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Model Output Discussion - cold spell to end Autumn

Paul

Please only post model discussion in this thread. 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

Thank you!

Message added by Paul

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18z says "nah, I haven't got a clue actually".

I don't think the models have so much picked up a new signal, more just highlighting how slight nuances in the flow, earlyish on, can send us down one road or another in this type of setup (unfortunately that usually doesn't work the same when we have a strong zonal Atlantic though)!

So basically, nothing to panic about yet. Could and probably will all change again tomorrow (for better or worse :) )

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the block fights back against all odds and we have....

+300


prectypeuktopo-7.thumb.png.8add87a31f549671207507493da60c99.png

 

HOT-King-Leonidas-300-Spartans-Shields-Movie-HUGE-Wall-POSTER-art-canvas-Movie-Poster-Print-great.jpg_640x640.thumb.jpg.284f2e609d651f4e9f7262c399a7588d.jpg

Edited by bobbydog
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GEFS mean now becoming similar to those UKMO op runs yesterday that were dismissed out of hand.

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Serious though how many times have we had this great model flopping.

not in so many years since the great ( that ecm )

though that is probably a bad example.

like so many.great posters have said in the past, our tiny island is so used to the default pattern of westerlies at winter that every model panics to find that default button.

the models only ever flip like this when they can’t compute.

the great winters are only ever extremes.

we are deffinately on the cusp of a great winter this year and I can only back it up with experience from knowledgeable posters on this site.

 

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8 minutes ago, feb1991blizzard said:

GEFS mean now becoming similar to those UKMO op runs yesterday that were dismissed out of hand.

Control at day 8 ish-

gensnh-0-1-180.png

urgh

gensnh-0-1-216.png

Edited by CreweCold

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Latest clusters in D10-D15 a bit like placing a bet on the Grand National:

ec-ens_nat_z500scenarios_2017112712_300.

Slight favourite for me is Atlantic ridge joining up with a Scandi ridge but that's probably no better than a 10/1 bet.

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22 minutes ago, Building Blocks said:

Having a had a look at the latest trends being picked up by the ECM 12z and now the GFS 18z, it looks as though a complex pattern is evolving at around the 7 day timeframe.

This is based around two areas of high pressure, a blocking high to the NW centred near Greenland and an area of high pressure to the SE over Europe and two areas of low pressure, one out to the SW in the azores and one to the NE up over Northern Scandinavia

How these interact is crucial, obviously affected by the much maligned Shortwaves! The most favoured outcome for coldies is for more of the Southern high pressure to link up with the Greenie high, maintaining an Atlantic block, and allowing Northerly winds to flow down through the country. Conversely, the worst case scenario is for more of the heights to sink south, thus setting up a West based NAO- with winds coming up from the SW as the azores low is allowed to move towards the UK due to a lack of Atlantic blocking.

Obviously, with these kid of setups, the North and East of the country is in the best position as it is closest to any northerly outbreaks that may occur.

Now there is still lots of time for change with this set up and little alterations East or West will have a great impact on whether the UK see's the cold upper 850hpa's move down across the country or whether we are stuck in a somewhat milder set up.

What will probably happen? An evolution somewhere inbetween. 

However, the coldie in me wants the Northerly winds to win the battle!

Anyone mind me re-posting this? As it is one of my first posts so took a bit of time and it got lost in the free - for - all that seems to occur watching nearly every model run on here. Its crazy but we all love it!

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17 minutes ago, s4lancia said:

18z says "nah, I haven't got a clue actually".

I don't think the models have so much picked up a new signal, more just highlighting how slight nuances in the flow, earlyish on, can send us down one road or another in this type of setup (unfortunately that usually doesn't work the same when we have a strong zonal Atlantic though)!

So basically, nothing to panic about yet. Could and probably will all change again tomorrow (for better or worse :) )

I think the trend away from protracted amplification of the upper flow continuing into the medium range stems from the split flow that develops off eastern N America. The southern arm extending east out into the Atlantic tries to recurve NE mid Atlantic which forces the Atlantic block toward Western Europe, while also giving a west-based -NAO. Whilst the northern arm flattens out over the top preventing the cold arctic getting far enough south.

917B7E09-5C1F-47B4-90A6-835FA8D347EA.thumb.png.702d5c7044173f89a8d6f106050b3852.png8E5DF988-3118-437A-A1F9-2E3EAB6DB7EB.thumb.png.1472e8e367ddcd506779fe81a3326ea3.png

The saving grace later in the 18z GFS run and, indeed, the 12z EC at day 10, is that the flow buckles big time over N America as a long wave ridge develops over the west coast, which teleconnects downstream to amplification over the N Atlantic to allow a Nly reload, but not as soon as early next week as them models were advertising before. A lot could change before then, so more sitting on the fence until we see another Nly reload.

F0A3A2F9-DACF-449F-B026-3FEC8F1D5230.thumb.png.93498b22dccdade4dabf1bdba150f8a5.png

Edited by Nick F
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Another winter , same bipolar comments in here . Look the pattern not the individual runs, we have a mobile highly amplified pattern in prospect with a strong probability of something substantial developing. Pulling out some arbitrary chart at 240 hrs+ is not going provide any insight into what is clearly a highly uncertain future. This is creating great difficultly for both mathematical modelling and subsequent algorithms alike.   

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5 minutes ago, CreweCold said:

Control at day 8 ish-

gensnh-0-1-180.png

Thing about runs like that (which are entirely plausible) is even if the trigger does end up getting pulled favourably, the uppers are likely to be watered down or end up with mild sectors rearing their ugly head, compared to the some of the clean evolutions of the last few days.

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15 minutes ago, Roadrunner said:

Hi all. I don't post here much. Mainly because my chart reading skills are still basic amateurish at best, even though I've been a member since 2004. Wow has it really been that long?!

What I have noticed in that time (and even before then when I was a member of the BBC snow watch site where I used to wait with baited breath for Nick Sussex's updates -  remember those days Nick with Dave Allen, Bill Farkin, Grebes etc?!) is that the model runs chop and change daily with not ONCE a smooth journey to any weather pattern whether that be blizzards in the winter or scorchers in the summer.

Each winter I try to not get excited by stellar model runs and the ensuing comments until the good stuff is still showing at T-24. I always fail miserably! Whatever happens this winter, I will be glued to the forum in the hope that just for one day I'll be able to use the damn sledge I bought my son that's been gathering dust in the shed for a few years now. 

I do often wonder though if there was a similar weather forum that covered, say, New York and the NE / great lakes states, whether they go through the range of emotions we all do during winter when the models flip and flop. Obviously for places like Buffalo they are probably almost guaranteed snow at some point so their stress levels are no doubt much lower than ours! 

Anyhow, looking forward to spending the crazy season with you all and whatever the outcome - enjoy the ride, even if you don't get what you want, it's only weather. 

Hi Roadrunner,yes I too remember those halcyon days on the BBC weather site, you missed Steve Murrs name and he was certainly one of the leading lights, I also post only occasionally these days (used to go under the name of Asphodel in those days). Forecasting the weather certainly seem harder these days when it comes to getting proper snow into our little island,indeed we have not had a proper fall for over 4 years. Perhaps we should follow the grebes!, I wonder what became of Bill Farkin,regards MIKE R.

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1 minute ago, feb1991blizzard said:

Thing about runs like that (which are entirely plausible) is even if the trigger does end up getting pulled favourably, the uppers are likely to be watered down or end up with mild sectors rearing their ugly head, compared to the some of the clean evolutions of the last few days.

Indeed. 

We're looking out at day 9/10+ now for another go at getting some snow potential to our shores in any widespread fashion. That's FI in anyone's book. 

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6 minutes ago, CreweCold said:

Control at day 8 ish-

gensnh-0-1-180.png

still there - and we get a bit of warmth this time...

gfsnh-10-384-9.thumb.png.807de4b23b48a50bfe94f3886c7d9b88.png

:good:

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5 minutes ago, CreweCold said:

Indeed. 

We're looking out at day 9/10+ now for another go at getting some snow potential to our shores in any widespread fashion. That's FI in anyone's book. 

That's very true, but i always feel its nicer to be looking for potential out at days 9/10 whilst already in cool/cold flow, which we will be up until Thursday/Friday. Always have slightly more patience when you don't have to walk outside and it be 15 degrees and raining!

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18Z GEFS are to be honest, a complete mess.

The op is one of the milder runs mid term if that means anything...

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If we are looking that far ahead wheres the chart for xmas day?

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4 hours ago, CreweCold said:

The issue is everything is interconnected-

We need this GH episode to manifest to allow the trop vortex to remain perturbed. The strat is still running cold and will require the blocking patterns we have seen modelled to allow the minor warming we are seeing occur frequently in FI.

As we saw last year, once the trop blocking ceases, we are likely to see the westerlies take hold, and without that minor warming to perpetuate the trop blocking pattern further into December, the rest of winter holds nowhere near the promise. It's easier to just to get this blocking episode over the line rather than rely on a pie in the sky SSW sometime later in winter.

gensnh-0-1-384.png

Control run of the GFS highlights the point I made earlier. The Greenland ridging fails and we end up with a westerly flow and the PV where we don't want it. Other ensemble perts highlight that without the Greenland ridging we end up on the wrong side of trop ridges/vortex splits...

gensnh-9-1-384.png

 

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4 hours ago, CreweCold said:

gensnh-0-1-384.png

Control run of the GFS highlights the point I made earlier. The Greenland ridging fails and we end up with a westerly flow and the PV where we don't want it. Other ensemble perts highlight that without the Greenland ridging we end up on the wrong side of trop ridges/vortex splits...

gensnh-9-1-384.png

 

But that ridge to our northeast is certainly interesting and nothing is a done deal just yet.

I certainly still see a reload but as nick suggested it's been put back a little but until a pattern settles a bit then we just don't know.

But the vortex and stratospheric battle continues and there's no doubt it's possible a warming event could be on the cards.

 

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In undoubtedly the opposition as now, it's usually best not to look at the model a little bit, because it takes time for models to be strengthened when the model changes. Today, as one of these days, where the models have never been shown to be different from that time yesterday, but perhaps the move of more energy could be shifted to the south jet's arm, and the opportunity of a greater the GFS continent says that he is usually interested in feeding the north arm.Sound is like a striped record, but the key force is the tallest, and where he decides his position, because it's a characteristic there is an impact on the magnitude we can see, and therefore the high SE (perhaps very temporarily) or model action is (stay on the gentle side of the polar jet) or the west (we put on the side of the frost in the jet), the ECM suggests the final situation, GFS and the extreme situation, the older models, the first scenario, the possible SE sink, the page that is shorter and less ... more tugnaw in the following, it might be a return here and now.

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Not a great fan of GFS 00z

 

- Doesn't seem too bad towards the end.

Edited by evans1892
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1 minute ago, carboncowboy75 said:

To my untrained eye the 0z doesnt look that bad but i am a novice

I'm certainly not great myself possibly quite foggy, dry and cold. I could be wrong. I'm sure others will correct me if not.

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