Model Output Discussion 1st Nov.2013

[nick sussex]

I think before people start stocking up on the anti-freeze its best to be a little cautious regarding what might be on offer. The spread of solutions on the ECM does not mean that a block will appear to the nw as a given, just that this indicates theres a decent cluster of members that do develop that, equally I don't think people should assume this will be a super Greenland high.

 

Of course the ECM ensemble mean won't give a true reflection of solutions with that type of spread so you end up with a diluted picture. I think its best to wait and see what comes out of the USA because we are reliant on the picture there remaining favourable. I think high pressure ridging north then toppling is still very much favoured but of course if low heights remain in northern Italy then this is a sort of holding pattern topple rather than  the OMG the sw'erlies are back yuk topple!

 

I suspect what the cluster of solutions shown by the ECM spread is where we get more amplification initially upstream which gets the high further north so the topple still happens but the jet is running further north hence we see that high further north even after the topple.

[bluearmy]

I constructed that chart back in September - and have been waiting to see if it came into fruition for two months!

 

Also, we have yet to see anything on any 100hPa charts suggetsing a split in the vortex over Greenland. That concerns me as previously that has always been shown by now if something was in the offing there.

 

the flow around the top of the mid atlantic ridge does look fairly flat with a possible reloading dumbelling scenario ed so there isnt necessarily a mean upper ridge over greenland.  also, the strat info we see freely is derived from the op rather than the ens. perhaps the ens paint a slightly different picture? 

[Cloud 10]

CFS ensemble week 3&4 showing substantial height anomalies over the pole

as we head into December.

 

Best taken with a pinch of salt though!

 

[radiohead]

Cold air pushing in earlier on the 18Z GFS. T138

 

 

But ends sooner too... (unless there is a reload later in the run)

 

Edited November 12, 2013 by radiohead

[DAVID SNOW]

Anybody heard anything from teits yet ?. Thought he would of surfaced by now!.

If I may Dave has some serious  health problems, as some will know and I hope sometime soon he can drop in and give his model opinion,

 

 Your input is missed Dave.

 

 Best wishes.

[BLAST FROM THE PAST]

Well it seems other models are showing the 'caution' I called this morning and the GEM output thoughts.  Nothing is nailed.  Lets see what develops but be prepared for either or and not a nailed cold blast. 

Signs of any split vortex over Greenland or other composites are IMO of no concern at present as we head into new climes.  Solar activity is on a different level with Jetstream behaving a lot differently. 

 

 

BFTP

[BLAST FROM THE PAST]

The High has toppled over the UK by T240 but look at the very low heights over Europe - it would either remain at mid-latitude or set up another cold shot.

 

Correct sometimes we see increasing amplification as each attempt passes sometimes like a 'bodyshot' softener

BFTP

[radiohead]

A cold "snap" indeed on the 18Z GFS, as it lasts about 24 hours. We'll see if a reload happens in FI.

[Cloud 10]

A cold "snap" indeed on the 18Z GFS, as it lasts about 24 hours. We'll see if a reload happens in FI.

 

The 18z looks to much in a hurry this evening with its pattern flattening.

 

 

I miss the old pub run. 

[nick sussex]

This GFS run certainly shows the importance of what happens in the USA, not enough amplification, the Canadian Arctic low just heads east into Greenland, by the time that shortwave develops and heads east its game over as too much energy has already spilled over the top of the high. Underwhelming! regardless of what the GFS lower resolution pulls out the foundations I'm afraid have already crumbled and slid over the cliff.

 

Looking at the state forecasts for the USA they're not that keen on the progressive nature of the GFS operationals, preferring to go with the slower ECM so lets hope that remains the case tomorrow and this GFS run isn't nearer the mark.

[damianslaw]

Models now firming up on a pattern change, courtesy of fractures in the strength of the polar vortex enabling colder air from the poles to infiltrate to some extent into the middle lattitudes.

 

The outcome is upstream amplification of the north atlantic trough. The question is how much amplification are we likely to see. The further north amplification can build the greater degree of cold will invade from the north and also the greater chance of a holding colder pattern.

 

At this juncture there should be no surprise to see the GFS toying with the idea of weak amplification and hence a shortlived northerly blast for heights topple across the country and we are left with a milder atlantic feed - albeit a different type to recent weeks with no major signals of a return to roaring westerlies and strong jet streak.

 

ECM today has suggested much more significant amplification and possibilities of a 'reloading' situation.

 

Whilst there are strong signals of a possible early winter blast to occur next week especially in the north, there are no strong signals for any sustained notably wintry weather, but at the same time, an early attack on the polar vortex at a time when it normally revs into its highest gear, will be a good foundation for increasing the chances of further more notably wintry episodes as we move through the early part of winter with an ominpresent build of heights to our west - the early signs of which are happening right now.

[Severe Siberian icy blast]

You can see between the 12z and 18z the one obvious difference is the fact one develops a strong low pressure in the south Atlantic and one doesn't and increases the high pressure there instead, not sure of how that affects the whole lot but massive differences between the two and much flatter high pressure in general

[nick sussex]

and off again 

 

Yes great if you're in Lapland! lol its over before the lower resolution, the GFS was just throwing out a few scraps at that point so that the NW Helpline doesn't get inundated!

[Gaz1985]

Dry with high pressure in control. No signs at all of anything remotely wintry on the 18z tonight bar a few frosts.

 

[StretfordEnd1996]

Dry with high pressure in control. No signs at all of anything remotely wintry on the 18z tonight bar a few frosts.

 

Are you talking about the whole run or just picking out pieces?

[Gaz1985]

Are you talking about the whole run or just picking out pieces?

 

Well I won't bother posting any further out as that is anyone's guess. Pretty much pointless.

[Captain Shortwave]

Well.... ummm.....

The NAVGEM looks ok.... 

[garbagebags]

Dry with high pressure in control. No signs at all of anything remotely wintry on the 18z tonight bar a few frosts.

 

Not true. You could see decent snowfall to low levels with the cold front pushing through on monday. Could even be heavy. I would call that more than remotely wintry.

[karlos1983]

Yes great if you're in Lapland! lol its over before the lower resolution, the GFS was just throwing out a few scraps at that point so that the NW Helpline doesn't get inundated!

 

I've taken it upon myself this year not to get in anyway excited above cold potential to far out, still having nightmares about That ECM!!! 

Dry with high pressure in control. No signs at all of anything remotely wintry on the 18z tonight bar a few frosts.

 

I'm just glad its the Pub run out in Fl

[radiohead]

Dry with high pressure in control. No signs at all of anything remotely wintry on the 18z tonight bar a few frosts.

 

 

That chart is far from dry.

 

[Severe Siberian icy blast]

What we can see even though we don't really get the cold set up we still get a very disturbed vortex again in fi. Great to see and bodes well for winter

[radiohead]

Ensembles will be interesting to see if the op was an outlier or had support. Could be wonky or the start of a trend.

[NorthernRab]

Dry with high pressure in control. No signs at all of anything remotely wintry on the 18z tonight bar a few frosts.

 

 

 

Except from the snow that could fall in Scotland, even to lower levels, which is considerable given the time of year.

 

Edit: Indeed, even the chart you've posted shows -7'C uppers over Scotland with -10'C uppers brushing the northern coast, which under high pressure could easily lead to day time maxes some 6'C or so below average, I would call this really rather wintry as opposed to not being "remotely" wintry.

Edited November 12, 2013 by NorthernRab

[Gavin Hannah]

The 12z has offed the best viewing material today. The low res had HP attempting to move into canada/greenland which would be an early xmas present for us.

Going to watch the 12z for the next few days and see what trends.

[Paul]

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