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Storms and Convective discussion- 15th August onwards


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Didn’t know we was expecting an avalanche today 🤔

Stonking day for storms. Had two cells with continuous thunder [but mostly no visible lightning again]. Here's some pictures of one storm that I tracked as it progressed up the M11 which produced some

Am enjoying a weekend away 60 miles S of Prague in the pretty town of Písek, the storm front that came in this evening was dramatic! 

Posted Images

I was just having a closer look at my graphs from yesterday's downpour..  I had a pressure rise of 3mb within 1 minute..

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Many times i've seen the pressure rise just as a pokey shower hits, but it's usually under 1mb (still noticeable on my graphs) 3mb in a minute is quite something though?!

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Considering that the storm is starting to lose its intensity, I will post the rest of the images I managed to get from tonights storm:

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Remember when I posted about me seeing a +CG? This is the picture I got from it. The bolt was so bright it almost completely blew out my camera and made it look like daytime for a split second.

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I tried some photography on my SLR once again and this time it was easier because the bolts were lasting longer, but then the battery on it died not long after so I had to stick to my crappy phone footage. It was so amazing to see the whole cumulonimbus lighting up - it was massive and looked almost exactly like @staplehurst's photo banner on Twitter.

Edited by Zak M
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9 hours ago, Jamiee said:

image.thumb.png.13385ddb0087050e2db5317f3801985d.pngimage.thumb.png.7f97ac0a20f9465aa2ad2ecefd184bb1.pngimage.thumb.png.d053c3addd2c58df1c087bc84e619f4e.png image.thumb.png.91098fad82cef839e0e5cdb375de3c2f.png

It looks like some convergence from that deepening surface low helped strengthen that phenomenal bit of rain affecting Southend & Shoeburyness.

Shoeburyness measuring 22.6 mm within the latter half of the hour.

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I certainly dodged a bullet here, would be the highest rain rates I'd have seen for a good many years.

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Wind direction also appears to have change during the brunt of it, according to an automatic PWS & the Met Office station at Shoeburyness.

That change in wind direction is absolutely fascinating. I was stood on the seafront watching the rain approach from the west whilst simultaneously getting blasted by the wind from the east. A fascinating hours worth of weather.

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Well I wasn't expecting much from yesterday and I was all alone in the office at 5pm last night when i heard the all mightiest shot gun style thunder. Very heavy rain and interesting fast moving cloud bases.

I did read a couple of reports of others hearing very loud shotgun thunder. I know the loudness of thunder is related to the distance of the strike obviously, but I wonder whether these storms has a prevalence of positive lightning strikes? 

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1 hour ago, John90 said:

Well I wasn't expecting much from yesterday and I was all alone in the office at 5pm last night when i heard the all mightiest shot gun style thunder. Very heavy rain and interesting fast moving cloud bases.

I did read a couple of reports of others hearing very loud shotgun thunder. I know the loudness of thunder is related to the distance of the strike obviously, but I wonder whether these storms has a prevalence of positive lightning strikes? 

There was certainly a lot of positive strikes. It's not normal to see the positive strikes outweigh the negative strikes.

xx_blitze-en-330-0_2020_08_27_7523_1600.thumb.png.c03bf1e245faf581bff8982c9d667d00.png xx_blitze-en-330-0_2020_08_27_21010_1605.thumb.png.bcc878e831ba360f83b05b8b8971a829.png xx_blitze-en-330-0_2020_08_27_21010_1520.thumb.png.3d145e05c67cc334c3c98ea32b207f31.png

That squall seems to have had a lot of positive strikes after passing Bournemouth.

Edited by Jamiee
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largethumb.thumb.png.c62daba33d584671970f66436010c62e.png

Day 1 Convective Outlook: Fri 28 Aug 2020

VALID 06:00 UTC Fri 28 Aug 2020 - 05:59 UTC Sat 29 Aug 2020

ISSUED 06:20 UTC Fri 28 Aug 2020

ISSUED BY: Dan

Writeup:

On Friday, Britain and Ireland sit underneath a broad upper trough/low with the main jet activity displaced to the south. Cold air aloft atop initially relatively warm SSTs, and then diurnal heating inland, will yield 500-700 J/kg CAPE across the English Channel and central/southern Britain. Numerous showers are likely over the English Channel in particular initially, but many others will develop inland through the day - particularly aided by low-level convergence zones (such as southern England) near the surface trough axis. Beneath the upper low, shear will be fairly weak and so pulse-type showers/storms are moist likely, their outflow then enabling daughter cells to develop nearby. Some small hail may be possible in the most intense cells, and enhanced vorticity near convergence boundaries may bring the risk of a few funnel clouds or weak waterspout/tornadoes. Small surface low over the North Sea near Norfolk could also be the focus of some sporadic lightning into East Anglia as it drifts south during the afternoon and early evening hours.

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30 minutes ago, Jamiee said:

There was certainly a lot of positive strikes. It's not normal to see the positive strikes outweigh the negative strikes.

xx_blitze-en-330-0_2020_08_27_7523_1600.thumb.png.c03bf1e245faf581bff8982c9d667d00.png xx_blitze-en-330-0_2020_08_27_21010_1605.thumb.png.bcc878e831ba360f83b05b8b8971a829.png xx_blitze-en-330-0_2020_08_27_21010_1520.thumb.png.3d145e05c67cc334c3c98ea32b207f31.png

That squall seems to have had a lot of positive strikes after passing Bournemouth.

Again my theory about the lightning detection apps seems to be supported by real world evidence:

Yesterday blitzortung was showing a lot more of the strikes that were appearing on the Lightning Alarm app. My theory is that Blitzortung is calibrated to pick up more significant strikes which are likely to be CG and/or positive (I’m assuming positive intra-cloud is possible 🤔 never really thought about this) whereas other apps tend toward the elevated stuff and a large proportion are of the IC and/or negative.

Yesterday demonstrates that due to conditions (low based, long land track and surface nature of the storms/squall) along with anecdotal evidence as noted above that these strikes were more powerful and tended W toward the + CG variety.

In nearly all cases the LA app picks up far more sferics regardless of the storm type (perhaps some of these are multiple detections of the same strike, and some could also be false strikes due to an abundance of incoming data / scatter effect) and I’m assuming this is predominantly due to all reasonably mature storms invariably having at least some kind of elevated activity.

Hoping this is of interest to some, as I’m finding it a really useful tool at the moment to distinguish the mode of storms, which helps determine their likely duration and ultimate fate 🙂

Edited by Flash bang flash bang etc
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Morning all.

Not a lot of obvious instability around here.  But with some surface forcing it may be enough to get things going. Showers about but not electrified.

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Just repeating what I mentioned in the regional thread..

Just had another monster downpour. 103.8 mm/hr rain rate. 10.6mm for today, so far.

10 days ago, it was the driest August I had recorded. Now, it's the wettest I have recorded. 115mm has fallen in those 10 days.

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3 minutes ago, Atmogenic said:

Beautiful cumulus congetus right now eating lunch   

CF9E581C-9B5D-49EC-965D-8B2ABD8FD4F5.jpeg

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What do they eat?

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1 hour ago, Flash bang flash bang etc said:

Again my theory about the lightning detection apps seems to be supported by real world evidence:

Yesterday blitzortung was showing a lot more of the strikes that were appearing on the Lightning Alarm app. My theory is that Blitzortung is calibrated to pick up more significant strikes which are likely to be CG and/or positive (I’m assuming positive intra-cloud is possible 🤔 never really thought about this) whereas other apps tend toward the elevated stuff and a large proportion are of the IC and/or negative.

Yesterday demonstrates that due to conditions (low based, long land track and surface nature of the storms/squall) along with anecdotal evidence as noted above that these strikes were more powerful and tended W toward the + CG variety.

The strikes near to us in Newbury were quite impressive, with deep booming thunder.

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