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Model Output Discussion - cold spell to end Autumn


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You know what - I havent seen 1 hopecast on here. People have put all their points of view across in a pretty good mannor- infact its been pretty good debate. The only post that sticks out a mile

Still coming slowly off a cautious fence Long term total global atmospheric angular momentum trends can tell you a lot about pattern changes due to the effects the rises and falls in global wind-

Afternoon All - A frantic few days on here with pages & pages of posts flying through in a matter of hours- I think we have 2 main discussion points at the moment-  1) The short to

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Posted
  • Location: Lytchett Matravers - 301 ft ASL
  • Weather Preferences: Snowy Winters, Torrential Storm Summers
  • Location: Lytchett Matravers - 301 ft ASL
    1 minute ago, *Stormforce~beka* said:

    How often does the temps on XCWeather update?

    Probably not for in here, but better off Looking on Wunderground for someone local to you

    e.g. https://www.wunderground.com/personal-weather-station/dashboard?ID=ITWYFORD9 

    Edited by karlos1983
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    Posted
  • Location: Wakefield, West Yorkshire
  • Weather Preferences: Anything except blazing hot summers!
  • Location: Wakefield, West Yorkshire
    22 hours ago, Paul_1978 said:

    Latest NAO and AO graphs. Some very negative AO members....

    nao20171206.gif

    ao20171206.gif

    Today's graphs hot off the press. Compare to yesterday's.....

     

    IMG_8498.GIF

    IMG_8497.GIF

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    Posted
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.

    Some post have had to be hidden, Please read the note Paul has put at the top of the page and keep to sensible model discussion only in here, Especially during these busy times as it just adds workloads for the team. 

    Thanks please continue ☺

     

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

    Latest fax on the Sunday low

    PPVL89.gif?31415

    Looks like the forecasters are narrowing it down to a path south of the border but this far out still time for adjustments i would think-that fax was for T84hrs from the 00z run.

     

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    Posted
  • Location: Lytchett Matravers - 301 ft ASL
  • Weather Preferences: Snowy Winters, Torrential Storm Summers
  • Location: Lytchett Matravers - 301 ft ASL

    Back in 2013 this broke southern counties hearts :cray:

    As early as the day before we were due inches and inches of snow, come the day though the channel islands and France stole the lot. 

    Slightly different setup, but forecast track should be monitored up to Saturday afternoon IMHO. Good luck

    Day before Event and a happy SW regional Thread

    gfs-2013031006-0-30.thumb.png.0fc2a029393ba82e2d68c0d2c501dee7.png

    Day of the event, Counselling sessions are still ongoing.

    gfs-2013031112-0-6.thumb.png.e896e9642f92aaf4d094ac0a6d570922.png

     

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    Posted
  • Location: .
  • Location: .

    So true, Karlos. Very similar to the Feb 2009 event I posted earlier.

    It's a heck of a cold airmass those fronts are coming into. I can see this sliding sliding sliding away. Happy to be found wrong but I still reckon a more north-west to south-east than west-east line for the centre is plausible.

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    Posted
  • Location: Wakefield, West Yorkshire
  • Weather Preferences: Anything except blazing hot summers!
  • Location: Wakefield, West Yorkshire

    Interesting stuff @Tamara Will take less notice of the AO/NAO forecasts!

    Edited by Paul_1978
    Typo
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    Posted
  • Location: NR LOURDES SW FRANCE
  • Location: NR LOURDES SW FRANCE

    I'm relieved I'm not having to  be subjected to the slider emotional rollercoaster!

    The fact the UK gets so little snow for its latitude often means these possible snow events become even more important which is totally understandable.

    This slider has really played some terrible mind games with snow lovers in this thread!

    There are many moving pieces here, as a slider its certainly up there with very complicated. The troughing to the east complicates matters as that's likely to phase with energy from the slider low, as that happens the track will get pulled more east than se so timing is important.

    Theres another added variable with a shortwave in the Atlantic which could run east and develop and head into France also phasing with the trough to the east which may pivot the snow line so overall its a forecasting nightmare. :cold-emoji:

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

    Just looking beyond the next few days and to the medium term there looks to be some readjustment of the pattern going on.

    Both suites show a weakening of the Alaskan/W.NA ridging around days 10/12-GEFs a llitle later.This releases the hold on the Canadian vortex which is currently being drawn back by the upstream amplified pattern,We can see the signs of the change upstream on the day 10 patterns.

       EDH1-240.GIF?07-12   gensnh-21-1-240.png                                

    More east to west pressure on the Atlantic heights with signs of the northern jet breaking through so this may just explain the uptick in the later temp.graph for London

    ensemble-tt6-london.gif

    No suggestions of full on zonal by any means but there may be a period of just below average(temp wise) westerlies rather than the current cold Arctic outbreaks from further north.

    Some re assurance for coldies perhaps is the continuing show of +ve ht anomalies to our ne and across the pole in the ens charts.

    Day 15 gefs

    gfs-ens_z500a_nhem_65.png

    ECM from the us site(which i wont post) pretty much shows the same picture.

    A bit of a cross roads coming up from days 10-15 as to whether the NH re-amplifies as the polar profile would suggest and where those ridges will show.

     

    Edited by phil nw.
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    Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

    Perhaps a useful summary if I'm interpreting it right;

    1. We should expect the western-N. American ridge holding the vortex to retrograde, with the interchange period potentially letting a bit of trough action escape into the N. Atlantic as the vortex lobe is able to expand (flatter on the southern flank; longer wavelength)
    2. However, the shifted pattern with ridging across the Aleutians should then serve to keep even that expanded vortex far west enough that high-latitude blocking is able to develop across Scandinavia and perhaps, due to the unusually perturbed tropospheric vortex state, a large section of the high latitudes of the eastern hemisphere
    3. This HLB pattern, supported by the waveguide set up by the move of GLAAM away from a La Nina-like state of GWO, is able to keep the jet stream diverted sufficiently south of the UK for some decent easterly potential. 

    All this, of course, dependent on the recent tropical trends (so excellently described by Tamara in recent days) continuing as desired. This being where I lose a few hairs now and then because this is the chaotic climate after all (but all things considered, I'm feeling pretty good about things at this time).

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    Posted
  • Location: Horsham, West sussex, 52m asl
  • Location: Horsham, West sussex, 52m asl
    24 minutes ago, Tamara said:

    Always worth taking a lead from the GSDM (Global Synoptic Dynamical Model) at all times in my opinion, but in the context of current discussions then NWP may be especially likely to oscillate in the period ahead, both with the tropospheric pattern, but also across the polar field in terms of the AO benchmark.

    Each post for quite some time from my own point of view has, in anticipation of possible outcomes, focussed on the upsides and then the downsides in terms of where atmospheric angular momentum is to be led during the upcoming transition of the MJO (tropical convection) from the current wave to the start of the next one.

    As stated yesterday, definitely coming off the fence with this one, though still stressing the need, as expressed in each post, to monitor how far AAM falls from the maximum disconnect with the La Nina base state currently happening - to the cyclical ebb as the tropics re-set patterns through the mid period of this month.

    The Phase 4 Global Wind Oscillation (at present) orbiting to Phase 8 and then in turn back to Phase 4 (and not heading back into Nina Phases 1,2 and 3) will underpin the bullish notions that the atmospheric circulation wants to continue to pave the way towards an even colder trend heading towards and into the New Year as the North Pacific ridge and Canadian vortex configurations relax sufficiently to allow height rises to the NE but without too much northern branch of the Jetstream to spoil deeper sources of upper cold air advection to head south-westwards across the North Sea.

    We could espouse the easterly of late December 2005 as an example of this sort of thing, but not at face value in terms of "intensity" (or otherwise )of cold air and snow distribution necessarily, or indeed replica precise timing to take too literally. It still has good purpose for illustration use though of how things could conceivably evolve in principle.

    I expressed slowly growing confidence in this sort of evolutionary possibility to NE heights yesterday. However the UK initially fares, the jist of it is that a deep source of cold air would be in place in this scenario that is highly unlikely to move very far in these circumstances and sets up a very very interesting January scenario

    Still with the attached caution caveat that prospects of a fall back in AAM sufficient to take the GWO back to Phases 1,2 and 3 is becoming less likely with each passing day of positive data -  *should* this occur then the more traditional La Nina pattern would re-surface which implies the North Pacific ridge and Canadian vortex combo not retrogressing and in this way pressurising the polar jet and neutralising an -AO profile. At the same time, the Azores/Atlantic ridge would be ascendant at the expense of greater influence of heights to the NE and too much energy transport to the N to allow the pattern to back deeper cold air advection westwards 

    Its highly possible that the models will show especially erratic trends on the way to the final destination, notwithstanding that as posted earlier on this thread, the GEFS suite is pointing a way towards the upside scenario in the extended period.

    But as a precaution anyway, in terms of keeping a sanguine open mind to keep enjoying the ride, I would suggest not allowing any model vicissitude to correspondingly engulf human emotions into equal vicissitude. On that basis best also to take AO/NAO forecasts with an equal pinch of salt - these will simply reflect the swings of NWP, and equally, ensemble suites

    The theme is the same old for me - the signals lead the models, the models don't lead the signals.

    Highly interesting start to the winter (for a change), if you don't let every model suite overwhelm you,  whichever way:smile:

    so @Tamara your musings reflect the thoughts of stewart (GP) on the mid to longer term prospects for the winter. waning of the pacific ridge and canadian vortex, allowing blocking patterns to form to our north/north east.

    to summarise your most eloquent post in more simple terms, -

    da wevva's lookin sick innit! 8)

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    Posted
  • Location: NR Worthing SE Coast
  • Location: NR Worthing SE Coast
    47 minutes ago, karlos1983 said:

    Back in 2013 this broke southern counties hearts :cray:

    As early as the day before we were due inches and inches of snow, come the day though the channel islands and France stole the lot. 

    Slightly different setup, but forecast track should be monitored up to Saturday afternoon IMHO. Good luck

    Day before Event and a happy SW regional Thread

    gfs-2013031006-0-30.thumb.png.0fc2a029393ba82e2d68c0d2c501dee7.png

    Day of the event, Counselling sessions are still ongoing.

    gfs-2013031112-0-6.thumb.png.e896e9642f92aaf4d094ac0a6d570922.png

     

    We got 4 inches from that event and 3 ft snow drifts so your wrong to say everyone missed out.

    Thats why I would still advise caution regarding Sunday’s slider,still  plenty of time till we know the final track of this slider,it will change until t0 I would imagine

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    Posted
  • Location: leicester
  • Location: leicester
    28 minutes ago, Nick F said:

    Afternoon Phil, entirely agree with your analysis.

    In the medium range the 00z EC and EPS mean this morning seem to be pointing to a deamplification of the 500mb flow pattern over the NE Pacific with a dampening of the PNA ridge … this leads to a slight relaxation of the eastern N American trough allowing the trop PV cold to shear off NE towards Greenland and far NW Atlantic and flattening the 500mb flow over the Atlantic and the more zonal look to the flow into NW Europe. However, this is quite a marked change from yesterday’s 12z EC, that tended to keep the flow more amplified over the Atlantic which allowed height rises to the N and NE of the UK as the Euro trough begins to fill southwards.

    Part of me thinks that the more zonal look from the EC this morning could be the lagged response (10 days) of the current ‘warm’ phases of the MJO working through on the northern hemispheric flow pattern, but a pattern that is inherently very amplified and will take a lot to deamplify. But this could be a temporary transition to a more mobile rather than blocked pattern over the Atlantic around mid-month. ENS, certainly GEFS anyway, less so EPS for now, definitely pointing to height rises to our N and NE after mid-month towards Xmas period - with the trop PV over E Canada and Davis Strait perhaps less likely to favour mid-Atlantic ridging as upper flow energy extends over the N Atlantic towards western Europe but increasingly on a southerly track. Would like to see the EC and EPS come back on board though with this idea. So until they do, would not pin too much hope on the height rises to the NE just yet …

    But, thank goodness we are fortunately not chasing cold spells in FI, as we have one unfolding over the next few days, with many areas in for a shout of seeing some snow falling, even if it doesn’t settle. Northern and western Scotland, N. Ireland + Nern Rep. of Ireland, NW England, Wales and Midlands look to be sweet spots for accumulating snow atm, so looking forward to seeing the pictures and reports flooding in here. Friday and Sunday look most prime periods for significant accumulations.

    Slight correction west already at 42 hours on the 12z

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    Posted
  • Location: New Ash green 150M / 500 FT
  • Location: New Ash green 150M / 500 FT

    Here we go then the 12s should be T72 for our slider now

    Fully expecting GFS corrections back towards the EPS suite & NAVGEM...

     

     

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    Posted
  • Location: st albans
  • Location: st albans

    Icon 12z as per the 06z with the low moving ne after the initial slide as it seems to phase somewhat with the upper trough 

    this is not a wonderful start to the 12z re Sunday’s potential event but if one model is going to look dodgy then this is the one I guess !

    Edited by bluearmy
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    Posted
  • Location: leicester
  • Location: leicester
    2 minutes ago, Steve Murr said:

    Here we go then the 12s should be T72 for our slider now

    Fully expecting GFS corrections back towards the EPS suite & NAVGEM...

     

     

    Steve theres correction west already at 48 hours lol!!could be a good run for sunday!!

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    Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth
    35 minutes ago, karlos1983 said:

    I cant be bothered, Delete!

    You have had incredibly bad luck around Bournemouth in the past decade!! 

    If you're nerves can stand it though, I can see a possibility for south coast snow from this event (10% chance at best). As the slider moves across the UK, it pivots and spins around a point as it phases with the low to the NE. If this happens through the channel ... the south coast will be in an E/NE flow (i.e. not off the channel) and hey presto, we nick the snow!!

    Sorry I know this is a bit of a regional one, but it is still a comment on potential model output and Karlos really does deserve cheering up...

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    Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
    1 minute ago, Steve Murr said:

    Here we go then the 12s should be T72 for our slider now

    Fully expecting GFS corrections back towards the EPS suite & NAVGEM...

     

     

    Without a doubt, Steve, that is what a lot of us will be hoping for...not too sure about some of the other lot, though...?:santa-emoji:

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    Posted
  • Location: New Ash green 150M / 500 FT
  • Location: New Ash green 150M / 500 FT
    18 minutes ago, Ed Stone said:

    Without a doubt, Steve, that is what a lot of us will be hoping for...not too sure about some of the other lot, though...?:santa-emoji:

    Its like a big tug of war- lucky we have a bit more puff !!

    its still a midlands event- its just the bits around the fringes !

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    Posted
  • Location: Chandlers Ford, south of Winchester.
  • Location: Chandlers Ford, south of Winchester.

    Heights higher over Greenland pushing the low on a more southerly trajectory again. Correction south again??? 

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    Message added by Paul

    Please only post model discussion in this thread. 

    For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
    https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

    For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
    https://www.netweather.tv/forum/forum/142-regional-discussions/

    Thank you!

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