Model Output Discussions 18z 31/01/2016

[weirpig]

These lows really are all over the place  this wont be resolved to very close the event

[snowray]

20 minutes ago, mickpips said:

So your taking ppn maps as gospel for the initial ( Friday low ) but discounting the secondary low ? as it 'may' end up in France. Very little movement of the initial low would mean that ppn forecast map to be incorrect too

Its more the depth of cold, or lack of it should I say, that concerns me when the 1st low hits. As it turns out the 2nd low is thankfully further North and drags colder air South to all areas on Sat/Sun as it moves away East.

Edited February 9, 2016 by snowray

[MKN]

4 minutes ago, weirpig said:

These lows really are all over the place  this wont be resolved to very close the event

I cant see any so called 'Event' right now, a wintry mix on one or two days both of which wont amount to anything on the ground. The potential for heavy snow seems to be drifting away imo. 

[Alexis]

GFS 12z really only gives us one slider now before pressure rises.

[weirpig]

1 minute ago, SnowTornado said:

I cant see any so called 'Event' right now, a wintry mix on one or two days both of which wont amount to anything on the ground. The potential for heavy snow seems to be drifting away imo. 

Yes i agree   but just a few flakes would be great

[Man With Beard]

UKMO T72/T96 has less separation between the two sliders, and so less chance for milder air to be sucked in ahead of the second low. This is because it keeps the second low shallower. With GFS history of overdoing lows, you'd have to side with UKMO for now.

p.s. that means maybe a bit more snowy

[nick sussex]

Differences between the GFS and UKMO at T96hrs.

The UKMO combines the shortwave energy into one system compared to the GFS which has the separate low tracking into the Channel.

Upstream the UKMO looks better going forward.

 

[MKN]

1 minute ago, Man With Beard said:

UKMO T72/T96 has less separation between the two sliders, and so less chance for milder air to be sucked in ahead of the second low. This is because it keeps the second low shallower. With GFS history of overdoing lows, you'd have to side with UKMO for now.

p.s. that means maybe a bit more snowy

Colder maybe but i cant see much in the way of precip. Either outcome to me either looks to be either lack of precip or lack of cold air in place.

[winterof79]

8 minutes ago, SnowTornado said:

I cant see any so called 'Event' right now, a wintry mix on one or two days both of which wont amount to anything on the ground. The potential for heavy snow seems to be drifting away imo. 

If the 12z on Tuesday happpens to be correct for the end of the week

[MKN]

Just now, winterof79 said:

If the 12z on Tuesday happpens to be correct for the end of the week

true although im basing it on the fact the outputs lately have been taking the event that looked possible back on sunday further away with each run to the point of there being no event. Id like to be wrong but cant see it based on latest outputs.

[snowray]

Yes UKMO much better, but there is no consistency at day 5 with any of the models, all over the place when something colder & snow turns up on the charts, which has been rare anyway, not much point even following the models they are more useless than ever right now. Suggestion, stick to the FAX charts upto T72.

[booferking]

2 minutes ago, nick sussex said:

Differences between the GFS and UKMO at T96hrs.

The UKMO combines the shortwave energy into one system compared to the GFS which has the separate low tracking into the Channel.

Upstream the UKMO looks better going forward.

 

How far North would the precipitation be on the UKMO Nick would the precipitation be more organized as one system.

[nick sussex]

Well the UKMO is better at T120hrs but develops a shortwave to the ne which stops the high getting further ne. At T144hrs its still cold for the UK but the GFS has a sharper troughing and the upstream pattern has displaced the Azores high so that's better at that point.

We're looking for the best combination, hopefully the ECM can incorporate the best of both the GFS/UKMO.

[snowray]

12 minutes ago, SnowTornado said:

true although im basing it on the fact the outputs lately have been taking the event that looked possible back on sunday further away with each run to the point of there being no event. Id like to be wrong but cant see it based on latest outputs.

This always happens these days of course. I seem to remember a few years ago that there was more of a 50/50 chance that a cold spell that was spotted at day 5 or even day 7 would actually come to fruition. 

Edited February 9, 2016 by snowray

[igloo]

not to bad looking from this evenings GFS shorter term snow from the midlands north then a slight milder spell then colder once again as long as the azores HP  stays further west than its usual spot this winter it looks good as illustrated on this chart

 

 

 

Edited February 9, 2016 by igloo

[Polar Maritime]

Again the GFS shows a cold N/W Pm flow around the 17th, Turning Northerly as the Low passes pushing High Pressure up towards Greenland and the Jet very much South of the UK giving a pretty messy picture out in the run..

Edited February 9, 2016 by Polar Maritime

[Alexis]

12z high res precipitation showing all rain for Friday, unless you're on a Welsh mountain. Afterwards it's looking dry and frosty for most before a toppler bring back more average conditions.

 

I'm struggling to see where any upgrade would come from now that 850s are 4 degrees higher than they were 36 hours ago.

Edited February 9, 2016 by Alexis

[A.J]

16 minutes ago, Alexis said:

12z high res precipitation showing all rain for Friday, unless you're on a Welsh mountain. Afterwards it's looking dry and frosty for most before a toppler bring back more average conditions.

 

I'm struggling to see where any upgrade would come from now that 850s are 4 degrees higher than they were 36 hours ago.

one ppn chart from one model run (and judging ppn charts at anything more than T24-36 is fraught with danger in terms of accuracy)......'upgrades' and 'downgrades' all come from the same supercomps reliant on the initial data entered....The output has chopped and changed over the past 36 hours not only model suite by model suite, but also run by run which is a sure sign that parameters are volatile so nothing should be taken as a given so a lot to play out, indeed all the way down to T0..............As John Holmes will always say, snowfall amounts and the snowfall locations are hard enough to forecast at T24, let alone T68

[bryan629]

This is crazy... just looking further out , around about day 9 . 

Here we have a reasonably long fetch Northerly all the way out of the arctic circle on a speedy flow south ... piling out of Svalbard , 

It actually looks quite good on the 500`s  with WAA firing up towards Greenland you might assume -8 uppers would be firing south with this chart. 

Then you take a gander upper 850`s and you have this.... 

Pffttt... iv`e seen better charts in Autumn ( not last Autum, obviously, lol ) compared to this , considering its approaching the coldest period of the year for cold in the arctic... 

On the plus side though at least the jet is staying south through the majority of the time.. so cant really grumble

 

 

Edited February 9, 2016 by bryan629

[mountain shadow]

2 minutes ago, bryan629 said:

This is crazy... just looking further out , around about day 9 . 

Here we have a reasonably long fetch Northerly all the way out of the arctic circle on a speedy flow south ... piling out of Svalbard , 

It actually looks quite good on the 500`s  with WAA firing up towards Greenland you might assume -8 uppers would be firing south with this chart. 

Then you take a gander upper 850`s and you have this.... 

Pffttt... iv`e seen better charts in Autumn compared to this , considering its approaching the coldest period of the year for cold in the arctic... 

On the plus side though at least the jet is staying south through the majority of the time.. so cant really grumble

 

 

Unfortunately the Strat warming pushed the coldest Arctic air into the US and East Asia, all we have left is cold dregs. 

 

[nick sussex]

 

33 minutes ago, Alexis said:

12z high res precipitation showing all rain for Friday, unless you're on a Welsh mountain. Afterwards it's looking dry and frosty for most before a toppler bring back more average conditions.

 

I'm struggling to see where any upgrade would come from now that 850s are 4 degrees higher than they were 36 hours ago.

Friday is the much more marginal set up, the next slider is really the one that could produce snow because that engages colder air feeding in from the ne. I'm still trying to work out the 850's for the UKMO,  Meteociel hasn't updated the closer UK view charts for several days, am trying to do this off the Canadian Mets global model outputs. In terms of the GFS being dry that's unlikely, you're likely find some troughs showing up closer to the time which won't be picked up at this early stage.

 

Edited February 9, 2016 by nick sussex

[bryan629]

6 minutes ago, nick sussex said:

 

Friday is the much more marginal set up, the next slider is really the one that could produce snow because that engages colder air feeding in from the ne. I'm still trying to work out the 850's for the UKMO,  Meteociel hasn't updated the closer UK view charts for several days, am trying to do this off the Canadian Mets global model outputs. In terms of the GFS being dry that's unlikely, you're likely find some troughs showing up closer to the time which won't be picked up at this early stage.

 

Hi Nick , I have been deliberating over trough developments over the North Sea as the sliders head south east, with the winds swinging easterly ... and as you say they wont be readily be modelled at this range anyway...  im reckoning on a thermal gradient of around 20 degrees , with North Sea SST`s being around 10 to 12 degrees at the moment... with -6 to -8 uppers ( if i have my maths correct) 

Do you think there is scope for instability within the easterly flow to develop a trough pushing inland from east to west .. 

[nick sussex]

39 minutes ago, bryan629 said:

Hi Nick , I have been deliberating over trough developments over the North Sea as the sliders head south east, with the winds swinging easterly ... and as you say they wont be readily be modelled at this range anyway...  im reckoning on a thermal gradient of around 20 degrees , with North Sea SST`s being around 10 to 12 degrees at the moment... with -6 to -8 uppers ( if i have my maths correct)

Do you think there is scope for instability within the easterly flow to develop a trough pushing inland from east to west .. 

Hi yes with the unstable flow and low parked over the North Sea you'd expect to see some troughs popping up. These will show up on the fax charts but are not forecast well days in advance.

We need to squeeze as low as possible 850's out of the set up and theres still time for those to change, hopefully a bit colder.

Even if the frontal boundary starts as rain its likely to change over to snow as the colder air to the ne undercuts this.

No agreement at T96hrs between the ECM/GFS/UKMO in terms of the detail for the UK, overall patterns are similar but as for where the initial snow will be its uncertain, however the  ECM looks better upstream than the GFS.

Edited February 9, 2016 by nick sussex

[lukemc]

Interesting outlook I am going to the Peak District on Sunday for 2 night staying in Glossop just asking if I have a chance of seeing snow on current projections? And do I have a chance of seeing something at home in Liverpool beforehand (sorry for the slightly off topic post - decided to post in here as it is quiet for the time of day)

 

Luke

[chris55]

So marginal but with light winds and a continental flow of sorts Saturdays slider does hold some interest RE snowfall. Plus the low ends up drawing in some colder air, rather than drawing in milder air, so a cooling low looks odds on.

 

Fridays Low looks to pretty much skirt to the south of most of us!