Model output discussions pm 31/12/15

[Mapantz]

I'd of thought it was quite obvious to see why the UK doesn't see regular (every year)  cold & snowy Winters. - It's called the Gulf stream/Jet stream. That's not the only factor of course, but it was something most of us learnt in school, in our early teens.
I certainly haven't wondered why it was so difficult so expect those sorts of uppers or conditions to hit our tiny island. Air cools faster over land, so large landmasses are likely to do better for cold weather than here. 
Don't take this post the wrong way, ie; being rude, but I see it as quite obvious as to why its so difficult to achieve.

[Cheshire Freeze]

2 minutes ago, Mapantz said:

I'd of thought it was quite obvious to see why the UK doesn't see regular (every year)  cold & snowy Winters. - It's called the Gulf stream/Jet stream. That's not the only factor of course, but it was something most of us learnt in school, in our early teens.
I certainly haven't wondered why it was so difficult so expect those sorts of uppers or conditions to hit our tiny island. Air cools faster over land, so large landmasses are likely to do better for cold weather than here. 
Don't take this post the wrong way, ie; being rude, but I see it as quite obvious as to why its so difficult to achieve.

That's not the issue though...I want to know when we do get N'lys why are we scraping by with uppers of -5 or -6 when any given location, even in the mid N Atlantic can easily achieve uppers much lower on a regular basis (as we saw in December). I'm not talking about the frequency of mean westerlys!

[feb1991blizzard]

Just now, CreweCold said:

It doesn't explain the lack of potent N'ly periods though does it. You'd expect more periods of zonal periods but when we get a N'ly it's coming from nowhere near the Atlantic. My issue is why the mid N Atlantic can get -20 uppers to a far more S'ly latitude than the UK on a more regular basis. In years and years of weather history you'd expect us to hit it at least once or twice every 25-30 years at least.

I see what you mean, even the most direct Northerly, 17th Dec 2010, the neatest, cleanest snap off of a PV and subsequent direct hit I have ever seen still only brought -10 / -12 uppers, although I still think in terms of regularity, it is because we are right on the Eastern most side of the ocean.

[blizzard81]

9 minutes ago, CreweCold said:

Exactly...and I'd wager that no-one has a firm theory as to why this is. At our latitude there has to be a reasonable chance of any given winter producing -20 to -25 upper air from the N. If a given point in the mid N Atlantic, completely surrounded by ocean can achieve it relatively frequently then why can't the UK?

Yes Crewe, it always astounds me when I see those mega low 850's flood down into the atlantic and never over us. I am always left with the thought that something aint quite right about it but year after year it happens again and again!

[Methuselah]

3 minutes ago, CreweCold said:

It doesn't explain the lack of potent N'ly periods though does it. You'd expect more periods of zonal but when we get a N'ly it's coming from nowhere near the Atlantic. My issue is why the mid N Atlantic can get -20 uppers to a far more S'ly latitude than the UK on a more regular basis. In years and years of weather history you'd expect us to hit it at least once or twice every 25-30 years at least.

No, it doesn't - but the fact that Greenland lies due north of the mid-Atlantic might??

[Cheshire Freeze]

3 minutes ago, feb1991blizzard said:

I see what you mean, even the most direct Northerly, 17th Dec 2010, the neatest, cleanest snap off of a PV and subsequent direct hit I have ever seen still only brought -10 / -12 uppers, although I still think in terms of regularity, it is because we are right on the Eastern most side of the ocean.

Still doesn't stack up though as I've seen the west coast of Canada/USA with severe uppers flooding S (and that's on the eastern edge of the largest ocean on earth). I don't see a valid reason for it and I completely agree with blizzard81 on this, it's just not right.

[cornish snow]

1 minute ago, blizzard81 said:

Yes Crewe, it always astounds me when I see those mega low 850's flood down into the atlantic and never over us. I am always left with the thought that something aint quite right about it but year after year it happens again and again!

Knocker's shield.

[karlos1983]

Meanwhile,

 

Edited January 5, 2016 by karlos1983

[Yarmy]

7 minutes ago, feb1991blizzard said:

The further East in an ocean though, the more moderation of temps but more importantly, more scope to fuel the Jetstream, our location isn't much further south than Siberia, if zonal winds completely reversed (ie, earth rotated the other way), we would get similar weather conditions.

 

Same problem for the Pacific Northwest US, although they still do generally better being connected to a large continental land mass to the North.

I agree though, you'd think it would be possible once in a blue moon to get those deep purple 850s over us. 

[Cheshire Freeze]

2 minutes ago, Ed Stone said:

No, it doesn't - but the fact that Greenland lies due north of the mid-Atlantic might??

And? I can't believe that water to the N of the UK in deep winter can have that much effect on a direct N'ly. The frozen sea of the Arctic acts like a land mass anyway.

[winterof79]

5 minutes ago, blizzard81 said:

Yes Crewe, it always astounds me when I see those mega low 850's flood down into the atlantic and never over us. I am always left with the thought that something aint quite right about it but year after year it happens again and again!

Due to the alignment of the Jet I believe.

http://www.meteociel.com/modeles/archives/archives.php?day=25&month=12&year=2015&hour=0&map=0&

Edited January 5, 2016 by winterof79

[Geordiesnow]

20 minutes ago, CreweCold said:

Exactly...and I'd wager that no-one has a firm theory as to why this is. At our latitude there has to be a reasonable chance of any given winter producing -20 to -25 upper air from the N. If a given point in the mid N Atlantic, completely surrounded by ocean can achieve it relatively frequently then why can't the UK?

I think you have unrealistic expectations if you expect the -25 hpa to hit the UK, It has hardly ever happened and with a warming climate, it could become less likely. The Mid Atlantic can get very cold air but only because of the way the jet stream goes which is usually West to East so therefore any frigid air from Cananda/USA is only going to head one way and that is into the Atlantic. the only way the UK will get those sort of upper air temps is from an Easterly and they don't occur all that often(not potent ones anyways) and you wil never get such a severe shot of air from a straight Northerly because of the long sea track to the North of us.

I suppose the signs are increasing of perhaps the most widespread coldest shot of the season so far but I think if this was back in late November/early December, people will be more excited/accepting because it would be early in the season but now we are approaching half way, i think people just want too see more than just cold sunny days and frost nights. 

Still detail will change but as others have said, I be very surprised if we see any meaningful WAA heading into Greenland, once those shortwaves are there, then its a long road back unfortunately but plenty of more runs to come. 

Edited January 5, 2016 by Geordiesnow

[feb1991blizzard]

Just now, CreweCold said:

Still doesn't stack up though as I've seen the west coast of Canada/USA with severe uppers flooding S (and that's on the eastern edge of the largest ocean on earth). I don't see a valid reason for it and I completely agree with blizzard81 on this, it's just not right.

As Ed Stone says though, the Geography to the North in the Atlantic is totally different to the pacific, I don't pretend to be an expert in this field but it cant be by chance, there is a reason and distribution of land mass must be very important.

[Cheshire Freeze]

2 minutes ago, Yarmy said:

 

 

I agree though, you'd think it would be possible once in a blue moon to get those deep purple 850s over us. 

Exactly the point I'm making.

[Woollymummy]

Sad to see the high pressure going from the arctic....

http://www.esrl.noaa.gov/psd/forecasts/reforecast2/wx_maps/html/z500_anom_nhbg_animation.html

[Bristawl Si]

The devil is in the detail and the detail will be decided 'on the day'.

How anyone can post charts 10 days hence and say in effect "it's a cold no show" is beyond my comprehension. By all means comment on what the charts are showing but writing in the past tense about days up to 10 days from now is crazy.

[ANYWEATHER]

And those Shortwaves do have a Big influence on model output....Just look at the ecm and gfs at this timeframe,,,,,

[snowray]

13 minutes ago, Greenland1080 said:

I agree but were the size of Florida something Steve M bangs on about in his posts as to why this tiny island constantly misses the bullseye. NE USA has many snow misses just visit weatherwx   to see them moaning. UK micro not macro.

The whole of Western Europe has been very mild though again this Winter so far. It is a valid point that at our latitude cold outbursts should in fact be more frequent than they are, with the cold air then moving South into Europe and a ridge forming over the UK to give us frost and Fog. There are lots and lots of historical charts showing this sort of thing, not necessarily extreme weather, but certainly Winter Weather. Guess the blocks are just setting up in all the wrong places, like this year over Southern Europe.

 

Have to agree about the UKMO 144h chart, rarely ever comes close. But the biggest shocker is ECM with its chopping and changing amplification and Greenland highs, can this model only cope with Atlantic type flows these days, is it getting close to becoming just another cannon fodder model?

GFS looks more solid to me right now, 12z ensembles show us cooling down generally for all of the UK next week thats good enough, so all to play for.

[Methuselah]

5 minutes ago, CreweCold said:

And? I can't believe that water to the N of the UK in deep winter can have that much effect on a direct N'ly. The frozen sea of the Arctic acts like a land mass anyway.

Well, if the Arctic sea-ice extended as far south (directly north of the UK) as Greenland does in the mid-Atlantic, you'd have a point??

Are we 'in danger' of wandering off-topic, CC?

[winterof79]

7 minutes ago, karlos1983 said:

Meanwhile,

 

You do find you have to skip a lot of negativity at this time but your post is straight to the point.Glasss 3/4 full.

[Summer Sun]

Give it time folks as Fergie has said this evening

Lets see what the models are showing in 24 and 48 hours time

 

Edited January 5, 2016 by Summer Sun

[Mair Snaw]

6 minutes ago, karlos1983 said:

Meanwhile,

 

Very interesting tweet that... some have said in here today and over the last couple of days that with a pattern change the models struggle to pin down whats going on and here we have it from the horse's mouth...  ( sorry Ian not implying your a horse)... think we need to chill a bit and take each run with a pinch of Rock Salt and see how things look at the weekend maybe then we may see the woods for the trees...

[blizzard81]

5 minutes ago, Greenland1080 said:

That' s so generic as to be factually impossible to verify.Sorry but we've just seen 2010 2013 .... Must be loads decades where this happens.

 

2010 and 2013 didn't see anything like -25 850's over the UK.

[SMU]

Im afraid that ^^ second tweet cannot be said with any degree of certainty...

its a case of finely balanced on the hedge tonight ....

enough evidence to suggest that based on history theres a chance it will go either way but probabilty wise favours the milder scenario ( again based in statistics & uks law of sod averages )

i duly note the ECM op was milder for debilt at day 9 & 1 suggesting a slightly to flat a pattern....

 

s

[Cheshire Freeze]

2 minutes ago, Ed Stone said:

Well, if the Arctic sea-ice extended as far south (directly north of the UK) as Greenland does in the mid-Atlantic, you'd have a point??

Are we 'in danger' of wandering off-topic, CC?

Maybe..

However take two northerlys..

One is a direct N'ly, straight from the pole affecting the UK

The second one is affecting somewhere in N Canada on our latitude

Now look at a globe and tell me why, at our latitude, the N'ly is watered down to nothing (despite not travelling far enough to actually modify all that much), whereas the Canadian N'ly is a mass of cold 5 times the size of our displaced cold pool which doesn't modify? At our latitude a -40 polar cold pool should not modify that much that we're left with uppers of -5 and a cold pool which is 5 times less large than it started out at!