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london-snow

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Posts posted by london-snow

    Model output discussion - The Hunt For Cold

    in Forecast Model Discussion

    Posted

    4 minutes ago, carinthian said:

    Looks like the UKMO latest on its own at144T.. No cold air advection on this run towards the British Isles. Interesting to see if the Met Office Forecast makes any adjustment on the fax at 120 t based on this output.

    UW144-7.gif

     

    This may tie in with why the METO in their extended forecast yesterday commented on things turning unsettled from the south and west. Lot’s of options on the table and right down to the wire springs to mind. It is great though to see the potential going forward bearings in mind it’s mid November.

    SE and East Anglia general weather discussion 03/03/2018 onwards

    in Regional

    Posted

    2 minutes ago, Snowy Bob said:

    Clipper please. 

    Finished work and so decided as the Redmen don't play til later and the six nations are a foregone conclusion and of course before any drinking needs commencing that I'll go for a walk instead of the gym. 

    Am currently on East Cliff. A but blowy. Have taken some pics for later. 

    Yup not sure where people are getting Thames streamer from and talk of 2009, This to me atm looks like a far southeastern event.

    Model output discussion - after the beast, what next?

    in Forecast Model Discussion

    Posted

    11 minutes ago, Steve Murr said:

    Nice post & just to add to this - Ive often thought of how to forecast snow without the aid of models due to there inability to quantify PPN totals from Streamers -

    you can do the same for anywhere but The following parameters are important:

    This is a very crude way -

    A) Timeline of optimal instability - 24 hours

    B)Max PPN rates from showers - ~2cm per hour

    C)% of time You can optimise from the optimal instability time - max 75% (0.75) because the streamer locale usually changes.

    This means the equation to the 'top out' values at sea level is A X B X C

    so my forecast sweet spot at sea level would be 36cms within the window available.

    In terms of elevation ( again crude ) based on reports I have seen from scotland then corresponding reports from Glencoe - that when sea level got a fall of 15cm, the Glencoe car park would be 2X (600M) ~ 30cm

    So I would go with a 0.33 increase in depth per 100M

    Tops of the downs are @ 200M Mostly - So 'top out' for the downs would be 59CM.

    This is on a par with 2009 where low ground of NW kent got to 30-35cm in a 30 hour window & the high downs were in the 50's.

    Taking the beast from the last week the GFS ppn rates/ snow depths look to be about 5-8X to low under convection where as the high res models like Hirlam / Aperge feel about 1.5X to short

    Best

    S

    Remember that top out forecast. 36cm which is in the streamer sweet spot location TBC?

     

    If correct 2009 gave me the biggest snowfall seen nigh on a foot and the meto issued a red warning albeit very localised other parts of the region received copious amounts also a great event that stands out in my memory although a quick thaw occurred and within a day or two the snow was gone. Would be great if we see even half that total over the weekend more runs needed however.

    • Like 2

    Kent, Home counties and south London general weather discussion 25/02/2018 onwards

    in Regional

    Posted

    All talk of another Kent clipper. Has anyone actually looked at the radar returns? 

    It shows a widespread convection of snow showers that are on and off currently. I’d punt that if we are to see any further significant snowfall overnight rather than fleeting showers then we ALL need to see a change in wind direction (Whatever flow suites you) I’m quite happy keeping the snow from today and for ages what seems keeping it to tomorrow, who knows what will happen overnight? 

    Kent, Home counties and south London general weather discussion 25/02/2018 onwards

    in Regional

    Posted

    18 minutes ago, Captain Shortwave said:

    Best of luck to all of you on the Essex coast and Kent, looks like a fun night. Some of the showers heading your way are really packing a punch with sizeable totals over parts of the Suffolk coast along with reports of thunder and lightning, and the convection potential actually increases further tomorrow.

    Oh come now please. How can most get excited when a few passing heavy snow showers that  acculimate to zilch during daylight hours be classed as the ‘Beast from the east’ I’d prefer ‘The nat from the north west’ at least that gave us a frost.

    Most if not all here are looking for lying snowfall not fleeting showers that melt in a few secs.

    • Like 2

    Kent, Home counties and south London general weather discussion 25/02/2018 onwards

    in Regional

    Posted

    4 minutes ago, Nick F said:

    Plenty of twigs on the T+00 fax for 18z this evening

    fax18z_260218.thumb.gif.baf6b86f2a8caf3d0b45e6115acb8a77.gif

    Wind seems to be veering more from NE to ENE upstream over the S North Sea and Holland, so hopefully we may see the snow showers currently affecting coastal E Anglia, Kent and E Sussex perhaps shifting a little more inland toward the W in the night.

    Well let’s hope those showers in Ipswich and just east of Norwich is a switch of course to begin with, those se of us have already a few cms, tomorrow with a few showers (That melt in sun) won’t cut it.

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