Model Output Discussions 12z 01/09/2016

[Northern Sky]

2 hours ago, fergieweather said:

Little useful to add. Akin to the EC update of Monday, there's a signal in the latest run for strong mid-Atlantic ridging during 1st week of Nov, with resultant colder NW flow. This is also favoured in latest GloSea5. Both models suggest a blocked scenario most likely 1st half of Nov, albeit with uncertainty/spread in exactly how this manifests (respective H/L positioning). Either way, zonality looks less likely than average through first half of the month. 

Presumably such a scenario would also continue to disrupt the formation of the polar vortex during the time it usually strengthens?

[Ali1977]

Pressure level charts for Oslo and Reykjavik paint the picture as to where the high pressure will sit in a week or so. Backs up the idea of a high in the Atlantic ridging north. 

[Frosty.]

The GEFS 00z mean paints an anticyclonic picture across most of the uk from around the middle of next week onwards into early november, especially further south..so, plenty of pleasant autumn weather looks to be on the way beyond the current showery blip.

[Frosty.]

There is some support from the GEFS 00z mean / perturbations for our first cold snap of the season during early November beyond the upcoming pleasant anticyclonic spell 

Edited October 21, 2016 by Frosty.

[bluearmy]

3 hours ago, blizzard81 said:

How far ahead does this forecast go? Is it 46 days? 

Yes

[Ali1977]

Mean pressure chart on the 1st Nov is pretty impressive !! Some of the ENS have quite extreme NH blocking.

[No Balls Like Snow Balls]

First snow risk of the season to appear on the London GFS ensembles! haha

 

 

 

 

Edited October 21, 2016 by No Balls Like Snow Balls

[Barry12]

The start of November continues to look interesting this morning on the ensembles, which backs up the ECM monthly and GLOSEA5 with mid Atlantic ridging and a disrupted polar vortex.

Edited October 21, 2016 by Barry95

[Mucka]

3 hours ago, mb018538 said:

Very quiet in here, much like the model output! Looks like we've got high pressure moving in next week, more uncertain after this though. No signs of zonality just yet.

Yes, we are in a bit of holding pattern as we wait to see how things develop for early Nov.

I guess there are only so many ways we can all say the same thing on future prospects, which is a good thing really as it means there has been good consistency with the signal for blocking to take hold in the Atlantic sector early Nov. 

Quite often we need a couple of bites at the cherry to get a proper block to our W/NW and often the models are too clean with their evolution when they first sniff out such scenario, so patience will be required I expect.

I have very much enjoyed this largely quiet and dry autumn and some late warmth in October will be very welcome, especially as this will be a long winter - one way or another. 

[phil nw.]

So the generally quiet and pretty dry Autumn goes on by the looks of today's runs so far,the Polar +ve height anomalies continue to be modeled to month end 

translating into a much weaker than normal main vortex especially on the Atlantic side so we continue to see a fragmented  jet.The pattern shows very little mobility with little in the way of widespread or appreciable rainfall expected across the UK- as shown in the latest ens graph

this looks typical for many areas through the coming week or 10 days.

It seems we are locked into a period of mid-latitude blocking with reduced activity from the jet across the north so the remarkably dry and mainly settled Autumn goes on. 

 

 

Edited October 21, 2016 by phil nw.

[mb018538]

Both the 12z GFS and 12z UKMO show an area of high pressure over the UK at 144 hours:

 



Better the further south and east you are, with some influence from the Icelandic low towards the NW.

[Ali1977]

No PV and plenty of ML blocking agin on the 12Z, some great looking ENS to follow I'm sure. Very messy picture around day 9 so can't really be sure of how this will play out just yet.

[Frosty.]

A peachy looking GEFS 12z mean from next midweek until the start of November as high pressure builds in and intensifies over the uk bringing very pleasant surface conditions by day but with cold nights with slight frosts and mist / fog. 

[Frosty.]

Looking further ahead into early november, the Gefs 12z mean suggests a cold shot of polar / arctic maritime is possible. 

[Ali1977]

The high isn't showing itself in just the right position yet to bring proper frosty nights just yet, a few too many lows milling about. 

[Methuselah]

Well, as the North Sea is warmer than usual, things could be interesting. At least for those of us near the East Coast? 

[Matthew.]

This Anti-cyclonic October looks to continue with something we haven't seen for a while next week, The ECM has HP overhead:

 

Edited October 21, 2016 by Matthew Wilson

[Ali1977]

ECM day 10 isn't without interest, -8c 850s just off Northern Scotland.

[Frosty.]

A gorgeous Ecm 12z develops as high pressure builds in strongly across the south introducing much milder and very pleasant surface conditions which gradually extend further north to cover most of the uk and then later in the run our high starts to retrogress, opening the door or at least leaving it ajar for our first cold plunge of the season..something for everyone!

[Day 10]

I cannot believe the hunt for day 10 is upon us once again! However this year looks like starting a lot better than the last few, so here's hoping the whole of the UK gets a least one proper snow event.

Good luck to all, I'm strapped in and ready for the ride...

[Ali1977]

Something like this will do in December. Some charts like this in the reliable timeframe would have this place buzzing. Off topic a bit, but confident something better than the last 3 winters is on the cards.

[lorenzo]

ECM interesting in the latter stages with the pull to Greenland. First image illustrates the rock in the global atmosphere courtesy of a notable Scandi/Taymyr anomaly. this before subsidence.

D10

From a model watching scenario this is interesting as the sequence does not appear to over-amplify the run, progression to meridional seems to have been dampened - perhaps the bias has been corrected.

Great then to get a good example to follow through until month end to see where the time frame lies, previous winter's saw 96-120 period being IMO the 'flip' period when ECM would lose the over-amplification bias and solutions would move to other modelling - GEM, catches this > JMA also, the flip notable for GFS/GEFS. Ens suites of use here...

Big wave break - great modelling for October - best start to a winter for a number of yrs considering wild cards - anything goes at present

[Froze were the Days]

I've been following the CFS 0z run religiously since the begining of October and there have been quite a few runs in January that have been showing strong blocking either from a Scandanavian HP or a Greenland HP. That run has been showing blocking too out to at least mid-November. No screaming zonality as of yet through November to Janauary although late Nov and parts of December look more unsettled (at times).

[damianslaw]

Significant consistency in the ensembles this week, day after day they continue to show heights eventually ridging into the mid atlantic and then northwards exposing us to a cold shot from the north, however, such a scenario continues to be shown at around the 240 hr mark, but it is notable how they have stuck to this happening -it would back up some of the longer range models suggesting a colder start to November at least compared to the normal, with a continuation of an exceptionally blocked mid autumn period - highly unusual it has to be said. 

In the meantime, lots more dry calm weather for many, temps around average, perhaps becoming milder middle of next week, but chilly nights in the offing and fog could become a notable feature taking a long time to clear first thing.

 

Edited October 21, 2016 by damianslaw

[Captain Shortwave]

Well it does appear that during week 2 we will see heights over Europe retrograde towards the Atlantic, but how far and hence how much influence any Scandi trough will have.

ECM ens

Day 7 and day 10

   

So by day 10 we have heights centred just west of the UK, at the moment the models suggest that temperatures will cool off at 850hPa, it is important to note that as potentially the surface temperatures might not be that different as despite having this Atlantic ridge, under light winds an inversion is likely and will restrict temperatures somewhat.

Still a long way off in terms of wintry potential with the first week of November a long way off and the ensemble guidance beyond day 10 is still weak, a mix of cold and mobile options on the table, though one would think the later may be biased towards the climatic norm (Westerlies). A lot of interest ahead as many have mentioned.