Model Output Discussion - 5th December - 11th December

[Terminal Moraine]

I know it's the CFS. But am i right in thinking it's showing a block forming around the 17th ?

http://www.meteociel...&carte=0&run=10

It does show a block and the same block also appears on both the ECM and the GFS, but on the latter two it's quickly blasted out of the way whereas CFS makes much more of it. It remains to be seen who's right.

[fizz511]

Here's a write up from Mr Data about the December 1990 snowstorm and Feb 1991 freeze from the Historical Weather thread: http://forum.netweather.tv/topic/34026-winter-1990-91-the-great-december-snowstormfebruary-freeze/page__hl__december%201990

Thanks Dan!

[Summer Sun]

These charts tend to be the best for showing any blocking.

http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/images1/glbz700Mon.gif

[Polar Maritime]

It does show a block and the same block also appears on both the ECM and the GFS, but on the latter two it's quickly blasted out of the way whereas CFS makes much more of it. It remains to be seen who's right.

Thanks T.M.

Something i will be keeping a close eye on, and has been talked about by a few lrf forcaster's. And now just starting to show up on the models.

Nice to see it all the same.. we shall see.

Edited December 10, 2011 by snowrob

[The Northern Ramper]

Interesting signals starting to develop, will keep an eye on developments over the next few days.

[Frosty.]

The latest meto 6-15 day update is the most wintry update so far and although the stiff upper lip nature of how it reads, with no mention of arctic blasts etc, it does indicate cold weather with snow and ice for most areas and also stormy weather which is likely to peak around next friday. The further outlook hints at pressure rising towards the south with the jet becoming positioned further north with most of the wet and windy weather ending up across nw britain and the far north eventually..this is all really just telling us what we already know from todays models so far but it's a good sign for cold fans in the south who have not seen any snow at all yet and very little in the way of frost.

[Thundery wintry showers]

Beyond the storm, he models are going for some sort of toppler next weekend - this should be the set-up that moves the Azoes High East/North East and gives us a generally mild final third of the month.

I think the toppler and subsequent pressure rises to the south (which have been showing on the ECMWF for a couple of days at least) are very likely to arrive. I don't have anywhere near as much confidence on the pressure rises being sustained and leading to a mild final third of the month though- they could just as easily amount to a short-lived ridge giving a few milder drier days before a colder and more stormy zonal pattern returns. This is what happened during December 1998 following the northerly outbreak around the 18th-21st- a few mild dry days before Christmas, and then a damaging storm on Boxing Day 1998, and showers in the subsequent polar maritime regime turned to snow in some northern and western parts on the 28th.

The low for next Tuesday doesn't look like too much of a concern to me re. damaging winds- just an ordinary Atlantic gale- and the GFS/UKMO have both moved towards ECMWF in shunting the low a bit further north, which allows colder weather and more widespread wintry showers due to the warm core of the low having less of an impact. However, next Friday's low has far more potential to produce damaging winds. Synoptically speaking the storm showing at present reminds me a lot of the one on the 9th/10th February 1988:

http://www.wetterzen...00119880209.gif

http://www.wetterzen...00119880210.gif

[PMPhotography]

The latest meto 6-15 day update is the most wintry update so far and although the stiff upper lip nature of how it reads, with no mention of arctic blasts etc, it does indicate cold weather with snow and ice for most areas and also stormy weather which is likely to peak around next friday. The further outlook hints at pressure rising towards the south with the jet becoming positioned further north with most of the wet and windy weather ending up across nw britain and the far north eventually..this is all really just telling us what we already know from todays models so far but it's a good sign for cold fans in the south who have not seen any snow at all yet and very little in the way of frost.

I find it interesting that they have mentioned the storms peaking on the 16th (Friday). Very unusual for the Meto to stick their neck out and name specific dates. Confidence must be high.

I'm presuming the colder weather they mention will be to do with heights building to the west after that, giving us a more Northerly flow.

Looking more promising overall. Certainly some fascinating weather on the way!

[Timmytour]

^{An hour without a post! This time last year there would have been enough within an hour to fill 20 pages!}

[NickyB]

^{An hour without a post! This time last year there would have been enough within an hour to fill 20 pages!}

I believe it's called the calm before the storm.

[mountain shadow]

Storm Mark2 stil on course for Tuesday. GFS 12z has it as a sub 950mb low just north of Ulster. What worries me more is the length of this next windy spell could be days rather than hours.

[Matty M]

appears like this storm for next thursday/friday is being pushed further and further northwest on the latest runs! Might end up in iceland come the time!

[Harsh Climate]

This storm on friday is looking like a bomb! :o

Looks like scotland will bare the brunt as usual , I know it sounds stupid but I would prefer it effect northern england where i live

Edited December 10, 2011 by Harsh Climate

[mountain shadow]

Still six days away and plenty time for change.

[pinball wizard]

Update from Simon Keeling:

Well presented run through of the models, however, I would like to point out one thing that is important - he doesn't explain WHY that particular evolution is any more likely than the others. Any one of us could find a run that we like and that produces the synoptics we're looking for, however its the explanation why a particular pattern may arrive that for me is important.

[Mark Bayley]

Heres the UKMO's take on Fridays potential storm. The low further south, with strong winds across England, Wales and NI.

The GFS places the low further north, with the strongest winds across Ireland, Northern England and Scotland.

I have a feeling the GFS could be closer to the mark, with further shifts north. This needs watching as it is potentially a very nasty storm. Beforehand Tuesday looks quite windy, although not as a strong as the previous storm.

Edited December 10, 2011 by Mark Bayley

[ukpaul]

The UKMO which tends to be more realistic than GFS with lows has it further south as per t144 but not quite so fierce, GFS edging it south compared to the 06z also, Northern England and possibly the Midlands getting the worst of it if that verifies. With ECM seemingly agreeing at the moment. although with a greater intensity, that looks to be the form horse as per the eventual track.

Edited December 10, 2011 by ukpaul

[mountain shadow]

Unless we see a marked difference in the ECM tonight I would say this month is looking like a week of storminess, a blink and you'll miss it northerly followed by the euro high giving a mild Christmas.

Anyone forecasting a cold second half to December is on a very sticky wicket unless we some major changes soon. Still no sign of any northerly blocking.

Edited December 10, 2011 by mountain shadow

[Summer Sun]

This storm on friday is looking like a bomb! :o

Looks like scotland will bare the brunt as usual , I know it sounds stupid but I would prefer it effect northern england where i live

GFS has certainly shifted that further north lets hope this trend continues over the next 6 day's. By Friday the worst of the storm may be else where.

[SuttonStorm]

I seem to remember from discussions last year, that the intensity of a storm has a bearing on its path. If I have got it right, a deeper storm will take a more northerly track whereas a slacker LP will track further south - not sure if anyone can confirm?

SS

[Thundery wintry showers]

It's often the case that a deeper low is correlated with it being further north, and thus if the low trends further north, while it might mean that England and Wales miss the severest of the winds, it could mean higher chance of hurricane force winds for the area that does get affected.

[nytram43]

Well presented run through of the models, however, I would like to point out one thing that is important - he doesn't explain WHY that particular evolution is any more likely than the others. Any one of us could find a run that we like and that produces the synoptics we're looking for, however its the explanation why a particular pattern may arrive that for me is important.

I think he said the Canadian models had had some accurate runs lately which is why he favoured this particular outcome. However, he also said he was only 20% confident, which is pretty low.

[Dorsetbred]

I'm still finding it interesting the track of the low for Friday, and how the models interpret it's track.

Still all to play for and will be for a few days yet I guess.

Edited December 10, 2011 by Dorsetbred

[SuttonStorm]

and given the tendency of the GFS to over-egg the depth of the LPs would indicate a more southerly track in reality?

SS

[Thundery wintry showers]

Possibly, although I've known instances where the GFS only slightly over-egged the intensity while UKMO/ECM significantly underestimated it, so something similar to what GFS shows can't be ruled out at this stage.