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Gandalf The White
18 July 2023 16:57:27

The current expert view -perhaps speculation would be a better word - seems to be that the jet is weaker because of a warmer Arctic, hence a lower temp gradient to drive the jet. A strong jet just blasts through and creates mobile weather but a weak one can be stuck in a blocking pattern with nothing to move it on, and hence a period of repetitive weather lasting a month or more, as experienced this year in the UK with rain in March, a warm June and a cool July.

Where that block gets set up can depend on various global factors. This year, recent unusual warmth in NW USA / W Canada seems to have set up a wave train, swinging north there, south over the Great Lakes, north over Greenland, south over Britain. There's a diagram in the link, but it's not dated so it could be just for illustrative purposes. However, a BBC weatherman a couple of weeks ago was showing something similar claiming it represented the current situation. https://www.bbc.co.uk/weather/features/66177220 

Last year the position of the loops was reversed, so we got the heat. Now we probably have to wait for the hurricane season to give the jetstream a jolt.

Originally Posted by: DEW 



That prospect was being discussed perhaps 10-20 years ago, certainly for the Northern Hemisphere summer. I don’t think it’s clear what the effect is during the other seasons.
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


Chunky Pea
18 July 2023 17:19:53
If you look back on the ERA reanalysis maps for this period  mid period in July right back to 1901 and onwards, you'll see the current pattern we are under right now is actually very typical. Coolish SW to NW flows driven by lows to the near north. End of July, on average, tends to be more southerly and warmer, but not necessarily any drier. 
Current Conditions
https://t.ly/MEYqg 


"You don't have to know anything to have an opinion"
--Roger P, 12/Oct/2022
lanky
18 July 2023 18:52:39
There was someone from the WMO (John Nairn - Extreme Heat Advisor) on Radio 4 PM with Evan Davis this evening discussing the set up for these (almost) record-breaking temperatures across the N Hemisphere

He attributed the basis for this as the lack of sea ice / warming in the Northern Polar region leading to a very longitudonal jet stream around the globe in the north or as he put it "too many waves"

This leads to a very static pattern in which the peaks and troughs in the jet stream don't move all that much and consequently generate stuck weather patterns in any particular area. For us in the UK we are in a semi-static trough in the jet stream and on the northern side giving cool wet conditions but further east in Europe they are on the south under a ridge hence their long dry hot spell.

I think our long periods of alternating hot, cold, wet, dry months as the jet gets stuck in different set ups before moving to the next is evidence of at least a valid theory (but of course could be correlation not causation !)
Martin
Richmond, Surrey
tallyho_83
19 July 2023 01:57:42
Night time min of 48.9c in Death Valley - California on 17th July 2023?!

https://www.newscientist.com/article/2382959-death-valley-may-have-just-had-the-hottest-recorded-midnight-ever/ 

Yet there was me complaining +18c is a really hot, muggy and uncomfortable night for sleeping!
Home Location - Kellands Lane, Okehampton, Devon (200m ASL)
---------------------------------------
Sean Moon
Magical Moon
www.magical-moon.com


Saint Snow
21 July 2023 10:18:39
Enormous hailstones in NE Italy

https://twitter.com/severeweatherEU/status/1681815415154941954 

https://metro.co.uk/2023/07/20/italy-hail-the-size-of-tennis-balls-injures-110-people-in-freak-storm-19161712/ 

https://weather.com/news/weather/video/italian-hailstorm-huge-stones-leave-100-plus-injured 

 

Martin
Home: St Helens (26m asl) Work: Manchester (75m asl)
A TWO addict since 14/12/01
"How can wealth persuade poverty to use its political freedom to keep wealth in power? Here lies the whole art of Conservative politics."
Aneurin Bevan
GezM
  • GezM
  • Advanced Member
21 July 2023 11:31:54

Night time min of 48.9c in Death Valley - California on 17th July 2023?!

https://www.newscientist.com/article/2382959-death-valley-may-have-just-had-the-hottest-recorded-midnight-ever/ 

Yet there was me complaining +18c is a really hot, muggy and uncomfortable night for sleeping!

Originally Posted by: tallyho_83 



Not a night time min. but very interesting nonetheless. I like heat but that's insane!
Living in St Albans, Herts (116m asl)
Working at Luton Airport, Beds (160m asl)
Ulric
21 July 2023 12:28:46

Three conspiracy theorists walk into a bar. You can't tell me that was just a coincidence!
Windy Willow
21 July 2023 12:53:44
Wasn't sure where else to post this, but a waterspout is probably considered unusual here in the UK.
Spotted off the Dungeness coast here in Kent

https://www.youtube.com/watch?v=0R8mKSnoomo 




South Holland, Lincs 5m/16ft ASL

Don't feed the Trolls!! When starved of attention they return to their dark caves or the dark recesses of bridges and will turn back to stone, silent again!
DEW
  • DEW
  • Advanced Member
21 July 2023 14:06:09

Wasn't sure where else to post this, but a waterspout is probably considered unusual here in the UK.
Spotted off the Dungeness coast here in Kent

Originally Posted by: Windy Willow 


😲
War does not determine who is right, only who is left - Bertrand Russell

Chichester 12m asl
CreweCold
22 July 2023 02:26:41
Scientists seem to think we're travelling along the route of the worst case scenario (or close to it) in terms of climate change-

https://www.bbc.co.uk/news/science-environment-66229065  

Given what we've seen over the past few years, I tend to agree. We seem to have fallen off a cliff edge and the acceleration of the trend is frightening. We can't be too shocked though because we were warned by some climate scientists that once we reached the tipping point things may unravel fast.

Where will we be in 20 years time? The mind boggles.

Crewe, Cheshire
55 metres above sea level
Jiries
22 July 2023 05:28:52

Scientists seem to think we're travelling along the route of the worst case scenario (or close to it) in terms of climate change-

https://www.bbc.co.uk/news/science-environment-66229065  

Given what we've seen over the past few years, I tend to agree. We seem to have fallen off a cliff edge and the acceleration of the trend is frightening. We can't be too shocked though because we were warned by some climate scientists that once we reached the tipping point things may unravel fast.

Where will we be in 20 years time? The mind boggles.

Originally Posted by: CreweCold 



Dangerous heat domes becoming yearly feature for all except UK suffer more Autumn nearly all year round.  UK average will narrow much further between winter and summer from 6C to 22C in 1961-90 to 12C to 18C with more temperate and no variety at all in 20 years time, that the trends we seeing now with mild winters, cold spring and summer with few hours of warmth spike then mild Autumn.
Viking3
22 July 2023 05:59:32
A colleague lives in Palm Springs in California and this was the METAR report at 3pm local yesterday:

KPSP 212253Z 32018G24KT 10SM CLR 49/08 A2970 RMK AO2 SLP051 T04890078

49C with 18 knots gusting 24 knots must feel like an absolute furnace!
Keith
Aboyne, Aberdeenshire
135m asl
DEW
  • DEW
  • Advanced Member
23 July 2023 07:51:13
Nova Scotia - normally an equable maritime climate - has had 10" rain in 24 hours with fatalities and a potential dam burst
https://www.reuters.com/business/environment/atlantic-canada-province-says-dam-could-breach-tell-residents-get-out-2023-07-22/ 
 
War does not determine who is right, only who is left - Bertrand Russell

Chichester 12m asl
DEW
  • DEW
  • Advanced Member
23 July 2023 08:20:36
https://www.itv.com/news/2023-07-22/italy-hit-by-second-hailstorm-in-three-days-as-video-shows-flooded-street 
 
War does not determine who is right, only who is left - Bertrand Russell

Chichester 12m asl
picturesareme
27 July 2023 12:50:23
You'll probably need Instagram to view but check out this beast of a supercell in Italy

https://www.instagram.com/reel/CvI2mjdNDWu/?igshid=MzRlODBiNWFlZA== 
 
ozone_aurora
27 July 2023 17:44:44
Some intense thunderstorms over NE Spain at the moment, which is nothing unusual, but also some intense thunderstorms over the Black Sea at the moment - is this unusual?
DEW
  • DEW
  • Advanced Member
27 July 2023 18:30:16

Some intense thunderstorms over NE Spain at the moment, which is nothing unusual, but also some intense thunderstorms over the Black Sea at the moment - is this unusual?

Originally Posted by: ozone_aurora 



The frequency is shown nicely in fig 4
https://www.vaisala.com/sites/default/files/documents/Lightning%20flash%20density%20in%20Europe%20on%20the%20basis%20of%2010%20years%20of%20ATDnet%20data_S.-E.%20Enno%20et%20al.pdf 

and the answer is that thunderstorms are frequent on the north side of the Black Sea, but I wouldn't know about the intensity.
War does not determine who is right, only who is left - Bertrand Russell

Chichester 12m asl
ozone_aurora
27 July 2023 19:16:50

The frequency is shown nicely in fig 4
https://www.vaisala.com/sites/default/files/documents/Lightning%20flash%20density%20in%20Europe%20on%20the%20basis%20of%2010%20years%20of%20ATDnet%20data_S.-E.%20Enno%20et%20al.pdf 

and the answer is that thunderstorms are frequent on the north side of the Black Sea, but I wouldn't know about the intensity.

Originally Posted by: DEW 


Cheers Dew! 👍
Quantum
03 August 2023 09:47:54
Not much media coverage on the South American heatwave which is bonkers because its occuring in midwinter. Some parts of central Chillie, Argentina and Uraguay have broken all time temperature records in Mid winter?!

I have to imagine the Foehn effect must be playing a pretty big role for this to happen.
 
Twitter: @QuantumOverlord (general), @MedicaneWatch (medicane/TC stuff)
2023/2024 Snow days (approx 850hpa temp):
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)

Total: 8 days with snow/sleet falling.

2022/2023 Snow days (approx 850hpa temp):

18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)

Total: 7 days with snow/sleet falling.

2021/2022 Snow days (approx 850hpa temp):

26/11 (-5), 27/11 (-7), 28/11 (-6), 02/12 (-6), 06/01 (-5), 07/01 (-6), 06/02 (-5), 19/02 (-5), 24/02 (-7), 30/03 (-7), 31/03 (-8), 01/04 (-8)
Total: 12 days with snow/sleet falling.
Jiries
05 August 2023 19:29:54
https://www.bbc.co.uk/news/av/world-europe-66418007 

Now that what a proper storm that brought deep cover hailstones.  A named storm for today really over reacting and just standard boring LP does nothing but rain and winds.
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