WInter Model Output Discussion 12z- 28/01/2013

[Rocheydub]

You won't see this at this timeframe.

What you will see in the next frames is a colder NW,ly.

http://modeles.meteo...fs-0-144.png?12

This is the first of two NW,ly outbreaks the second will occur around +200 onwards.

Hardly inspiring though in my search for cold!!! Standard winter fare.

Some slight differences (as expected) at 162 with the orientation of that low coming off the eastern seaboard, may actually allow pressure to zip up to Greenland, but it's probably being modeled further south than we'd want, would prefer to see it run up the west side of Greenland away... dragging the PV with it! This would allow pressure rises near Greenland, and the subtle difference to that blob of vortex over Scandi has grabbed my interest too... I like the look of where this run is going... So far.

We'll see!

EDIT: Actually, scrap that. Looks like it will topple quicker on this run out to 180...

Edited January 29, 2013 by Rocheydub

[TEITS]

Hardly inspiring though in my search for cold!!! Standard winter fare.

Some slight differences (as expected) at 162 with the orientation of that low coming off the eastern seaboard, may actually allow pressure to zip up to Greenland, but it's probably being modeled further south than we'd want, would prefer to see it run up the west side of Greenland away... dragging the PV with it! This would allow pressure rises near Greenland, and the subtle difference to that blob of vortex over Scandi has grabbed my interest too... I like the look of where this run is going... So far.

We'll see!

If your expecting anything more than this at this timeframe then you're going to be disappointed. This is a very straightforward pattern and its what happens after these NW,ly outbreaks that is uncertain because of the modelling of the PV. Chances of a GH developing before +240 is zero!

[Summer Sun]

This is the best I can find so far for snow fans from GFS

By the 6th the Azores starts to push back in again

Edited January 29, 2013 by Gavin.

[TEITS]

Here comes the next NW,ly as I said earlier.

Much better potential beyond as the PV is weaker and further W.

[Rocheydub]

If your expecting anything more than this at this timeframe then you're going to be disappointed. This is a very straightforward pattern and its what happens after these NW,ly outbreaks that is uncertain because of the modelling of the PV. Chances of a GH developing before +240 is zero!

Well, I'm not expecting it to be honest, but it doesn't stop me hoping!

If anything, with pressure less over Iceland by a good 10mb at the end of high res, it is a poorer run. This pattern is fairly stuck for the next 8/10 days ok!

I've broken so many nails lately with the straws I've been clutching at. PV does look weaker in fairness... Here's hoping.

[Summer Sun]

At t240 we get this

24 hours later we get this

Which leads to this

The prospects for sustained cold in the next 10 days remain slim tonight

Edited January 29, 2013 by Gavin.

[Panayiotis]

Well, I'm not expecting it to be honest, but it doesn't stop me hoping!

If anything, with pressure less over Iceland by a good 10mb at the end of high res, it is a poorer run. This pattern is fairly stuck for the next 8/10 days ok!

I've broken so many nails lately with the straws I've been clutching at. PV does look weaker in fairness... Here's hoping.

Sorry but you have so much confidence in something which you shouldnt! 10days=240hrs do you call that the reliable? A lot can change in that period, and you've shown that yourself between 2 consecutive runs! Edited January 29, 2013 by Panayiotis

[TEITS]

Damn PV reforms.

No chance of GH if that happens. This is what I was referring to earlier because this is completely opposite to the 06Z although in fairness is closer to the 0Z GFS.

[bradymk]

I think what TEITS is saying is important and needs to be reinforced

If your expecting anything more than this at this timeframe then you're going to be disappointed. This is a very straightforward pattern and its what happens after these NW,ly outbreaks that is uncertain because of the modelling of the PV. Chances of a GH developing before +240 is zero!

People need to be aware of this and that any sustained and "deep" cold is unlikely until right at the end of the GFS forecast period. This is when I feel the most potential lies for a colder more sustained pattern but it all depends on the PV. Before that, some colder snaps from the NW/N likely which can be quite decent for some northern and western areas but nothing significant until post day 10-15 which is reinforced by the MetO further outlook. I may be wrong but for me this is going to be a gradual cooldown with more and more temporary cold snaps from the NW with a possibility of a much colder and more sustained pattern developing later. With low heights to our south, reloads from the north and north west are likely but these are not likely to be too significant for southern areas anyway. But a better pattern for northern areas.

PS. I would not put too much faith in GFS low res when its changing run to run. Its poor at the best of times.

Edited January 29, 2013 by bradythemole

[phil nw.]

Certainly some consistency in the general pattern from the GFS HR part of the run.It follows the 00z means on both it`s own and the ECM suite up to T180hrs.

A chilly North Westerly mobile pattern with short colder Northerly incursions of Arctic air.

That Azores High slow to move west at this stage but should start to give way later in week 2 as forecasted in the later ensembles.

Both UK and GFS show the first Northerly for the end of the week

http://modeles.meteo...gfs-0-96.png?12

http://www.meteociel...72-21.GIF?29-16

coming in behind that diving low with some quite cold uppers of -6 to -8C.

Quite a cold looking GFS with only brief less cold intervals before the next shortwave drops south east renewing the cold.

Could see a few snowfalls up north especially the higher ground in the next 10 days.

[Rocheydub]

Sorry but you have so much confidence in something which you shouldnt! 10days=240hrs do you call that the reliable? A lot can change in that period, and you've shown that yourself between 2 consecutive runs!

Yes it can change, but the chances of it reversing and HLB developing are significantly less, than those currently displayed on the NWP verifying. You must surely accept that?? It is the form horse!

[cornish snow]

Still a newbie when it comes to the models but iv'e got a question which keeps occuring every time i view them.

Why is it that it always seems so much colder over in the hudson bay ,newfoundland area than north scandi siberia area?

They are both share similar latitudes and are large land masses.

Just allways seems those lovely purples are reserved for the other side of the pond.

I think the answer could have something to do with the PV been located there most of the time,but i could be wrong about this.

[mulzy]

No big change today. The models continue to show the cycle of the displaced Azores High pushing up and tumbling down again. Cooler than average at times but there are very little signs of any sustained cold at this juncture - we can safely write off sustained cold (for lowland Britain) till February 10th in my opinion.

Edited January 29, 2013 by mulzy

[bluearmy]

I think what TEITS is saying is important and needs to be reinforced People need to be aware of this and that any sustained and "deep" cold is unlikely until right at the end of the GFS forecast period. This is when I feel the most potential lies for a colder more sustained pattern but it all depends on the PV. Before that, some colder snaps from the NW/N likely which can be quite decent for some northern and western areas but nothing significant until post day 10-15 which is reinforced by the MetO further outlook. I may be wrong but for me this is going to be a gradual cooldown with more and more temporary cold snaps from the NW with a possibility of a much colder and more sustained pattern developing later. With low heights to our south, reloads from the north and north west are likely but these are not likely to be too significant for southern areas anyway. But a better pattern for northern areas.

PS. I would not put too much faith in GFS low res when its changing run to run. Its poor at the best of times.

i really cant agree that deep cold is not likely before the 14th feb. i would be happy to accept 7th/8th feb but thereafter, the modelling is too far away and clustered to make that statement. low res gfs ? forget it. you virtually say the same thing anyway but then contradict yourself somewhat. ecm london ens show av mean maxes around 3-4c 8th to 10th. take out the less cold scatter and that goes even lower.

[TEITS]

A reality check for some I feel.

The coming pattern is likely to see two NW,ly outbreaks. The first around the 5th Feb and then the second around 8th Feb. At this stage its difficult to be specific about the details but its highly likely the flow will initially be NW before veering N,ly. What this means is that N/NW including Wales are more likely to see any shower activity with the greatest chance of snowfall in higher elevations. The least likely areas to see any wintry weather is the SE who are likely to remain largely dry. This also includes many parts of S England with the exception of Norfolk.

What you are unlikely to see is bitter cold because for starters the upper temps are unlikely to drop below -8C. At this stage no blocking will develop around Greenland and its pointless searching for this in the model output upto +240.

I had hoped to see a trend towards blocking in distant FI. However because I like to be objective and unbiased in my posts I feel the chances of this occurring is lessening. I know the 06Z did suggest this but im becoming less confident this will occur. This doesn't mean we won't see a change in future model output though.

From a long range forecasting perspective something is causing this reluctance of blocking to develop over Greenland in the same way we have seen a reluctance of the NAO to go negative. I only wish I knew what it is because I agree with Steve M something is muting the signals that point towards a different pattern than one we are seeing.

Quick question. Have we seen an increase in Volcanic eruptions across the Tropics recently? You may wonder why im asking but this could be a cause if there has been.

Edited January 29, 2013 by THE EYE IN THE SKY

[Jason M]

I think the emsembles will be very interesting. I'm expecting them to be poor, but I don't want to start throwing in the towell at this stage.

Re the models I have noticed over the years that when the 'blob' AZH gets picked up there will often be lots of very dramatic cold ennsemble runs but that over the space of several days these reduce in number until all hope is eventually crushed under the mighty blob (sorry, got a bit dramatic there ).

There is very strong agreement on the broadscale between models and runs, so the pattern is very robust. This is illustrated by the differences in the deep low being modelled for the weekend. No matter how deep, no matter what its track the AZH storms back regardless.

In past times this pattern usually ends up with a UK high and a slow sink into zonality. Its for these reasons that i'm interested in the ensembles. If the trend of today continues in the next couple of runs I will be very concerned for our chances (although too early to call time as were still in Jan!!!!).

Jason

[Isolated Frost]

6z 84 illustrates the Friday situation very well- the immense jet streak off the eastern seaboard is disrupted by the tropospheric ridge- leading to a fragmentation, and an amplified jet slides west of the upper trough.

Mild sector trapped in the progressive low is increasingly mixed out through Fri- the 18z Fri prognosis shows the intense sub-970mb pressure system over the midlands.. the temporary colder pool to the north and north-east is to follow; the system moves from the WSW, with the main areas of precip being Ireland, the Midlands and Northern England, heavy rain for most with some heavy snow on higher ground, though the likelyhood is for rain to snow-

-8c t850s for many northern parts on Saturday morning- pushed on by a signal for a N/NE upper wind; lots of convection for the east coast..

Friday and Saturday look increasingly interesting, with strong winds, heavy and increasingly wintry precip with very low central pressure-

edit- 12z weakens the system from 969mb to 976mb, and pushes it further south.. signal then for Ireland, the Midlands and East Anglia- with colder air flowing in for the north thereafter

[Isolated Frost]

This is what makes our climate interesting to say the least- 12z prognosis

1c in Liverpool, 11c in Oxford... real temp difference on this incoming system, some big temperature fluctuations... the precip signal on this one also says

very snowy for parts of North Wales and the ultimate marginal event for much of NW England/W Midlands, veering on the side of snow for most though... another big event coming up?

NOTE the 6z had the central pressure over Leeds at 18z Fri, the 12z has it over London... the former had a big snow/rain event over NW/NE England and Yorks, this current run is all about NW England/N Wales/Mids... big changes to come and a fun day Friday!

[bradymk]

i really cant agree that deep cold is not likely before the 14th feb. i would be happy to accept 7th/8th feb but thereafter, the modelling is too far away and clustered to make that statement. low res gfs ? forget it. you virtually say the same thing anyway but then contradict yourself somewhat. ecm london ens show av mean maxes around 3-4c 8th to 10th. take out the less cold scatter and that goes even lower.

Thanks BA, was just my take on things but I take your much more experienced view with more value than mine I think my post may of been a bit too GFS based because I was impressed by the ECM means this morning but must admit I had not seen the london ens. And it was pretty dull of me to dismiss no significant cold until post day 10 when also saying not to take any notice of GFS low res, a blonde moment Edited January 29, 2013 by bradythemole

[Tim Bland]

CFS keeping the dream alive with a sustained cold and snowy blast from the east via a huge Scandinavian high http://www.meteociel.fr/modeles/cfse_cartes.php?ech=360&code=0&carte=0&mode=0&run=10

Followed by an Atlantic ridge and channel low

http://www.meteociel.fr/modeles/cfse_cartes.php?ech=438&code=0&carte=0&mode=0&run=10

Edited January 29, 2013 by Tim Bland

[UV-RAY]

Another day and another nail, still the output suggest much as it as done in the last few days, brief RPM in between any warm sectors. The Azores high appears to make an half hearted push towards Greenland but this quickly gets flattened by any residual energy left from the PV lobe. I think if we don't start seeing a change in the upstream pattern by the start of next week then that would be half of February in the bag. The outlook remains poor for sustained cold and looks likely to continue that way for some time yet,

Edited January 29, 2013 by Sceptical Inquirer

[bluearmy]

i really think some of you should wait untill all the 12z data is out before making statements of 'fact'.

the 12z gefs will be better than you expect if you have low expectations. very mixed beyond day 11/12 though a trend to throw a ridge to our ne with the euro trough cut off is apparent

Edited January 29, 2013 by bluearmy

[Wayneywoo]

I do find it "interesting" that members are so quick to allow themselves to change their mind/opinion based on one model run.

Some may say, "yes but it's been a number of runs now..." well if that was the case then why is there so much difference of opinion?

I do think that, as was the case with the cold spell we have just had, that anything can happen and to be certain of an outcome that is around a week to 10 days away is a little premature...

I do, however, enjoy reading all the posts so keep 'em coming

[Weathizard]

i really think some of you should wait untill all the 12z data is out before making statements of 'fact'.

the 12z gefs will be better than you expect

Was just going to post this, sick of reading about 'another nail' 'game over' ect I'm in the far south so I'm in the worst position but even I'm positive, ECM ens and the GEFS 12z are pretty decent especially the GEFS compared to the 6z suite. Also I don't believe the PV is being modelled correctly and I think coming soon will be a bigger reaction in the trophosphere.

[Captain Shortwave]

Unfortunately I feel that the interesting crux for the weather pattern for the UK for most of February is still just out of range of the hi-res GFS, the polar vortex looks on it's last legs and seems to want to transfer energy from Canada to Eastern Siberia which would leave the door open to high rises to our north. Unfortunately the polar vortex just reforms on this run. ECM will be interesting as t216 and 240 should perhaps shed some light on our weather patterns in the next few weeks (or will inevitably leave us clueless again haha). So cold snaps this Saturday and by the looks of it tuesday into wednesday. Could get some surprises and that low crossing us this Friday could provide some interest.