Model Output Discussion:

[cooling climate]

The UKMO at t96 nearly identical to the ECM 0z at this time frame so it appears it was

no more than a wobble by the models over the weekend as the UKMO will without doubt

lead to a very blocked and cold pattern on this run.

Full marks to GP if it verifies (which I am quite sure it will now at this range ) for continually

forcasting heights over Greenland. I along with others could see this happening but not

until further into the cold spell as the high was expected to retrograde.

[Totoro]

Looking good, but nowhere near 'nailed on' yet. When the 144 output is showing consistently across all models in the 48 to 72 hour range THEN I'll start taking it a bit more seriously. :lol:

[snowmadchrisuk]

Looking at the 1200 GFS 850's look surprisingly high especially when they were so low just a couple of days ago.

SS2

This is just the first day of a big multi model patten change , I can assure you it won't take more than 24 hours for the cold to become established . I have a feeling GFS is still putting to much energy into the Atlantic and I think this will start to reduce over the next few runs , we need this high to back further West so it's harder for the Atlantic to squeeze back in .

[Iceberg]

Nowhere near as keen on the UKMET GM 144 as the 120.

The trough tilt is bad on the 144 and risks sending the energy above the block again, still it's an improvement, but still develops too much ridging to our south.

[andymusic]

I have a question? How come the charts are so different i have been looking at the GFS and the diff on the 12z to the 06z is just weird which one of the runs is wrong do you think?

Not wrong - just more updated data fed into the computer to produce the results - the models are now realising that the atlantic is gonna have a much tougher time with the blocking cold so the latest data being fed in is correcting the earlier data

[snowmadchrisuk]

Nowhere near as keen on the UKMET GM 144 as the 120.

The trough tilt is bad on the 144 and risks sending the energy above the block again, still it's an improvement, but still develops too much ridging to our south.

I'm not going to worry about that +144 UKMO at the moment , the GFS has a 1040 mb block North of Scandinavia where the UKMO put's a 1015 low. With the Block extending into Greenland on the UKMO all that energy to the East looks suspect to me . I think we can all agree tonight has been a good start and a big improvement for Cold prospects .

[MR EXTREMES]

Yep, 12Z GFS has the required pattern at 144, with the tilt and weakness in the spainish/med to act as a pressure release and the undercut....

The 120Z from the UKMET GM is even more of a backtrack and just lets the lower undercut at will.

So cold and cold from both models.

i would like to add it is cold rather than very cold not a very strong beasterly but better than sw flow.

all i can say this is very intresting stuff.:lol:

Edited February 1, 2010 by badboy657

[weather eater]

Leaving aside the UKMO, there is a huge turn around from the GFS 06z to the 12z. Obviously lots of changes to come, but in terms of the easterly as portrayed by the 12z it takes a hell of a long time for the cold uppers to get to our shores, not so much a beast as a cuddly pet.

[bluearmy]

the key appears to be the height rise to our sw. in this instance, we dont need a 'helping hand' from the ah to encourage height rises to our north/east. they are already there! any rise in heights to our sw prevents the second undercut which is vital to advecting the cold and the blocking westwards in a manner which delivers cold to us. the ecm 00z was nigh on perfect in this regard with the double whammy of low height rise to the southwest and better orientation of ridging from greenland to deflect the trough se. i dont imagine for one minute that we will see the 12z as effective but its a start which has been picked up by the other models during the day.

yesterdays 00z GEM looked very similar to todays 12z ukmo. unusual in the way that the models keep picking up solutions and then dumping them within T144/T168.

[nick sussex]

The UKMO although not great at 144hrs does one important thing at 120hrs by cutting the shortwave se'wards into France, its this trend we want to see from the rest of the models this evening.

Considering where we were yesterday this is a big change and for this reason and given the obvious model variability we're not out of the woods yet.

[weather eater]

Upgrades to come me thinks

I would hope so, but the one thing we should have all taken on board over the last couple of days is, be cautious of all output beyond 120hrs, be it beasts from the east or pests from the west.

[chionomaniac]

the key appears to be the height rise to our sw. in this instance, we dont need a 'helping hand' from the ah to encourage height rises to our north/east. they are already there! any rise in heights to our sw prevents the second undercut which is vital to advecting the cold and the blocking westwards in a manner which delivers cold to us. the ecm 00z was nigh on perfect in this regard with the double whammy of low height rise to the southwest and better orientation of ridging from greenland to deflect the trough se. i dont imagine for one minute that we will see the 12z as effective but its a start which has been picked up by the other models during the day.

yesterdays 00z GEM looked very similar to todays 12z ukmo. unusual in the way that the models keep picking up solutions and then dumping them within T144/T168.

Yes and I wouldn't be surprised to see the ECM 12Z different to the 0Z run. Mind you this inter run and inter model variability is to be expected at the moment. I'll have a guess on a middle of the road ECM tonight!

[snowmadchrisuk]

The MJO Forecast whats to quickly take the MJO into phase 8 , the last time this happened was just before the last Cold spell started :lol:

[nick sussex]

Yes and I wouldn't be surprised to see the ECM 12Z different to the 0Z run. Mind you this inter run and inter model variability is to be expected at the moment. I'll have a guess on a middle of the road ECM tonight!

Hi Chiono

Is the backing west of the pattern with the upper trough moving in the same direction down to the reverse zonal winds? And if so how long is this expected to last?

Edited February 1, 2010 by nick sussex

[chionomaniac]

The MJO Forecast whats to quickly take the MJO into phase 8 , the last time this happened was just before the last Cold spell started

MJO phase 8 composite for February suggests a west based -NAO but with good Atlantic blocking.

Hi Chiono

Is the backing west of the pattern with the upper trough moving in the same direction down to the reverse zonal winds? And if so how long is this expected to last?

Hi Nick.

Yes, it is but the backing west at the upper levels of the strat is exceptionally slow whilst the pattern is transferring downwards. The pattern I think will continue into the foreseeable future, however there could be a new upper trough backing west into Scandi after this (10+ days) . My guess is for slight height rises over Svalbard. These transfer to Greenland and intensify before further retrogression over Canada to leave a west based - NAO (GP keen on this) with the troughing being forced ahead of this. We shall see because the mean zonal wind forecasts have been as changeable as any over the last week.

[TEITS]

All im going to say about the 12Zs so far is again we have taken another step in the right direction. The UKMO +96/+120 is a good example of my earlier drawings as we now see LP drop SE rather than NE.

http://www.wetterzentrale.de/pics/Rukm1201.gif

However this is still work in progress because after such a change in the model output it most likely will take a few days before the pattern settles down. I have fairly high confidence of the +96 charts but its how influencial the blocking becomes after this and the behaviour of the trough to our W. Personally I just wish it would weaken and sod off.

[Frosty.]

The GFS 12z in FI looks fairly anticyclonic and rather cold but it might evolve into something more exciting on future runs, the main thing is the atlantic seems to go back to sleep as next week progresses allowing the cold blocking to spread west and deep FI shows excellent hp retrogression leading to a Northerly blast with a similar build up to late feb / early march 2006. If the vigorous atlantic low this weekend is less intense, it could help speed up the return of cold conditions.

[Southender]

All im going to say about the 12Zs so far is again we have taken another step in the right direction. The UKMO +96/+120 is a good example of my earlier drawings as we now see LP drop SE rather than NE.

http://www.wetterzentrale.de/pics/Rukm1201.gif

However this is still work in progress because after such a change in the model output it most likely will take a few days before the pattern settles down. I have fairly high confidence of the +96 charts but its how influencial the blocking becomes after this and the behaviour of the trough to our W. Personally I just wish it would weaken and sod off.

Hi TEITS.

Is this the system that is progged to develop off the coast of Georgia/Carolina in the next 24-36hrs?

It's interesting watching it on the N.Hem charts.

You can see it just exiting the coast of the aforementioned with 1010mb. If i'm looking at the right system?!

Would be nice if it exited a few hundred miles further South over Florida...

Edited February 1, 2010 by LeighShrimper

[nick sussex]

MJO phase 8 composite for February suggests a west based -NAO but with good Atlantic blocking.

Hi Nick.

Yes, it is but the backing west at the upper levels of the strat is exceptionally slow whilst the pattern is transferring downwards. The pattern I think will continue into the foreseeable future, however there could be a new upper trough backing west into Scandi after this (10+ days) . My guess is for slight height rises over Svalbard. These transfer to Greenland and intensify before further retrogression over Canada to leave a west based - NAO (GP keen on this) with the troughing being forced ahead of this. We shall see because the mean zonal wind forecasts have been as changeable as any over the last week.

Thanks Chiono

Looking at that MJO composite that still looks okay for cold weather but we don't want to see the west based negative NAO too far west, theres always a fine line here with how far west the trough over Scandi comes, but anyway at least the outlook is more positive but i'm always wary of sudden model switches and we'll need to see a few more runs before we can safely wave goodbye to any mild mush!

[snowfish]

I would hope so, but the one thing we should have all taken on board over the last couple of days is, be cautious of all output beyond 120hrs, be it beasts from the east or pests from the west.

Love that!

[Cecil Hogmanay Melchett]

GFS Ens look like an upgrade to me!!

ukmo 144h has a continental feed across the UK.

[snowfish]

All im going to say about the 12Zs so far is again we have taken another step in the right direction. The UKMO +96/+120 is a good example of my earlier drawings as we now see LP drop SE rather than NE.

http://www.wetterzen...cs/Rukm1201.gif

However this is still work in progress because after such a change in the model output it most likely will take a few days before the pattern settles down. I have fairly high confidence of the +96 charts but its how influencial the blocking becomes after this and the behaviour of the trough to our W. Personally I just wish it would weaken and sod off.

lol TEITS - Thanks for the smile that post created....poorish kind of day.... lol!

[snowmadchrisuk]

Classic sign of a patten change , In FI the Control has gone one way and the operational has gone another .

[Snowyowl9]

Short term upgrade snow was the last thing I expected and thats tomorrow.

http://www2.wetter3.de/Animation_12_UTC/30_30.gif

http://91.121.93.17/pics/Rmgfs424.gif

Unbelievable model turnaround otherwise.

[Guest North Sea Snow Convection]

In terms of the trough to the west, if you think about what the models were suggesting yesterday, then there has been an enormous downsizing of the atlantic stength and eastwards extension - not just over the BI but beyond it too. Lets remember exactly just how far the UKMO was expecting the south westerlies to get on Saturday! Right across into Scandinavia, and taking the -AO pattern away with it too.

In this sense there is every reason to have confidence in further weakening of the troughing, and this in turn should allow the blocking to our north east and north to become more and more influential.

The UKMO at t144 is ok imo - and, taking into account the changes already seen around the t96 to t120 area, I think that improvements are likely to keep coming as t144 becomes nearer.

I am much more bullish and optimistic about the prospects for a cold easterly in the outlook period now, than I was last Friday.

Edited February 1, 2010 by North Sea Snow Convection