Thundersquall
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Posts posted by Thundersquall
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Ian, do you actually understand the gravity of this situation? I need time off, I have been working too hard, you're a weatherman, so sort it out! I also have this fabulous plan for a snow giraffe.
Remember the surprise some of us got in the Bristol area Sunday evening 20th December 2009 with the famous Bristol Channel Snow Streamer?
That event occured with snow showers moving in on a westerly flow.
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Any chance of those snow showers over N Wales reaching Bristol and
other locations in the West Country?
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Just had a look at the 12Z run from GFS. Wow - didn't expect to see charts like this!
Basically temains cold until end of run, with snow trying to edge in from the SW
every now and then!
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There is now about 100cm of snow which has fallen over the last week or so.
A metre of snow in about a week? Wow - that's a lot even for the Cairngorms!
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Great 06Z run from GFS which shows this cold spell lasting until at least 16th January.
Basic synpotics are Greenland High and Western Europe depression to out southeast, lasting until about Friday 8th
January, then a Scandi High takes over and linking to another Greenland High by mid-January,
the low to our SE lasting until 10th/11th January, then replaced by low to our SW.
I am taking no notice at the moment beyond 16th January, as this is way, way too far ahead.
Greatest chance of snow for the Southwest, West Country and Wales seems to be Tuesday night 5th into Wednesday 6th Janaury.
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The Netweather Extra 5-minute radar suggests it's snowing over Central Southern England.
Has there been any snow there?
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I would say the Low pressure system will end up, as usual, tracking too far south and we'll get very cold, but mainly dry conditions.
Just had a look at the 12Z charts from GFS, and yep.... that Low's tracking too far south!
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Bwlchgwyn 375m asl
Wind 07018G28Kts
Mod Snow
M00/M01
Snow Depth= 38cms
Next village down virtually nothing. Pays to have been above 250m asl.
Wow, 38 cms is just over 15 inches!
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I looks like our potential cold spell next week (because this is not a cold spell at the moment) hinges on the low next week staying south. to far north & the real cold air and potential for loads of snow will be snuffed out.
I bet it goes to far north.
I would say the Low pressure system will end up, as usual, tracking too far south and we'll get very cold, but mainly dry conditions.
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these are convergence zones, its where two airmasses are opposed to each other directionally and where they meet it forces air upwards creating a stream of showers, they often sit about for a while.
Are the showers that have lined-up from just east of Bath to just south of Reading to just west of London caused by a convergence zone?
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Not certain exactly where to post this, but the 5-minute radar clearly shows a line of stronger echoes running along or just to the south of the M4 Corridor.
RG1 is central Reading.
Wonder if this will turn wintry through this evening and into tonight?
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At first sight I thought the T+240 chart from ECM didn't look promising as far as a prolonged cold spell is concerned.
But does the shape look like an Omega block forming? Shortwave to west of High pressure ridge could save the day?
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That's an amazing run from ECM. Those charts for the 12Z run seem to suggest at least a chance of something wintry for the southern UK, lasting from Sunday until at least Thursday / Friday.
Nice second Channel Low forming on Thursday 7th January.
Just a slight problem, though, is we're starting to lose that Greenland High by Thursday and more noticeably by Friday.
It's slipping southwards in the direction of the Azores.
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ECM T+168 - nice long easterly fetch from as far east as Finland and parts of western Russia.
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The charts from NOGAPS are good and show that Channel Low well. It's fun to move the mouse over the chart times and watch that Channel Low move across!
Really cold air following that Channel Low into next week if this all goes to plan.
http://www.meteociel.fr/modeles/nogapse_cartes.php
Absolute peach of a chart at T+120 from the ECMWF 12Z! :lol: :lol:
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I went to the Malvern Hills yesterday afternoon to witness the snow event. Can anyone on here explain why West Malvern got about two inches or more snow, whilst the Wyche Inn at Upper Wyche got hardly any settling snow at all? It seemed the Malverns acted as a barrier to the easterly wind and somehow set-up a process which turned the sleety snow to snow proper.
Also, quite oddly it seemed the lower ground to the west in Herefordshire had settling snow as well, whilst the lower Severn Valley to the east got nothing.
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Just viewed the latest 12Z run from GFS. Amazing run of cold up to at moment 12th January. Just hope this isn't a cold outlier.
Favoured places for snow appear to be more southern counties of England and Wales, as successive low pressure systems try and fail to push milder air northwards, instead anchoring themselves to the southwest of Cornwall. This approaching Sunday into Monday 4th January looks like the greatest threat of something wintry for the West Country and South Wales.
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Just seen a few reports of sleet and snow on this thread - please correct me if I'm wrong
but I don't think this was forecast?
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The 12Z ECMWF chart for T+240, now shows a monster LP in the Atlantic with central pressure of less than 944mb. The 00Z chart didn't show this at all!
Just goes to show we can't tell what's going to happen yet in 10 days time.
00Z:
12Z:
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On a more positive note regarding this approaching colder spell, scanning the computer model charts and snow-risk charts, there's a good chance of something happening Tuesday night into Wednesday.
With not much wind any precipitation could hang around for a while!
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Looking at the charts, I think the situation evolves as soon as T+48 hours, as that small High pressure cell moves over the UK.
But later on this looks excellent on the 18Z run, with real heights building under that developing Greenland High.
Haven't seen a chart like this for a long time!
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That thunderstorm over Bristol this evening was a cracker! Two very loud cracks of thunder overhead and some cloud-to-cloud forked lightning. Several more quieter rumbles of thunder were noticed before and after this.
We had a very heavy shower this morning but no thunder and lightning which cleared about 10:50 am-ish but after that it was mainly sunny with fair-weather cumulus. Nice enough to go out for a jog between 3:00pm and 4:30pm.
Therefore we had about 7 hours of mainly fine weather. So this big storm came as a surprise in the evening.
To see this storm develop open Netweather Extra Radar and key-in BS9 as the postcode. Running the slides in smoothed rather than pixellated mode between 1735 and 1810 and you can see how quickly that storm exploded into life
presumably after crossing the Brecon Beacons. Upon closer inspection I think the waters of the Severn Estuary played a big part in developing this storm, pumping extra moisture into the shower.
This was the situation around 6:15pm over BS9. You may just make out the intensity directly overhead was in the
region of 90-120mm/hour:
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Just to give this a bump, the radar now has the 5 minute lightning detector plugged into it, so you can overlay the very latest lighting strikes onto the radar - which is proving very useful today! This is included in the radar only subscription, which is £3.49 a month or £23.95 a year.
If you would like to upgrade to the Extra lite service, this costs £6.49 a month, £25.99 for 6 months or £43.99 for a year, this gives you access to all the radar features, the stand alone 5 minute lighting detector, in depth forecasts + more.
If you've any questions about the services, feel free to email or pm me, or reply into this thread
I pay the roughly £9.49 per month rate - I assume this is the full package?
Cheers - TS.
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Has anyone started a thread for weather forecast for the Bristol International Balloon Fiesta?
The forecast charts from GFS suggest light winds Thursday until Sunday.
:)
South West England Cold Spell Discussion
in Spring Weather Discussion
Posted · Edited by Thundersquall
Looks like tomorrow will be a day for keeping an eye on the precipitation type graphics on the 5-minute radar (UK 5 minute radar (V4) and the new Beta version (New - Radar V5 Beta). The Beta version is already showing patchy sleet over Dorset, and the possibility of snow over the Crewkerne area, and also just now to the west of Salisbury.
It will be interesting to see what happens to that band of rain crossing over Truro in Cornwall.