Model Output Discussion:

[TEITS]

Personally I think the excellent model runs continue this morning. I admit early next week isn't looking as wintry but lets be honest after recent model runs are we really assuming the models have early next week correct. Despite all of this you could say the medium range has upgraded as I suggested last night.

The positives today are.

1. Models definitely bringing the colder air in earlier.

2. Much better agreement on the ensembles with the rogue members disappearing this morning.

http://cirrus.netweather.tv/ensimages/ens.20100205/00/t850Cambridgeshire.png

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

3. Medium range upgraded. A strong signal from the models that the HP will eventually back towards Greenland.

http://www.wetterzentrale.de/pics/Recm2401.gif

Just remember last cold spell many complained that it looked dry. However remember how this panned out. Early next week details will not be sorted until this weekend.

Edited February 5, 2010 by THE EYE IN THE SKY

[Archie_Lewis]

Personally I think the excellent model runs continue this morning. I admit early next week isn't looking as wintry but lets be honest after recent model runs are we really assuming the models have early next week correct. Despite all of this you could say the medium range has upgraded as I suggested last night.

The positives today are.

1. Models definitely bringing the colder air in earlier.

http://www.meteociel...M0-72.GIF?05-12

2. Much better agreement on the ensembles with the rogue members disappearing this morning.

http://cirrus.netwea...bridgeshire.png

http://www.knmi.nl/e...agse/index.html

3. Medium range upgraded. A strong signal from the models that the HP will eventually back towards Greenland.

http://www.wetterzen...cs/Recm2401.gif

Just remember last cold spell many complained that it looked dry. However remember how this panned out. Early next week details will not be sorted until this weekend.

Great post TEITS

However compared to the last cold spell, the cold next week could be dominated by high pressure, less chance for convection, troth developing etc. The last cold spell had the high further north of course.

[John London]

Personally I think the excellent model runs continue this morning. I admit early next week isn't looking as wintry but lets be honest after recent model runs are we really assuming the models have early next week correct. Despite all of this you could say the medium range has upgraded as I suggested last night.

The positives today are.

1. Models definitely bringing the colder air in earlier.

http://www.meteociel...M0-72.GIF?05-12

As a complete novice at this model watching could you explain your last post to me. You state above that we shouldn't assume the models have got it correct for early next week, but then you post a chart for Monday next week stating that Models definitely bringing the colder air in earlier.

[TEITS]

Great post TEITS

However compared to the last cold spell, the cold next week could be dominated by high pressure, less chance for convection, troth developing etc. The last cold spell had the high further north of course.

Could be but the movement of the cold pool over Scandi will continue to be a headache for the models. The direction of which could easily change within the +72 period.

Back to the nearer timeframe and im still shaking my head in disbelief at +48.

http://www.wetterzentrale.de/pics/Rtavn481.png

At one stage mild SW,lys were suggested into Scandi. My word the models were way off the mark with this.

As a complete novice at this model watching could you explain your last post to me. You state above that we shouldn't assume the models have got it correct for early next week, but then you post a chart for Monday next week stating that Models definitely bringing the colder air in earlier.

Sorry I posted wrong link.

Look at the +48 chart I posted and you will note even on Sunday morning colder air is arriving from the E.

One pattern I have noticed in the last 36hrs of models is the cold backing W is arriving earlier than suggested.

Edited February 5, 2010 by THE EYE IN THE SKY

[Lewis]

Heavy snow showers pushing in on the Yorkshire/Lincs coastline From sunday midnight

I like the way the colder air has shifted west much earlier, as TEITS said above, only yesterday it was showing mild SW winds. What we are seeing today is a good sign, make sure you get the cold air in first, which we are doing. With it shifting West much quicker, it's certainly a good sign for the medium range patterns.

[TEITS]

Heavy snow showers pushing in on the Yorkshire/Lincs coastline From sunday midnight

I like the way the colder air has shifted west much earlier, as TEITS said above, only yesterday it was showing mild SW winds. What we are seeing today is a good sign, make sure you get the cold air in first, which we are doing. With it shifting West much quicker, it's certainly a good sign for the medium range patterns.

Yes and what i've noticed is as the +120 timeframe has moved into +48/+72 the general pattern has been to shift everything slightly further W. So with this in mind it is possible that the models might shift the cold pool further W during this weekends runs.

[mountain shadow]

High Pressure is slightly further north on this run, meaning the cold air is slightly further west.

http://cirrus.netweather.tv/gfsimages/gfs.20100205/06/108/h500slp.png

Still lots of changes going on.

[TEITS]

Let's have a little more analysis and objectivity here and stop taking much notice of anything past 72 hours.

Yes but there is a difference between commenting on what a particular run shows and believing it. If we restrict the posts to +72 their would be very little to discuss on here.

Based on the runs so far this morning its currently being suggested their will be two attempts of pulling in the cold pool to our E.

http://www.wetterzentrale.de/pics/Rtavn1321.png

[chionomaniac]

But, there is also a signal from GWO composites for high pressure to our west / NW transfering towards the UK over time. The trumping factor in all of this is the influence of downwelling zonal wind anomalies from the high troposphere - models are lurching all over the place w/r/t the polar field - symptomatic of poor modelling of the upper atmosphere.

As was suggested, the most safe assumption for downwelling to drive the Artic Oscillation negative is for this to happen from mid month. Before that, we see a relative angular momentum reaching its greatest anomaly of the winter and a strong phase 5 projection. This augers for height rises to our north and north west.

My guess is that mid term modelling is picking up the signal for phase 6-7 type progression which is for the ridge to become more orienated to our west and trough becoming re-established to our east with enough flow over the top to keep it as a mid latitude feature.

The movement of the high back towards Greenland programmed t216+ can only be accredited to stratospheric downwelling. Possible but given the way models have failed to cope with this, unwise to place too much faith in this.

Either way, cold becoming established and not going anywhere fast. Precipitation, hmmm, that's the thing.

Good post GP.

One thing that has been consistent over the last few days is the mean negative zonal winds forecast for the troposphere between 50-60ºN. They are there every day for the next 10 days. It does look that these are the result of stratospheric downwelling, but do you know if there is any other reason for them based on tropospheric teleconnections?

Cheers.

c

[Lewis]

The HP pushing further North, allowing the colder air to sink westwards from the east, some very cold pools of 850's out there. Upto now this probably the most feasible evolution with the colder air progressing west much earlier. The HP pushing further North tuesday, with the colder air from the east (the easterly) forming and pushing westwards.

Super upgrade, because everything comes into a more reliable time frame, yesterdays charts was showing the transformation to the Easterly later in FI. (Friday if i'm correct). So it's moved forward by 2-3 days.

Certainly not a odds on, but a lovely "perfect" run.

Edited February 5, 2010 by Storm Force Lewis

[Southender]

Better run from GFS this morning. HP not as quick to dominate. Tentative signs at +168, that it wants a trip to Greenland as well...

Lets hope this continues, over the next couple of days.

Edited February 5, 2010 by LeighShrimper

[Cecil Hogmanay Melchett]

Better 6z gfs Cold uppers well into the UK by Wed.

[Totoro]

Yes but there is a difference between commenting on what a particular run shows and believing it. If we restrict the posts to +72 their would be very little to discuss on here.

Couldn't agree more. However, what I'm trying to prevent is the reactionary posts to anything past t+72 as if such output will definitely occur. I'm not saying don't discuss things past t+72, simply don't take them as fact. Your posts are pretty much spot on TEITS, but those from some other posters are far more emotive and reactionary which often leads to general unpleasantness.

[Southender]

Well, this run should cheer most of the doom mongers up a little.

Much less HP influence, stronger E/NE flow and much more in the way of convection. Those in NE/E/SE parts of the UK will be particularly pleased with this run.

Lets see more upgrades like this over the next few days please.

[D KARLSON]

We are now locked in to some kind of cold outbreak from the east ,but as GP points out precipitation is another thing entirely.

Winds will veer northeasterly and bring some pretty beefy snow showers to the east and south east butr after say tuesday its just speculation ,but it could well be that we are entering another long and protracted cold period with the models suggesting retrogression northwest of the high which is a reasonable guess at this range.

Ive said this before ,but we have been so spoilt this winter people are demanding snow on tap ,havig said that we are liely to at least a few snowy spells out of this cold outbreak but when and where will be the key and know come the end of february there will be people complaining weve had too much

[Lewis]

Cracking run, in terms of precipitation and windows for the white stuff, it gives us all a chance.

On this run, EA and SE would be in prime position, with Kent well, if this comes off and your in Kent you'll love it!

As we transfer the colder air from the East on Sunday it gives coastal counties from NE england, right down the coast too the Kent coastline a chance for heavy snow showers, very convective aswell. Tuesday more or less the same although the snow showers transfer much further South, Wash southwards I would say.

Wednesday, the colder pool really digs in with the flow switching ENE, again EA/SE england prime position for something special, i expect a lot of embeded troughs in the flow, vast amounts of instability. If you live on the east coast, or the SE england. Your really going to enjoy this run.

Thursday/Friday, spectacular for accumulations of snow for many areas, again favoured areas are the east and SE. With showers pushing far inland, M4 corridor for a pasting.

I'm not ramping, just giving my thoughs on this output, as ever nothing is nailed and it's another evolution from the GFS 06Z. Things can still change quite widely.

Edited February 5, 2010 by Storm Force Lewis

[nick sussex]

Nice to see the GFS 06hrs run remain consistent with the overall pattern, the whole set up looks plausible which is always a good sign. I'm quite happy we've managed to get to todays model runs without too much drama, for me today was the crucial day as the Scandi shortwave comes into closer range.

[FENDER.]

Looks very good for eastern areas. However for those away from the east and s/e probably just dry and cold. The winds look to slack to penetrate much inland?

[Wayneywoo]

Someone help me understand this.

A west based -NAO which is what GP has forecast is for HP to north and LP to south over western atlantic, east coast of America and east based -NAO, same but over us in effect - LP over Azores, HP over Greenland/Scandi?

Now with the -NAO being west based forecast, does this not mean that LP systems as they come along our south, have more of a chance of actually coming closer to us as apposed to going over France/Spain when the -NAO is over us?

Would the Jet not come closer to our shores to the South and so driving the LP systems closer to us hence more PPN chances? I also think that it does raise our chances of having warmer air pushed up to us?

Edit:Wasn't sure where to post this MODs...Maybe Technical Thread?

Edited February 5, 2010 by Wayneywoo

[TEITS]

Excellent trend continues of a block towards Greenland.

http://www.wetterzentrale.de/pics/Rtavn2281.png

Obviously due to the timeframe makes this uncertain. However taking into account the ECM/ensembles this does look the favourite at the moment.

Moving back to the closer timeframe and my uncertainity with +120 continues. Look at the +48hr chart again and note how earlier the colder E,lys start moving in. Now the reason for this is a few days ago the models had the Atlantic LP further E and deeper.

Now look at +120.

http://www.wetterzentrale.de/pics/Rtavn1201.png

What might occur over the next few days(not saying it will) is we might find the block and the cold pool further W than currently suggested. The reason being is due to what has happened for Sunday. The block to our N and the Atlantic LP might be further W than progged with the Atlantic LP weaker than currently suggested.

[Southender]

As TEITS said, excellent signals for the HP that is giving some a headache to take a holiday to Greenland.

Day 10 (Yes lala land) but look where it has gone. A beast of Greenie HP to.

Once (IF) it ends up in Greenland, a reload from the NE follows. No sign of Mother Atlantic at all across the entire run.

Edited February 5, 2010 by LeighShrimper

[BLAST FROM THE PAST]

Clearly a big shift in the models this morning following on from the 18z last night with agreement on no trigger low from the Norway region, leaving weak High pressure close by. Any easterly is put back and we are then reliant on further variable to retrogress the High towards Greenland, the most likely call given that the models can't forecast an easterly at T96, is that won't be one at all.

The initial cold set and start of the evolution is because of pressure high to our NW and this then allows an easterly following on from NE'lies. Any signs of the HP sinking a little will only help to feed strong easterly winds for the southern parts of the UK. The HP to our NW/NNW will tend to try and settle towards the UK more but that will affect the precip set up only. This setup is going to be the driest thr further North and NW you are. Best chance of snow will be eastern England and in particular SE and also southern counties as LPs slip W to E through N France due to all the energy heading into southerly tracking jetstream. 06Z as much better run than the 0Z and so details are up for grabs BUT the main controller will be to our NW and southerly jet preventing any sinking.,...Just to add...a 10 day event before LP attacks from NW having broken the block down.

BFTP

Edited February 5, 2010 by BLAST FROM THE PAST

[Iceberg]

Quite a similar 06Z to the 00Z from GFS, it's probably a tad too progressive in bringing inthe cold air (the 06Z NAE is perhapes 12 hrs behind). But the fact that we can talk about the NAE means that the onset in now around 48 hrs away for the very start, for the far east.

A little bit of tweaking again on exactly how far south and how strong the high comes, but as BFTP says retrogression of the high really is a no brainer, with the strong southerly Jet, stagnent west coast US LP dragging in some WAA and the upper cold pool and associated instability as the deep cold misses us and goes into mid and south europe.

Yet again longer term we get a messy picture (which these conditions often produce). I still very much stand by the Death by 1000 cuts comment.

After the flip flopping at the begining of the week and last weekend, we have to admit that the models have settled down now and that by and large there are now no trigger SW's etc to make the 144-200 range unpredictable. 500 miles here or there doesn't really matter in the general trend hence the good ensemble agreement.

[TEITS]

Nowhere near as big a shift since your 16C/17C prediction for this sunday hey ian

Reminds me of something I was going to say earlier.

The ECM ensembles are incredible with the mean just below zero. Note how the less cold members have disappeared compared to yesterdays ensembles.

http://www.knmi.nl/exp/pluim/vijftiendaagse/Data/15DAAGSE_06260_NWT.png

The reason im highlighting these is at one stage it looked possible that the mean would rise to around 9C!

This winter really has made me look at the models in a different way and has been a great learning experience. Hopefully come next winter everyone will judge the model output on its own merits rather than using past disappointments.

[Guest North Sea Snow Convection]

Not saying it is going to be exactly the same or will last as long, but there is a suggestion of Feb 1986 about the charts. Very very blocked, the atlantic sent to coventry (with a small c!) quite dry a lot of the time, homogenously cold and last but by no means least some snow showers about.

Very nice indeed!!

It is a reasonable suggestion to make I think about a retrogression. I think that ironically if the easterly had arrived a week/ten days ago as was suggested by the models at the time, then it might well have meant that the cold would not have this same potential for longevity as it has now. The MJO has been able to progress towards where we want it to be, angular momentum is more favourable and also the negative zonal wind anomalies have had time to be able to trickle to where we should want them to be.

Personally I think the chance that the models are taking on these zonal wind anomalies is a good one in terms of where the high goes (towards Greenland) over the next 8 to 10 days.

Edited February 5, 2010 by North Sea Snow Convection