Winter 2020

Discussieer mee over alles wat met het weer, weerkunde en de wereld eromheen te maken heeft
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Ted
Berichten: 4013
Lid geworden op: 31-03-1984

Bericht door Ted » 31-10-2019 18:27

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Laatst gewijzigd door Ted op 14-02-2021 12:17, 1 keer totaal gewijzigd.

Ko
Berichten: 5914
Lid geworden op: 08-06-2013

Re: Winter 2020

Bericht door Ko » 31-10-2019 19:48

Ted schreef:
31-10-2019 18:27
De kans op een koude winter is groter dan andere jaren.
Had je dat gister niet kunnen zeggen? Heb de Hellmann al ingevuld met 73 :lol:

Maar een koudere winter bij een positieve Nao? Tenminste, als je de verhalen mag geloven gaat ie van negatief naar positief.
De winters waren mooi, heel vroeger.

Marco
Berichten: 31
Lid geworden op: 07-05-2017

Re: Winter 2020

Bericht door Marco » 31-10-2019 23:24

Ja, toch maar een koude winter vanwege de zeer lage zonneactiviteit. Zie artikel http://www.weer.nl/nieuws/detail/2019-1 ... erne-tijd/

Hans
Berichten: 1709
Lid geworden op: 31-12-1997

Re: Winter 2020

Bericht door Hans » 31-10-2019 23:42

Eerst zien, dan geloven....

Sebastiaan
Berichten: 12244
Lid geworden op: 31-12-1977

Re: Winter 2020

Bericht door Sebastiaan » 01-11-2019 10:35

Marco schreef:
31-10-2019 23:24
Ja, toch maar een koude winter vanwege de zeer lage zonneactiviteit. Zie artikel http://www.weer.nl/nieuws/detail/2019-1 ... erne-tijd/
Reinout -de schrijver van dit stuk- vertelt op 16 november meer over de zeer lage zonneactiviteit tijdens de bijeenkomst voor winterliefhebbers bij MeteoGroep. Er zijn nog een paar plekken. PB mij of Paul.

Sebastiaan
Berichten: 12244
Lid geworden op: 31-12-1977

Re: Winter 2020

Bericht door Sebastiaan » 05-11-2019 15:29

Bijdrage Tamara. Ze stelt dat het huidige patroon van lage AAm, sterk hoog in het noordoosten van de Pacific en verder 'stroomafwaarts' een rug, trog, rug en trog typisch is voor de late herfst. Ze geeft verder aan dat in haar visie de seizoensmodellen het waarschijnlijk juist zien. In ieder geval voor de eerste helft van de winter.

But despite so many claims to the contrary, this is in truth a very typical late autumn low angular momentum driven pattern that features an anomalously amplified wavelength as dictated by a strong NE Pacific ridge leading the downstream configuration of ridge/trough/ridge/trough

These low momentum phases in autumn are often punctuated by an intra seasonal higher phase tropical cycle which augments the underlying natural downstream Atlantic ridge profile that the default La Nina type circulation imprints. Forget the actual ENSO base state here - it is the tropical/extra tropical circulation that the atmosphere is adopting to the base state that matters in terms of wind-flow inertia to determine the jet stream behaviour - and it remains likely in my opinion that a Nina type disconnect will persist through at least the first half of the winter

So the current intraseasonal phase tropical signal is attempting to pass the Pacific over the coming period and this is providing an added boost to the amplified ridge/trough profile. Much of the seasonal modelling is in excellent agreement with this signature for November, so a continuation of trough disruption likely to continue this side of the Atlantic for a while yet based on the meridional aspect to the wavelength. The CANSIPS, as one of the various majority of models in agreement with the longer term evolution of the pattern is a very close matching example indeed of what is advertized to persist well throughout November

As the tropical signal ultimately heads back towards the Indian Ocean following this period, and returns alignment to the default circulation, the period beyond this looks accordingly highly susceptible to a renewed collapse of angular momentum and occurring very conceivably at the same time as the seasonal wavelength change occurs as November progresses closer and into December. Such a renewed drop in momentum implies increased energy returning to the polar jet and re-alignment of sub tropical ridging as trade winds re-dominate the Pacific.

With this in mind, and with the the stratospheric vortex uptick to over 40 m/s prior to upcoming temporary (relative) reduction in speed - it means that the November planetary wave poleward momentum providing some perturbing of the tropopause has to be taken into context of longer term angular momentum trends related to the tropical cycle - and also related to the transition of the QBO which is still within its transition phase to easterly. This transition unlikely to complete till late winter. On that basis its hard, at present at least, to see how a disconnect will sustain beyond the tropospheric support available over the coming few weeks and this in my opinion would point in such circumstances to an elevated chance of quite a pattern change during December.

And yes, before the usual response(s) appear, I am perfectly aware of all the arctic feedbacks that are chattered endlessly in these threads every year with cast iron guarantee and which always are supposed to lead to the *big one* - but these still require a conducive tropospheric/stratospheric pathway to engage them and in turn provide a sustainable pattern to make it snow...

I am not a forecaster, and don't pretend to be able to second guess the weather - but continue to differ from the popular bias view and can see support for the seasonal modelling suggestions of a milder much more south westerly driven type ultimately taking over heading into/or during the early part of the winter. The seasonal models can be wrong, and will surely be wrong again at sometime - but that doesn't mean they are always wrong and especially when it is clear to see from a bias free diagnostic approach that less appealing solutions are indeed also possible than the one most want to fit to suit their preference.

Those *other*solutions might entail a NW/SE type of split, with reduced air frost risk and the wettest and windiest weather transferring accordingly away from more southern parts and some hope perhaps for some quieter drier weather here after so much rain this autumn - and at least for the benefit of a very small minority of those who visit this thread, also a much welcomed chance to reduce heating bills at least during the day.

With that in mind, the CANSIPS model closely reproduce this prevailing thinking with the seasonal wavelength change showing a much less amplified Pacific/Atlantic ridging regime during December - and a European downstream ridge replacing the disrupted trough. At present at least, most of the other main models have close variations on this same theme

https://www.netweather.tv/forum/topic/9 ... nt=4094711

Ted
Berichten: 4013
Lid geworden op: 31-03-1984

Bericht door Ted » 05-11-2019 20:33

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Laatst gewijzigd door Ted op 14-02-2021 12:16, 1 keer totaal gewijzigd.

Gerben
Berichten: 16631
Lid geworden op: 08-09-2013

Re: Winter 2020

Bericht door Gerben » 05-11-2019 20:49

Hoe zie jij dan de winterkansen Ted? Leg eens uit?

John
Berichten: 7852
Lid geworden op: 31-10-1980

Re: Winter 2020

Bericht door John » 05-11-2019 22:00

Gerben schreef:
05-11-2019 20:49
Hoe zie jij dan de winterkansen Ted? Leg eens uit?
Daar heeft Ted op 31 oktober al over geschreven.

Een zuidelijke westcirculatie kan soms tot winters weer leiden, maar het is geen standaard.

In bijvoorbeeld december 1981 hadden we langere tijd een zuidelijke westcirculatie.

Hans
Berichten: 1709
Lid geworden op: 31-12-1997

Re: Winter 2020

Bericht door Hans » 06-11-2019 20:54

Ik volg de kaarten niet (meer) en het zou een keer weer heel verrassend zijn als we een koude(re) episode krijgen.....

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