SE, London & EA - Weather Discussion

[Eagle Eye]

Interesting band of rain moving slowly east, not sure of the exact direction, sort of ENE, looks like it could be a squall line. There's quite high DLS (Deep-Layer Shearing) and moderate LLS (Low-Level Shearing), so I wouldn't be that surprised about the organisation and there may be a few funnel clouds possible or even a tornado or 2 and maybe some sparodic lightning.

To quote TORRO

"A cold front will cross all areas through the second half of Thursday night and Friday. Aloft, a sharpening upper trough will approach the front, with strong divergence and positive vorticity advection overspreading the frontal zone, especially during Friday. Additionally, diurnal heating will take place ahead of the front across parts of England and Wales on Friday, cloud-cover permitting of course.

Strong low-level wind shear, and vertical speed shear, will exist in the vicinity of the front. At this stage, models are less suggestive of a classic cold front 'line convection' event, with more cellular activity simulated. The most likely evolution is a mixture of modes.

A zone through the central RoI, into Wales, the Midlands, and perhaps Lincs/E Anglia should see the best overlap of instability/dynamic forcing, and wind shear. However, the discussion region has been given a much wider area, as at least *some* stronger precip signals amongst fairly decent shear is evident.

With the stronger cores/line segments, gusty winds and perhaps a tornado or two are possible. Additionally, and especially in the zone mentioned above, occasional CG lightning is possible, especially through Friday, when diurnal heating may contribute to a few hundred J/Kg of CAPE.

The front may become less active as it moves into parts of Cent S/SE England later on Friday, as upper support moves away, but the region is included as a fairly sharp pressure trough is noted on some models for the cold front."

[Iceman2606]

6 October 2022 Time-Lapse

 

[Eagle Eye]

21 hours ago, TN9 said:

My last message said about typical la nina set up  ,but gfs doesn't seem that consistent, it wants to keep pulling the high back and forth then ,one of yesterday's runs changed totally around and gave us here in south a bit of excitement, then today backed off again,so I'm not over confident it knows what the score is too far out at the moment 

Here's a combination of my last few posts about the Stratosphere and the MJO in the Model thread to hopefully clear things up about what we're looking for this Winter and in the meantime.

"

Looking closely into the future and right now we have a pattern driven into the exact opposite of a vertically propagating wave pattern into the stratosphere that ends up with a negative NAM (Northern Annular Mode). That typically has an enhanced Scandinavian ridge and a Northern Pacific troughing. In a La Nina Winter, a Scandinavian ridge may be quite likely however troughing in the Pacific hasn't looked that evident over recent years and so the vertical wave propagations into the stratosphere won't have the right momentum to cause the negative NAM. This was a particular problem last year and caused us to rely on surface conditions and northerlies if I remember correctly. However, 2021 still had a SSW and it's not necessarily a problem that will last all of Winter, there could be forcing over Siberia that causes the cold air to plunge south over the North Pacific and trough as they propagate into the Stratosphere. If this problem does last through Winter, then we may have to rely on the northerlies that may end up being a feature if we're lucky, if not then a SSW or something similar may be possible.

Essentially, waves move up from the troposphere to the stratosphere, if we want to have a pattern in the Stratosphere that's good for us to have snow we want low pressure troughing over the North Pacific and high pressure building over Scandanavia because that would cause a certain momentum cycle of air that weakens the air speed in the stratosphere which causes cold air to displace itself from the poles to us and that could cause an SSW or even more simply a negative NAO.

 

That last part sort of explained by these images.

 

A very mobile pattern at the moment causing some uncertainty with any ridging unlikely to be sustained as they are held down by low pressure with a clear different between north and south.

When looking at the wind high up in the stratosphere, what we want for a negative NAM is a weak stratospheric vortex, there are no specific values for this as far as I know but a generally weak vortex is always a good thing in Winter. It allows the spread of colder air south and waves being depressed through the atmosphere and warm air begins filling up rapidly over the Arctic (up to 50 degrees Celsius in just a few days). Beyond that and here's a direct quote from the Met Office "As the cold air from high up in the stratosphere disperses, it can affect the shape of the jet stream as the cold air sinks from the stratosphere into the troposphere. It is this change in the jet stream that causes our weather to change.".

With a little help from James Peacock we know that a WQBO and a non-neutral La Nina isn't a sentence to no Winter at all, instead a SSW may be a small possibility but a possibility, with a weakening of the jet stream over Winter, it cannot be ruled out.  We still need everything to be just right but we need it to be just right once over multiple months. Like I said before a Scandinavian ridge and a Pacific troughing are the wave distribution that allows for probably the best outcome for us.

 

Ignoring the current surface pattern, we can easily see that the current MJO amplitude is very low which is what is causing this typical October weather at least partly because there is little atmospheric push for high amplitude ridging but we can see that it looks to be going back toward the higher amplitude values, there will probably be a delay so this cold spell that's trending may still happen (depends on surface conditions). The seasonal models have been showing some sort of ridging building up in Winter and that may be a possibility because the MJO is coming back into strong forcing. Whilst only a background signal it gives an idea of the state of which we're going into this Winter in. If we end up with an overly active MJO amplitude, then that Scandinavian ridging is possible whereas low amplitude means less chance of one forming you would think because the wave pattern would have less forcing (I may be way off the mark here but high amplitude coincides with better Winters historically speaking).

Over the past, October has been very similar in terms of amplitude 'phases' and so we're entering this Winter very similar to most years but noticeably different to 2020/21 and arguably the low amplitude 'phase' has occurred a lot quicker than last year, the most similar October's are probably 2017 (we all know what 2018 ended up being ) and 2015 where January 2016 ended up with some snow in areas further south than normal. I think the main thing is to monitor for North Pacific troughing and Scandinavian ridging in the tropospheric levels, they are likely to be the most important factors in this Winter specifically due to not having an E QBO.

You can see the forecasts showing a more amplitude wave with the anomalies being centred over the Western Pacific as we re-enter the higher-amplitude phasing.

So after the last couple days I have managed to talk in relative depth about the MJO state, tropospheric state and what is needed, the Stratosphere state and have gone into small depth about the QBO state. The pointers and seasonal models still suggest mild but that doesn't mean that we can't have a cycling of the atmosphere into a SSW or a negative Northern Annular Mode for a time this Winter because the drivers are arguably over driving the atmosphere and pushing up and when something comes up, something must also come down but from what direction is the big question for this Winter. Even in a westerly phase, we've already seen that a collapse from the North is possible and maybe even from the Northeast based off cycling.

 

Having a look at the GEFS ensembles and into the future you can see the signs of the signs of the increase in Western Pacific anomalies associated with the increasing MJO amplification patterns.

You can see the amplification at 240 hours due to the increasing oscillating patterns.

This is still a while out and specific areas and patterns are unlikely to have been picked out by the GEFS at this point however it's showing signs of the increasing oscillation being output by the GEFS based off the increasing MJO strength as we find ourselves coming out of a low amplification cycle that has lasted since about mid way through September. This would suggest that there is increased ridging chance as we move into November, however, for the time being the surface pattern is likely to remain influenced by low pressure and high pressure cycling without significant ridging amplification.

 

The colder pattern is still looking like it'll become of the main players on the cards going towards mid way through October and it may take a while for ridging to reach us and build up so this October may actually end up being quite cold. Looking beyond it and November's background signals are probably for a more high pressure dominant month.

"

Adding on to that, this year a SSW is probably about 25% likely but we've seen a lot of stranger things happen. MJO wise and the amplification for blocking is coming into place slowly after the drop off in recent times but it'd where it is that can often be the problem. As well as that we've got to get Pacific Troughing which is difficult but not impossible but with an over active Pacific wave engagement it may be possible. 

[Iceman2606]

Sunset and a moonrise this evening over Northamptonshire.

[moogyboobles]

I'm having to go outside to warm up! Cold in my house, lovely in the sunshine.

[MAF]

2 hours ago, moogyboobles said:

I'm having to go outside to warm up! Cold in my house, lovely in the sunshine.

the sun is really strong here in SE london, clothes dried on line quick today.  

our house faces east n the front so the last few hours of sun will warm the living room up. although i have the oven on today for a roast meal so the kitchen has warmed up too. kitchen is front of the house. 

[Tn9]

been beautiful here ,bit chilly to start but  since then its  run away with its self  

[Tn9]

52 minutes ago, MAF said:

the sun is really strong here in SE london, clothes dried on line quick today.  

our house faces east n the front so the last few hours of sun will warm the living room up. although i have the oven on today for a roast meal so the kitchen has warmed up too. kitchen is front of the house. 

bet your  bathroom faces north and feels like siberia ,you think ill have a shower in a minute but no ill leave it to heating kicks in lol 

[MAF]

7 minutes ago, TN9 said:

bet your  bathroom faces north and feels like siberia ,you think ill have a shower in a minute but no ill leave it to heating kicks in lol 

actually it's in the middle of the house, so no daylight at all. although it is a wet room with just a shower, so you don't tend to spend long in it anyway. 

[Tn9]

35 minutes ago, MAF said:

actually it's in the middle of the house, so no daylight at all. although it is a wet room with just a shower, so you don't tend to spend long in it anyway. 

Lol  ,I remember advert which was about heating funny enough, British gas i think ,baltic in the bathroom  siberia in your slippers or could have bali in your bedroom and Hawaii all  over the house ,shame it cost so  much now ,but even siberia is warming up

[Blessed Weather]

Lovely day here with plenty of sunshine and a high of 16C. And as the sun sets, a great display of cirrus cloud as the cold front approaches from the NW, captured superbly by the satellite which shows the advancing darkness as night descends from the east. My house is where the marker is.

[Blessed Weather]

Very wet start here thanks to the cold front now crossing the Region and bringing some useful rainfall for the gardens.

07.55:

[Reefseeker]

2 hours ago, Blessed Weather said:

Very wet start here thanks to the cold front now crossing the Region and bringing some useful rainfall for the gardens.

This morning was the first time for months I woke to the sound of persistent heavy rain that didn't just come in fits and starts, it sounded lovely. Of course the kitchen fitters arrived in the rain as a result but it doesn't appear to have held them up ripping the kitchen apart. It's technically a 'refurb' but with half the units down, it sort of feels like a new one is being put in.

Fingers crossed that the grass is now returning to green across the whole region; just as our plants are enjoying the rain, the colder nights are rather annoying them!

[Freeze]

Cold night got down to 5c by 1am, but then started to rise after that, shame as it could've got close to freezing. Lovely sparkling sunny morning though! 

[moogyboobles]

1 hour ago, Freeze said:

Cold night got down to 5c by 1am, but then started to rise after that, shame as it could've got close to freezing. Lovely sparkling sunny morning though! 

Down to 3 degrees here which was a surprise. A proper chilly morning.

[Tn9]

On 09/10/2022 at 18:09, Blessed Weather said:

Lovely day here with plenty of sunshine and a high of 16C. And as the sun sets, a great display of cirrus cloud as the cold front approaches from the NW, captured superbly by the satellite which shows the advancing darkness as night descends from the east. My house is where the marker is.

Right ,I know where you is now  ,guess that's where it all happens lol ,I've been reading (cor can ya ) via this site..(not as good as netweather by the way obviously  )but interesting none the least ,skip the polar vortex bit ,they pummelled it into me so much I feel part of it ,but interesting stuff they do say ..plus an evening sky (bonus)

 

 

Polar Vortex and Winter Weather are affected by October Snow depth in an unexpected way, data shows, with a large snow extent now being forecast » Severe Weather Europe

WWW.SEVERE-WEATHER.EU

---

Winter Weather in the United States and Europe depends on the Polar Vortex, which can be impacted by the October Snow cover, new data shows

 

[Dami]

You always know the universe is not on your side when after having a mare week all told, my daughter forgets her PE kit, i go back to school with said kit and when i come out the building it is raining. And not just not any type of rain. This was large drops of i got soaked rain. 

so thanks for that. 

[andymcpool]

Feeling fresh on Clapham Common.

Edited October 12, 2022 by andymcpool

[Dami]

@lassie23

More fog today! So that's 2 snow flakes now i shall see!

[lassie23]

3 hours ago, Dami said:

@lassie23

More fog today! So that's 2 snow flakes now i shall see!

Still none daan sarf

[Eagle Eye]

Summer 2022 was the warmest on record according to the C3S climate bulletin (for Europe at least)

"The average surface air temperature over the continent for the months of June, July and August was 0.4°C above the record set by the summer 2021."

Edited October 13, 2022 by Eagle Eye

[Iceman2606]

10 October 2022 Time-Lapse

 

[Methuselah]

And, meanwhile, the Beeb are forecasting thunderstorms on the 22nd October!

[Dami]

well blow me, we had rain again. Must be autumn.

[Tn9]

On 12/10/2022 at 08:32, Dami said:

You always know the universe is not on your side when after having a mare week all told, my daughter forgets her PE kit, i go back to school with said kit and when i come out the building it is raining. And not just not any type of rain. This was large drops of i got soaked rain. 

so thanks for that. 

If you was in the desert gasping, it would have been a god send... if you was floating in flood waters it would have been the devils work...but  gorgeous here today not a cloud in the sky since fog cleared couple of spits and spots yesterday but nothing to write home about