A huge 'anti-vortex' - among the largest on record - now dominates the mid-upper stratosphere, with the polar vortex (V) split in two main circulations & one very minor one, all displaced well away from the North Pole. earth.nullschool.net#current/wind... - ThreadSky

peacockreports.bsky.social • 1 day ago

A huge 'anti-vortex' - among the largest on record - now dominates the mid-upper stratosphere, with the polar vortex (V) split in two main circulations & one very minor one, all displaced well away from the North Pole.

https://earth.nullschool.net/#current/wind/isobaric/10hPa/orthographic=10.53,85.18,477/loc=-145.722,74.759

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peacockreports.bsky.social•10 hours ago

24 hours later (almost), we still have three 'anti-vortex' circulations but the dominant one has eased off a bit.

While relatively weak, the one over the western North Atlantic has helped to split the polar vortex to the point that the vortex above Canada will now head westward.

peacockreports.bsky.social•10 hours ago

Then, starting this weekend, a new bout of stratospheric warming is forecast to begin above Siberia & in a sense recharge the primary 'anti-vortex', as well as effectively kicking the polar vortex while it's down - a crippling blow that it's unlikely to recover from.

peacockreports.bsky.social•1 day ago

In fact, this is as close as I can ever recall seeing to a single 'anti-vortex' locating right over the North Pole, making for a complete reversal of the usual setup.

Usually, these singular circulations don't pack enough of a punch to shove the polar vortex so far aside.

peacockreports.bsky.social•1 day ago

Despite all that, it seems the knock-on effect will be typical of a wave-1 type event (dominated by a single anti-vortex), where the reversed circulation takes 3-6 weeks to propagate down, & might not even reach the troposphere to impact surface weather patterns.

vanjads.bsky.social•1 day ago

Thanks for sharing!

peacockreports.bsky.social•1 day ago

The extended ECMWF forecast model suggests surface weather impacts begin within the last week of March, with high pressure more prevalent than usual over the Arctic.

That means a southward shift in the polar jet & the path of low pressure systems...

peacockreports.bsky.social•1 day ago

...with a propensity for temperatures in the US, western Europe, & N Asia to be near or below average (not very evident in chart due to uncertainty in strength of impact from the stratosphere).

Also, much of Europe & N Asia has a raised risk of above normal precipitation.

peacockreports.bsky.social•1 day ago

For my UK & Ireland following - the layout of the above average precipitation signal suggests lows could tend to track fully south of here, much as we're seeing this week, with rain or snowfall primarily from showers driven by contrast of warmed surfaces & cold air aloft.

peacockreports.bsky.social•1 day ago

Of course, as this is looking several weeks ahead, that can only be considered a possibility. There's also a risk of having to contend with slow-moving lows trundling overhead instead. Or they could stall to the southwest like we saw last weekend. Many plausible scenarios!

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