Jump to content

Archived

This topic is now archived and is closed to further replies.

Wivenswold

Storm Potential July 1st onwards - Technical Discussion

Recommended Posts

Morning, 

 

As usual in these set-ups I think a separate thread is needed to keep general storm chat and observations away from factual and scientific analysis of the set-up. I'm not actually qualified but enjoy learning about how storms work but less interested in the general banter that clogs up the main Storm discussion tread at times like this. 

 

Mods, feel free to rename, move or delete as appropriate. 

 

Share this post


Link to post
Share on other sites

Good idea to keep the more tech stuff out of the main storm thread and especially for this week as the forum will get busy from tonight.. 

Share this post


Link to post
Share on other sites

That said, it'll probably be all quiet here until tomorrow when the finer details are nailed down. 

Share this post


Link to post
Share on other sites

 Still way to early for any sort of detail forecast.

 

 One thing to remember is that all the instability in the world is no use if there is no triggering mechanism for storms.

post-2809-0-33604400-1435569906_thumb.pnpost-2809-0-38321900-1435569913_thumb.pn

So plenty of instability mid day wednesday.

post-2809-0-98230700-1435569921_thumb.pnpost-2809-0-87566400-1435569930_thumb.pn

There is not really any triggering mechanism forecast at this point of the day.

Looking at the forecast Skewt's then there is a marked warm nose at 850hpa height which would suggest most of the instability would be elevated.

post-2809-0-00249700-1435570389_thumb.pn

These would give hazy sticky upper level storms with not much rain. I don't think these types of storms really need much of a trigger.

 

A little later in the day and things change a little with some marked dry air coming in at a height of around 400hpa.

post-2809-0-93076300-1435570590_thumb.pn

This still overlaps somewhat with instability.

post-2809-0-13919100-1435570654_thumb.pnpost-2809-0-19927400-1435570661_thumb.pn

The forecast Skewt shows the difference clearer.

post-2809-0-38304400-1435570823_thumb.pn

That is a lot closer to a surface based storm. Wind shear however has changed with less directional shear and a touch more speed shear.

 

Most likely looking at the model output this early will not tell us much and we might expect timing to be inaccurate and it could all move eastwards.  Interesting but lets wait until we get a little closer before we start predicting any thing.

 

 

Share this post


Link to post
Share on other sites

Thanks for this - rather been lost in the quest for heat. Might be some interesting overnight storms imported from France this week, I think!

Share this post


Link to post
Share on other sites

At what altitude would those cloud tops be?

Share this post


Link to post
Share on other sites

At what altitude would those cloud tops be?

 

Possibly 30,000 feet (10000 metres) if its roughly 238mb. You can google for conversion.

 

Both GFS and NMM forecasting some fantastic Theta-E and Lapse rate values.

post-7331-0-15892500-1435618638_thumb.pn

post-7331-0-92693900-1435618657_thumb.pn

Share this post


Link to post
Share on other sites

  I still would not like to make a forecast for tomorrow. Diurnal heating has not really driven thunderstorms yet over the northern mountains of Iberia  today (there is still time) which worry's me about the forecast. There are different predictions in the models for precipitation rates. So this update will have to be about broader scale developments again.

 First there is still the question of a triggering for storms. Although an elevated mixed layer will destabilize I tend to like a trigger for any surface based storms. Compare the areas of maximum instability and precipitation on the following two charts.
post-2809-0-08962000-1435676329_thumb.pnpost-2809-0-32265600-1435676338_thumb.pn
 The culprit is of course Convective inhibition.
post-2809-0-58846100-1435676371_thumb.pnpost-2809-0-47631200-1435676380_thumb.pn
 That does not appear to be the whole story though because if I look at the 500hpa vorticity charts then there are clear signs of storm development. These I think are elevated storms.
post-2809-0-78775400-1435676620_thumb.pnpost-2809-0-66257600-1435676627_thumb.pn
 That again is not the whole story because we have suggestions of low level wind convergence zones towards Wales and western parts of the UK. These I think might be the focus of surface based storms as moisture pools in these regions.
post-2809-0-99557000-1435676652_thumb.pn
 There might even be more to the story tomorrow in that later on drier air comes in aloft. Notice how there is not a clear demarcation edge as it moves north which would tend to suggest potential storm development along that edge. Equally there is a weak area of vorticity advection at the 700hpa level moving northwards late afternoon. This may or may not be important, I am not sure yet.
post-2809-0-32679200-1435676693_thumb.pnpost-2809-0-20104600-1435676700_thumb.pn
 Forecast SkewT's suggest a relaxing of the cap from the north moving southwards during the afternoon.
post-2809-0-89852000-1435676726_thumb.pnpost-2809-0-02388300-1435676736_thumb.pn
 What confuses me though is how the cap it is modeled to almost disappear completely in the north of England. I am not convinced by this as a cap does not normally weaken that much over a short distance and is usually overcome by high temperatures and dew points.

post-2809-0-21590400-1435676782_thumb.pn

 So a mixed and confusing picture and still a chance that nobody will see any storms at all. After all those Iberian storms have not appeared yet today.

 

post-2809-0-23826900-1435676819_thumb.pnpost-2809-0-00930100-1435676830_thumb.pn

post-2809-0-67538900-1435676872_thumb.pnpost-2809-0-54322800-1435676850_thumb.pn

Share this post


Link to post
Share on other sites

  I still would not like to make a forecast for tomorrow. Diurnal heating has not really driven thunderstorms yet over the northern mountains of Iberia  today (there is still time) which worry's me about the forecast. There are different predictions in the models for precipitation rates. So this update will have to be about broader scale developments again.

 First there is still the question of a triggering for storms. Although an elevated mixed layer will destabilize I tend to like a trigger for any surface based storms. Compare the areas of maximum instability and precipitation on the following two charts.

attachicon.gifmlcape10.pngattachicon.gifrainprecip10.png

 The culprit is of course Convective inhibition.

attachicon.gifmlcin10.pngattachicon.gifsbcin10.png

 That does not appear to be the whole story though because if I look at the 500hpa vorticity charts then there are clear signs of storm development. These I think are elevated storms.

attachicon.gif500vort12.pngattachicon.gif500vort15.png

 That again is not the whole story because we have suggestions of low level wind convergence zones towards Wales and western parts of the UK. These I think might be the focus of surface based storms as moisture pools in these regions.

attachicon.giflowwind12.png

 There might even be more to the story tomorrow in that later on drier air comes in aloft. Notice how there is not a clear demarcation edge as it moves north which would tend to suggest potential storm development along that edge. Equally there is a weak area of vorticity advection at the 700hpa level moving northwards late afternoon. This may or may not be important, I am not sure yet.

attachicon.gif500humid17.pngattachicon.gif700vort15.png

 Forecast SkewT's suggest a relaxing of the cap from the north moving southwards during the afternoon.

attachicon.gifbirmskewt12.pngattachicon.gifbirmskewt18.png

 What confuses me though is how the cap it is modeled to almost disappear completely in the north of England. I am not convinced by this as a cap does not normally weaken that much over a short distance and is usually overcome by high temperatures and dew points.

attachicon.gifmancskewt18.png

 So a mixed and confusing picture and still a chance that nobody will see any storms at all. After all those Iberian storms have not appeared yet today.

 

attachicon.gifrainprecip12.pngattachicon.gifrainprecip14.png

attachicon.gifrainprecip16.pngattachicon.gifrainprecip18.png

 

a good read and first class analysis from brick, well worth reading folks.

Share this post


Link to post
Share on other sites

  Modelling is not that much different overnight from Yesterday and there is still the risk of no storms at all today.

 

  An extract from Estofex had the following to say.

 

There are two factor that may limit the overall severity of the situation:
A/ Degree of initiation. With no strong synoptic-scale upward motion and in the capped airmass, it may be difficult to initiate storms. Initiation will be more likely in the evening hours as 850 and 700 hPa temperatures begin to drop from the west and cold front affects the area.
B/ Stable boundary layer. Due to the very hot airmass around 850 hPa, it will require a lot of heating to destabilise the boundary layer and allow storms to root in it. Thus, especially in the early period, most storms will stay elevated (with primarily hail threat), as they move from France towards England. Surface based development will be most likely in the late afternoon and early evening hours.

Level 2 is introduced for the area, where best CAPE/shear overlap is simulated, as well as with the best chances for the surface based storm initiation.

 

Go to the web site to see more   http://www.estofex.org/

 

Overnight soundings hint at the problem.

post-2809-0-65411300-1435743307_thumb.gi

 

Catch the mid day soundings at the following web site  http://62.202.7.134/hpbo/sounding_europe.aspx

 

That is a convective temperature of 37 Degrees. The cap however should begin to relax as the cold front approaches.

post-2809-0-95605300-1435743377_thumb.pn

Satellite water Vapour imagery suggests a curve of vorticity moving north and eastwards which should help development, but these might just initiate elevated storms. There is also a suggestion of some pre cold front troughing.

post-2809-0-62554800-1435743650_thumb.pn

 

To see more see Web Site   http://oiswww.eumetsat.org/IPPS/html/MSG/RGB/

 

 

Surface wind convergence varies during the day which could be focuses for development.

post-2809-0-73723200-1435743956_thumb.pnpost-2809-0-98517400-1435743962_thumb.pnpost-2809-0-72918200-1435743969_thumb.pn

 

The drier air aloft still sneaks in late on.

post-2809-0-00070300-1435744057_thumb.pn

 

I am not posting up any more of the modelling charts for today as I think events will over take the models at this point. So in conclusion I would say there is a risk of severe storms today, particularly with regard to hail, although I would still not like to pin point where and if they will occur.

 

post-2809-0-86768000-1435744647_thumb.pn

 

 

Share this post


Link to post
Share on other sites

Some great posts today ,and its great that we have the patience to wait for developements to happen in a science which is as we all know not an exact science .

put yourselves in a plane at say 40,000 ft and its one hell of a size area looking down at to try and predict where an area of storms will develope .After over 45 years of listening to forecasts even 12 hrs ahead many many surprises pop up .

todays recent  Gfs run is very interesting for my area yet 12 hrs ago it looked different .

The cold front to our west i feel is the key ,how active how fast moving time of arrival ,throw in the boiling kettle which is the UK ,in a nutshell Very complex ,i,m not directing this post at experienced Members but those new to the Weather Game ,which is a Game of many unknowns ,cheers gang , :drinks:

Share this post


Link to post
Share on other sites

Just copying this in here:

 

 

 

Only just got the chance to do a forecast for storms for later, but better late than never:

 

Storm & Convective Forecast

 

attachicon.gifconvmap_030715.png

 

Issued 2015-07-03 09:47:04

Valid: 03/07/2015 0600z to 04/07/2015 0600z
 
CONVECTIVE/STORM OUTLOOK - ISSUED 3RD JULY 2015
 
Synopsis
 

Slow-moving upper trough over the mid-N Atlantic to the west of the British Isles will become increasingly negatively-tilted over the next 12-24 hrs. Nose of 100knt jet at 300mb rounding the base of the trough will push NE across the western UK this evening with corresponding increase in SWly flow generally aloft. A sharpening shortwave trough will eject NE towards the UK from the base of the upper trough. At the surface, hot and moist airmass characterised by high theta-w values (16-18C) currently over France will advect back NW across the UK this evening and overnight to the south of northward moving warm front. Surface cold front moves in from the SW tonight, which combined with shortwave trough moving in from the SW and general cooling aloft, will create large scale ascent and destabilisation of the of high theta-w plume.

 

… ENGLAND, WALES, IRELAND and N. IRELAND …

 

A shortwave trough is very evident on water vapour imagery this morning between the Azores and NW Iberia around 15W, this will continue NE today and will later engage high theta-w plume spread NW from France across southern/central Britain and Ireland this evening and overnight. Over-running of the shortwave and associated cooling aloft atop of warm moist plume will create steep lapse rates and strong instability in the warm sector between warm and cold fronts moving N tonight. GFS indicates up to 800-1200 j/kg MLCAPE towards Sern and Ern England in the warm sector spreading N across England and Wales , somewhat less further west towards Ireland. Large scale ascent created by approaching shortwave, cold front and falling heights will support storm development initially over SW approaches, The English western English Channel/N France before storms develop further east then spreading in a broad line N and NE across S England, Wales, Ireland, Midlands and eventually N England and N Ireland later in the evening and overnight.

 

Storms will likely organise quickly, given 40-50 knts of 0-6km deep layer shear indicated with winds veering and strengthening sharply with height. This will support bowing line segments or even a few supercells, capable of producing large hail given fairly high CAPE values and also a damaging wind threat – so have issued a general SLIGHT risk across central, S and E England and Wales – where CAPE is highest. Winds backed easterly to the SWly flow aloft will also generate large Storm-Relative Helicity (SREH) values across S England later this evening, which suggests a tornado or two is not out the question if mesocyclones form – particularly before midnight when there maybe still sufficient diurnal warmth. Have included a hatched area rather than a higher risk here for the tornado threat, for now, as well as the risk of large hail and wind damage … given uncertainties over exactly where and when storms will form before moving NE across England and Wales later in the evening and overnight – the greatest uncertainty lies with eastward extent of storms given less forcing for ascent and more capping of the atmosphere towards SE England, despite more favourable severe parameters.


 
Issued by: Nick Finnis

 

Share this post


Link to post
Share on other sites

A memorable storm tonight would be a perfect way to go on one last chase in my trusty old work van Doug before I have to accept the inevitable and retire him from service.

Doug and I have been chasing storms for the last 3 summers and it was with him that I watched last year's colossal July 17th/18th storm develop and pass through.

Had some amazing times in that van and very sad to see him go. It really is like losing part of the family but time to move on.

To see another amazing storm tonight would be a fitting farewell to an old pal - maybe even a direct lightning strike would be nice - kinda like a Viking burial!

On a serious note though - I don't actually want to be struck by lightning - but I want him to see one last storm before he goes.

;-(

(Actually makes me feel quite emotional thinking about it)

Share this post


Link to post
Share on other sites

×
×
  • Create New...