Storm & Convective Discussion April 2016 Onwards

[William Grimsley]

7 minutes ago, weather09 said:

Yep, always difficult to predict likelihood of storm activity in any given area.  Can only point out the risk, and provide reasoning as to why there's a risk. This week was always expected to have low-risk days, anyway, given the setup we're under, so no real disappointments, in all. Really like the pics of convection people have been posting this week.  

Tomorrow, near enough same as today (i.e. low risk), so doesn't warrant the detail.  One thing to note, however, is how low dewpoints were today across the bulk of the country - generally 2-4C looking at obs throughout the day. Perhaps a factor explaining the lack of deep convective activity well inland.  Tomorrow, looks like moisture will be slightly better - models predicting sfc DPs to 8-9C, tops. Not impressive by any means, but it makes the difference. That, together with heating and marked light, converging flow would across central parts suggests a heightened risk tomorrow.  GFS not keen on building the CAPE, but few 100j/kg a safe bet where heating is maximised. Euro4 keen to break out shower activity afternoon/evening period. We'll see.

Looks good, unfortunately we have a thundery rain band coming up for the south tomorrow afternoon so convection here will be very limited, I'm hoping we get some thunder from the rain band that moves in later on tomorrow! Does anyone think there's a chance for me?

[Summer Sun]

VALID 06:00 UTC Thu 14 Apr 2016 - 05:59 UTC Fri 15 Apr 2016

ISSUED 20:20 UTC Wed 13 Apr 2016

ISSUED BY: Dan

Broad, elongated W-E orientated upper trough, stretching from Scandinavia to eastern Atlantic, west of Biscay, will begin to split on Thursday, as upper ridging approaches from both the north and south. Nonetheless, cold mid-levels atop diurnal heating will produce another day with 300-400Jkg-1 CAPE, with scattered showers and a few thunderstorms likely to develop through the day, especially late morning through to early evening.

Low-level wind convergence will once again play a key role in generation of convection, especially close to coasts. In broad terms, forecast profiles look moister than the past couple of days, with more cloud likely as a result and subsequently reducing/limiting amounts of insolation. Also, surface temperatures will be a little lower than the past day or so, and hence the slight reduction in CAPE exhibited in various models. However, with the upper trough splitting, the jet stream arm over southern France will begin to bulge northwards, serving to increase DLS to some 20-30kts.

Given these conditions, it is likely that showers will be more widespread over the SLGT area than the past couple of days, but with a lower chance per shower of producing lightning. Available DLS will help organise cells to an extent, which may allow better updraft/downdraft separation for cells to last longer and produce lightning. Mean westerly flow aloft also suggests showers/storms will be slightly faster moving than past couple of days, and while this would initially reduce the rain totals (and risk of flash flooding) it also allows backbuilding to occur, and so there is still a risk of 10-15mm falling in just 1 hour. There remains a chance of a few funnels or a weak tornado close to convergence zones, especially where surface winds become backed, and the strongest cells may also produce hail up to 1.5cm in diameter.

http://www.convectiveweather.co.uk/forecast.php?date=2016-04-14

[Wilxy]

Evening All.

Today was a interesting day convective wise, headed out towards Newbury to begin with today as a starting point to see if anything got going then some friends from the isle of wight came to the mainland for a chase and we headed for Salisbury where a very brief funnel cloud developed within the rain core but by the time I tried to find a place to pull over it wasn't visible as the rain was obstructing the funnel cloud, soon after that once I had got towards Salisbury hail began to fall which to me suggested that it was close to producing thunder, after that the shower moderated in strength and nothing more happened, as I was heading home some more showers developed over the West Country and along the M4 corridor, the showers over Newbury and the one over Farnborough produced some thunder and lightning but nothing from the showers where I was near as I was heading home but apart from that it was a Interesting days weather and has certainly been a great week convective wise.

Just a Couple of Pictures from today

Edited April 13, 2016 by tomjwlx

[Allseasons-Si]

Good post's mapantz and 009

very informative by you both and perfectley understandable,we keep forgetting that it's still spring and it has been quiet warm in the sunshine but get out of it and you can still feel the chill in the air,lets hope this convective spell last's well into summer with some good plumes affecting the uk instead of a kent clipper veriety and viewing webcams across the pond,also with the sst's around our shores being a little above average,that will help prevent storms dying out over the channel(a bit),still havn't had a storm here this year but close and heard a couple of rumbles south of here

all in all not a bad year so far and there has been some nice cloud pics to take from the last few days,chin up guys,remember that we are only in april and looking forward to the rest of spring/summer and early autumn for that elusive storm

might chase tomorrow if they are within,well if i have time to get to them before they die out,hopefully they will be a bit closer tomorrow,good luck guys

p.s,anyone get that storm on vid over Canterbury.

[Flash bang flash bang etc]

Well tomo I'm starting off in Eastbourne for a quick camera job then up to beckenham for some IT work. So whilst I'll be 'at work' I'll be doing so in areas that in recent days have been more prone to convective showers that have the 'fun element' ie: Lightning - which is where my interests lie.

While I do love seeing developing convection I'll be honest and say without lightning it's all just big clouds to me so hoping tomorrow I do get to see something, although I'm travelling because I have to so its not a big deal if it all goes flat.

Here's hoping, but preparing for nowt!

 

[Greeny]

Ah hell I'll post some charts

Tomorrow has an elongated upper trough that sits across the breadth of Wales England and Ireland as shown in the chart below, coupled with steepened lapse rates that follows the trend of the trough

The convective precipitation chart also follows that pattern..

GFS predicts thin cloud cover into the afternoon..

Wind convergence is also present however as an additional trigger for storms to fire. Again this stretches across the country and slowly moves north within the highest storm risk area..

500hpa winds (around 18000 feet) suggest storms that do fire will take a typical Northeasterly path and perhaps a little stronger for storms to move quicker than the ones from today..

At the same height temperatures of around -30 will be present and where storms will be present could contain hail..

Surface based CAPE will be rather meagre according to GFS but can still fire some storms given diurnal heating and wind convergence zones.

Not much deep layer shear to throw into the mix so as before storms that do fire will probably be pulse like in nature.. (without the chart low layer shear may be non existent)

Temps being reasonable again tomorrow, between 11 - 13C which could max at 15-16 degrees for diurnal heating and dewpoints higher than today as mentioned by Weather09 to give us a little more moisture. I must admit though this afternoon did feel a bit humid in the heat for once whilst the isolated storms was around. Anyway precipitable water (PWAT) again is very similar to what it was today. There maybe many places not seeing a thing again tomorrow and to me it seems a smaller area that today too but as an amateur I could be mistaken. I will add the convective overview with the temp chart..

Anyway good luck to all who are in for a chance tomorrow to at least get a rumble or two. A little bit of advance forecasts sees some moisture coming up from the continent and then next Thursday another reasonable day forecast of CAPE albeit a little early just yet so I don't think we are going to get a long period of time without anything just yet. Forever the optimist, good things come to those who wait! When it does arrive you will indeed really appreciate it!

Edited April 13, 2016 by Greenday

[Neilsouth]

Local Forecast : One or Two Thundery showers affected the UK

National Forecast : A few nasty storms about today, especially towards Kent

 

Did the lady on the local actually check the radar today? 

[Ben Sainsbury]

16 minutes ago, Neilsouth said:

Local Forecast : One or Two Thundery showers affected the UK

National Forecast : A few nasty storms about today, especially towards Kent

 

Did the lady on the local actually check the radar today? 

Aha brilliant! I always have something to complain about too! aha

[Mesoscale]

Check out this tornado in Belgium yesterday.
 

And a waterspout that turned into a tornado in Northern Spain, did some damage to trees. 
 

 

Edited April 13, 2016 by Mesoscale

[Cheshire Freeze]

Weird area of heavy precipitation has formed in N Wales....I say weird because it looks to slowly be heading N but (the only way I can describe it) the heavy pulses seem to be being sheered due E. Almost like water being sprayed at an object and it running to either side rather than through.

[Gordon Webb]

THU 14 APR 2016: A SLIGHT chance of thunderstorms:

Broad, elongated W-E orientated upper trough, stretching from Scandinavia to eastern Atlantic, west of Biscay, will begin to split on Thursday, as upper ridging approaches from both the north and south. Nonetheless, cold mid-levels atop diurnal heating will produce another day with 300-400Jkg-1 CAPE, with scattered showers and a few thunderstorms likely to develop through the day, especially late morning through to early evening.

Low-level wind convergence will once again play a key role in generation of convection, especially close to coasts. In broad terms, forecast profiles look moister than the past couple of days, with more cloud likely as a result and subsequently reducing/limiting amounts of insolation. Also, surface temperatures will be a little lower than the past day or so, and hence the slight reduction in CAPE exhibited in various models. However, with the upper trough splitting, the jet stream arm over southern France will begin to bulge northwards, serving to increase DLS to some 20-30kts.

Given these conditions, it is likely that showers will be more widespread over the SLGT area than the past couple of days, but with a lower chance per shower of producing lightning. Available DLS will help organise cells to an extent, which may allow better updraft/downdraft separation for cells to last longer and produce lightning. Mean westerly flow aloft also suggests showers/storms will be slightly faster moving than past couple of days, and while this would initially reduce the rain totals (and risk of flash flooding) it also allows backbuilding to occur, and so there is still a risk of 10-15mm falling in just 1 hour. There remains a chance of a few funnels or a weak tornado close to convergence zones, especially where surface winds become backed, and the strongest cells may also produce hail up to 1.5cm in diameter.

Edited April 14, 2016 by Gordon Webb

[Gordon Webb]

so to sum up the above forecast

so more mositure more cloud less heating less cape more showers less chance of lightning per shower higher dls in places showers may survive longer and have slightly higher chance to produce lightning showers moving a little faster but may allow backbuilding

seems if everythnig goes right in one location you may get some T & L but there is also a few get out clauses if you don't

[Gordon Webb]

seems to be a bit of cloud and ran about already and a little further north than i would have expected and a few more showery bits further south sunshine for some might be in short supply today

Edited April 14, 2016 by Gordon Webb

[alexisj9]

4 hours ago, CreweCold said:

Weird area of heavy precipitation has formed in N Wales....I say weird because it looks to slowly be heading N but (the only way I can describe it) the heavy pulses seem to be being sheered due E. Almost like water being sprayed at an object and it running to either side rather than through.

Probably some sort of wind shear. 

[Flash bang flash bang etc]

Loads of AcCas about first thing this morning. Great to look at but by the time I got to the coast it was all starting to burn off and move northwards. Got some sun but coming and going with cloud now.

All the storms are gonna be in the north, which is where I was yesterday. Sod's law really.

[Nick F]

Breeze convergence zone shown on GFS below, likely to be the focus for storms developing across central areas today:

Netweather storm forecast for today:

Storm & Convective Forecast

Issued 2016-04-14 08:47:43

Valid: 14/04/2016 0600z to 15/04/2016 0600z

CONVECTIVE FORECAST - THURSDAY 14TH APRIL 2016

Synopsis

Broad upper trough extends SW across northern and western Europe, an area of low pressure to the SW moves NE towards SW England by midnight, shallow low pressure centred over the N Sea. A slack, warm, moist and unstable flow covers England and Wales. A cool and stable flow covers Scotland.

... Sern EIRE, WALES, MIDLANDS, Sern N ENGLAND, LINCS, E ANGLIA ...

Cold mid-level temperatures and surface heating will create sufficiently steep lapse rates for showers to become increasingly heavy and turn into thunderstorms locally in the above areas. Given weak synoptic forcing, storms will likely be focused near a E-W breeze convergence zone indicated by models to extend from central or north Wales towards Lincs/Norfolk. Thunderstorms maybe accompanied by hail, with an isolated risk of large hail >1.5 cm. Also there is a risk of localised flooding, given weak winds aloft leading to slow-moving nature of storms and large spot totals from heavier downpours. In mind of this, have issued a MARGINAL risk of severe weather for above areas. Funnel clouds and even brief/weak tornadoes or waterspouts can't be ruled out with stronger strorm updafts given weak upper winds/surface convergence.

[Gordon Webb]

 

can I assume that orange line is the breeze convergence line where the focus for storms will be as I cannot read these maps very well

Edited April 14, 2016 by Gordon Webb

[Chris.R]

Might be our turn a bit now. Warning out for the far south of the region. 

[Ben Sainsbury]

14 minutes ago, Chris.R said:

Might be our turn a bit now. Warning out for the far south of the region. 

Who gave out the warning?

I see the Met Office, what I find strange is that we've already had 2 days of similar conditions and they haven't issued a warning, maybe today they are more confident with this setup?

Edited April 14, 2016 by Ben Sainsbury

[Gordon Webb]

 

at 3pm seems to tie in with convergeance zone marked by Nick so I'm hopeful the worst will actually be to my north by then I can Always hope

[Gordon Webb]

14 minutes ago, Ben Sainsbury said:

Who gave out the warning?

I see the Met Office, what I find strange is that we've already had 2 days of similar conditions and they haven't issued a warning, maybe today they are more confident with this setup?

 

yep they have all areas in this warning affect from 1pm to 9pm which is stretching it a bit as the greater instability moves north with time according to GFS and this warning only states what has been forecast for two or 3 days now heavy showers / thunderstorms which not everyone will see

 

think they're bit behind on this

[Chris.R]

 Anyone know what the direction storms will be travelling is today? Looks like NNW becoming NW to me but I might be  looking at the wrong thing. 

[Gordon Webb]

not really much in the way of sunshine here at the moment rather cloudy with showers on way from south

[Gordon Webb]

latest news 24 from bbc has heaviest downpours at 3 or 4pm north midlands moving North and even though i don't like repeating myself even though i do quite often  it seems this ties in with the area of focus and convergence that nick mention in his forecast and the bbc graphics are far less intense than what they were yesterday where they had lightning symbols here there and everywhere

still dull here

[NO LONGER POSTING]

Really not expecting much today, I hope I am wrong it's just there is a lot of cloud moving North with the next lot quick on it's heels to the South..

 

The window of "heating" is very minimal