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pyrotech

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    Storm Dennis Atlantic Storm 4

    in Storms & Severe Weather

    Posted

    1 minute ago, Gray-Wolf said:

    Down to 922 mb in the centre of the low

    Anyone got data on previous min pressures from Atlantic lows?

    I do not like the rainfall Radar a.t.m.......add in the orographic enhancement to the signals we are seeing and I can see why there's so much activity here through the day?

    I reckon I'm pulling a late one tonight......and it's not even a Hurricane making landfall!.......though that central pressure would eclipse many of the ones I've watched home....

    Keep safe Folks!

     

    913mb i believe is record

    • Like 2

    Storm Dennis Atlantic Storm 4

    in Storms & Severe Weather

    Posted

    28 minutes ago, Mapantz said:

    It starts to look a little confusing as we're almost upon the event, so it can make the totals look less on one chart. However, if you add them up over the two charts, it's still looking pretty bad!

    Sorry, by upgrade i mean that rainfall total increased by almost 20mm for the period in that area

    • Like 1

    Storm Dennis Atlantic Storm 4

    in Storms & Severe Weather

    Posted

    Just now, Ice Day said:

    It has to be wrong, surely?

    No, its probably right. There will be a defined squall line crossing into Wales around midnight and crossing the UK Eastwards

    That line will have very fierce winds and torrential rain, 

    It will be around 10 miles wide but you will know when your in it.

     

    So wind gusts will increase during the squall by at least 10knts  so 80mph or 90mph gusts are a risk for a short period of time for a few places locally, mainly near coasts and at height

    • Like 1

    Storm Dennis Atlantic Storm 4

    in Storms & Severe Weather

    Posted

    9 minutes ago, Mapantz said:

    No posts were removed or hidden. If you meant this one it is only two posts above your last reply.

    No it was the one where i mentioned two forecasters i had spoken too, i thought it  was because i mentioned them so i did not in next post, but now original post has turned up again, maybe gremlins in my computer

    Storm Dennis Atlantic Storm 4

    in Storms & Severe Weather

    Posted · Edited by pyrotech
    wrote 45m instead of 45Ft

    1 hour ago, ancientsolar said:

    looking at 70mph gusts in Wales... and seeing how the winds were advertised as 70-80mph for last weekend.. and there were a couple of 90mph, I wouldn't take anything for granted.~ Most of our towns are in the valleys, flooding isn't such a concern,. but landslides are and the wind can be funnelled up the valleys increasing strength.. so again.. take nothing for granted.




     

    Not sure what happened to last reply i made to this, time taken etc.

    Anyway  i feel flooding may be an issue for the valleys as water table is very high and some estimates are between 120 -133mm of rain in 24 hours.

    If we look back at Cumbria floods 2009 the set up is very similar.

    Cumbria was November but as then Sea surface temperatures were around 2c above normal, Orographic rainfall and of course intensified due to warm air being dragged in from the South. The fronts are very similar, as is where the centre of Dennis will be Saturday.

    Landslips are very high due to viscosity of the ground  so maybe disruption to road and rail.

    Blackwood may escape but i think Cynon valley may be hit badly, I suspect South Devon at a similar timescale and Lancashire, Cumbria and West Yorkshire may also see issues. Sunday risk extends to South East England.

    I viewed the Buoy reports via my website and 45ft waves West of Ireland are monster seas. Suspect shipping will be avoiding that area.

    Here is pressure chart for Cumbria 2009 and one for Dennis 

    Screenshot 2020-02-14 at 19.45.36.jpg

    Screenshot 2020-02-14 at 20.13.59.jpg

    • Like 1

    Storm Dennis Atlantic Storm 4

    in Storms & Severe Weather

    Posted

    24 minutes ago, ancientsolar said:

    looking at 70mph gusts in Wales... and seeing how the winds were advertised as 70-80mph for last weekend.. and there were a couple of 90mph, I wouldn't take anything for granted.~ Most of our towns are in the valleys, flooding isn't such a concern,. but landslides are and the wind can be funnelled up the valleys increasing strength.. so again.. take nothing for granted.




     

    I just spoke to Ian and Derek and 120mm is showing on the met office computer and some models are showing 133mm that i have seen.

    Ensembles are interesting for your area, and most of UK with the operational being a complete outlier with much lower precipitation than all the other members including the control.

    As for the valleys being safe, i would not be so sure, that is a lot of water in short space of time, with a high water table. Your right about landslips that is certainly possible with the increased viscosity. I have just viewed the buoys on my website and 45m waves now West of Ireland , thats some storm.

    Wales/Cymru Regional Weather Discussion

    in Regional

    Posted

    4 minutes ago, Frozone said:

    Unbelievable that they have multi-million pound computer processing equipment at their disposal and they can't even forecast a bit of frontal snow, even a few hours in advance!

    Firstly you should remember that every computer predicted the snow.

    ICON, GFS ECM Euro4 not just Met Office computer.

    Secondly, the temperatures are very close to freezing, in fact at 5pm A48 was at 0c

    So dangers are, snow falling on roads washes away the rock salt, leaving wet roads that could freeze between council salt runs.

    That very dangerous for commuters.

    So already we had a risk and i would suggest with winds some mountain roads are currently treacherous, Thats why Rhigos and other mountain rds in that area have been closed.

    The disruption MAY be less than originally thought, however thats just for here. Cornwall have had stranded vehicles and areas in the Amber warning have had significant snow so although IMBY it may not be bad it does not mean for others its not either. The front is likely to stall and then decay from the East but a few Cms are still likely to fall overnight.

    A lot of schools will be closed tomorrow, especially in valley areas is most likely.

    The snow did ease for many and that could be seen as a hole on the radar, but for many is South East wales this is not over yet and although not huge amounts in low areas, some higher areas may still see over 3 inches of snow.

    Side rds will be dangerous with black ice, snow and frozen crushed snow all probable in morning.

    P.s still snowing steadily  in Cardiff and these last two winters have at least given us a snowfall with some interest. Winters in excess of two years ago being more about cold rain and flooding. 

    Enjoy the snowfall and stop worrying about how much, worst case scenario is you travel to a hill to have a play in snow tomorrow.

     

    • Like 4

    Wales/Cymru Regional Weather Discussion

    in Regional

    Posted

    The reason No Amber Warning yet, is the likelihood for any particular localised area.

    Today a Amber is very likely, but until now plenty of scope for worst hit area to move North or South

    Amber warnings are not just given out like a free gift. They need careful consideration. The Yellow has been waarning the public that snow likely.

    If Amber then organisations have plans to follow

    Schools may automatically shut

    Councils have to set plans

    Emergency service plans like Police will be initiated

    So an Amber has very signifigant implications  that most people never know about.

    Nothing has changed and the forecast is close to as forecast, maybe slightly South so Coastal areas  seeing snow later too

    • Like 2

    Wales/Cymru Regional Weather Discussion

    in Regional

    Posted

    Looking at all the model runs, Wales is in the sweet spot.

    GFS - takes it further North , but Wales gets a few hours of snow, especially inland, some snow for Cardiff and Coastal areas but this model suggests sleet later

    ECM keeps it all further South, This keeps all of Wales in line for Snow for most of the day

    Met Office model, shows due points perfect south of Wales and a sustained period of snow

    In addition, winds are a brisk Easterly, helping to keep temperature low and blowing any lying snow into drifts

    I suggest heads of the valleys etc will see disruption and many school closures

    This is the one time where a little further North or South still leaves most of Wales in the firing line, just where i am is dubious with those dew points according to GFS, but some areas would still see 10cm of snow further North, valleys etc. 

    • Like 3
    • Thanks 1

    Wales/Cymru Regional Weather Discussion

    in Regional

    Posted

    This is one of those scenarios where a little elevation will help

    The 850MB temps are marginally on the right side

    The dew points are going to be close, so those near the Bristol Channel may lose that factor for a time

    Evaporative cooling where heavy precipitation falls will bring snow line lower.

    So its all eyes on where that low tracks but i think if anywhere near as forecast, Hills of valleys will see snow

    heads of valleys and some parts of Powys may be a sweet spot

    Cardiff and Southern Coastal areas a mainly sleet and wet snow event, with more snow at times.

    Small corrections will of course change this, possibly bringing snow to lower levels but right now some margins are very knife edge

     

    Lets get Tuesday out the way before considering Thursday in any depth, however a second bite of the cherry looks possible.

    So somewhere in Uk may see something a little disruptive, France will see a very snowy 24 hours and this heads towards the Alps where with different temperature profiles over last few days - this extra layer of snow may increase the avalanche risk significantly. 

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