lorenzo

North - standstill.. South - pasted.

While on average the “downward impact” of SSWs is robust, not all SSWs appear to couple down to the surface. Most studies agree that about two thirds (Charlton-Perez et al., 2018; Domeisen, 2019; White et al., 2019) of SSW events are characterized as having a visible downward impact (e.g., persistent negative phase of the NAM or NAO in the lower troposphere and/or the lower stratosphere, (e.g., Domeisen, 2019; Karpechko et al., 2017). One factor affecting the appearance of downward impact is the tropospheric NAM index prior to and at the time of the SSW. If the NAM is already negative, there will be a vertical connection to the negative stratospheric NAM. On the other hand, if the tropospheric NAM is strongly positive prior to the SSW, the appearance of vertical coupling is less likely, at least initially. The same is true for the NAO: if a negative NAO is present at the time of the SSW, the downward coupling is instantaneous but short-lived, while otherwise the negative NAO often appears after the SSW event (Domeisen et al., 2020). The stratosphere is one of several factors influencing the NAM, with most NAM variability being generated within the troposphere (and from surface interactions). The stratospheric influence becomes clear, only statistically, in regressions or in composites of many SSWs. Specifically, the concept of surface amplification of the polar pressure signal (Figure 3) will not be apparent during every SSW, but it becomes clear when averaging over many events. This is because the troposphere is highly variable, and the stratosphere represents a modest influence that is active during the cold season. Just a moment... AGUPUBS.ONLINELIBRARY.WILEY.COM Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4983681

The Greenland trop lead break is not on the models yet... damn this is gonna be some sporty NWP,

Damn

Old school charts u say.. Only one route for this filament

hahahahha - loving that a9 peril - and hell mend em !

Let's be honest johncam - changes are afoot and our old friend 'Shannon Entropy' is gonna kick off royally in the next week. We have waited through a gruesome December and just on cue for the New Year is a meaningful spike in AAM, a solid SSW projected, a heavily degraded vortex and the flip of a Nino winter within an eQBO. If those are not things to whet the appetite for what may lie ahead then am unsure why we slavishly follow each model run other than to greet about things. The dynamical processes of the above regardless of what they deliver are what I love to see - the tropospheric NWP in chaos, the wave breaks heralding changes, the Stratosphere connections to the trop, the AAM MT events, the MJO pacific passages teleconnecting. All of this stuff makes the 0z the 06z, the 12z the 18z run along it's narrative. 14 years ago we just had hints of - oh, what is the MJO. or, what is AAM, or what is the strat. Now we see how they interact and dance, now we see how heat-flux builds, now we see Canadian Warmings, now we see Nino standing patterns, now we see IOD more clearly and TC influence. Now we see a whole lot more - and in ten years time we will see more again. All of which is on this very place, on this very forum from different angles all round. We are staring down the barrel of some MT action, an imminent MMW- maybe SSW or SS Wino as I call it for early Jan SSW In name only, perhaps a second once the Pacific rolls thru and MJO attenuates. Am not meaning to pick on Johncam at all here - am just responding for the general doom n gloom stuff today to try and create some perspective on - we are looking for winter and dream synoptics we can only enjoy if we live in LongYearBen - we are in the AGW age - 2010 was an anomaly. Let's enjoy the twists of this winter, the recent understanding we have all gained with the dance between GWO, Strat and Trop and hope from a cold perspective of something meaningful during early Jan to set up a notable few weeks of winter.

Just spied this on twitter... interesting perspective

Nothing to see here... carry on

https://arxiv.org/pdf/2308.04775.pdf re: afore mentioned particle physics...am glad I have weather as a hobby vs these CERN Folks - jeez !

Nice one @Paul - been worth the wait then !!! Willing it get colder here and some evaporative cooling to kick in! Waiting for @Scottish-Irish Skier particle physics lession and @LomondSnowstorm to update on the ever so dodgy 925hpa layer Meanwhile - back under the floorboards @Hairy Celt for the business end of Xmas Day !

What's a Polar Bears favourite shape?? An Arctic Circle ! Possibly THE best Xmas cracker joke I have seen in years..

Things are getting fun already.. somewhere between now and New year we are gonna have a pub run for the ages...

A whole bunch of AAM anoms to kick in too..

While on average the “downward impact” of SSWs is robust, not all SSWs appear to couple down to the surface. Most studies agree that about two thirds (Charlton-Perez et al., 2018; Domeisen, 2019; White et al., 2019) of SSW events are characterized as having a visible downward impact (e.g., persistent negative phase of the NAM or NAO in the lower troposphere and/or the lower stratosphere, (e.g., Domeisen, 2019; Karpechko et al., 2017). One factor affecting the appearance of downward impact is the tropospheric NAM index prior to and at the time of the SSW. If the NAM is already negative, there will be a vertical connection to the negative stratospheric NAM. On the other hand, if the tropospheric NAM is strongly positive prior to the SSW, the appearance of vertical coupling is less likely, at least initially. The same is true for the NAO: if a negative NAO is present at the time of the SSW, the downward coupling is instantaneous but short-lived, while otherwise the negative NAO often appears after the SSW event (Domeisen et al., 2020). The stratosphere is one of several factors influencing the NAM, with most NAM variability being generated within the troposphere (and from surface interactions). The stratospheric influence becomes clear, only statistically, in regressions or in composites of many SSWs. Specifically, the concept of surface amplification of the polar pressure signal (Figure 3) will not be apparent during every SSW, but it becomes clear when averaging over many events. This is because the troposphere is highly variable, and the stratosphere represents a modest influence that is active during the cold season. Just a moment... AGUPUBS.ONLINELIBRARY.WILEY.COM

Merrx Xmas All - have a magic day - especially you lucky buggers with SNAW !

Merry Xmas all - have a magical day ! Some fun modelling ahead for NWP geeks, nice Xmas gift for 2023 and early 2024 !

Okay this is mind boggling ! PSC in the moonlight. Link to original post https://x.com/sjb_astro/status/1739014965514649779?s=20

NWP is nowhere near the correct solution yet... lots of changes ahead.

Hello daughter vortices..

Not one of my own images but just got sent this from Aberdeenshire..

Tremendous images - sorted for desktop wallpapers now !