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27-06-2020, 21:03   #1756
Oneiric 3
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Originally Posted by Gaoth Laidir View Post
The KO index is fairly good in warm and muggy situations like last Thursday where convective instability was present (we needed someting to lift the air to get convection started). It takes into account the difference in temperature and moisture between low and mid levels. A KO value of <2 means thunderstorms are likely, as long as there is some lifting mechanism present (from an upper shortwave and/or uplift over terrain/convergence). The sounding from that Wicklow storm below shows a KO Index of 0 (box on the right), which tallies with what happened.



CAPE is the first thing to look at, though. If there is no CAPE then that's it. If there is CAPE then it must be released, which is what didn't happen Thursday afternoon because there was too much of a cap (warm layer of air 1-2 km up) that stopped surface air parcels from rising high enough (to the level of free convection). If the CAPE is released then the Lifted Index (LI) is the next thing to look at as it tells us how many degrees warmer the rising air parcel is than its surrounding air at the 500-hPa level, however this only relates to surface-based convection. A similar index for eleveated convection is the Showalter Index, which is like the LI but for a parcel raised from the 850-hPa level, not the surface. In the sounding above the SI is about -3. A value of -4 or less means severe thunderstorms.

The other indices in that sounding are the Vertical Totals (VT) and Total Totals (TT). The VT is just the difference in temperature between 850 and 500 hPa (the higher the better) and the TT is the VT plus the the difference between the 850-hPa dewpoint and the 500-hPa temperature. A value of >50 means severe thunderstorms are possible and >56 means severe storms with tornadoes.

The EUMeTrain website is an excellent learning tool for lots of different situations. This page describes some of these indices in more detail.
This post should be given its own thread and pinned to the top of the main page. Informative posts like this, not to mention the work put into it, are too easily lost forever in dynamic threads like this.
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28-06-2020, 10:43   #1757
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This post should be given its own thread and pinned to the top of the main page. Informative posts like this, not to mention the work put into it, are too easily lost forever in dynamic threads like this.

Couldn’t agree more. Thanks so much to Gaoth Laidir. It’s exactly why it’s so good for punters to be able to tap into all the combined knowledge of the real experts on this board. A lot to get to grips with but I can already understand a bit more of what I saw in the build/up to last week.

Gaith Laidir, I’ll go to that website and read a bit more on all this. Thanks again.
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01-07-2020, 09:55   #1758
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Small chance of some thunderstorms in south Munster, more so along coastal areas and Coastal Cork I would think has the highest chance as convection matures and reaches an area of convergence . Low chance and short lived if they do happen I reckon in the afternoon.
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01-07-2020, 19:21   #1759
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Lightning in Carlow and N Wexford
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01-07-2020, 19:32   #1760
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Thunder and torrential rain - Carlow/Wexford border. Very angry looking sky to the S/E. Wonder if we'll see some sparks.
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01-07-2020, 19:44   #1761
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Thunder and torrential rain - Carlow/Wexford border. Very angry looking sky to the S/E. Wonder if we'll see some sparks.
Yes looking towards mount Leinster from Ardattin near tullow , it looks impressive
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01-07-2020, 20:11   #1762
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My view of that thunderstorm looking towards Gorey

https://twitter.com/Arklowweather/st...523897346?s=19
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01-07-2020, 20:43   #1763
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Looking at radar I would expect a few sparks in the south Dublin area soon too.
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01-07-2020, 21:00   #1764
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Looking at radar I would expect a few sparks in the south Dublin area soon too.
I disagree, not a lot to suggest embedded activity
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02-07-2020, 00:18   #1765
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Seen these on fbook apparently taken near Ballycanew co wexford this evening
Attached Images
File Type: jpg Screenshot_20200702-001504_Facebook.jpg (574.1 KB, 152 views)
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02-07-2020, 00:21   #1766
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2nd shot
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02-07-2020, 00:52   #1767
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Impressive looking if it's real.
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02-07-2020, 00:53   #1768
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AFAIK it was near Ballycarney and there was another near Monageer.

Last edited by Cantona's Collars; 02-07-2020 at 02:14.
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03-07-2020, 13:48   #1769
pauldry
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Just wondering is there anywhere to get the rainfall figures from last Fridays intense Thunderstorm in Sligo and Leitrim?

Markree has 5mm so they didnt get it but Sligo had 39mm as did Leitrim and North Mayo hence landslides.in Drumkeerin.

Yet Finner and Markree dont have much rain from it.

Where do I get accurate data for places that were hit?
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03-07-2020, 14:58   #1770
Danno
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Just wondering is there anywhere to get the rainfall figures from last Fridays intense Thunderstorm in Sligo and Leitrim?

Markree has 5mm so they didnt get it but Sligo had 39mm as did Leitrim and North Mayo hence landslides.in Drumkeerin.

Yet Finner and Markree dont have much rain from it.

Where do I get accurate data for places that were hit?
Try Sligo Airport data here: https://wow.met.ie/stations/20200703...ix3byyb96spgyy

Click on Data Display to set your parameters.

Friday June 26th - 18mm
Saturday June 27th - 25mm
Sunday June 28th - 32mm
Monday June 29th - 12mm

That is 87mm over a long weekend!


Also of interest there:

Quote:
14/06/2020 15:30 17.3 7 See details
14/06/2020 16:00 16.0 24 See details
Went from 7mm to 24mm in half an hour!

Last edited by Danno; 03-07-2020 at 15:05.
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