the south of the country? Or will that low just pile in - very hard to read if that low will go NE or SE....

    You don't want the link up because the energy will just go over the top,you need the energy to split west of the UK,its a shame the Azores high wasn't a bit more amplified as that could ridge north and then the shortwave clears se and the ridge just reinforces the block.

    Edited by nick sussex
    • Like 4
    Link to post
    Share on other sites
    Posted
  • Location: Horsham, West sussex, 52m asl
  • Location: Horsham, West sussex, 52m asl

    I've been meaning to ask for a while... What in the name of Greek touchery is Shannon Entrophy?

     

    well.... entropy is a measure of the uncertainty of a random variable. a theory thought up by a bloke called Claude Shannon, hence 'Shannon Entropy'

    it can be applied to a number of instances of random variables (take the lottery numbers as an example of a random variable)

    however, it is an ideal term to use in weather forecasting, as the weather becomes more randomly variable, the longer the forecasting period is.

    a good way of 'visualising' shannon entropy is by looking at the ensemble graphs.

     

    for example, here's the 2m temperature graph for aberdeen-

     

    Posted Image

     

    as you can see, the scatter (range of temperatures) over the forecast period is quite narrow. this means shannon entropy is lower and we can be more confident that it will be lower due to the fact that the temp range in aberdeen in january, won't vary too much. (it's not as if the ensembles will be showing a range of -30c to +30c in january however mad our weather is!)

     

     

    then we move on to the air pressure graph-

     

    Posted Image

     

     

    huge scatter, due to the uncertainty of the forecast, as the random variables in the weather are subject to complicated changes early on in the run, even over a hemispheric scale, not just local to our little island, which obviously leads to a very wide range of scenarios later on. shannon entropy is therefore very high.

     

    I'm very uncertain what it means. Posted Image

     

    to what level of uncertainty are you uncertain? are you sure you are uncertain? or are you not certain if you're sure?....Posted ImagePosted Image

    • Like 1
    Link to post
    Share on other sites
    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    I have to laugh the UKMO has garnered hardly any attention this evening with the GFS FI taking over but the UKMO is a big upgrade in terms of cold potential and isn't at T240hrs!

     

    It might be a one hit wonder but for me anyway is a lot more interesting than a northerly at T240hrs which is so reliant on a favourable upstream pattern at the crucial timeframe.

    • Like 8
    Link to post
    Share on other sites
    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

     

    hi

    A request please?

    Tamara your posts are well worth reading, well thought out and objective but a favour please?

    Rather than copy the whole of your previous post, why not precis it or better still give a link to it so that those who wish can re read your previous post?

     

    many thanks

    • Like 3
    Link to post
    Share on other sites
    Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

    Blimey UKMO is close but oh so far away!

    Posted Image

    Can't see the 850's yet can anyone?

     

    They are out now

     

    Posted ImagePosted Image

    Posted ImagePosted Image

    Edited by Summer Sun
    • Like 1
    Link to post
    Share on other sites
    Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire

    Looking at the GEFS there may be one slight potential issue WRT any possible cold in around 10 days time.....although there appears to be a very strong signal (at that timeframe) for the PV to have a hole knocked out of it, it's pot luck as to whether we get lucky or not. Quite a few perturbations fail to deal with the Canadian vortex and so perpetuate the unsettled, Atlantic driven pattern.

     

    If this PV weakening/displacement etc etc is due to stratospheric reasoning then maybe one of the more learned members RE strat can suggest where they think the vortex may locate to circa day 10. Personally I'd like to see a 4 wave pattern and thus more broken PV (this increases the odds of a UK cold spell) but I suppose beggars can't be choosers!

    Link to post
    Share on other sites

    GEFS mean is not very pretty for cold at +192, or at +300

     

    Posted ImagePosted Image

     

    Some nasty storms popping up on the ensembles, worth keeping an eye on maybe, the ingredients are in place and has been a theme recently.

     

    Posted ImagePosted Image  Posted Image  Posted Image   Posted Image  Posted Image  Posted ImagePosted Image

    Edited by Bobby
    • Like 4
    Link to post
    Share on other sites
    Posted
  • Location: Near King's Lynn 13.68m ASL
  • Weather Preferences: Hoar Frost, Snow, Misty Autumn mornings
  • Location: Near King's Lynn 13.68m ASL

    They are out now

     

    Posted ImagePosted Image

     

     

    Ha! I'd always assumed they only went to T72. Every day's a school day.

    Link to post
    Share on other sites
    Posted
  • Location: West Sussex
  • Weather Preferences: Extreme cold & snow
  • Location: West Sussex

    Well putting aside the GFS lower resolution I'm much more interested in tonights UKMO which is not so straightforward as first might seem, the high is actually strengthening between 120 and 144hrs.

     

    Low pressure over Italy and still disrupting energy over the UK, the Azores high is a bit of a spoiler but that output is the best for a few days after the constant edging east of the pattern.

    Yes Nick and so is the strength of the 850's cold

    Posted Image

    Posted Image

    Posted Image

    • Like 2
    Link to post
    Share on other sites
    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    Ha! I'd always assumed they only went to T72. Every day's a school day.

    There is some support for the UKMO in the GEFS, if we could order a couple of hundred miles westwards correction I'd be very happy. But we have been here before during the last few days and things have stalled, I don't know whether its a coincidence but the last few evenings the 12hrs runs seem to have had the pattern further west.

    • Like 1
    Link to post
    Share on other sites
    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    Yes Nick and so is the strength of the 850's cold

    Posted Image

    Posted Image

    Posted Image

    I had to take a double look because I normally view the charts from the NH perspective but clearly on the European view you can see the high extending west, please can we have a westwards correction!

    Edited by nick sussex
    • Like 6
    Link to post
    Share on other sites
    Posted
  • Location: Farnham, Surrey
  • Weather Preferences: Cold, Sunny and Dry with a Hard Frost.
  • Location: Farnham, Surrey

    Let's hope the UKMO comes good. Quite frankly the storms showing up in FI are making me go pale. No more....please! Chimney stacks saturated, more leaks than a Welsh allotment and the garden is a swamp. Cold and dry.....

    • Like 6
    Link to post
    Share on other sites
    Posted
  • Location: Longwell Green, near Bristol
  • Weather Preferences: Storms, Gales, frost, fog & snow
  • Location: Longwell Green, near Bristol

    GEFS 12z London ens trending colder;

    post-12721-0-89518200-1389982076_thumb.j

    The mean (that's the red line) trending downwards throughout, hitting near enough -4c at the end.

    Nothing majorily cold yet, and neither would I expect so at this very early stage, but promising signs as we enter the last month of winter proper.

    Anyway, all in cuckoo land currently. The difference this time though is we have some stratospheric positivity for the first time this season.

    Edited by AWD
    • Like 2
    Link to post
    Share on other sites

    GEFS 12z London ens trending colder;

    Posted Imageimage.jpg

    The mean (that's the red line) trending downwards throughout, hitting near enough -5c at the end.

    Nothing majorily cold yet, and neither would I expect so at this very early stage, but promising signs as we enter the last month of winter proper.

     

    Looking at the ensembles most of the cold air is polar maritime sucked down by sometimes powerful depressions sourced from the PV to the NW rather than from a northerly or easterly source.

    Edited by Bobby
    Link to post
    Share on other sites
    Posted
  • Location: leicester
  • Location: leicester

    Wel its topsy turvey again tonight with the UKMO throwing out a half decent run- synoptic wise it looks good, but perhaps in the mains- cold rain for most ( all be it a bit colder rain than before) The wider spectre shows the arctic profiles reaching very very strong anomalies at day 8/9, however that link up high needs to filter all the way over to svalbard or greenland ( with link up) to really be of use... Things sizzling away tonight- The UKMO being a big positive from the 00z run- can we see a decent ECM that actually runs then varifies..... it appears at 96 its a good start- http://www.meteociel.fr/modeles/ecmwf/runs/2014011712/ECH1-96.GIF?17-0ECM 96 shows an oval low which sould support the UKMO evolution- possible undercutting Also @ 96 uppers @ -2 to -4, a surface feed from the deep south *COULD* see some snow on the forward flank of the fronts... S

    yes steve just taken a look and it looks very interesting!!there was always a chance this would happen and we see things back west slightly!!so maybe a frontal snowfall at 96 hours for some!!
    Link to post
    Share on other sites
    Posted
  • Location: Catchgate, Durham,705ft asl
  • Location: Catchgate, Durham,705ft asl

    Split vortex at 120 hrs,trough disruption near the UK,cold pool advancing from the east.

     

     

     

    • Like 2
    Link to post
    Share on other sites
    Posted
  • Location: hertfordshire
  • Location: hertfordshire

     

    I have to laugh the UKMO has garnered hardly any attention this evening with the GFS FI taking over but the UKMO is a big upgrade in terms of cold potential and isn't at T240hrs! It might be a one hit wonder but for me anyway is a lot more interesting than a northerly at T240hrs which is so reliant on a favourable upstream pattern at the crucial timeframe.

    Agreed if the UKMO t144 northern hemisphere chart verified I would grab the runwith both hands.Heights are building to the northeast with Arctic high comingsouth and very cold uppers heading west.
    • Like 3
    Link to post
    Share on other sites
    Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

    High pressure moving closer at t144

     

    Posted Image

     

    Coldest air remains in eastern europe

     

    Posted Image

    Edited by Summer Sun
    Link to post
    Share on other sites
    Posted
  • Location: Addington
  • Weather Preferences: Love a bit of snow
  • Location: Addington

    This is what I wanted to see from the ECM

    Further west corrections would be lovely

    Link to post
    Share on other sites
    Guest
    This topic is now closed to further replies.
    ×
    ×
    • Create New...