Model Output Discussion 23/11/2012 18Z onwards

[cyclonic happiness]

GEFS 850hPa Ensemble Analysis,

Oh dear! That's an horrific mess, what do you believe after day 4 on-wards lol.

This is turning into on of the most flip-floppy, bumpy rides we've ever had whilst looking for cold spells, I think that's the only thing ALL of us can agree with?

[chionomaniac]

The paradox of weather forums much in evidence. When the pattern becomes problematic for NWP, and inter and intra run consistency falls apart, people seem more inclined to buy into operationals rather than less so!

Stick with your ensemble means.

Pretty much a solid trend still there for a substantively and sustained below average period. The models still trying to resolve mean position and residual energy left in the Canadian sector vortex after the split. An interesting little trend within a trend, shift in the block position around Svalbard and AO becoming more negative in time. I can only assume those commentaries on ensembles are being viewed from a Euro-centric view. If there was an issue, would have expected means to become diluted, but not any sign of this.

Agree entirely with this - and of course this has big consequences for us downstream.

Here are some charts from the model bias page http://www.hpc.ncep....bias/index.html

Great toy for checking out the variations.

Here are some images using the last 10 runs of the 12z. At 72 hrs and also 144 hrs for the UKMO ECM and GFS.

UKMO / ECM / GFS - 72 hours

UKMO / ECM / GFS - 144 hours

Will leave the dissection to our experts each has it's own little trend. I prefer the ECM overall but that's just me !

I suspect that blues show where the models are underestimating heights (ie the heights are actually higher there than the model forecasts) and the oranges where models are overestimating heights in the period concerned.

Looks like the GFS may be over estimating the northern arm of the polar jet, leaving the blue circumpolar trail just to the north of that jet stream. This is confirmed by the blues and oranges in the mid latitude that the more amplified pattern than forecast would lead to.

Edited November 24, 2012 by chionomaniac

[Buriedundersnow]

does anyone think with that low pressure coming north over us today is there any chance that it could turn to snow over scotland on its northern edge before turning back to rain or will any wintry stuff just be over high ground cos its baltic up here the day and will only get colder now as the day goes on

[Pennine Ten Foot Drifts]

Some interesting/worrying (depending on your outlook) weather over the next few days, and a couple of charts stand out for me:

Sub 985 tightly wound low sat in the North sea, potential for some very strong winds on southern and western flanks, (60-70 mph gusts quite possible, maybe more), plus torrential rain for all the areas that need it least. I'm also wondering if there's any danger of a storm surge for the east coast ?

Then Monday night in to Tuesday morning:

Possibility of snow on the northern edge of this system ? (at least for higher ground - particularly Peak District, Pennines and Snowdonia).

So never mind what might/might not happen at T192+, the next 3-4 days has much indeed to keep an eye on.

[Frosty.]

does anyone think with that low pressure coming north over us today is there any chance that it could turn to snow over scotland on its northern edge before turning back to rain or will any wintry stuff just be over high ground cos its baltic up here the day and will only get colder now as the day goes on

Yes there is a good chance of some freezing rain later tonight and tomorrow morning into scotland as the rainband hits the colder air, as there will be an early frost tonight up there after a sunny day, maybe some sleet or wet snow to higher ground in the heavier bursts, that wintry risk looks like increasing slowly in the week ahead.

[Polar Maritime]

Yes something to keep an eye on..

[Buriedundersnow]

thanks frosty.

one other question is i've been watching the thread over the past while to see what people are saying about the upcoming cold spell why does everyone seem to not want to count the bom model when it has been quite constant in bringing in the cold where other models seem to be all over the place but when i read things about the met office saying the cold spell is on the way and looks like it could possibly last for atleast a few weeks surely the bom has been the model that has shown better over this past while when other models are really struggleing might it be the case that the bom has things right while other models are getting a bit over eager with the little things

[Dandy]

thanks frosty.

one other question is i've been watching the thread over the past while to see what people are saying about the upcoming cold spell why does everyone seem to not want to count the bom model when it has been quite constant in bringing in the cold where other models seem to be all over the place but when i read things about the met office saying the cold spell is on the way and looks like it could possibly last for atleast a few weeks surely the bom has been the model that has shown better over this past while when other models are really struggleing might it be the case that the bom has things right while other models are getting a bit over eager with the little things

As mentioned before the BOM is modeled on the UKMO I believe, with a few tweaks (aussie ones).

.....it's been a mad global year for weather !!!

[Frosty.]

Yes something to keep an eye on..

Yes PM, some wintryness on the way, this upcoming cold spell has a lot of potential, especially for the eastern half of the uk but widespread frosts eventually for all areas, looks like a pattern that could really become locked in.

[Polar Maritime]

Yes lot's of twist's and turn's over the next few days as the cold air dig's in, there could be some surprise snow fall in places . More flip flopping to be expected from the models, but overall a cold/very-cold blocked pattern that could last a few weeks or even longer is just around the corner.

Edited November 24, 2012 by Polar Maritime

[weather eater]

Without a doubt the 06z is not a great run, however it is the sixth GFS run in a row with a different evolution in the crucial 72hr – 144hr period, so that needs to be kept in mind when viewing its output, If any of the GFS12z the UKMO and the ECM support it this evening then it may have gained some credence as a trend.

[swfc]

Can someone post a link for the updated meto update,cant find it

[Methuselah]

Without a doubt the 06z is not a great run, however it is the sixth GFS run in a row with a different evolution in the crucial 72hr – 144hr period, so that needs to be kept in mind when viewing its output, If any of the GFS12z the UKMO and the ECM support it this evening then it may have gained some credence as a trend.

Indeed it is. And, what're the odds on the 12Z being the seventh?

[SMU]

EYES DOWN FOR A FULL HOUSE-

can we get some consistency into 120 & 144- I think tonight we will do.

S

[phil nw.]

Can someone post a link for the updated meto update,cant find it

Here you go,

[chionomaniac]

Too many posts in here that are not relevent enough, and it seems that it is more important for some to post something rather than something in context.

Any posts not discussing the models may find themselves in the bin.

[johnholmes]

just before you all get totally engrossed in the 12z how about taking a quiet look at the last post in the Technical thread. It MIGHT calm a few nerves!

[cooling climate]

Here we go again, looking forward to a good afternoons model watching.

Hope to see the UKMO leading the way here and being backed up by the

other big two(ECM and GFS). Never really rated the BOM so not going to

start now just because its showing some fantastic synoptics.

[SMU]

good news at 54 we have lost the shortwave just off the coast of norway- which was prohibiting the westward flow-

Good start!

S

[A Winter's Tale]

Good afternoon. Through this evening, the low that is bringing more persistent rainfall and some windy conditions to southern areas should extend further north across England and cloud cover should increase ahead of the rainfall. Temperatures could be quite cold in Scotland this evening but staying dry. Later in the evening heavier rain should arrive in south western areas and rain edges into southern Scotland - many areas overcast but western Ireland could stay dry and relatively clear.

Tonight, much of England, Wales, southern and eastern Scotland should see persistent rainfall - heaviest in eastern areas and falling as snow on the munros - whilst Ireland stays dry and clear and southern and south western areas should be drier and possibly clearer later in the night. Minimum temperatures 2 to 10C.

Sunday morning - drier and clearer conditions should develop across Wales southern and western areas of England whilst Scotland and northern and eastern England keep the cloudy skies and the rainfall which should be a little patchier and lighter by now. Cold, dry and clear for much of Ireland but cloud cover may increase in the south with the arrival of rainfall.

During Sunday afternoon, skies over Scotland should remain overcast with patches of light rain in the north east, clear skies for eastern parts of England as cloud cover increase across south western areas with some heavy rain in Wales, the south west and southern Ireland. Maximum temperatures 5 to 11C.

Overnight on Sunday, there could still be some rain near the north east coast of Scotland, but the majority of the precipitation should be located across Wales and northern, central parts of England. Drier in Ireland with some light rain showers near the west coast. Minimum temperatures between 1 and 10C.

Monday - there could still be rainfall for quite a few areas of Great Britian, particulary for north eastern areas, in what could be a largely cloudy day away from western areas whereas Ireland could enjoy plenty of sunshine. Maximum temperatures 5 to 12C.

During Monday night, Ireland and Scotland should be dry and clear other than a few showers around the west coast. A cloudy night for England and Wales with some rain, most likely in eastern areas. Quite a chilly night with lows of 2 to 7C.

For Tuesday, low pressure could situated to the east bring in northerly winds in what is looking like a cool day, dry for many with some sunshine with showers down the north sea coast. Maximum temperatures 4 to 8C.

Tuesday night could be largely dry, clear and cold with a few showers down the north sea coast. Lows of 1 to 5C.

Wednesday is also currently looking like a dry, cold and largely sunny day with just a few coastal showers with highs of 4 to 7C with dry and clear conditions continuing overnight, possibly a widespread frost with lows of 0 to 5C.

Beyond this, signal is for further blocking, continued cooler/cold weather. But this is a particulary complicated and unclear scenario, as a result specific details is lacking clarity, probably a more unclear picture at the earlier timeframe than normal so I'd imagine that it will take more days of model watching for a clearer picture to emerge, but regardless of what the models are showing it should be enjoyable nonetheless and I'm still intruiged by the outlook and looking forward to whatever it throws at us. Certainly, from a perspective of winter weather, we are in pretty good situation to start the season, it remains to be seen whether the upcoming colder spell will bring favourable set-ups for wintry precipiation for the British Isles, but certainly the wider picture looks promising but we can only guess at this stage at what specific weather events could occur. An interesting situation to start off the winter, and this upcoming spell of northern blocking could possibly be followed by another. But in the meantime, we've got some interesting, active and changeable weather during the coming and eventful near-future.

[samadamsuk]

Hi All.

Looks to me like the UKMO is the only model now running with a propper cold pool moving across us - I'm happy to be wrong here of course. I have a pretty hit and miss connection of model links -

Sam

[Continental Climate]

A couple of days ago on the models we had massive ridging right up to greenland of our atlantic high now barely reaches iceland http://www.wetterzentrale.de/pics/Rtavn841.png lol just goes to show in these situations FI really is aboput t96 not saying this is gonna be a rubbish run mind you just commenting

[samadamsuk]

Looks like the 12z is shaping up better, echoing Seve's comments above. To my eye the low over se france/italy is deeper too, giving a beteter angle of WAA into the oncoming cold

Edited November 24, 2012 by samadamsuk

[bluearmy]

as far as this op gfs run is concerned, looking a bit better east of svaalbard. hopefully we can avoid too much energy headed west in that area which cuts off the arctic high and prevents the cold uppers heading sw. not much difference yet though.

[ITSY]

A couple of days ago on the models we had massive ridging right up to greenland of our atlantic high now barely reaches iceland http://www.wetterzen...cs/Rtavn841.png lol just goes to show in these situations FI really is aboput t96 not saying this is gonna be a rubbish run mind you just commenting

That is a great chart, we should really be happy with outputs like that at t+84!! it's the secondary injection of hp that is the interesting part...and JUST LOOK where that easterly comes from - mid Russia.

Clearly lots of differing opinions. I think this looks like an excellent run. by t+114 we have sub-4 uppers nationwide, an easterly, an arctic high set up around svalbard and a secondary HP making its way north in the Atlantic. I could be wrong though.

Edited November 24, 2012 by ITSY