Model Output Discussion - Deeper into Autumn

[jules216]

On 20/11/2022 at 07:15, jules216 said:

A few daily records broken in Czechia this morning. Station Orlicke Záhorí -17,5°C. Looks like typical weather over here where any rare cold spell bypasses Slovakia to the north by 200km where Poland and Czechia gets hammered by snow, then a la carte next night clear. Had to put up with this all winter 2020/21. Waiting for the next week debacle where advecting high pressure will have a trough sitting somewhere in Germany so their Alps,Austria and Once again Czechia get hammered while I be pulling a south easterly and rain under 3°C like who days ago. This happend on and off All winter 2020/21, no wonder because that winter is a very good analog anyway.

Few days on and All of the sudden high pressure from Greece comes to the rescue, from potential cold easterly comes +3 uppers mid range forecast. All the potential winter charts remain over 240hr+ 

[Methuselah]

I'm thinking that, so long as the LP over Biscay doesn't deepen, things are looking quite good regarding cold?

[That ECM]

still enjoying the theme.

Edited November 23, 2022 by That ECM

[minus10]

Clearly see the block in place at t300 on gfs6z.

Colder air making its way west...

 

 

[phil nw.]

5 minutes ago, minus10 said:

Clearly see the block in place at t300 on gfs6z.

Colder air making its way west...

 

 

A great illustration of why you have to give time for the block to orientate favourably.

Then we get the cold air.It isn't a matter of a flick of a switch.

The period days 7 to 11 is the first stage where we are looking for the pattern change via the amplification.

[That ECM]

Just now, phil nw. said:

A great illustration of why you have to give time for the block to orientate favourably.

Then we get the cold air.It isn't a matter of a flick of a switch.

The period days 7 to 11 is the first stage where we are looking for the pattern change via the amplification.

Agreed, I like looking at the jet out in lala land and worry about detail nearer the time.

[Tim Bland]

Now I’m interested

[phil nw.]

Just now, That ECM said:

Agreed, I like looking at the jet out in lala land and worry about detail nearer the time.

Yes keep focusing on getting the high first.

We know from experience how we get different solutions in later time frames.

Undoubtedly we are now at the stage where we will get  a block of some sort so that the first hurdle.

[feb1991blizzard]

6 minutes ago, Tim Bland said:

Now I’m interested

Now im interested.

[Methuselah]

Calling Gary Lineker... Maps of The Day! 

 

Edited November 23, 2022 by Ed Stone

[Eagle Eye]

Exact modeling aside

Look at it on the face of it;

MJO constantly recycling through phases 6 and 7, therefore a Nino-esque AAM regime, that way the westerly jet is slowed down. 

What happens when the westerly jet is weakened?

1) The amplification of oscillating waves gets stronger.

2)Warm Air Advection pushed up the waves

3)Blocking

4)If it gets close enough to the Arctic or even just to Greenland then...

5) -NAO due to pattern flip.

Of course this doesn't happen every time

But with more chances the risk of a -NAO from at least one of them increases.

Of course a -NAO doesn't always bring cold but it increases the chances significantly.

Not only that but WAA near the Arctic increases vertical Eddy Heat Flux. So the SSW chance increases.

Without the current modelling flips and changes. There is a signal of some sort of blocking, mainly focused to the North of us, perhaps to the North West.

Take it on the face of it and its very good as an initial setup.

[feb1991blizzard]

Just now, Ed Stone said:

Calling Gary Lineker... Map of The Day!    

perhaps its just a pc virtue signalling map to keep snow fans happy but then it just vanishes into thin air!

[sheikhy]

Gfs mean looking very blocky at 216 hours!

[Daniel*]

Baby steps EPS now going strongly for -NAO and sustained the Atlantic influence will be increasingly weakened.  

[MATTWOLVES 3]

I'm gonna use this post just to highlight those increasing number of ens that favour Blocking of the NH as we move into December. They are currently only at the 10 day range but you can clearly see the TPV is struggling with either getting its act together or becoming displaced from its more natural home!

I think we are currently setting up for a slow burner to something much colder towards mid month. A little word of caution to any trainees don't get to hung up over each and every operational run because there will be run to run tweaks occurring on regular basis as this pattern counts down...use the ens as more of a solid foundation to a pattern change.

Absolutely no dramas folks...im pretty happy today as I just love that Xmas vibe!

Do have a sterling day.

[Scott Ingham]

12 hours ago, Eagle Eye said:

I tell you what, there are quite a few members going for that -NAO.

I think the best chance for the foreseeable future is almost definitely to do with that WAA associated pattern flip, that may block out the Atlantic with a Greenland high and that's where the -NAO comes from.

Beyond that and we may keep getting more opportunities as the MJO looks to be cycling back round and eventually that could go back to phases 6 and 7 again and so we get that associated Nino AAM which brings forth the -NAO increased chances.

Even then, the increased Eddy Heat Flux associated with vertically propagating waves and a SSW is still not off the cards.

I don't think it'll be boring model watching.

 

This is right on cue. Im thinking between the 5th and 8th for some VERY INTERESTING weather

11 hours ago, CreweCold said:

Yep significant cold clustering now 

Things are now starting to show. The 240 chart from this mornings ECM interests me a lot

[Downburst]

I've been waiting a very long time for some decently persistent High Pressure, so looking very good indeed. In the meantime, a lot of rain to get through to the end of the month. It had to give up sometime. 

Mind you, has anyone seen that Rufford Ford on YouTube, still plenty of opportunity in the next week for absolute madness car destroying oddities on there before letting up into December.

[Eagle Eye]

ECM 00Z was actually really good for cold air mixing in from large scale WAA pushing the blocking up much quicker than the GFS in a relatively close term into a very -NAO looking pattern. So I'm now waiting to see what the 12Z will be like.

 

[matty40s]

36 minutes ago, Downburst said:

I've been waiting a very long time for some decently persistent High Pressure, so looking very good indeed. In the meantime, a lot of rain to get through to the end of the month. It had to give up sometime. 

Mind you, has anyone seen that Rufford Ford on YouTube, still plenty of opportunity in the next week for absolute madness car destroying oddities on there before letting up into December.

Problem with rufford ford now is too many people and too many channels. 

[Met4Cast]

The last two GFS runs highlight why following individual det runs in the extended is a frivolous process. The det on the 00z run was a mild outlier, the det on this mornings 06z run was a cold outlier. Lots of spread in the extended highlighting the uncertainty.

Overall picture moving into early December is one of blocked broad-scale patterns, but whether the UK can tap into proper cold isn't so clear cut within the signals.

[Kasim Awan]

I like the tendency in current output for lows to slide SE & high pressure to cover the space north of it, this sort of tendency can produce quite snowy spells in the UK.

See January 2013 - a similar pattern, shows the potential nicely

We all know that the probabilistic approach is the closet we can get to "accurate" of a forecast, even though it is not a definitive forecast, because it allows us to rephrase the conflicting signals within the atmosphere and parse them into a comprehensive assessment of probabilities

That in mind I do think the risk of a cold & snowy outcome is within that scope given the magnitude & consistency of the signal for a slow development of blocking, with a cold / frosty and more collapsed blocking type outcomes sharing a similar risk of verification. The slow tendency for development to me is indicative that the background signals which are currently favoring a blocked, easterly set up are gaining momentum at a slow rate. This means, perhaps, that further attempts at blocking will likely increase in returns overtime, as the cyclical nature of blocking meets the steady gain of easterly momentum, meaning each push is met with a little less resistance, and eventually we might hit the jackpot.

Edited November 23, 2022 by Kasim Awan

[bluearmy]

alexa, show me a run to run change height anom chart we don’t want to see become a trend at day 16
 

[feb1991blizzard]

2 minutes ago, bluearmy said:

alexa, show me a run to run change height anom chart we don’t want to see become a trend at day 16
 

is that the Gefs mean?

[blizzard81]

4 minutes ago, bluearmy said:

alexa, show me a run to run change height anom chart we don’t want to see become a trend at day 16
 

That is a right kick to the gonads. Looks like the complete opposite to last night's if it is the ecm. I wondered why those ecm 360 mean charts hadn't been posted this morning. Now I know why. 

[Methuselah]

The GFS temperature ensembles have donned their flip-flops it seems? But, on balance, I'd rather things turned either very cold or very mild than we end up with a pile of middling grot!