Model Output Discussions 06z 04/11/16

[Cheshire Freeze]

Just now, Seasonality said:

Not sure where you got that from, the gfs mean pressure anomaly is indicative of an area of HP stretching from Greenland to Iceland and the ECM seems to show a height anomaly directly over the UK but nothing there exactly screams west based NAO.

There are a LOT of WB -NAO in the GEFS...just flick through them and you'll see. FWIW we don't want to see the trop vortex completely lifting out of the Canadian sector because this opens the door for an overshoot of retrogression. A smaller, daughter vortex over that way, a Greenland ridge and a Scandi trough would be the ideal scenario.

[feb1991blizzard]

2 minutes ago, Seasonality said:

Not sure where you got that from, the gfs mean pressure anomaly is indicative of an area of HP stretching from Greenland to Iceland and the ECM seems to show a height anomaly directly over the UK but nothing there exactly screams west based NAO.

I'm talking the end of the run.

[Seasonality]

Just now, CreweCold said:

There are a LOT of WB -NAO in the GEFS...just flick through them and you'll see. FWIW we don't want to see the trop vortex completely lifting out of the Canadian sector because this opens the door for an overshoot of retrogression. A smaller, daughter vortex over that way, a Greenland ridge and a Scandi trough would be the ideal scenario.

Cheers, haven't flicked through the ensembles yet. Suspect it might all change come the 12z.

[nick sussex]

Just now, bluearmy said:

The 06z gefs is smelling pretty west based with low pressure to our south for the time being but it's trending less wintry in that regard though if we do get cold uppers in before the blocking retrogresses too far then it could end up more eventful

 

I hate west based negative NAO's. Waste of blocking I'd rather not be subjected to seeing the fish freezing in the mid Atlantic whilst the dig in the jet sends milder air north into western Europe. Hopefully  we don't end up there.

[feb1991blizzard]

Just now, CreweCold said:

There are a LOT of WB -NAO in the GEFS...just flick through them and you'll see. FWIW we don't want to see the trop vortex completely lifting out of the Canadian sector because this opens the door for an overshoot of retrogression. A smaller, daughter vortex over that way, a Greenland ridge and a Scandi trough would be the ideal scenario.

There have been for a few runs CC, just now theres enough to swing the mean towards a clear w-based -NAO, in these situations close to a potential cold spell, if i have time i go through the whole suite and would do likewise for the other models if i had access, that's why i made my forecast, its not just a knee jeurk reactionary post.

[Cheshire Freeze]

Just now, nick sussex said:

I hate west based negative NAO's. Waste of blocking I'd rather not be subjected to seeing the fish freezing in the mid Atlantic whilst the dig in the jet sends milder air north into western Europe. Hopefully  we don't end up there.

I think I remember GP posting the other day about the strat ridge going straight through Greenland with lower heights either side (Canada and Scandi) as we enter December. Now that is the pattern we want to be seeing come to fruition. Winter 2010-2011 ended with a the arrival of a west based NAO...they tend to be pretty depressing.

[Cheshire Freeze]

4 minutes ago, feb1991blizzard said:

There have been for a few runs CC, just now theres enough to swing the mean towards a clear w-based -NAO, in these situations close to a potential cold spell, if i have time i go through the whole suite and would do likewise for the other models if i had access, that's why i made my forecast, its not just a knee jeurk reactionary post.

Don't worry, I'd noted the same thing. 

The issue I have is I cannot recall an occasion in history where a west based -NAO was quickly followed by something more suitable for our shores. In fact nearly every WB event I've seen has ultimately led into a period of cyclonic weather for the UK. That is why I'd like to try and avoid it if possible!

Edited November 16, 2016 by CreweCold

[Ali1977]

21 minutes ago, bluearmy said:

The 06z gefs is smelling pretty west based late on with low pressure to our south for the time being but it's trending less wintry in that regard though if we do get cold uppers in before the blocking retrogresses too far then it could end up more eventful

 

FI is looking west based, but back to the more reliable the block is now starting to look likely to our North - I think the ECM will show this this evening.  The position of the block is all the play for if you ask me.

It would be interesting if Ian F could give us an idea where the block looks most likely if it were to occur in early Dec. Not long ago I'm sure it was mentioned that NE/E winds maybe more likely which doesn't suggest a full on WB Neg NAO, more likely a Block to our North.

Edited November 16, 2016 by Ali1977

[Tonk1978]

Hi all

A first post from me after many winters following this fabulous forum, it really is entertaining, exciting and educational all at the same time. Thanks to all who have helped me learn so much fascinating stuff over the years.

Clearly a mix of options on the table as we get to months end, however, one way or another there are are enough signs for cold fans to be very encouraged. I think we may have to get through a mildish easterly before we see more of a N/NE opening the door for proper cold.  Whatever happens it is a nice change at this time of the year not to be staring at the same zonal chart day after day. It's an intriguing set up for sure.

Also having lived in possibly the snow starved hotspot of central southern England most of the past 38 years (Weymouth, even Feb 1996 delivered a freezing, slushy, sleety mess!!) I am now stationed further east, albeit still a limpet to the tropical south coast in East Sussex. So ever so slightly, these unusual synoptics bring me a tad more hope of seeing a proper dose of the elusive white powder. Perhaps.................

[Zakos]

25 minutes ago, feb1991blizzard said:

That's a vary strong signal for the pattern to be too amplified and thus a West based pattern, the high is too far west.

 

I think this is certainly something we cannot exclude from the output because a number of runs are showing the high backing too far west, e.g 00z and 06z GFS.

This leaves us prone to atlantic attack, however, even in this scenario, with such a weak and southerly tracking jet stream we actually maintain the easterly flow right into December and until the end of the run.

on yesterday's 12z and 18z, the high also backed west, but with enough blocking remaining in the atlantic to give us a cold airflow from the N/NE.

Several possibilities on the horizon, nothing set in stone, however the trend currently remains towards better long term cold potential as November draws to a close. ECM not really on board yet, plenty of time for change.

Edited November 16, 2016 by Zakos

[jvenge]

14 minutes ago, Zakos said:

on yesterday's 12z and 18z, the high also backed west, but with enough blocking remaining in the atlantic to give us a cold airflow from the N/NE.

 

Isn't that the most likely? Negative AO and AMO giving a greeny high and putting Europe into an easterly and the UK into N/NE (I'd guess more likely NE?). I'm a bit of a noob though. 

 

[nick sussex]

West based negative NAO's are dodgy if you're looking for snow, it depends how far west. If you're lucky you get low pressure moving ne into the UK at the weak point of the block but not winning out and disrupting with some frontal snow. However theres a fine line between snow fun and abject misery for coldies.

The worst type of west based negative NAO is when the pattern is so far west that you get deep digging troughing to the west of the UK which forces the Euro high back ne into southern Europe. You'll look at the fax charts with the 528 dam line shown around 40% north to the west of the UK but with western Europe based in that hideous 546 + .

In lengthy cold spells you often get some oscillation of the negative NAO between more east then west but importantly never too far west to allow sw'erlies in.

The problem with the outputs at the moment even though they show some blocking is the suggestion of low pressure to the sw near Iberia, this downstream over central Europe funnels Med air in, for the UK its essential to have low pressure more towards northern Italy. That's normally a banker for UK cold.

Anyway we're dealing in hypotheticals here because we don't know definitely yet what the set up might be. Anyway that's my west based neg NAO moan over for the next few days. I have my toys ready to throw out of the pram if that does verify but fingers crossed it doesn't happen!

[Frosty.]

There's nothing mild on the extended GEFS 6z mean, temperatures look below average across the board and cold across scotland. Scandi trough develops, heights rise to the w / nw and there is scope for something wintry by late Nov / early Dec with no sign of the usual mild zonality.

Edited November 16, 2016 by Frosty.

[bluearmy]

3 minutes ago, nick sussex said:

West based negative NAO's are dodgy if you're looking for snow, it depends how far west. If you're lucky you get low pressure moving ne into the UK at the weak point of the block but not winning out and disrupting with some frontal snow. However theres a fine line between snow fun and abject misery for coldies.

The worst type of west based negative NAO is when the pattern is so far west that you get deep digging troughing to the west of the UK which forces the Euro high back ne into southern Europe. You'll look at the fax charts with the 528 dam line shown around 40% north to the west of the UK but with western Europe based in that hideous 546 + .

In lengthy cold spells you often get some oscillation of the negative NAO between more east then west but importantly never too far west to allow sw'erlies in.

The problem with the outputs at the moment even though they show some blocking is the suggestion of low pressure to the sw near Iberia, this downstream over central Europe funnels Med air in, for the UK its essential to have low pressure more towards northern Italy. That's normally a banker for UK cold.

Anyway we're dealing in hypotheticals here because we don't know definitely yet what the set up might be. Anyway that's my west based neg NAO moan over for the next few days. I have my toys ready to throw out of the pram if that does verify but fingers crossed it doesn't happen!

even the smelly 06z gefs (inc bc) have mean pressure nw Italy around 1010mb so its not a great concern as yet.

[nick sussex]

Just now, bluearmy said:

even the smelly 06z gefs (inc bc) have mean pressure nw Italy around 1010mb so its not a great concern as yet.

That's good to hear!  My toys are safe for the timebeing!

[Zakos]

21 minutes ago, jvenge said:

Isn't that the most likely? Negative AO and AMO giving a greeny high and putting Europe into an easterly and the UK into N/NE (I'd guess more likely NE?). I'm a bit of a noob though. 

 

In my opinion, yes I think we will end up with a cold N/NE/E flow at some point in the next 2 weeks. 

Potentially very cold, but its too far out to tell really at this stage.

As for a Greenland high, the GFS has trended towards this pattern over the last 3 days.

The ECM is still not on board at the moment, everything should become clearer in the next few days, hopefully!

 

 

 

Edited November 16, 2016 by Zakos

[Glacier Point]

.. and there are differences between -NAO west for December and February. Factor in a potentially massively distorted hemispheric profile, and traditional rules of interpreting this feature may not wholly apply.

[Summer Sun]

NAO and AO both heading negative

[phil nw.]

Latest London grah shows the ECM op at the top end of the  temperature members.An increase in rainfall next week which obviously reflects the approach of Atlantic lows as the upper trough digs south in the coming days.

 

Rather cold and cyclonic seems the tag for the next week or so,more so further north where snow fall is quite possible,especially over higher levels.

[knocker]

That's some high pressure and cold anomaly over Russia.

 

Edited November 16, 2016 by knocker

[warrenb]

Yep looking at the models, we are going west based -NAO

[Seasonality]

5 minutes ago, warrenb said:

Yep looking at the models, we are going west based -NAO

Have a read of the various posts on this by some of the more expert posters, it isn't a certainty and it isn't necessarily a bad thing.

[Gray-Wolf]

Obviously you guys are far more genned up on the structures that impact our weather but is there an precedent for what we are seeing across the far north so far this year? Surely the AO falling back negative talks of further WAA from depressions entering the basin and keep any vortex well out of its normal position ( if it can form at all?) so how do the models , out beyond T72, deal with a situation outside normal modelling parameters? Nullschool had the pole at 0.1 c at 15:30 yesterday??? With 15c to 20c anoms widely across the basin surely that has to impact the rest of the hemisphere?

[terrier]

Looking at the output today it's does seem like we're heading towards a west based nao which isn't always great news for us. But as alluded to above by glacier point this maybe not a bad point to start winter. 

[warrenb]

2 minutes ago, Seasonality said:

Have a read of the various posts on this by some of the more expert posters, it isn't a certainty and it isn't necessarily a bad thing.

I have been reading models for a long time, and at no point alluded to it being a bad things, just discussing what the models are showing.

I believe that we shall have a west based -NAO but this will propagate East as time goes on.