Stormy Weather II

[oddoneout]

Currently 23.5 C according to the weather station up the road - that's hot for 10. a.m. in these parts.

The onshore airflow will moderate the roasting those of us further inland are experiencing!
I was later than I intended walking into town and decided to abandon further errands after dealing with an essential PO trip and drop off to a friend. The air was hot, the glare and heat from the pavements were horrid and the very high pollen count started to affect breathing. If it gets cooler towards evening I might venture out again - it was very pleasant out last night - as Friday is not looking good for shopping and by then I will have run out of bread and milk.

[Serial_Apologist]

Thunderstorms now massing over the west country and across the Channel, ready to pounce later tonight.

[LMcD]

Thunder and lightning and rain!

[Joseph K]

We've managed to avoid the storms.

I don't remember the last time it was as hot as it was last night...

[Serial_Apologist]

This sky was visible without aid from colour filters or glasses at 5.30 this morning as the northern edge of a huge MSC centred off Brighton passed overhead. BBM would have had it!

https://www.bbc.co.uk/weatherwatchers/report/4720b156-2d56-4186-9a2c-147329e84fc3/

Never seen anything like it in 65 years of amateur weather observing.

[gurnemanz]

This sky was visible without aid from colour filters or glasses at 5.30 this morning as the northern edge of a huge MSC centred off Brighton passed overhead. BBM would have had it!

https://www.bbc.co.uk/weatherwatchers/report/4720b156-2d56-4186-9a2c-147329e84fc3/

Never seen anything like it in 65 years of amateur weather observing.

Amazing photo. MSC? No capito.

[BBMmk2]

26C today! Still a massive PHEW!

[BBMmk2]

This sky was visible without aid from colour filters or glasses at 5.30 this morning as the northern edge of a huge MSC centred off Brighton passed overhead. BBM would have had it!

https://www.bbc.co.uk/weatherwatchers/report/4720b156-2d56-4186-9a2c-147329e84fc3/

Never seen anything like it in 65 years of amateur weather observing.

OMG! I don’t think we had this. The South Downs May have blocked it, perhaps?

26C today!!! Still phew!

[DracoM]

What's an MSC?
Please excuse crass ignorance.





AND..............
it's raining here - a warm, humid rain.

[LMcD]

What's an MSC?
Please excuse crass ignorance.





AND..............
it's raining here - a warm, humid rain.

At a guess - MSC = Major Storm Centre?
24.1 C, hazy sunshine here. HORRIBLY muggy.

[oddoneout]

It started to rain at 9 just as I was getting ready to go into town for the market and other errands. I carried on anyway since it was evidently going to get too hot for comfort later. the rain quickly gave up - before it even got properly going in fact - and by the time I was heading home about 10-30 the temperature had shot up suddenly, so the right decision. It's now well over 30, but a breeze going through the house is pleasant.
Last night was horrid, not just hot but sticky, and a sense of general unease. Between 3 and 4 hours of fitful sleep. The sky at 3am was pretty, dawn later wasn't anything special - but I'm glad we didn't have that apocalyptic version, that would have put paid to any chance of getting back to sleep!

[Serial_Apologist]

What's an MSC?
Please excuse crass ignorance.

Meso convective sub-synoptic system.

There are basically 7 types of thunderstorm, worldwide.

1) Single cell, or pulse - single isolated cumulus developed into cumulonimbus, as in showers embedded in cool polar airstreams or in unstable hot summer conditions when surface-based storms generate over super-heated areas of ground such as cities or valleys.

2) Multi-celled - when initially single-celled storms combine by linking together: often the basis of myths about storms returning, when what has usually happened is that the storm which passed has died away and a new storm growing in its vicinity has moved in.

3) Orographic - storms formed where winds have been forced upwards on hitting mountains or hill ranges. Sometimes even a tall cliff can be a sufficient trigger.

4) Frontal: such storms can be "embedded" within frontal structures - more usually cold than warm fronts in Britain, since the undercutting action of cold air forcing the warm sector air ahead upwards acts as a greater trigger than warm front advection.

5) Straight line: These are also known as squall lines and can occur independently of, and frequently ahead of, cold fronts, usually initiating above the "boundary layer", or layer at which rising humidity condenses into cloud, because the triggering mechanism takes place higher, in the mid-troposphere, anywhere between 8,000 and 12,000 feet asl. These are the classic elevated, or high-base thunderstorms, non-dependent on surface heating for intiation or maintenance, and can produce copious amount of (mainly cloud-to-cloud) lightning.

6) Super cell: storms, of or within any of the above type, which literally revolve: counterclockwise in the northern hemisphere, clockwise in the southern, as a consequence of complex intersecting incoming airstreams at different levels within the cloud causing "shear" or spin. They are in effect mini-depression or low pressure systems in themselves, in which energy concentrations can lead to the formation of funnel clouds which may become tornadoes if completely descended to ground surface. These are the most severe and concentrated storms, often indicated from a distance by observing cumulus growing through and upwards beyond the anvil cap, when convective growth is forced to spread out sideways into the characteristic anvil shape under the lid presented by the stratosphere.

7) MSC: associated with frontal systems and straight line systems breaking up into sections, owing to differential impacting pressures: temperature differences, dry air sandwiched between layers of higher humidity, variable wind speeds and degrees of shear can lead to concentrations of convective energy which enable storms in any of the above categories to self-sustain when normal sustaining factors - heat input, stage of cloud development (all cumulonimbus storm clouds going through 3 stages: growth, maturity, decay) - are no longer present. Single cell storms and cells within straight line squalls last no more than 20-30 minutes before their electrical energy is exhausted; MSC storms can grow from multi cellular storms combining into single expanding storm systems. Such storms can expand over thousands of square kilometres in tropical regions, particularly in the monsoon seasons, and last several days.

8) Hurricane: these systems usually form out at sea where sea surface temperatures are above 28 C as initially west-moving straight line shower systems (see 5)) triggered by lower atmospheric eddies within the Trade Winds: the showers can begin to revolve around a potential centre (anticlockwise north of the Equator), surface pressure falling until incoming winds can compensate for upward convection, the spiralling air entrained, shaping the showers into inward spiralling storm bands until a central deepening core, the "eye", forms, surounded by the "eyewall", into which the showers become drawn, and where winds and precipitation are at their most intense. MSC systems often slowly revolve, but without forming an "eye" - many marine tropical depressions grow no further than this stage; hurricanes are like much larger MSCs, of different origination, and on hitting dry land they lose their energy source, provided by warm seawaters, and decay into MSCs.

[DracoM]

Absolutely wonderful. MANY thx.

[Petrushka]

Another very hot day here with absolutely no sign of the forecast thundery downpours which the BBC was still giving out late this morning, There's hardly been a cloud in the sky for most of the afternoon. Very poor forecasting!

[DracoM]

Keep hearing distant rumbles among the fells - very distant, but nowt here!