Model Output Discussion - 28th November - 4th December

[Summer Sun]

http://www.wzkarten3.de/pics/Rjma1681.gif

A bit windy in the North Sea!

[Snowmad79]

I don't think there will be any blizzards next week apart from across the far north and scottish hills and mountains further south, the gfs and ecm 12z on the face of it, shows quite a potent cold snap for the north but snow does not penetrate south of the hills in the midlands so the south looks like remaining snowless for some time to come but at least it will become colder.

Usually the case when Northwesterly/ topplers are forecast. This is why the model thread seems generally negative even though north of the midlands have potential for winteryness and possibly snow. These setups give me confidence in the fact that my area atleast wouldn't be totally snowless even if these setups are the only ones we get throughout winter.

[feb1991blizzard]

Just flicking through some of the other models the GEM looks tasty post T144 but thats the 0z from last night. The best of the rest i can find is the BOM 180-186.

http://www.meteociel...ode=0&archive=0

Some low level snow quite far south from this me thinks.

All FI of course and prone to being thwarted by shortwaves not being modelled well at this range and im nowhere near convinced of anything apart from Scotland and parts of Northern England. The most promising of the winter at this kind of range so far but that just shows how poor the output has been.

Edited November 28, 2011 by feb1991blizzard

[clark3r]

pressure still rising in the north east on ecm in FI

[Frosty.]

Usually the case when Northwesterly/ topplers are forecast. This is why the model thread seems generally negative even though north of the midlands have potential for winteryness and possibly snow. These setups give me confidence in the fact that my area atleast wouldn't be totally snowless even if these setups are the only ones we get throughout winter.

It would probably also favour the nw midlands as showers stream through the cheshire gap. As long as the models remain approximately as they are tonight, there would be wintry snap for northern britain and maybe central britain but then the % drops off quite a lot by the time we reach southern england which alas is where most viewers of this model thread are from, probably have to wait for a possible beasterly sometime in jan or feb for a proper wintry spell down there when the strat warms through and more blocking is likely although even then we will need some luck for the blocking to be in the right place!

Edited November 28, 2011 by Polar_ Low

[feb1991blizzard]

pressure still rising in the north east on ecm in FI

News to me. Pressure low everywhere to the North of UK for the whole run from what i can see.

[clark3r]

News to me. Pressure low everywhere to the North of UK for the whole run from what i can see.

north east of scandinavia!

[nick sussex]

Differences as early as 120hrs over in Canada between the UKMO and the GFS/ECM.

The UKMO won't deliver a PM flow with that upstream pattern so until theres some agreement I'd refrain from getting too excited about snow prospects for those areas currently favoured.

For newbies who don't know the general bias of the GFS in particular, polar maritime or polar flows it progs at 144hrs and onwards are often watered down in terms of depth of cold and duration.

This bias has been noted by NOAA , this is less of a problem when you have proper Greenland blocking and a northerly with that, I'd say regarding the depth of cold especially in marginal situations wait till within 96hrs.

Overall not much difference in the output this evening, shortwaves will continue to provide some variability and the Azores high is likely to make its presence felt past 240hrs.

[SuttonStorm]

NIck - I imagine you are slightly happier regarding your skiing prospects now - looking quite wintry next weekend in your neck of the woods!

SS

[weathe20]

So the ECM is showing something of interest so everyone is jumping on that. The GFS usually gets this situations wrong nearer the time and the UKMETO is different too. So the models dont show the same thing, so why is everyone so keen on this cold snap?

[Frosty.]

I noticed the gfs 12z really suppressed the azores/atlantic high but I believe the reality will be for the high to have more influence next week with milder Tm air returning.

Edited November 28, 2011 by Polar_ Low

[feb1991blizzard]

north east of scandinavia!

With you now, i was viewing on meteociel which doesnt show as large an area, anyway it would take the mother of all retrogressions to deliver though anyway.

[IanM]

Where are you viewing the 12z UKMO? It's still the 00z on Wetter and here on Netweather it hasn't updated for days?

SS

Sorry, it didn't flag as failed. the UKMO charts should update in the next 15-30 mins.

[Mark Neal.]

I know its just under a week out but the gfs weather chart for 6am-(Mon 5th Dec) shows the precip type down to Oxfordshire border as snow, first time i have seen this near my area for a good while, hopefully a trend!

Edited November 28, 2011 by Mark Neal Ballooning

[feb1991blizzard]

Differences as early as 120hrs over in Canada between the UKMO and the GFS/ECM.

The UKMO won't deliver a PM flow with that upstream pattern so until theres some agreement I'd refrain from getting too excited about snow prospects for those areas currently favoured.

For newbies who don't know the general bias of the GFS in particular, polar maritime or polar flows it progs at 144hrs and onwards are often watered down in terms of depth of cold and duration.

This bias has been noted by NOAA , this is less of a problem when you have proper Greenland blocking and a northerly with that, I'd say regarding the depth of cold especially in marginal situations wait till within 96hrs.

Overall not much difference in the output this evening, shortwaves will continue to provide some variability and the Azores high is likely to make its presence felt past 240hrs.

Totally agree but its just nice to actually see something being progged as ive said it just shows you how rubbish a start we have had, just a good job theres 3 maybe 3 and a half months to get something meaningfull in - thats worth a alone.

[shedhead]

I know its just under a week out but the gfs weather chart for 6am-(Mon 5th Dec) shows the precip type down to Oxfordshire border as snow, first time i have seen this near my area for a good while, hopefully a trend!

Unfortunately those type of charts are pretty unreliable, especially at that range, tending to overdo any snow potential quite significantly at times.

Edited November 28, 2011 by shedhead

[nick sussex]

NIck - I imagine you are slightly happier regarding your skiing prospects now - looking quite wintry next weekend in your neck of the woods!

SS

Overall although there might be some new snow much depends on whether the ECM is correct, that would be very welcome.

The problem is that it's going to take an awful lot of snow to get the resorts in decent shape and the Azores high is waiting to pounce later. Euro highs can often be okay for the Alps and Pyrenees if they orientate in a way to keep the flow from the east or ne down here.

That is as long as you've built up a good base of snow before the high arrives.

I think the resorts are going to need every last cm of snow out of this more nw/se jet tilt before the high arrives.

[ukpaul]

So the ECM is showing something of interest so everyone is jumping on that. The GFS usually gets this situations wrong nearer the time and the UKMETO is different too. So the models dont show the same thing, so why is everyone so keen on this cold snap?

It's got cross model support in a reasonable time frame both are showing a cold snap for next Sunday-ish to Tuesday-ish (from others such as BOM and JMA too), after that and further into FI and things diverge but those are only useful for general impressions anyway.

Not going to be much of an effect in this neck of the woods but should be good for many. Here in the South East I wasn't expecting much until mid-Jan so happy for anyone else to get what they can while they can, personally I'm looking forwards to our 'autumn in a week'.

[nick sussex]

Totally agree but its just nice to actually see something being progged as ive said it just shows you how rubbish a start we have had, just a good job theres 3 maybe 3 and a half months to get something meaningfull in - thats worth a alone.

I agree, normally these charts wouldn't raise much interest but of course given the non weather of the last month they're a change.

Given it takes alot to please me in terms of wintry synoptics the fact that i'm enthused to see a front finally bring some snow to the mountains says it all!

We just have to accept that for the timebeing the NH pattern isn't great for any decent cold spells, no need for people to be too downhearted about this, perhaps this winter will get better with time as opposed to last year which started off great and went downhill to produce the utterly tedious January and February.

[Gibby]

Very busy with work at the moment so just a quick summary from me tonight.

It looks like a potentially unsettled and possibly stormy spell of weather is up and coming with a mixture of periods of rain and gales aalternating with rather cold and showery interludes when snow could fall on higher hills to quite modest levels at times from the Midlands northwards. GFS keeps things this way right out into FI with a brief respite from a ridge of high pressure at the tail end of the run. GFS's ensembles show 850's close to or a little below the long term mean while things become rather less wet later in the run. UKMO shows unsettled and rather colder conditions for a time late this week and through the weekend mirrored by ECM which goes on to show things flattening out somewhat by midweek next week allowing rather milder Atlantic winds with rain and drizzle to return by then as High pressure to the SW pushes Low pressures away North along with the Jet stream.

[nick sussex]

Quite alot of uncertainty over in the USA and Canada in the medium term as noted by this evenings discussions by NOAA:

http://www.hpc.ncep....ons/pmdepd.html

It's a long read this evening!

Reading that a better chance that the UKMO 12hrs run is too flat with the pattern over there.

I've just pulled out this quote which will have an impact on the pattern off the eastern seaboard.

DAY 5...THE MAIN ISSUE IS RESOLVING THE EVOLVING PATTERN

DOWNSTREAM OF THE AMPLIFYING RIDGE OVER THE NORTHERN PACIFIC.

GENERALLY SPEAKING...AN AMPLIFYING RIDGE IN THIS PROXIMITY FAVORS

THE POTENTIAL FOR CONSIDERABLE DIGGING OF DOWNSTREAM PERTURBATIONS

INTO TROUGHS OR POSSIBLY CLOSED LOWS ALONG WITH INTRUSIONS OF

POLAR OR ARCTIC AIRMASSES INTO THE ROCKIES OR NORTHERN PLAINS.

TOTAL SOLUTION SPREAD IS QUITE LARGE BEYOND DAY 5...BUT GIVEN THE

ANTICIPATED LARGE-SCALE RIDGE A SOLUTION SIMILAR OR BETWEEN THE

00Z ECMWF/12Z GFS IS EXPECTED ALBEIT WITH UNCERTAIN DETAILS.

ECM ensemble maps upto 168hrs:

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2009112700!!/

Edited November 28, 2011 by nick sussex

[bluearmy]

Quite alot of uncertainty over in the USA and Canada in the medium term as noted by this evenings discussions by NOAA:

http://www.hpc.ncep....ons/pmdepd.html

It's a long read this evening!

Reading that a better chance that the UKMO 12hrs run is too flat with the pattern over there.

I've just pulled out this quote which will have an impact on the pattern off the eastern seaboard.

DAY 5...THE MAIN ISSUE IS RESOLVING THE EVOLVING PATTERN

DOWNSTREAM OF THE AMPLIFYING RIDGE OVER THE NORTHERN PACIFIC.

GENERALLY SPEAKING...AN AMPLIFYING RIDGE IN THIS PROXIMITY FAVORS

THE POTENTIAL FOR CONSIDERABLE DIGGING OF DOWNSTREAM PERTURBATIONS

INTO TROUGHS OR POSSIBLY CLOSED LOWS ALONG WITH INTRUSIONS OF

POLAR OR ARCTIC AIRMASSES INTO THE ROCKIES OR NORTHERN PLAINS.

TOTAL SOLUTION SPREAD IS QUITE LARGE BEYOND DAY 5...BUT GIVEN THE

ANTICIPATED LARGE-SCALE RIDGE A SOLUTION SIMILAR OR BETWEEN THE

00Z ECMWF/12Z GFS IS EXPECTED ALBEIT WITH UNCERTAIN DETAILS.

ECM ensemble maps upto 168hrs:

http://www.ecmwf.int...t!2009112700!!/

i know iceberg picked up on this amplificaiton in the flow over the eastern pacific last week. several years ago, it was an extreme alaskan ridge that split the vortex and delivered a cold spell for us. however, looking at the runs from a NH perspective, one can see that despite the ridge getting far enough north to dig a decent trough into the states, it is quite quickly flattened by the jet and makes little impact into the arctic - thus the p/v remains intact and appears, if anything, to be strengthening, the further the modelling goes into december. i expect the only chance we have of proper surface cold conditions before xmas would be an inversion from a mid lat block. quite feasible i would have thought, for the southern half of the uk. of course, slightly below average in the north with a strong wind will certainly feel cold.

[ribster]

I know its just under a week out but the gfs weather chart for 6am-(Mon 5th Dec) shows the precip type down to Oxfordshire border as snow, first time i have seen this near my area for a good while, hopefully a trend!

Indeed, nice to see it on those charts. The models do seem to be gearing up for some sort of cold shot, however fleeting. One or two upgrades and you never know, one or two people might be pleasantly surprised. The picture seems to be slowly but surely improving as we descend into winter.

[Jhonny Peter Carson]

As a betting man, I would put money that this GFS low that hits Scotland late on the 2nd Dec, will not be downgraded and will stay for the three days with as yet unseen strong winds and snow, even at lower levels. I beleive that Piers Corbyn predicted this to happen on the 2nd. That would be a bit of a coincidence so I am prepared to take Corbyn at his forecast.

[Cheese Rice]

I'm refraining from hyping up the GFS North westerly which I would probably do well from.

Until we see agreement from the UKMO I'll reserve judgment.

UKMO has a Low pushing south in effect squashing the Azores high. GFS/ECM doesn't even have this low, so I'm going for a mix between the ECM/GFS at T144, the ECM has a shortwave but nothing that will upset the flow.

ECM-

GFS-

UKMO-

So yes while it would be a potentially interesting spell of weather for the Northern half of the UK. Until the UKMO jumps on board we will just have to wait longer till we can say this pattern is nailed.

Edited November 28, 2011 by Cheese Rice