Storm & Convective Discussion - 01/06/15 onwards

[Harry]

here's a few cloudscape pics I've tken in the past few minutes....as you can see, instability in the mid-levels making it presence known with a mixture of AC, Ac Cas with virga, and even some Ac Floccus (I think)...a very good sign for later....currently 22c here, with a light SW breeze and some increasing humidity at the surface...

 

 

 

 

IMG_20150604_135026.jpg  IMG_20150604_135033.jpg  IMG_20150604_135102.jpg  IMG_20150604_135125.jpg

IMG_20150604_135331.jpg IMG_20150604_135341.jpg

 

 

edit, just noticed how blurry some of these are......that's vodafone's crappy smartphone's for ya...lol

 

Very nice...not witnessed anything like that for best part of 9 months...I love this time of year

 

Some interesting mid-level clouds to the west of London but unable to get snaps...at a glance the top look vaguely like anvils.

[ThunderBuddy21]

[Luke Best]

Very nice...not witnessed anything like that for best part of 9 months...I love this time of year

 

Some interesting mid-level clouds to the west of London but unable to get snaps...at a glance the top look vaguely like anvils.

They really do don't they?! Love days like this.

[Spikecollie]

A bit weird here in the Aire Valley - quite breezy, a considerable number of inoffensive cumulus and nicely warm. Alas I must sign off for now, but I should be able to get back on in Limousin tonight. Happy storm watching and waiting, and stay safe whatever you're doing!

[Dami]

wish i had taken pics of the clouds where i was, disappearing as quick as they grew.

[NO LONGER POSTING]

Live from Heathrow

[alexisj9]

wish i had taken pics of the clouds where i was, disappearing as quick as they grew.

If it was cumulus had some that going on here, now have alto cumulus hanging around, very slow moving and feathers, (is that cirrus?)

Edited June 4, 2015 by alexisj9

[Harry]

If it was cumulus had some that going on here, now have alto cumulus hanging around, very slow moving and feathers, (is that cirrus?)

 

The feathery wispy clouds are indeed cirrus.

[Ben Sainsbury]

In case anyone later is observing any thundery activity via a lightning detector, this one always seems to be the most realiable to me if anyone wants to use it, it's here: http://www.lightningmaps.org/realtime

[Harry]

MetO rainfall forecast not inspiring to me - this also resembles what somebody described this morning (i.e some linear showers with main storms firing east of England oversea (ironically)). Doesn't quite resemble the fairly explosive atmosphere we are expecting...interesting

[Captain Shortwave]

MetO rainfall forecast not inspiring to me - this also resembles what somebody described this morning (i.e some linear showers with main storms firing east of England oversea (ironically)). Doesn't quite resemble the fairly explosive atmosphere we are expecting...interesting

The 06z Euro4 output has the event pretty much over by mid-Afternoon with the last of the showers heading into the north sea. Lets hope the other models are on the money and we get widespread thundery activity. It won't be the first time the Euro4 has been very pessimistic and has been wrong.

[NO LONGER POSTING]

The 06z Euro4 output has the event pretty much over by mid-Afternoon with the last of the showers heading into the north sea. Lets hope the other models are on the money and we get widespread thundery activity. It won't be the first time the Euro4 has been very pessimistic and has been wrong.

 

Last Thundry day we had the Euro 4 didnt have a clue 

[UKSupercell]

That time of year again!!!

Gonna be typically pessimistic and bet on an East Kent clipper scenario.

 

All hell will break loose at dawn in Thanet; after UKIP took the council they got an earthquake two weeks later there, now they'll get large hail and a tornado. You heard it here first. Farage has shaken things right up, ok enough of politics.

An exaggeration but I'll gamble on Kent seeing the most action. 

[thundercrazy]

Cells now exploding over Northern Spain on latest sat24 image, pretty confident we will see something good from this

[Flash bang flash bang etc]

Really good clouds over Heathrow area - will be heading back home today via a few good high up spots and have my proper cams so looking forward to getting some good precursive shots of the lovely skies!

[shaky]

some of the clouds look brilliant around here!!!definitely a sign of a warm humid night ahead of us and maybe some thundery activity!!

[BrickFielder]

 There seems to have been a fair bit of consternation about why the models moved weather eastwards over the last few days. I honestly expected this to occur based on previous occasions with two root causes identified. The first is that it is very diffcult to predict a low pressure system before it has really developed with models tending to have a bias towards continental modelling accuracy as opposed to maritime modelling (UKMO and netweather NMM being the exceptions) . The second is that there are differences between accuracies in satellite monitoring of air conditions and actual air soundings done with a balloon. If previous modelling anomalies are anything to go by, then we should expect a downgrade in instability over the next few modelling runs, only for it to pick up slightly for the 00z tomorrow.We might also expect the forecast to move very slightly westwards from the 18z onwards (30 miles or so).

 On Tuesday when I looked at the forecast I was concerned a bit about timing, with an expectation that mid level instability would move in and exit eastwards earlier than modeled. Current Modelling shows mid level instability moving in from midnight instead of Tuesdays modelling of the early hours of the morning. Instability moves out of the UK by mid afternoon for all but the south east and East Anglia.

 The driving force for destabilization of the plume appears to be a jet streak moving up through the bay of Biscay (I think the absence of a forcing mechanism is why storms are not initiating over France yet).

 Models suggest the first development should be over Spain late today which trundles up to the channel islands. This development is unlikely to be surface based over the UK apart from as it crosses the coast and as daylight heating begins to affect it  (Limits severity and generally prohibits tornado activity). Differences in surface based instability and mid level instability show this.

 

This could be in the form of an MCS with a leading super cell. There is a slight risk of the lead storm developing a weak tornado as daylight catches up with it (Possibly towards Hull or northwards depending on timing and positioning - current models suggest it might be over the sea before 8am when it might start to become surface based). If it materializes then it should give a moderate lightning show and there is a chance precipitation will be elevated (not much reaching the ground).

Small lobe of vorticity at 500hPa (mid level height) might suggest super cell development.

 

700hpa (height) Vorticity charts suggest a warm front moving north over the UK with a trough/ cold front trailing. Destabilization occurs just behind the warm front over night and in the warm sector under peak day light heating. I think the trough/front gets absorbed into the main cold front later on in the day.

 

The overlap between mid level and low level shear tomorrow might be quite narrow and depend on the existence of a low level jet.

 

Any storm developing where that low level jet is would have properties which in theory could create a tornado. The problem is that the NMM model does not develop storms there but rather just eastwards along a convergence zone.

 

So all the ingredients are there in different places for a severe storm, they just don't quite come together on this modelling output. My general rule though is that if it comes together on the model it will not on the day and if it does not come together on the model it is more likely to on the day, except when the models are completely wrong and you get no storms at all.

 

Unfortunately it is still too early for modelling to give much in the way of detail and the model outputs displayed in this post are mostly likely wrong in some aspects. Timing of this event means further model analysis of detail will be of little use compared to actually observations. I guess this post is aimed at those who would like to understand how different aspects need to come together for storms to develop rather than any serious forecast of what will happen tomorrow. Still it is nice to ponder and wonder sometimes.

 

Edited June 4, 2015 by BrickFielder

[NO LONGER POSTING]

 There seems to have been a fair bit of consternation about why the models moved weather eastwards over the last few days. I honestly expected this to occur based on previous occasions with two root causes identified. The first is that it is very diffcult to predict a low pressure system before it has really developed with models tending to have a bias towards continental modelling accuracy as opposed to maritime modelling (UKMO and netweather NMM being the exceptions) . The second is that there are differences between accuracies in satellite monitoring of air conditions and actual air soundings done with a balloon. If previous modelling anomalies are anything to go by, then we should expect a downgrade in instability over the next few modelling runs, only for it to pick up slightly for the 00z tomorrow.We might also expect the forecast to move very slightly westwards from the 18z onwards (30 miles or so).

 On tuesday when I looked at the forecast I was concerned a bit about timing, with an expectaction that mid level instability would move in and exit eastwards earlier than modelled. Current Modelling shows mid level instability moving in from midnight instead of tuesdays modelling of the early hours of the morning. Instability moves out of the UK by mid afternoon for all but the south east and East Anglia.

 The driving force for destabilisation of the plume appears to be a jetstreak moving up through the bay of biscay (I think the absence of a forcing mechanism is why storms are not initiating over France yet).

500windspeed05.png500wind14.png

 Models suggest the first development should be over Spain late today which trundles up to the channel islands. This development is unlikely to be surface based over the UK apart from as it crosses the coast and as daylight heating begins to affect it  (Limits severity and generally prohibits tornado activity). Differences in surface based instability and mid level instability show this.

sbcape05.pngmlcape05.png

 

This could be in the form of an MCS with a leading super cell. There is a slight risk of the lead storm developing a weak tornado as daylight catches up with it (Possibly towards Hull or northwards depending on timing and positioning - current models suggest it might be over the sea before 8am when it might start to become surface based). If it materializes then it should give a moderate lightning show and there is a chance precipitation will be elevated (not much reaching the ground).

rainprecip01.pngrainprecip04.png

Small lobe of vorticity at 500hPa (mid level height) might suggest super cell development.

500vort04.png

 

700hpa (height) Vorticity charts suggest a warm front moving north over the UK with a trough/ cold front trailing. Destabilization occurs just behind the warm front over night and in the warm sector under peak day light heating. I think the trough/front gets absorbed into the main cold front later on in the day.

700vort04.pngmlcape05.png

 

The overlap between mid level and low level shear tomorrow might be quite narrow and depend on the existence of a low level jet.

925wind.png

deepshear13.pnglowsheer13.png

 

Any storm developing where that low level jet is would have properties which in theory could create a tornado. The problem is that the NMM model does not develop storms there but rather just eastwards along a convergence zone.

lowwind13.pngrainprecip13.png

 

So all the ingredients are there in different places for a severe storm, they just don't quite come together on this modelling output. My general rule though is that if it comes together on the model it will not on the day and if it does not come together on the model it is more likely to on the day, except when the models are completely wrong and you get no storms at all.

 

Unfortunately it is still too early for modelling to give much in the way of detail and the model outputs displayed in this post are mostly likely wrong in some aspects. Timing of this event means further model analysis of detail will be of little use compared to actually observations. I guess this post is aimed at those who would like to understand how different aspects need to come together for storms to develop rather than any serious forecast of what will happen tomorrow. Still it is nice to ponder and wonder sometimes.

 

World class post.. Better than all our cloud pics 

[Harry]

All very interesting - I must say I'm still undecided about whether to be optimistic or pessimistic about tomorrow in truth. I've taken the day off now so I am free to roam as it were. I had planned to wait for storms around my location (06z to 12z) before darting east to the east Kent coast to await anything which fires around that location or moves in from the south/west. 

Regrettably however the models are keen not to develop anything over Kent, but rather take overnights area to the West of London and fire stuff north of London around noon and thereafter. 

 

That said, as BF rightly says, models tend not to be overly accurate and in my experience, Kent in particular often lacks in terms of charts in the CAPE department (possibly as a result of being entirely surrounded by water). This in turn often leads models to be reluctant to show any real storm risk or precip breaking out here. Experience shows however Kent certainly can fire storms and often boasts SBCAPE models are reluctant to show. 

 

I think for the time being I will keep to my plan, and hope we have more of a 28/06/11 day than what is currently modelled. 

 

Is it me or are those MLCAPE projections far higher than a normal plume event?

Edited June 4, 2015 by Harry

[Mapantz]

It has exploded across parts of Portugal and Spain..

Look at the difference between 1 and 3.

Edited June 4, 2015 by Mapantz

[Harry]

No forecasts from ConvectiveWeather.co.uk (formerly UKASF) as yet...so that's Nick F away in the US, Estofex down and no UKASF...this will be the first significant plume event without any of those in place for quite some time.

[Thunderbolt_]

The sky is starting to turn much more convective here in Manchester now.

 

[cheese]

We have similar skies in Leeds. I'm going to keep my eye on things tomorrow as I think there is a chance of something occurring - even if it's just a distant flash of lightning. Better than what we've had so far this year - nothing.

[William Grimsley]

Interestingly, I think Devon has had the most visual instability this afternoon. Layers and layers of Ac Cas along with TCu!

[Mokidugway]

Sky's full of cirrus so change on its way ,not expecting anything though ..