Convective / Storm Discussion Thread - 27th Feb onwards

[Convective]

First of hopefully many forecasts this year.

[Nick F]

Storm & Convective Forecast

Issued 2017-03-27 22:06:15

Valid: 28/03/2017 00z to 29/03/2017 00z

CONVECTIVE / STORM FORECAST - TUESDAY 28TH MARCH 2017

Synopsis

A large scale upper trough extends south across much of the far N Atlantic to the west of the British isles, a shortwave trough moves NE on the eastern flank of this trough across the British Isles on Tuesday, triggering some heavy showers and isolated thunderstorms as it co-incides with diurnal heating.

... IRELAND, WALES and ENGLAND ...

Shortwave trough / closed upper vortex is evident on WV imagery to the SW of Ireland this evening moving out of northern Bay of Biscay. This shortwave will continue NE over Ireland / western UK on Tuesday - creating forced ascent of air and cold mid-level air embedded in this trough will steepen lapse rates all of which combined with surface heating in sunny spells during the day will support convective cloud development leading to scattered heavy showers and isolated thunderstorms which will move NE across the above areas.

Strengthening SWly flow into the afternoon and some some wind veering with height from the surface will increase deep layer shear to 30-50knts which, with a up to 500 j/kg CAPE forecast, may organise convection enough to generate some isolated hail to 1cm with stronger updrafts. Dew point - temperature spread across eastern England will be fairly high, so cloud bases will be fairly high here, while temperatures in the west will be fairly subdued limiting scope for strong storm activity. So not anticipating any organised severe weather. 

Issued by: Nick Finnis

 

[Chris Lea-Alex]

12 hours ago, Convective said:

First of hopefully many forecasts this year.

Isle of man is right in between those amber blobs. You getting owned!

[Arnie Pie]

14 hours ago, Mapantz said:

@Arnie Pie Might be on tomorrow!

 

I`m across in Halesowen( close enough) on sibling duties for the foreseeable......cameras are packed just in case

cheers for the heads up Mr Pantz

[Boro Snow]

just watched the latest BBC forecast no mention of any storms, have things changed

[toggerob]

Its not going to be a full-blown 'summer thunderstorms' risk, but rather heavy showers with the possibility of slight hail and occasional lightning. That being said the warmth of the sun is noticeable this time of year as it rises higher in the afternoon sky, once this morning's fog and mist cleared it was quite pleasant.

[matty40s]

Line of showers now forming arc NW and se of the Severn estuary. Not good as painting a boat outside in droitwich today.

[MP-R]

Currently having a very light shower of 50p sized raindrops, while the sun is also shining and feeling warm lol. Certainly feels like the first 'summery style' convective day. Can see cbs out west too.

[matty40s]

 

Bugger.. 

[Supacell]

Well we have some sferics being detected to the SW of Birmingham

[matty40s]

I know, that's what just passed over me

[Sparkiee storm]

Thought I heard a rumble to the south, then looked at the radar and saw that over the Birmingham area.

[Nick F]

Lightning detected over Midlands in the past hour, thundery showers now moving away NE toward N England. Were sferics over Ireland too earlier.

[pip22]

17 minutes ago, Nick F said:

Lightning detected over Midlands in the past hour, thundery showers now moving away NE toward N England. Were sferics over Ireland too earlier.

I'm under that red blob near Liverpool. It is very dark here and looking like its gonna thunder.

[Chris.R]

 Just heavy rain for a minute before but feels good today.  Nothing producing lightning up here. 

Edited March 28, 2017 by Chris.R

[Supacell]

I can't wait until the true thunderstorms, only about another month until the proper storm season kicks in. It's gone dark here as the ex-thunderstorm from Birmingham trundles towards with it's residual rain.

[Mokidugway]

Very convective feel out now ,first of the year 

 

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Wed 29 Mar 2017 - 05:59 UTC Thu 30 Mar 2017

ISSUED 16:48 UTC Tue 28 Mar 2017

ISSUED BY: Dan

... IRELAND / NORTHERN IRELAND ...

On the forward side of an upper trough, strong deep layer shear overlapping some marginal instability (in the post-frontal environment) may be sufficient to allow a few scattered showers / weak thunderstorms to develop during Wednesday afternoon. Relatively low LCLs and backed/curved low-level hodographs gives the potential for a brief tornado, albeit low-level flow is quite slack.

... S WALES / SW ENGLAND ...

A low risk of some embedded elevated convection on the forward side of the frontal boundary within a higher WBPT plume during Wednesday evening and night.

http://www.convectiveweather.co.uk/forecast.php?date=2017-03-29

[Arnie Pie]

Spot on @Manpantz

Manage to be in the right place to catch my first thunderstorm of the season, directly overhead, while at the cider hut in Romsley .

A potent little cell with plenty of updraft that gave out a couple of flashes and 5 mins of pea hail which left a covering on our bowls green.

with my cameras at my parents house....I took a couple of photos on my brothers phone.........which i will upload when we work out how to ( techno dino`s) 

 

Edited March 29, 2017 by Arnie Pie

[Chris Lea-Alex]

2 hours ago, Arnie Pie said:

Spot on @Manpantz

Manage to be in the right place to catch my first thunderstorm of the season, directly overhead, while at the cider hut in Romsley .

A potent little cell with plenty of updraft that gave out a couple of flashes and 5 mins of pea hail which left a covering on our bowls green.

with my cameras at my parents house....I took a couple of photos on my brothers phone.........which i will upload when we work out how to ( techno dino`s) 

 

Is that ball lightning on the right?

 

[NUT]

A few flashes and bangs kicking off in Ireland now

[Windblade]

Yes, I see that on the radar. Looks like a small thundery shower, but none the less I'd love to see it. Just started spitting here in tower hamlets, although its been quiet all week in the southeast in general (I work in different areas each day but am always south east based). The weekend looks a little more promising, but also uncertain at this stage so will have to wait and see.

 

Question - I am aware that storms require heat to form (that much is obvious as the clouds are made of evaporated water) so with that in mind how is it possible to get storms in cooler conditions? How else can they form? I always assumed they needed a lot of heat for evaporation to occur and build into a huge cb? There is the term "surface based", but aren't all storms and clouds surface based anyway as that's where the water that condenses into clouds comes from? Don't get me wrong - I understand exactly how storm clouds (cb's) form and how storms become electrified etc. My question relates to exactly how can a storm possibly form any other way except by using evaporated water from the heated surface (surface based) and so why are storms often referred to as "surface based" as if there's another way they can form? Am I missing something?

 

Trying to broaden my knowledge here, so if anyone can help me out I'd be grateful.

Edited March 29, 2017 by Windblade

[Mapantz]

21 minutes ago, Windblade said:

Yes, I see that on the radar. Looks like a small thundery shower, but none the less I'd love to see it. Just started spitting here in tower hamlets, although its been quiet all week in the southeast in general (I work in different areas each day but am always south east based). The weekend looks a little more promising, but also uncertain at this stage so will have to wait and see.

 

Question - I am aware that storms require heat to form (that much is obvious as the clouds are made of evaporated water) so with that in mind how is it possible to get storms in cooler conditions? How else can they form? I always assumed they needed a lot of heat for evaporation to occur and build into a huge cb? There is the term "surface based", but aren't all storms and clouds surface based anyway as that's where the water that condenses into clouds comes from? Don't get me wrong - I understand exactly how storm clouds (cb's) form and how storms become electrified etc. My question relates to exactly how can a storm possibly form any other way except by using evaporated water from the heated surface (surface based) and so why are storms often referred to as "surface based" as if there's another way they can form? Am I missing something?

 

Trying to broaden my knowledge here, so if anyone can help me out I'd be grateful.

You're probably looking for the term; elevated thunderstorms.
I've been in a pretty good location for these over the years, as some move up from France, bringing little in the way of rain, but frequent lightning and not much in the way of audible thunder.

A couple of links:

http://www.theweatherprediction.com/habyhints3/729/
http://www.weather.gov/source/zhu/ZHU_Training_Page/thunderstorm_stuff/elevated_convection/elevated_convection.html

Re Saturday; Nice to see another chance of some thunder, perhaps a bit more widespread.

[Chris.R]

34 minutes ago, Windblade said:

Yes, I see that on the radar. Looks like a small thundery shower, but none the less I'd love to see it. Just started spitting here in tower hamlets, although its been quiet all week in the southeast in general (I work in different areas each day but am always south east based). The weekend looks a little more promising, but also uncertain at this stage so will have to wait and see.

 

Question - I am aware that storms require heat to form (that much is obvious as the clouds are made of evaporated water) so with that in mind how is it possible to get storms in cooler conditions? How else can they form? I always assumed they needed a lot of heat for evaporation to occur and build into a huge cb? There is the term "surface based", but aren't all storms and clouds surface based anyway as that's where the water that condenses into clouds comes from? Don't get me wrong - I understand exactly how storm clouds (cb's) form and how storms become electrified etc. My question relates to exactly how can a storm possibly form any other way except by using evaporated water from the heated surface (surface based) and so why are storms often referred to as "surface based" as if there's another way they can form? Am I missing something?

 

Trying to broaden my knowledge here, so if anyone can help me out I'd be grateful.

 I'd say storms don't necessarily need heat to form but more a temperature contrast between  areas; whether that be the warm sea or the warm land in contrast with colder air aloft.  The sun heating the land causes this in summer (insolation) and the warm sea in winter. Also, as far as I understand, storms can form through temperature contrasts in different hights of the atmosphere; for example a warm inversion layer below colder air as in a plume. This can create elevated convection which is by definition not surface based as it doesn't rely on conducive conditions at the surface. This is why you see storms on summer nights   Even without any insolation.

Edited March 29, 2017 by Chris.R

[Windblade]

Hey guys,

Thank you for explaining, and for the links. I'm not sure I understand all the terminology in the articles but I think I get the general idea behind it all. I've witnessed thundersnow on two occasions (both at night - it's an awesome spectacle and something not easily forgotton) and it's always baffled me how it was possible for a big enough cloud to form that then becomes charged when the temperature was at freezing or below. I've always gone by the assumption you need an excess of heat for evaporation to occur in a high enough quantity to make a storm and would also explain why there are hardly any winter storms. I didn't realise if there was a big enough temperature difference it can create a different kind of storm. Still, if thats all you need why aren't there more storms in the winter?

Edited March 29, 2017 by Windblade