Nick F

Convective / Storm Discussion Thread - 27th Feb onwards

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Thought I'd start a new thread as other one was rather long and started back in September. Monday looking rather lively across many areas convective-wise, as a cold vortex originating from southern Greenland drops SE over UK and creates rather steep lapse rates atop of moist maritime flow which will be weakly heated in the increasingly strong sunshine as we head into early Spring. Enough CAPE and wind shear forecast for me to warrant a marginal risk of severe weather toward SE England and E Anglia - primarily for isolated strong/damaging convective gusts in heavier showers/storms, but a brief isolated tornado can't be ruled out with veering winds and increasing strength with height.

Storm & Convective Forecast

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Issued 2017-02-26 23:12:52

Valid: 27/02/2017 00z to 28/02/2017 00z

CONVECTIVE / STORM FORECAST - 27TH FEB 2017

Synopsis

Upper low/cold vortex, that broke away from Polar Vortex over Greenland over the weekend, moves SE across the U.K. During Monday, steepening lapse rates and creating an unstable airmass across the U.K. A surface low, just NW of EIRE at noon Monday, will drift east across S Scotland in the afternoon / evening, a cold front will clear E Anglia and SE England early afternoon followed by troughs moving through in the increasingly cold but unstable SWly veering Wly flow.

... EIRE, N. IRELAND, ENGLAND, WALES, W SCOTLAND...

Increasingly cold air spreading east aloft (500mb temps <-35C across western U.K.) will create steep 850-500mb lapse rates (31-32C fall with height) atop of moist maritime airmass which will be weakly surface heated in sunny spells. As a result, models simulate 200-400 j/kg CAPE by early afternoon / peak warmth, this will support heavy showers and scattered thunderstorms which, given low heights / freezing levels, will produce hail, sleet and snow over hills (and lower elevations in heaviest cells) and also strong convective gusts. 

A low risk of localised severe weather does exist on Monday in association with more organised areas/band of storms that develop along cold front moving east across England and Wales during the morning and also one or two troughs following into the afternoon, particularly across the southern end where stronger winds aloft near jet and veering with height may allow forced convective updrafts along to organise. More organised bands of convection/storms would be capable of drawing strong winds aloft down toward the surface as isolated damaging gusts - perhaps 50-60mph inland and 60-70 with exposure in heaviest showers/storms. Also, winds veering and increasing with height may allow updrafts to rotate into a few funnel clouds or even isolated brief tornado/waterspouts. Therefore have issued a MARGINAL risk for southern counties + E Anglia where overlap of CAPE, wind shear / stronger winds aloft are enhanced.

Issued by: Nick Finnis

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I'm hoping to get lucky, even if it is just a rumble of thunder. I have found over recent years, that Winter has provided me with a lot of showers with thunder mixed it - probably more than the Summers over the past 5 years (not including 2016) but this Winter hasn't seen much of that. However, we're at that time of year where the sun is getting a little bit stronger, with cold air lurking near by, so hopefully, a few more set ups  like these occur. 

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Great and refreshing to see! Here's to a stormy and plumey 2017 :D 

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I have mixed feelings about this forecast. Flying into Gatwick later this afternoon so it could be a bumpy ride.

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Some nice little cluster of storms breaking out in northern France at the moment...

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First hail of the year, a light tinkling on the window for half a minute

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Almost pitch black sky to the east now the suns out, after a heavy hail, graupel shower.

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58b44f0f178dc_Radar4.05pm27thFeb2017.thumb.jpg.5f9737bff71dbe1975d98047b55cec5e.jpgYay, first stormy looking day of the year for me. The radar image was taken about 4pm.

 

 

 

These pics were taken just before 4pm today over Tower Hamlets. Incredible height of the towering cumulus and check out that dark base! Stunning.

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Edited by Windblade
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Been quite a quiet day so far here not much in the way of rain was hoping for some hail and if lucky some thunder but nothing so far...Roll on storm season hoping this year provides some good thunderstorms.

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Like the warmer parts of the year, looks like northern France and Belgium stole all the storms again, despite pretty cold uppers and relatively mild/moist surface airmass. French storms triggering along cold front which cleared southern UK overnight.

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A look at the skew-ts and 12z radiosonde ascents though suggest airmass is rather moist all the way up to the tropopause across much  of the UK today - which doesn't favour electrification of convection. So sferics been rather sparse today and convection messy.

Another chance on Tuesday for some convection with hail and the odd rumble of thunder in the cold polar NWly flow destabilised by weak surface heating in sunny spells.

Edited by Nick F
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Bright flash and loud bang about 10 mins ago, first of the year.

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1 minute ago, DAVID SNOW said:

Bright flash and loud bang about 10 mins ago, first of the year.

Awesome! 

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We've just had incredibly heavy hail here and its incredibly dark - like night time. Surprised there have been no flashes considering how dark things have got. Still, this is a great start to the year. Looking forward to seeing what happens on the storm front this year after the worst year for storms I can ever remember (2016).

Edited by Windblade
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1 minute ago, Windblade said:

Awesome! 

:)

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6 minutes ago, Windblade said:

We've just had incredibly heavy hail here and its incredibly dark - like night time. Surprised there have been no flashes considering how dark things have got. Still, this is a great start to the year. Looking forward to seeing what happens on the storm front this year after the worst year for storms I can ever remember (2016).

That passed through here it did go very ominous, some good type of weather for once, slushy deposits :p, I heard a mumble of thunder. And yep 2016 was absolutely dire. 

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5 minutes ago, Daniel* said:

That passed through here it did go very ominous, some good type of weather for once, slushy deposits :p, I heard a mumble of thunder. And yep 2016 was absolutely dire. 

Think that's about to hit me, pitch black to the West!

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I was right, some heavy rain and hail here. Saw what could have been a flash, but had the TV on so may have just been a reflection in the window, didn't hear anything

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Hey it's the CBeebies,lol

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IMG_1151.JPG

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Saw my first rainbow of 2017 this evening (bonus - it was a double!). Also driving home there were cells in pretty much every direction which looked beautiful as the sun was setting. Couldn't take any pics sadly as I was on a dual carridgeway, but even so it was a sight to behold and that coupled with the double rainbow the stormy skies of this afternoon and the radar imagary (including several uk strikes) has not only lifted my spirits (after a difficult start to the year for me) but has filled me with hope for a stormy 2017.

  

Edited by Windblade
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1 hour ago, Mokidugway said:

Hey it's the CBeebies,lol

IMG_1150.JPG

IMG_1151.JPG

They look like tornadoes! :laugh: Great pic!

Edited by Windblade
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A nice long rumble of thunder here just now, the first of 2017 and fingers crossed many many more to come this year. 
A nice rainbow here earlier as the sun was setting and some small hail earlier in the day. Certainly looking forward to the summer and some nice plumes moving up from the south!

- A second rumble a few seconds after the entire sky lit up. Polystyrene ball size hail and everything covered in white :)

Edited by <<Ryan>>
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12 hours ago, Spikecollie said:

Some nice little cluster of storms breaking out in northern France at the moment...

That probably explains the turbulence for a while on my flight from Mallorca to Gatwick this afternoon, we were in that vicinity at the time. Lightning also seen whilst driving home on the A21 this evening, around the Tunbridge Wells area.

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Posted (edited)

Springs almost here, two weeks to go (by my calculations - I don't go by the "1st March - quick everyone its spring!") but by the solstice which starts halfway through september so by my clock (and the weather patterns) spring starts around halfway through march.

 

Looking forward to the season getting underway proper. Bring on the storms.

Edited by Windblade
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8 minutes ago, Windblade said:

Springs almost here, two weeks to go (by my calculations - I don't go by the "1st March - quick everyone its spring!") but by the solstice which starts halfway through september so by my clock (and the weather patterns) spring starts around halfway through march.

 

Looking forward to the season getting underway proper. Bring on the storms.

 You mean the equinox? :-) 

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Some beefy looking storms with lightning near the channel islands.

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