Model Output Discussion

[chrisbell-nottheweatherman]

GFS Parallel is showing blues for 120 hours+ (sub-540 DAM).

Let's hope the ECM doesn't spoil things.

Edited December 11, 2009 by chrisbell0033944

[MR EXTREMES]

GFS parallel run shows practically no ppn for the south from Thursday onwards :-(

please listen im on the southcoast we rarely get anything the models are in agreement there is alot of snow will fall here there mostly up north east ect.

take no notice remember the summer time when we have thunderstorms predicted and they never happen or on the flipside when there not predicted and the do happen dont listen to much to details that are 5 days or more out.

things change day by day including the models so anybody that is feeling left out just sit back enjoy the ride something will come.

[swfc]

Looking at the northern hemisphere charts its encoraging to see plenty of blocking right out to 240 hours.The chances of quite a few reloads looks on to me as we head towards and threw xmas.

[I remember Atlantic 252]

this is still FI, all hoping for a good 12Z ecmwf, next weekend a battle, low to south, and to north, I still say snow potential is huge for most areas, but all well in FI, (and before the 12Z ecm)

[snowmadchrisuk]

Ecm looking great at +96 , It has backtracked totally from last night's disaster run, This only goes to prove ECM isn't always correct even at short range.

[andy_leics22]

I think it's just you - looks far too mild to me:

http://www.wetterzentrale.de/pics/Rtavn4817.png

We'll have to wait till next week with the colder uppers and lower heights (hopefully) until any real snow potential begins. Wednesday/Thursday looking the best so far for the UK but remember the position of the shortwave is changing quite a lot so the whole setup could end up a few hundred miles further S still (like the 6z).

4-5c max temps too mild for snow? Not really, depends what the dew is and the upper air. -5c upper air and a dew of 0 coupled with an air temp that is 4c it can fall as sleet or snow depending on the intensity of the shower.

Synoptics looks good, however i am quite concerned at poor depth of cold that does arrive, 850hpa temps of -6 to -8c dont necessarily = snow.

It snowed here a few years ago with an upper air of -2c, the ground temp was around 1c. It can easily snow in -6 to -8 upper air, it's almost a garauntee at this time of year if theres precip with it.

[Harsh Climate]

Overall very good this evening , I would just like to say I can still see Snow showers in the midlands on Sunday , I can't see why nobody else is picking up on it , -5 850 , 528 dam and precipitation over the Midlands all night into Monday according to the latest UKMO charts. Does anybody else see this or is it just me ?

Chris

Gfs is predicting minimum temps of 3c, so dont think its likely to be snow. Maybe sleet at best.

[kold weather]

Expect the AO to flip +ve by the 21-23rd of December even if the models are a little on the progressive side. What that means is there is probably an enhanced risk of the Atlantic coming back in from the SW as the phase 4 charts would suggest an attempt to a return of November type synoptics. However the key that may save us is if the jet is far enough south and the upper low over Scandinavia remains we do have a decent chance of keeping a cold surface high close to the UK and that could be hard for the lows to get rid off. Its very much an old school pattern though and I'm not sure we've seen that many last for a long time recently.

[snowmadchrisuk]

4-5c max temps too mild for snow? Not really, depends what the dew is and the upper air. -5c upper air and a dew of 0 coupled with an air temp that is 4c it can fall as sleet or snow depending on the intensity of the shower.

It snowed here a few years ago with an upper air of -2c, the ground temp was around 1c. It can easily snow in -6 to -8 upper air, it's almost a garauntee at this time of year if theres precip with it.

Yes Andy , as you live 5 mins from me , We have had situations a lot more marginal that what is shown for Sunday night where we have been Snow watching.

[Matty M]

Nice ECM at 120hr has totally reverted away from its extreme shortwave mess into a sweety pie at 120hrs.

[Alex95]

ECMWF out to +120 over on Meteociel and it looks like a snowfest to me, low pressure across the Channel / Southeast England sinking south-westwards and bitter easterly winds spreading to northern regions. Could turn out better than the GFS? Not quite as much ridging into Greenland the the GFS though at this stage.

Edited December 11, 2009 by alza

[Snowaddict]

EXCELLENT ECMWF out to T+120...

Shortwave slips into the British Isles with cold air being advected west and strong northeasterly winds...

Even at T+96 it will feel very cold..

Just goes to show what changes can develop...

I would ignore anything past T+144 at the moment there are so many changes..

But it now looks as if the chances of snow next week have been upgraded significantly across the UK & Ireland, all depending upon the depth of the cold air...

Synoptics are fantastic

[johnholmes]

Expect the AO to flip +ve by the 21-23rd of December even if the models are a little on the progressive side. What that means is there is probably an enhanced risk of the Atlantic coming back in from the SW as the phase 4 charts would suggest an attempt to a return of November type synoptics. However the key that may save us is if the jet is far enough south and the upper low over Scandinavia remains we do have a decent chance of keeping a cold surface high close to the UK and that could be hard for the lows to get rid off. Its very much an old school pattern though and I'm not sure we've seen that many last for a long time recently.

not really what the AO ENSM prediction is showing KW nor does that idea have much backing from the hemispheric 500mb anomaly charts-but then, nothing in meteorology is ever certain!

More on the above in my lrf later this evening.

[andy_leics22]

INCREDIBLE!!!!!

I criticised the ECM in the past few days, i'm still not sure whether it can be trusted right now but it's funny because the GFS has gone more towards what the ECM was saying yesterday and the ECM today has gone towards what the GFS was saying yesterday :lol: :lol:

I've got absolutely no idea whats going to happen.

[snowmadchrisuk]

EXCELLENT ECMWF out to T+120...

Shortwave slips into the British Isles with cold air being advected west and strong northeasterly winds...

Even at T+96 it will feel very cold..

Just goes to show what changes can develop...

I would ignore anything past T+144 at the moment there are so many changes..

But it now looks as if the chances of snow next week have been upgraded significantly across the UK & Ireland, all depending upon the depth of the cold air...

Synoptics are fantastic :lol:

I'm not so sure there won't be a warm sector for the South with that low at +120 .

[Matty M]

I still expect many changes in the coming runs.

But a signal to underplay this Svalbard Shortwave is crucial and is why this easterly delivers.

The development of the shortwave or scale of depth is actually the key to this easterly.

[kold weather]

I believe John those AO predicitions are based off the GFS ensembles, therefore they will shift the same as the ensembles but I could very well be wrong with that. You are quite right in that it maybe very stubborn to be gone and I suspect the ensembles tonight are somewhat too progressive...but they are somewhat similar to what the broad signals (such as the GWO, etc) would suggest but timings probably are off.

Anyway 120hrs ECM looks decent, warm sector probably an issue for anyhwere south of the NE on this run much akin to the GFS run earlier. A little more progressive in bringing it down as well then 12z GFS as well.

[andy_leics22]

Ok the ECM has gone berzerk at T144

[snowmadchrisuk]

INCREDIBLE!!!!!

I've got absolutely no idea whats going to happen.

GFS has the low at it's +120 as well and just brings in a few showers for the south and east .

[bluearmy]

the shortwave headed sw is the one on yesterday evenings T120 FAX just west of norway. all the cold air is on the east side of the occlusion. its very difficult from the pressure charts to see exactly how this is likely to play (if it happens like this at all). the uppers wont tell the whole story either. could be a difficult one as it approaches - lets see what the T120 shows tonight.

[I remember Atlantic 252]

INCREDIBLE!!!!!

I criticised the ECM in the past few days, i'm still not sure whether it can be trusted right now but it's funny because the GFS has gone more towards what the ECM was saying yesterday and the ECM today has gone towards what the GFS was saying yesterday :lol: :lol:

I've got absolutely no idea whats going to happen.

FI yeah but that seems only good for Scotland?

[Snowaddict]

I still expect many changes in the coming runs.

But a signal to underplay this Svalbard Shortwave is crucial and is why this easterly delivers.

The development of the shortwave or scale of depth is actually the key to this easterly.

Indeed Matty & just look at T+144...

Absolute turnaround from ECMWF...

But as you say, yet more changes heavily likely given the inconsistencies lately & the difficulty in modelling this setup..

[Harsh Climate]

''I think after this we need to look at the reasons why we cannot get stable High latitude blocking in the winter months, yes the ECM has chopped and changed but the evolution now looks very plausible and the other models are now trending to move the High back SE.

A very sorry episode for the GFS in particular. Best to make the most of at least a more seasonal feel before the return to Atlantic weather. ''

An absolute belter from ian brown yesterday!!

If the current model runs verify, it will have been a superb peformance from the GFS, I hope then people will actually show the GFS the respect it deserves and accept that the ecmwf is not infaluble.. :lol:

[Matty M]

A nice flow indeed,

Gonna collapse to all for retrogression of the high to greenland but could remain cold the whole way through.

http://www.wetterzentrale.de/pics/Recm1441.gif

[Alex95]

Right, out to +144 and a very potent easterly, obviously I'd prefer a NE wind being in Northeast England, but this orientation can still be almost as good snow wise, and possibly herald more severe frosts? A lot of snow from this run I think, still not sure whether it will bring in a potent Greenland high or not.

On second thoughts, this may be slightly ENE which is no problem as far as I can see. NE does best on this run again as the snow sets in here first, and lasts. NE Scotland might be slightly too close to the high pressure for very heavy snow. Also, Greenland high finally at +168, similar to the GFS FI with a northerly reload likely from +192 onwards.

Edited December 11, 2009 by alza