Convective / Storm Discussion - 31st July onwards 2013

[Richie V]

What I find incredible here in south yorkshire is that it is currently the hottest point of the day and It's 20z! 28.1c

[weatherobsuk]

Completely clear skies half an hour ago now, now replaced by banks of AC CAS which have some convective potential within. Temps not set to go below 17'c overnight so fingers x'd that by the morning we'll see a shower or two within the pre-front instability.

[MrNooo]

There was Ac-Cas building here lunchtime up until around an hour ago, seemed to be building quite nicely downwind of here, sky blue here now though.

[cheese]

Some very dark clouds to the west of here. Not sure if they're a harbinger of convective activity, but they do look threatening. 

[Weather-history]

Altocumulus castellanus moving quite fast, a litte bit of a breeze and feels as though the temperature has dropped.

[paul m]

Some very dark clouds to the west of here. Not sure if they're a harbinger of convective activity, but they do look threatening. 

Can see them over Castleford way from here

[Stuart]

Synopsis:

Sharp Atlantic upper trough will pivot and migrate northeastwards towards the British Isles. On the forward side, a very strong jet will be present, while at the surface a cold front will track eastwards across Britain, clearing a very warm, moist airmass initially present across eastern areas.

 

Discussion:

Various clusters of elevated convection are expected through the early hours across western parts of Britain, migrating NNEwards but with a general shift towards the east.

... CS + SE ENGLAND, S + E MIDLANDS, EAST ANGLIA ...

Most models suggest a new surge of mid-level convection across northern France through the early hours, this then tracking northeastwards across CS England from 04z onwards, covering many parts of the Midlands, East Anglia and the SE during Friday morning. The GFS (which tends to have a better handle on convective weather), on the other hand, remains largely dry and hence it is questionable as to how likely it is for this activity to occur. Nonetheless, various WRF/NMM solutions also develop some elevated convection/showers during Friday morning. A couple hundred J/kg MLCAPE suggests that a few isolated cells may produce some sporadic lightning, but it is thought that widespread lightning activity is rather unlikely, hence only an ISOL threat for this potential.

General trend is for mid-level convection to decrease in coverage towards the noon hours, with better insolation expected through the afternoon. With the moisture plume still in place, and a weak cold front nudging eastwards, there is potential for surface-based development through Friday afternoon and early evening across Lincolnshire, north Cambridgeshire and west Norfolk in particular, hence the inclusion of a SLGT here. If such isolated thunderstorms do develop, 600-900 J/kg CAPE and 50kts DLS would allow cells to become organised, capable of producing hail 2.0-3.0cm in diameter and perhaps a tornado.


... SW ENGLAND, C + E WALES, W + N MIDLANDS, N ENGLAND ...

In the post-frontal environment, slight cooling aloft and diurnal heating will generate 300-700 J/kg CAPE, leading to the development of scattered showers and a few thunderstorms. Converging low level wind fields and 50kts uni-directional DLS will cause showers/thunderstorms to become well-organised and form a distinct NE-SW orientated line, with cell clusters migrating NNEwards along this line. The main line axis will shift slowly eastwards through the day, beginning on the western flank of the SLGT around midday, and decaying near the eastern flank of the SGLT towards evening. Some hail is possible in any stronger cores, and given PWAT values near 25mm and shower training over similar areas, there is the slight potential for some localised flash flooding. An isolated tornado cannot be ruled out, but cloud bases are likely to be fairly high, minimising this risk somewhat.


... NORTHERN IRELAND, REPUBLIC OF IRELAND, SCOTLAND ...

Cooling aloft, diurnal heating and a couple of shortwave troughs will result in scattered showers and a few thunderstorms, and given 20-40kts DLS and low-level convergence, showers/thunderstorms will tend to band into distinct lines, with individual cells/clusters migrating NNEwards, but the general lines of showers/thunderstorms nudging slowly eastwards through the day. Given some 500-900 J/kg CAPE and favourable shear, hail 1.0-1.5cm in diameter is possible in any stronger cells. 20-25kts LLS, slightly backed surface winds and low LCLs suggests the potential for a funnel or weak tornado.

 

http://ukasf.co.uk/storm-forecasts/267

[robt]

Looks like theres a few bits and pieces building over towards Sheffield/Barnsley. Just watched a Cu/Cb build from nothing in 10 minutes.

[cheese]

I wonder if these clouds could develop into something?

 

 

they're growing larger as I type.

Edited August 1, 2013 by cheese

[Muffelchen]

The clouds over Morley

Yep, we had these a couple of hours ago here too. Strange, they were moving quite fast from the SW and then fizzling out as they reached the North Sea coast. This continued for about half an hour until they gradually fizzled out back towards the SW. Clear here now and still 26°C!!

[robt]

I wonder if these clouds could develop into something?

 

 

they're growing larger as I type.

Think those are the same ones I can see building.

[Darren Bown]

Clear here, with large cumulus clouds the the far south.

[Utahraptor]

There is currently a group of big thunderstorms to the west of Ireland, I don't know if they will effect the UK. I doubt that I will see any storms though, it has just been fast moving low cloud and drizzle all day.

 

[cheese]

Well those clouds just collapsed. Maybe something tomorrow?

Edited August 1, 2013 by cheese

[Cloud 10]

A case of close but no cigar for NE England today,although there is a nice convergence

zone over the area at the moment which almost looks like a small LP.

 

 

 

Some storms just to the west of Ireland on the radar as mentioned above,as well as

a few showers in the North Sea.

 

 

 

I have to say despite the lack of storms,it has been a lovely summer's evening.

Edited August 1, 2013 by Cloud 10

[Utahraptor]

 I doubt that I will see any storms though, it has just been fast moving low cloud and drizzle all day.

 

 

I guess I spoke too soon. A storm has now popped up in NW Ireland.

 

 

The low cloud has also mostly gone, and now I have a view of what looks like a Cb to my south west, although it is hard to make out...

 

[Chris.R]

Temp is now 16c, has dropped 10c in 3 hours due to a westerly breeze coming from somewhere. Could have done with out that!

[Eskimo]

Temp is now 16c, has dropped 10c in 3 hours due to a westerly breeze coming from somewhere. Could have done with out that!

Did the Westerly breeze come from the West? 

[Nick F]

Valid: 02/08/2013 0000z to 03/08/2013 0000z
Headline: ... THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FORECAST ...

Synopsis
Long-wave upper trough edges in closer just to the west of British Isles on Friday, with a depression around 985mb expected west of Scotland/N of Eire at 12z, while cold front lies roughly North York Moors to Dorset at 12 noon moving east. A very warm, humid and unstable airmass will exist ahead of the cold front. A well modified and unstable polar maritime flow will also affect the north and far west post cold front.

S/SE ENGLAND, THE MIDLANDS, E ANGLIA AND LINCS

Rather warm and moist airmass characterised by dew points in the high teens and WBPTs of 18C will exist ahead of cold front moving in from the west. Mid-level warm moist air advection also occurring with steep lapse rates as cooler air overruns aloft may support the development of elevated showers and storms early on in the morning, as a shortwave trough moves NE from N France in the early hours. These showers and storms spreading from the south across the above areas during the morning. Otherwise, surface heating of the warm/moist airmass ahead of cold front moving in from the west may support additional storm development, which maybe surface-based given moist boundary layer. Wind profiles are forecast to increase in speed and have some veer with height as the cold front and parallel jet approaches from the west, with 40-50knts of deep layer shear indicated, which will aid storm organisation ... with large hail, excessive rainfall and damaging wind gusts possible. 600-900 j/kg of CAPE is forecast towards E Anglia, E Midlands and Lincs in the afternoon and if surface winds back enough or a sea breeze front moves inland there will be an enhanced risk of an isolated tornado with any storm here too.

IRELAND/N IRELAND, W WALES AND SCOTLAND

Post cold front, airmass will still be moist and with colder temperatures spreading from the west aloft, increasingly unstable to surface heating - more particularly across Ireland and western Scotland, where post cold front subsidence will have weakened more here. So scattered thunderstorms are likely to develop across Ireland and W Scotland during the day. Storms may organise into line clusters along wind streamlines and vorticity lobes rotating around deep low to the NW, with a risk of  hail. strong wind gusts and excessive rainfall leading to flash flooding where storms train over some places. Moderate low-level shear is also indicated, so an isolated tornado can't be ruled out either.

Issued by: Nick Finnis

 

[Muffelchen]

Some storms just to the west of Ireland on the radar as mentioned above,as well as

a few showers in the North Sea.

 

viewimage.png

 

 

I have to say despite the lack of storms,it has been a lovely summer's evening.

It's a pity they are not electrified: one of the wonderful things about living in this 'desolate' part of the world is the North Sea and its relationship with thunderstorms. Many nights there are storms way out over the sea and you can see the lightning flashes in the distance, sometimes travelling along the horizon. It is very spooky indeed and slightly surreal but I have seen it many times now (not tonight sadly). It must be a North Sea thing as I grew up in Pembrokeshire and I never saw anything like it in spite of having a much warmer sea on three sides!

Still really warm out and feels it: currently 23.9°C with 70% humidity which is lower than I expected if I am honest.

[Nath]

Outside temp 25.4C, in my room 32.8C, horrific tonight and sweating buckets.  With these conditions surely a storm has to occur!!

[Richie V]

I'm rather surprised theres not much chatter for fridays offerings?!

Tomaz at 00:00 on news 24 seemed rather excited! Storms starting on the south coast and quickly developing north anywhere east of east wales, some sharp ones into the midlands and yorkshire by afternoon "if you get one boy will you know about it"!

[smoggyjester]

So is Hampshire likely to get any storms this morning? Thanx in advance

[Richie V]

Smoggy, watch the news 24 weather at 01:00!

[smoggyjester]

Ok take it worth watching