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Convective Outlook - Ireland & UK - Thurs July 16th

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Author Topic: Convective Outlook - Ireland & UK - Thurs July 16th  (Read 452 times)
martinastro
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« on: July 16, 2009, 11:46:12 am »



Storm Forecast Issued: 2009-07-15 21:12:00
Valid: 2009-07-16 00:00:00 - 2009-07-16 23:59:00

Regions Affected
*SE & CS ENGLAND*, Midlands, Home Counties, Southwest England, south Wales, Scotland, Northern Ireland, Ireland ( all of the UK is included in the WATCH )

Synopsis
A complicated setup on Thursday, and one that will require close monitoring. An area of LOW pressure to the northwest of Scotland, and a second LOW pressure rapidly approaching from the southwest, will determine the weather conditions across the UK. Across Scotland, Ireland and Northern Ireland, daytime showers and thunderstorms will develop in response to daytime heating and local convergence zones. Light winds will ensure that the showers/storms will be slow-moving, and hence a risk of flash-flooding. Hail may accompany some of the showers/storms, though it must be highlighted that the risk of thunderstorms is somewhat less than recent days. Any showers/storms that do develop should decay during the evening hours. Elsewhere, cyclogenesis is forecast to occur over the Bay of Biscay as a sub-tropical area of LOW pressure deepens rapidly. At the same time, a plume of warm and moist air is advected across France towards the UK on the eastern flank of the LOW. The interaction of the two is expected to result with thunderstorm initiation across northern France during the late afternoon and evening hours. As the LOW rapidly approaches from Biscay, the thunderstorms are expected to rapidly merge into a large MCS, which is then forecast to move into the South/Southeast of England. The exact track of this MCS is far from certain – there is a lot of differences between the models, with some indicating that it may not even make it to UK shores, but may move across NE France and into Belgium instead. Nevertheless, the MCS will be developing in a very favourable environment for severe thunderstorms, and may take on supercellular characteristics, including the threat of moderate hail, locally extreme rainfall and perhaps tornadoes. Over Southwest England, an upper warm front will develop outbreaks of persistent rain during the afternoon hours, moving into the south Midlands/south Wales during the evening. Models are struggling with this scenario as to whether this rain will be electrical or not – current thinking is electrification will increase here in the evening hours, though it is not expected to be too widespread. Given the uncertainties present with regards to positioning, intensity of rainfall and eletricification, an update may be issued during Thursday as and when necessary.
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jgs001
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« Reply #1 on: July 16, 2009, 11:49:21 am »

Interesting... What's an MCS Martin ? It looks like I'm in for a hammering.. wonder if there'll be any photo ops here.
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John
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martinastro
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« Reply #2 on: July 16, 2009, 12:18:48 pm »

Hi John, MCS is short for Mesoscale Convective System which is a cluster of enormous thunderstorms, often severe storms, which are so large and nasty that they can completely alter the atmosphere of the country they are over. They are very often supercell storms and usually grow over Europe and get imported across the channel to the UK when the correct conditions are there. With luck one or more of those might make it to the S UK coast this evening or tonight and produce spetcaular storms with the risk of flooding, large hail, and tornadoes. On the other hand it could turn out to be a damp squip!. Hope that helps.  Smiley
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jgs001
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« Reply #3 on: July 17, 2009, 08:11:40 am »

Thanks for the explanation, that might explain the almost continuous (every 20-30 seconds) flashes for over 4 hours last night. Based on the number of elephants, the storm centre kept moving on and coming back, or rather I guess there was more than one. No chance for a photo op mind you... The kids were scared silly by all the noise.
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John
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Big Dipper
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« Reply #4 on: July 17, 2009, 01:45:45 pm »

Same with my cat this morning John. This is the third time I've powered up my PC as we've had a couple of cracking storms & heavy downpours this morning (about time, too IMO) so didn't want to take any chances despite having power surge devices in place.
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Andy
martinastro
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« Reply #5 on: July 17, 2009, 05:18:04 pm »

Great to hear you guys got some storm action and that the forecast was spot on!. The sferics charts today are showing a crazy amount of lightning all over the S and SE sections of Britain. Must have been some serious storms in places. I wonder if there have been any funnel, waterspout, or tornado reports from those?. Been away all day so only getting caught up now.
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« Reply #6 on: July 17, 2009, 05:46:57 pm »

Quote
The sferics charts today are showing a crazy amount of lightning all over the S and SE sections of Britain.
But only a couple of minor interruptions for rain at Lords (England v Australia, 2nd Test Match, 2nd Day)
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martinastro
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« Reply #7 on: July 17, 2009, 06:57:00 pm »

BBC Newsline just showed a very good pic of a funnel cloud over Antrim from the 15th.
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jgs001
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« Reply #8 on: July 17, 2009, 11:07:19 pm »

Nought here Martin, just some rain... and short showers at that.
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John
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« Reply #9 on: July 17, 2009, 11:20:34 pm »

Quote
The sferics charts today are showing a crazy amount of lightning all over the S and SE sections of Britain.
But only a couple of minor interruptions for rain at Lords (England v Australia, 2nd Test Match, 2nd Day)


Well if the lightning shared my view of cricket, then it probably must have fallen asleep!  Wink Grin
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Andy
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