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Convective Outlook - Ireland & UK - Mon July 13th

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Author Topic: Convective Outlook - Ireland & UK - Mon July 13th  (Read 501 times)
martinastro
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« on: July 12, 2009, 05:57:17 pm »

From Tony Gilbert



Moderate Risk of General Thundery Showers Eire, SW UK, Wales through to northern UK & Scotland 09Z-21Z

Slight Risk of Tornado Development SW UK & S. Wales 15Z-21Z

UKMO Fax charts are currently undergoing changes with every update. Though looks to forecast some early pre frontal troughing Wales & Scotland ahead of the occlusion over Eire. The two appear to merge at some point over the UK but this ATM is not that clear!

 The synoptic conditions that stand out with this convective outlook is a diverging split jet at 500mb and just a head of this a very strong upper jet stream arcing toward a near anti cyclonic flow. Though this elevated flow may have the effect of creating a zone of NVA (or weak PVA) within the differential upper shearing layers!  Though ATM some moderate PVA at least is noted up to 700mb SW UK & Wales later in the day. If I had not identified this factor I doubt that I would have made any reference to the risk of tornadoes.

Within the red box mid level shear is showing around 45kt. This combined with relatively weak surface vector should easily create a well supportive  convective regime. Also up to 90 deg / 30kt shear vector below 850 mb creates enough low level vorticity for the basic level risk of tornado genesis. Negative points here regarding tornado development is that we are basing this risk within the dynamics of an occluded front with as expected very restricted potential instability through lack of any dry air incursion.

A convective gust calculation based on the mean average wind flow between 800 mb and 600 mb for this region is approximately 40kts (non severe)

The remainder of the white box zone can expect fairly scattered isolated thundery showers for much of the day with the prime risk being cloud to ground lightning.

Certainly some uncertainties here regarding timing and hense outcome and will probably need an update in the morning


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scott86
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« Reply #1 on: July 12, 2009, 06:16:17 pm »

intesnse thunderstorm over lisburn!!!! lightning is unbelievable!!!!!
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John9929
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« Reply #2 on: July 12, 2009, 06:23:01 pm »

Seen some of it from Maghaberry, continuous thunder here but it by-passed us here. Still rumbling on as I write.
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John9929.
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« Reply #3 on: July 12, 2009, 06:27:21 pm »

Have just caught images of a spectaculur shelf to the north of me!
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martinastro
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« Reply #4 on: July 12, 2009, 06:31:05 pm »

You guys sound like your getting a good show..get some images please. By the way, this is the outlook thread for Mon..but no worries. Amazingly there was no outlook forecast for Sun, I'm assuming the forecasters are taking a break for the 12th weekend.

Sunday evening has 500-600 CAPE and LI o f-1.

Good job catching that shelf Padraig...happy days  Smiley
« Last Edit: July 12, 2009, 06:34:52 pm by martinastro » Report Spam   Logged

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« Reply #5 on: July 12, 2009, 06:39:48 pm »

i think ive just broke my camera, was trying to get a good capture of the lightning then there was a huge ic bolt right above the house,, the thunder was instantaneous and damn loud! and the camera flew out of the hand as i was jumping out of my skin!! completely took me by surprise!
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martinastro
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« Reply #6 on: July 12, 2009, 07:05:42 pm »

What an experience Scott!!, I hope your camera is OK...fingers crossed.

Large chunky shelf cloud passed over here, not much in the way of rain but there where several areas of strong rotation under the sculptured base, still visible here at the min and still rotating.
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« Reply #7 on: July 12, 2009, 07:16:33 pm »

another heavy shower here at the minute but i cant hear much because of Oxegen nearby booming away
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« Reply #8 on: July 12, 2009, 07:24:30 pm »

camera seems to be ok, got a vid up on youtube,, it isnt great but the thunder was constant!
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« Reply #9 on: July 12, 2009, 08:02:46 pm »

That's fantastic Scott!!, excellent job and stunning thunder!  Wink

That shelf cloud I reported earlier turned into a thunderstorm over the NE section of Maghera. It was quite stunning with clusters of almost continuous long duration rumbles of thunder which was a thrill to hear on sucn a sunny Sunday evening. Nice rainbow cutting through the back of the storm too with distant shelf hugging low to the ground. Seemed to be an equal combination of low level and mid level convection. Storm wasn't really photogenic but the thunder was excellent!.

That storm might pass near Brian's location...
« Last Edit: July 12, 2009, 08:04:24 pm by martinastro » Report Spam   Logged

martinastro
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« Reply #10 on: July 12, 2009, 08:06:17 pm »

Here's the lightning activity so far this evening from ATD sferics. Matches up well with the reports...

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« Reply #11 on: July 13, 2009, 12:48:20 pm »

Started really nice this morning and in the sun it was quite warm but now theres very heavy rain that hasnt stopped for a good while spreading up from the south im surprised theres no thunder in it
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« Reply #12 on: July 13, 2009, 01:25:53 pm »

over an hour now with this torrential rain have just heard thunder over the Dublin direction again
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martinastro
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« Reply #13 on: July 13, 2009, 02:18:16 pm »

Big storms in central Ireland and heading for NI now.
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« Reply #14 on: July 13, 2009, 04:33:25 pm »

Weather is starting to pep up a bit for me now, but sure does look like you folk have been having some REALLY lively weather today!  Smiley
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