October has been a month of wild pressure swings. Despite being a key transition month presenting often turbulent weather, it feels like the swing from a 1040 high to 950 low (series of storms) with return to 1040 high early Nov has been more extreme than usual.

The effects of these deep lows and consequent anomalous ridges creating an upward ripple through the troposphere is the likely cause of a potentially ‘unprecedented early sudden stratospheric warming’ event.

So, a record breaking early polar vortex breakdown is likely next week.

If it indeed happens, it’s effects aren’t immediate with downward energy transfer taking 2-3 weeks to reach the surface.

Important factors to consider.

• SSW actually happening? (likely!)
• what type?
• where does the displacement/split/collapse occur?
• does it feed into troposhere?
• where does the blocking setup?
• how much cold is available?

ECM operational suggests a displacement type SSW with vortex pushed and stretched towards Atlantic side of the pole.

Based purely on a 10mb perspective, this screams out a strengthening of the westerlies from N America to Europe… Result? MILD, WET, often STORMY!

As well as the above, it’s more important to focus on the lower 50 to 70mb level following a 10mb warming as this better reflects potential 500mb impacts.

WHAT’S HAPPENED AND WHAT’S AHEAD?

Like we saw during a spell in October, November starts off with a strong blocking high which likely lingers over or near UK through the opening 7-10 days of the month. While precip is likely to be less initially, temperature is subject to position of the high though below average temps look likely beyond this weekend.

Following a weakening Atlantic front drifting SE down the UK, week 1 has high pressure anchored over Scotland and looks to become the most anomalous positive anywhere in the hemisphere.

Beneath the high, cloud becomes trapped and where skies clear, fog, possibly freezing fog becomes a lingering issue, either way it looks to turn chilly with breezy conditions around the coasts of UK and Ireland on the periphery.

7-day MSLP anomaly

While firmly drier than average though showers and small rain bearing features are possible, it’s mild but turning cooler over time.

GFS Ens has the high lingering through day 7-14 but note the cooling trend.

Like week 1, week 2 is drier than average. Not good for South!

There’s a lot of uncertainty towards the end of week 1 in terms of temps. Many may get excited about a developing -AO/NAO with GFS driving arctic air into the UK.

The operational GFS has been opening that door to much colder air as it often does in the 7-10 day window while ECM hasn’t.

I would lean more towards the ECM and with very subtle changes in HP position, we could actually go mild rather than cold despite -AO/NAO. Remember it’s early and there can be a lack of cold air to tap. The slight shift east of the high and S or SW flow pulls up subtropical air, slightly west and polar-maritime air brings wintry showers. The margins are small.

So blocking weeks 1 into 2 likely but weeks 3-4 (mid/late Nov) suggests a potential return of a more active zonal jet and possible storms back into Europe but a further south track undercutting a northerly block?

GFS ens (& ECM) shows the high breaking down or pulling north.

Flip from dry back to wet?

Milder too?

The ECM agrees with the pattern shift.

The above shift fits a repeating pattern loop observed in Oct with anticyclonic to cyclonic (1040 high to Storms Austen & Boelo followed by 3rd system) with origins traced back to Indian Ocean.

Roughly 10 days prior to the stormy Atlantic-Europe pattern, we observed an uptick in Indian Ocean tropical activity, initiated by an MJO phase 2-3.

Looks like we’re seeing that uptick in tropical activity over the Indian Ocean early November so 10 days from now? Return to stormier Europe?

The build-up of pressure we see to start the month likely doesn’t dissipate but gets forced north into higher latitudes while we see another Atlantic jet extension taking aim back at Europe. More named storms? Perhaps with more southern tracks into Iberia, France, S UK?

Both GFS Ens and ECM show a strong dry, high pressure dominated NW Europe November.

Precip

I keep to the back of my mind what’s just happened and where the MJO is re-amplifying with Super Nino background…

Temperature-wise, while I think we see a chilly 1st half with perhaps an easterly attempt if high lifts north? I can honestly see a battle develop!

It could be interesting to see whether a possible return of Atlantic low pressure clashes with anything colder from continent. We’ve seen these scenarios play out all too often and we know the usual outcome! Atlantic often wins and when you’ve a super Nino, WQBO, warm Atlantic and MJO phase 2-3, I’d strongly back the Atlantic winning!

Perhaps best case for cold lovers is the N UK stays in the colder, drier air, stormier but milder South?

Overall, GFS and ECM suggest average to slightly below average temps for UK and Ireland into continent.

CFSv2 is warmer UK/Ire/N Europe, cooler south.

GFS and ECM snow next 35 days. GFS a little more optimistic over high ground compared to ECM.

I’m struggling with how the month as a whole finishes temperature and precipitation-wise. Sure, a cooler, drier start but does a potential breakdown or shift east or north of the high open the flood gates to very mild, wet southwesterlies? Given MJO phases 2-3?

Both GFS and ECM above show a strong DRY signal but do I fully believe this for the 30-day period??

Another caveat is IF we happen to see an SSW & coupling, could we have a cold finish? My hunch says not really!

The Verdict

Cooler, Drier Scotland, N Ire, Scand… Warmer, Wetter Eng, Wales and S Europe Incl Med Region with potential Medicanes!

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