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End of the week & weekend storm risk


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Posted
  • Location: Sunderland
  • Weather Preferences: Hot Summer, Snowy winter and thunderstorms all year round!
  • Location: Sunderland

12z NMM is out, and it does prog more elevated instability tomorrow evening for some southern counties, but the air mass isn't particularly moisture laden (theta-e & pwat values are rather uninspiring) so the output is not all that keen in breaking out precipitation, it's feasible that some storms might fire over northern France with troughing over N France adding additional forcing and the focal point for any elevated destabilization, whether any surface based storms can survive the trip across the channel, and, whether any elevated storms can maintain any strength as they move into less favourable environments over southern England overnight, is another question 

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Posted
  • Location: Bexley (home), C London (work)
  • Weather Preferences: Thunderstorms
  • Location: Bexley (home), C London (work)

To be fair AJ, it's not too far off what I've been thinking. 

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Posted
  • Location: Bristol
  • Weather Preferences: Thunderstorms and Snowstorms
  • Location: Bristol

From what I can see according to current details (which is likely to change), the most severe storms look to be across NW Wales into NW England; as mentioned before the best instability is situated here, along with decent SRH which will aid the development of storms, the dewpoints looking more than favourable between 13-15'c.  Vertical Shear looks decent to support the developed thunderstorms. In terms of a trigger along with surface temps of 20+'c dirnual heating should be no problem, this included with a front out to the west. And plenty of avaliable moisture is a neccessary which is avaliable. Therefore all the ingredients are there at this moment in time, we shall see!

Edited by Ben Sainsbury
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Posted
  • Location: Norwich, Norfolk, East Anglia
  • Weather Preferences: Sunny, stormy and I don't dislike rain only cold
  • Location: Norwich, Norfolk, East Anglia

I like the pattern from the PWAT chart 00Z 07-05-016 :)

pwat 07-05-16.png

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Posted
  • Location: Dorset
  • Weather Preferences: warehamwx.co.uk
  • Location: Dorset
1 hour ago, William Grimsley said:

It's interesting you say that. @Mapantz and @ajpoolshark have said different...

Wait, what? I don't remember saying anything.. lol

If you're referring to yesterday's light-hearted posts? It's more to do with the fact that you get yourself too worked up and ultimately set yourself up for disappointment- not all the time, but quite often in these setups. Just relax! :)

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Posted
  • Location: Sunderland
  • Weather Preferences: Hot Summer, Snowy winter and thunderstorms all year round!
  • Location: Sunderland
3 minutes ago, Greenday said:

I like the pattern from the PWAT chart 00Z 07-05-016 :)

pwat 07-05-16.png

IMHO buddy, they don;t look particularly special, mediocre energy, capping in place inferring more energy and forcing is required than modelled, lapse rates ok, might help overcome other less favourable forcing mechanisms, and pwat - meh......just my opinion, but those charts don't cry out thunderstorms tomorrow night, rather some shallow convective rainfall for the far south west....still, it is early May and anything would be a bonus.....after the miserable winter most of us have endured, a few sporadic lightning flashes would be welcomed.....let's hope the models are underplaying the developing situation and we get a decent light show :)

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Posted
  • Location: Norwich, Norfolk, East Anglia
  • Weather Preferences: Sunny, stormy and I don't dislike rain only cold
  • Location: Norwich, Norfolk, East Anglia
5 minutes ago, ajpoolshark said:

IMHO buddy, they don;t look particularly special, mediocre energy, capping in place inferring more energy and forcing is required than modelled, lapse rates ok, might help overcome other less favourable forcing mechanisms, and pwat - meh......just my opinion, but those charts don't cry out thunderstorms tomorrow night, rather some shallow convective rainfall for the far south west....still, it is early May and anything would be a bonus.....after the miserable winter most of us have endured, a few sporadic lightning flashes would be welcomed.....let's hope the models are underplaying the developing situation and we get a decent light show :)

I like your take on the convective overview chart, when I said I like the look of the PWAT chart I mean its taken the shape of possibly a bunny wanting a hug or it appears and says duh dah! Lol. I'm not sure how much the Lifted index has a role in elevated storms but they are not forecasting even borderline instability..

SBCAPE LI 07-05-16.png

A plume of high theta-W begins to make its way into the south from 12Z onwards (in order of 12 15 18 21 and 00Z)..

Theta-W 12Z.jpgTheta-W 15Z.jpgTheta-W 18Z.jpgTheta-W 21Z.jpgTheta-W 00Z.jpg

The current run shows it overspreading the entire swathe of England and Scotland on Saturday. Its certainly going to feel plumey I reckon. Also PWAT from the April plume was forecast to be less than that but it turned out to be a good night for quite a few places in the east. I'm not an expert in the overnight stuff so will have to wait and see.

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Posted
  • Location: Sunderland
  • Weather Preferences: Hot Summer, Snowy winter and thunderstorms all year round!
  • Location: Sunderland
Just now, Greenday said:

I like your take on the convective overview chart, when I said I like the look of the PWAT chart I mean its taken the shape of possibly a bunny wanting a hug or it appears and says duh dah! Lol. I'm not sure how much the Lifted index has a role in elevated storms but they are not forecasting even borderline instability..

.

lol.....I see what you mean....to coin a phrase I should've gone to specsavers

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Posted
  • Location: BRISTOL
  • Location: BRISTOL

It would be good to see something over the next few days but it honestly wouldn't bother me if I didn't I've had 5 thunder days this year already when usually I'm on 0.

Would be nice to have a sunny warm weekend and enjoy it but if there's to be thundery weather that would be a bonus.

Charts are chopping and changing all the time and certainly can't be used as weather guaranteed to happen because of what it shows at one particular time or another.

Better to just follow the thread keep up to date and eyes on the sky.

Best of luck :)

 

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Posted
  • Location: Cheslyn Hay, South Staffordshire. UK 159mtrs ASL
  • Location: Cheslyn Hay, South Staffordshire. UK 159mtrs ASL

Its just ace reading some posts on a run up to a thundery potential! Love the banter :)

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Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

Day 2 Convective Outlook

VALID 06:00 UTC Fri 06 May 2016 - 05:59 UTC Sat 07 May 2016

ISSUED 20:29 UTC Thu 05 May 2016

ISSUED BY: Dan

As a sharpening Atlantic upper trough continues to dig southwards towards Iberia, while pivoting slowly northeastwards, warm advection will occur on the forward side from France towards S/SW Britain, especially so on Friday evening/night. Cooling aloft and gradually falling heights with a shortwave running northwards on the eastern flank of the upper trough, atop this increasingly warm, moist airmass, will encourage convective initiation across northern France and the English Channel on Friday evening, with a few elevated showers and perhaps thunderstorms forming (given steep mid-level lapse rates) and then moving towards the N/NNW on Friday night.

NWP guidance continues to offer differing solutions - UKMO suite consistently taking most mid-level activity across SW England and S Wales, whilst a blend of GFS/ECMWF prefer a more easterly path towards Cen S England then into the Midlands by Saturday morning. Models notoriously struggle with elevated convection, both in placement and extent/intensity, and so it is unsurprising to see the differences at this range. As is often the case, bifurcating flow aloft could potentially produce 2 primary axes of interest, one perhaps towards Devon/Cornwall and another towards IoW/Hampshire/Dorset, with a relative minima in between. 

For now, too much uncertainty exists to narrow down areas of interest, hence the broad LOW, although it is noted that most guidance since Wednesday evening have tended to shift a little farther westwards. Instability also looks marginal which might limit how electrically active such mid-level showers will be. Given the complexity, this forecast may be updated nearer the event.

 

http://www.convectiveweather.co.uk/forecast.php?date=2016-05-06

Edited by Summer Sun
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Posted
  • Location: East Devon
  • Location: East Devon

The thing I have noticed is you don't always need decent instability showing for elevated storms (at least here), in fact it usually doesn't on the free GFS charts on Netweather as that's only surface based CAPE. There have been two occasions this year, one affecting eastern areas, and one affecting Cornwall, where elevated storms formed with a modest plume and limited Mid Level CAPE showing in the outputs.

There was also a surprise occasion last summer where unexpected storms formed and affected the SW despite virtually no CAPE whatsoever being shown on any charts I saw, including ML CAPE. I watched distant CG's against a sunset background.

Of course, that doesn't mean we will get such events this time or with any old plume. I am not sure what the other supporting conditions were like for these events.

Wetterzentrale charts do suggest a pool of instability moves into the south Friday night, doesn't look like much but I've seen decent elevated storms from similar amounts on these charts.
Rtavn3611.gif

Like others I'm also unsure about this event.. I do feel some central-northwestern areas (e.g. NW England, Wales, and perhaps parts of the Midlands) have the best chances this weekend due to the surface based risk here.

Edited by Evening thunder
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Posted
  • Location: Norwich, Norfolk, East Anglia
  • Weather Preferences: Sunny, stormy and I don't dislike rain only cold
  • Location: Norwich, Norfolk, East Anglia
1 hour ago, ajpoolshark said:

lol.....I see what you mean....to coin a phrase I should've gone to specsavers

Haha I'm glad you spotted it now :) I like the way the western side of France creates a contour for his belly.

What I also find funny is that it looks like its body is skirting around France but using his arm to push France away (see picture) :nonono::rofl:

UK's turn.jpg

Edited by Greenday
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Posted
  • Location: Birmingham
  • Location: Birmingham

Yes, models still signalling at potential for deep moist convection (DMC) across far SW UK (SW England/Wales) and offshore tomorrow evening and into early Saturday, as cold front and pre-frontal shortwave impulse moving up from the south engage moist low-mid level air mass of substantial theta-w/WBPTs advecting across the region.  These elevated showers/storms likely rooted above 850mb, and therefore SBCAPE (potential energy for parcel lifted from surface) and MLCAPE (parcel instability averaged within lowest 100mb) not best guide to determine how unstable the environment is, and likelihood of deep convection.  For this, one can refer to MUCAPE, which is the most unstable energy for a parcel within the lowest 300mb, therefore taking into account lowest section of the mid-level. 

gfs_mucape_eur36.png fax36s.gif

As can be seen, 12z GFS is developing few 100J/KG CAPE over SW, where increasing low-level warmth and moisture advection together with approach of upper trough and height falls from the west steepens mid-level lapse rates (generally close to 7C/km or slightly above which is sufficient) and generates substantial instability for DMC and storms. 

Just some quick thoughts to add to the discussion anyway.  Hazard to go into detail re. Saturday and Sunday daytime/evening periods at the moment as a little uncertain as to coverage of storms.  

Edited by weather09
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Posted
  • Location: Bexley (home), C London (work)
  • Weather Preferences: Thunderstorms
  • Location: Bexley (home), C London (work)

Bloody hell, where's William gone!!! Those last 4 posts will please him immensely.

I do hope for him it comes off for the SW at some stage this weekend...after what's proven to be a very generous April for me, I don't want to be greedy and would happily pass up much enjoyment just for this weekend and catch some balmy rays :D

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
1 hour ago, Evening thunder said:

Like others I'm also unsure about this event.. I do feel some central-northwestern areas (e.g. NW England, Wales, and perhaps parts of the Midlands) have the best chances this weekend due to the surface based risk here.

Yep, that's where the diurnal home-grown threat looks to develop both Saturday and Sunday. Monday perhaps seeing storms developing further east through M4 corridor during the day, plus some imports into the SE. Mixture of breeze / moisture convergence, surface heating and orographic lift the main mechanism for storm initiation, not a great deal of forcing aloft showing, with the main low displaced over Biscay.

Risk of isolated elevated storms flaring-up from time to time over the coming days too away from these areas, more particularly overnight and mornings as isentropic lift of the warm and moist conveyor aloft, a few weak disturbances running north, while upper levels cool nocturnally creates mid-level instability. Some elevated storms possible for western E Channel,  SW England, Wales and eventually parts of EIRE Friday night into Saturday morning.  Perhaps isolated risk of elevated storms erupting further east across southern areas Saturday and Sunday nights and early mornings, some if it imported - but looks a low risk atm.

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Posted
  • Location: Norwich, Norfolk, East Anglia
  • Weather Preferences: Sunny, stormy and I don't dislike rain only cold
  • Location: Norwich, Norfolk, East Anglia

Just to get a few more of these under my belt when it comes to model forecasting before hyping a potential plume event with more certainty. I think I'm getting the jist. To me it didn't seem like William and his area could be ruled out and that his area is in the zone of interest for Friday evening/night. I wish him the best. I don't know if he will go chasing but at least now he has that on his side from just a year or 2 ago. That can really help to get the best of any local storms that do occur.

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Posted
  • Location: Condorrat, Cumbernauld G67
  • Location: Condorrat, Cumbernauld G67

I think my part of the world COULD see something on Sunday. Going to be interesting...............................

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Posted
  • Location: Douglas, Isle of Man - 380ft/116m ASL
  • Weather Preferences: Warm summers, cold winters.. How it should be!
  • Location: Douglas, Isle of Man - 380ft/116m ASL

8ba9588.jpg bc822c5.jpg

Edited by Convective
Updated to include second risk zone
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Posted
  • Location: Leicester (LE3)
  • Location: Leicester (LE3)

Can someone clarify lightning within 50km of a point please? 

For example, the first chart above has a "technical term" yellow splodge, so if I took a pin and stuck it in anywhere within that yellow splodge, then drew a 50km circle from the centre pin point, including any area within that circle, even if it part of the circle is outside the yellow splodge, there could be lightning?

Sorry if that's a rather complicated description, couldn't think how to shorten it!!!!

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Posted
  • Location: Douglas, Isle of Man - 380ft/116m ASL
  • Weather Preferences: Warm summers, cold winters.. How it should be!
  • Location: Douglas, Isle of Man - 380ft/116m ASL
1 minute ago, Speedway Slider said:

Can someone clarify lightning within 50km of a point please? 

For example, the first chart above has a "technical term" yellow splodge, so if I took a pin and stuck it in anywhere within that yellow splodge, then drew a 50km circle from the centre pin point, including any area within that circle, even if it part of the circle is outside the yellow splodge, there could be lightning?

Sorry if that's a rather complicated description, couldn't think how to shorten it!!!!

That's the literal meaning of it on my attempt at a forecast. Whether or not the same applies for other forecasts, I'm not sure :) 

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Posted
  • Location: Dorset
  • Weather Preferences: warehamwx.co.uk
  • Location: Dorset
2 minutes ago, Speedway Slider said:

Thanks... 

Also, do you know what "Meh" stands for? 

Meh.png

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Posted
  • Location: King’s Lynn, Norfolk.
  • Weather Preferences: Hot and Thundery, Cold and Snowy
  • Location: King’s Lynn, Norfolk.

All eyes on tomorrow evening then in southwestern areas and Wales etc, then the possibility of some decent homegrown stuff over the midlands into the northwest over the weekend. South East and east Anglia looking more interesting now for the start of next week, subject to change however. 

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