Model Output Discussion 12z 04/12/2012

[Tom Jarvis]

can i just say that i am suprised that this thread hasnt gone into meltdown with these sort oif charts showing in the near reliable time frame.

if charts stay the same for the 12z i will probably see what happens when this thread goes into meltdown

[EML Network]

Incredible set of Ensembles and charts this morning / afternoon.

And what a lovely surprise that was this morning, with snow falling down here for a whole hour.

I am trying to hard not to get excited, but running through the various ''runs'' , I'm counting 16 of the 20 that will produce uppers cold enough for snow at + 180 onward ...the countdown has begun, I just hope and pray that these charts varify ...I won't believe it, until it's within + 72 ! (purely to stop myself from having a nervous breakdown)

[Buriedundersnow]

with snow threats recently being upgraded all the time does anyone think that the snow tomorrow might be far more widespread with the upper temps being forecast where they have to be

[Uncle_Barty]

With easterlies, not until it arrives!! Been stung in the past as close as t72 so best not get carried away BUT the difference here is this is a MEGA block and we are well within the block, in most cases we are an the real outside. The further WEST the pattern gets the better. But I never trust the models with Easterlies, been suckered in a lot by them in the past only to be bitterly let down.

This, a thousand times! Never nailed in my book, and certainly not before t+24/36

That said, very cold weather now looks more likely than not at this stage. Certainly no sign of my favourite Bartlett any time soon.

Only thing is the UKMO not being quite on board.

[MKN]

With easterlies, not until it arrives!! Been stung in the past as close as t72 so best not get carried away BUT the difference here is this is a MEGA block and we are well within the block, in most cases we are an the real outside. The further WEST the pattern gets the better. But I never trust the models with Easterlies, been suckered in a lot by them in the past only to be bitterly let down.

I think our biggest concern is if the models start to show the high pressure to close to us so we end up with cold and frost and not much else before the Atlantic pushes in further down the line. Hopefully we can get to within +72 with the same as the GFS/ECM are showing today

[Bottesford]

I think our biggest concern is if the models start to show the high pressure to close to us so we end up with cold and frost and not much else before the Atlantic pushes in further down the line. Hopefully we can get to within +72 with the same as the GFS/ECM are showing today

Or worse the dreaded North Sea low cloud! Need deep cold feed (which I'm not seeing on the charts) to prevent it being a cloudfest especially as the North Sea isn't *that* cold just yet.

[Wayneywoo]

can i just say that i am suprised that this thread hasnt gone into meltdown with these sort oif charts showing in the near reliable time frame.

if charts stay the same for the 12z i will probably see what happens when this thread goes into meltdown

I'm not very active on here since I got stung soooo many times in the past. The epic failed easterly that gets mentioned was probably the biggest let down of all time. It got as close as say T+72 and then just disappeared and I think it was agreed on by the majority of the models, at least the biggies that get mentioned (ECM, GFS, METO...).

What I can tell you is if things do improve as they look like they will, forum meltdown is detected when you have trouble connecting and posting!

I am extremely encouraged by the output of late and can see this only going in one direction however I still am restraining myself, admittedly it's beginning to get harder and harder!

[SteveB]

Some operational GFS runs have maintained this as a discrete feature cut off from the main body of the PV and taken it into the SW States. This has forced the retrogression further westwards.

Adding to the last post, I suspect the background factors will sharpen the ridge development around Iceland and maintain this, meaining the retrogression (if and when) will have an axis around a quasi Greenland-Iceland-N.Sea block, possibly extending into Norway and dropping through Finland (and then hopefully SW though northern Europe).

Could it be argued, we could be looking at a win-win situation, or is there the usual spoilers that could bring an end to the party before it even starts?

[latitude]

Could it be argued, we could be looking at a win-win situation, or is there the usual spoilers that could bring an end to the party before it even starts?

I think the ECM spotted the spoiler from that LP from Southern Greenland last time around. This week we should of been colder a lot colder. Cant remember at what time frame the ECM spotted the spoiler?

[Buriedundersnow]

with regards to the snow forecast for thursday will this not be a more widespread snowfall than that the other night.

looking at the models GFS, ECM and UKMO and the 850 temps all three models dont show anywhere in the uk gettin above around -2 or -1 uppers where as in the last snow fall the other night the only reason there wasnt snow in the south was due to a warm sector passing over england and wales now i'm in scotland and the warm sector passed to our south and the snow didnt turn back to rain as predicted in my location and stayed as snow till the front had passed over and i live right at sea level.

with the upper air temps to stay lower over the whole of the uk with this next low moving thru do u not think with the fact it stayed snowing here with uppers around the same last time as is predicted to be the lowest anywhere will see in the uk this time round and it never turned to rain even though it was predicted to last time there might be a greater snow event on its way even though they arent predicting it to be.

i posted this yesterday but everyone was so busy with the great model runs we were getting but if there is anyone who understands marginal snow events on here could they maybe let me know if my thoughts are correct or am i barking up the wrong tree was just wondering as been noticing lately the way snowfall keeps getting upgraded or under forecast

[TEITS]

What a difference 24hrs makes with these ensembles.

http://cdn.nwstatic.co.uk/ensimages/ens.20121205/06/t850Cambridgeshire.png

Far less scatter and as a consequence the mean has dropped about 4C compared to previous ensembles. However if I was being really picky I would like to see more ensembles dropping around -10C. I fear for those near the exposed coasts, upper temps around -7C would still give max temps around 4/5C and even 20miles inland around 3/4C.

[Frosty.]

is there the usual spoilers that could bring an end to the party before it even starts?

Not according to the latest meto update, it has if anything, increased the wintry potential for next week compared to yesterday's update with talk of wintry showers almost anywhere and even a risk of significant falls of snow to eastern hills plus widespread sharp frosts and freezing fog, so I believe we have moved closer to the outcome shown on the gfs and ecm so far today, a very wintry outlook but still a risk of milder interludes to the far south and west.

Edited December 5, 2012 by Frosty039

[snowy weather]

i posted this yesterday but everyone was so busy with the great model runs we were getting but if there is anyone who understands marginal snow events on here could they maybe let me know if my thoughts are correct or am i barking up the wrong tree was just wondering as been noticing lately the way snowfall keeps getting upgraded or under forecast

That's what I was thinking. In my opinion throughout the last couple of days where I live temperatures have always been lowered in the .run up to a certain day and the snow today which in the south east I only learnt about at late last night so I think the chances are very high in my options opinion. Would lover to hear expert analysis on this

[Mark Bayley]

Wonder if the GEFS is onto something with MJO activity, phase plots for this model on the move through to the 17th December.

MJO December Phase 1 Analog - it seems we have been looking at this off and on for a while now, and also GEFS Ensemble mean from the 00z run.

The ridges match pretty well and again support that trend for a Greenland high down the line, if this gets going on top of an already strong outlook then I think we are going to need a bigger ramp..

The GFS has been keen for a while now in an eventual move to a higher amplitude phase one, heres a chart from when i presented my December forecast late last week

And heres this weeks

Edited December 5, 2012 by Mark Bayley

[Weathizard]

What a difference 24hrs makes with these ensembles.

http://cdn.nwstatic....bridgeshire.png

Far less scatter and as a consequence the mean has dropped about 4C compared to previous ensembles. However if I was being really picky I would like to see more ensembles dropping around -10C. I fear for those near the exposed coasts, upper temps around -7C would still give max temps around 4/5C and even 20miles inland around 3/4C.

Really? I thought with an easterly flow and the wind chill effect even with -7 uppers we'd still achieve very low daytime maxima (1c'ish) or is there more too this than meets the eye? Or perhaps I'm just outright wrong.

The good thing with this though is that they are trending colder every run, I've noticed this as you said, they have trended a lot colder, I am not going to worry about the 850's anyway, as long as we get the Beast in the 850's will plummet and surely the surface cold it will create over Europe will help with the cooling?

[Frosty.]

Yesterday the models were indicating an end of the line easterly just about reaching the uk before it ran out of steam but today it looks much more like a full on easterly/sely blast will easily cover the uk by midweek or through the second half of next week onwards. The north sea will fuel snow shower development to eastern coasts and then they will blow well inland, it's actually classic stuff if it all works out right.

[Absolute Zero]

Really? I thought with an easterly flow and the wind chill effect even with -7 uppers we'd still achieve very low daytime maxima (1c'ish) or is there more too this than meets the eye? Or perhaps I'm just outright wrong.

The good thing with this though is that they are trending colder every run, I've noticed this as you said, they have trended a lot colder, I am not going to worry about the 850's anyway, as long as we get the Beast in the 850's will plummet and surely the surface cold it will create over Europe will help with the cooling?

Unless ive missed something here i don't believe windchill has any effect on the actual temp. It just makes it feel colder as the warm air from around your clothing is being blown away. Also a strong wind will cause moisture in your skin to evaporate faster and cause it to cool down.

[Catacol]

The upbeat feeling on here is good to read. :-)

The synoptics themselves are not such a surprise I think - too many people were upset that the cold didnt arrive this week, and the evolution to the easterly took a few days longer than nwp ensembles were initially suggesting, but they WERE suggesting it and now op runs are getting a little more consistent and a little bit close...

I try only to work on ensembles now really, and am still searching for that Feb 91 chart. This ensemble chart from ECM is about as good as it gets I reckon. From this weekend on the op runs will become really interesting especially once they hit the 120h range. We need some luck from here...

Edited December 5, 2012 by Catacol_Highlander

[Buriedundersnow]

The GFS has been keen for a while now in an eventual move to a higher amplitude phase one, heres a chart from when i presented my December forecast late last week

And heres this weeks

could u plz explain for us that dont understand these charts where on this is best for cold and snow and where is worst for cold and snow thanks

[Weathizard]

Unless ive missed something here i don't believe windchill has any effect on the actual temp. It just makes it feel colder as the warm air from around your clothing is being blown away. Also a strong wind will cause moisture in your skin to evaporate faster and cause it to cool down.

Quite right sir, well and truly told. Must learn more in this area. I'm not bad at chart reading but the daytime temps in a easterly flow, I just thought would be colder.

[Rob K]

Could it be argued, we could be looking at a win-win situation, or is there the usual spoilers that could bring an end to the party before it even starts?

With the UK being where it is, there are always potential spoilers! However I would risk saying that the pattern looks pretty well locked in to bring an easterly for at least a few days, but that could be a weak and modified northeaster, a southeasterly, a slack easterly flow or a full-blooded beast from the east, depending on the exact position and shape of the block.

[Absolute Zero]

Quite right sir, well and truly told. Must learn more in this area. I'm not bad at chart reading but the daytime temps in a easterly flow, I just thought would be colder.

Agreed, without a good cold pool an Easterly can be over rated.

[Chess01]

Anyone think this will last until christmas

[lorenzo]

could u plz explain for us that dont understand these charts where on this is best for cold and snow and where is worst for cold and snow thanks

To answer as quickly as I can and not derail the thread, the MJO forecast on the plots above can be used in conjunction with analogue charts to present a trend for how the Northern Hemisphere will shape up in terms of key features. Couple of fact sheets on this teleconnection in MJO link. In this case the MJO phase supports the development of a Greenland high, another of our winter holy grail set ups.

[weatherguy]

Agreed, without a good cold pool an Easterly can be over rated.

Get the easterly flow first, the cold uppers will come.