pyrotech
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Posts posted by pyrotech
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The models are struggling due to MJO - Its just moved into phase 4 and very active in Continental Maritime area with possible cyclone forming, You then have an area around Southern India where potential for circulation is possible too. That means all prediction about a moderate phase 4 are up in the air. (Pardon the pun)
This could move the MJO back into Circle of death prematurely
Negative NAO and moderate phase 4 ( 7 -10 days lag) are total contrasts
Until the models get a grip on that area those small margins up with us will matter a lot, The main thing to watch is the possible Cyclone near south of India as i believe thats what makes the difference ( we want some activity around that area to keep our high to the West next week.
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Mjo going into phase 4 not helping here, Negative NAO but with the lag the MJo wants everything to start moving Eastwards.
the outcome will be very interesting as it effects where the high will be and so the Jetstream.
This weekend we see the Jet try to move North for a time, before diving back down over the Uk Early next week, If we can keep the effects of negative NAO for few more days we may get rewarded.
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7 minutes ago, Iceaxecrampon said:
06z
Fun and games start as early as T+51 Wednesday for the East Coast
Can someone inform me why does all the ppn seem to hang for two days in the North Sea? obviously these are only guideline charts.
Bonkers in FI
The models are showing dry cold air crossing the continent and into a relatively warm North sea, the warm air from the North sea adds moisture to the air which the cold air can not hold and so we see snow showers as the cold air crosses the north sea and potentially inland for around 15 miles depending on wind speed. At that time the Cold air is unable to hold enough moisture to maintain showers further inland although streamers will occur in prone places.
East coast may get slight covering from this and is why Far Eastern counties are much better in this Scenario where the models later show options to open doors for other areas.
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Some had enough to get a sledge out
Some had enough to ice a cake
others are still looking for their first flake
seems Wales and South west were in one of the worst places for snow this time
Looking at early feb now for possibility of anything significant
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dew points in cardiff too high
we need evaporative cooling
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Dew points rose by almost 3c in last 40 mins , now just -0.5
2m temp remained at 2c
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Would seem then that i was just West enough
Seems that warmer air around the channel is messing this up for us.
Where as the air is moist crossing the Irish sea but relatively warmed. As its crossing the Hills its cooling again and so unable to hold its moisture. Hense snowing.
As it approaches the coast here maybe the slightly warmer air is that tipping point where its able to hold moisture in the air, where as it crosses the Channel it would likely beef up again over Bristol.
Change of wind direction may help
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Tropical Cardiff tonight
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Jay
its moderate snow now in west cardiff
Culverhousecross area
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2 minutes ago, bradythemole said:
I think it's going to miss Cardiff to the west, can you believe it?! Looks a good shower too. Hard to tell
No if intensity stays its right on track, probably just passed Bridgend now on leading front and heading towards Pontyclun
The intensity as it comes closer is the risk
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Jay
For Cardiff we are watching for shower activity in the current flow just North of Carmathen.
The one that went thru there recently was large and was North and South of carmarthen and the lower part just hit Swansea
If that stays potent then Cardiff may get a slight covering in the hour
Later tonight the chances increase again.
Talking a Cm or two thou not huge amounts, but id take that after the last few years
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In fairness the snow rain mix was forecast pretty well
Was shown as mainly rain by Meto with elevation for some snow
The cravat was it could cause a surprise
It'd didn't , it did pretty much as forecast
Now we watch the possible mayhem in South East Uk as it turns further to snow.
Mean while, here in gods country we get temperatures and dew points lowering
Ice forming and snow showers late into the evening
These will be in bands, hit and miss, so some areas getting many some getting few
But these will be very much snow and only very low areas possibly seeing sleet
Plus lets see if we get that easterly next week, here in SW UK we get best snow events from undercutting lows
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Snow down now to story arms
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2 minutes ago, benb said:
Grey and rainy in Pembroke, atm.
Hoping for enough on the Preselis for my boy's first sledge on Saturday morning...
Wishful thinking or are we in with a shout?
A fair chance of a covering with the showers this evening and overnight. Dew points should be favourable and showers there frequent for a time.
I hope he get to use that sledge
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32 minutes ago, Jackfrost said:
Rain now turning to snow over the Beacons.
Dew points still too high but dropping
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temperatures in Cardiff peaked at 10:02 this morning and seem to now be slowly dropping.
In Brecon temperatures peaked at 09:38 and dropped steadily since
both have a long way to go but possibly on the right road
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1 minute ago, andymusic said:
Heads of the valleys is clear right now on traffic cams too - so patience my friends is required here
nothing to report up at Pen y Fan - Storey Arms yet either
Here in Cardiff temperature is 7.6c
Dew points just crept up from 4.2 to 5.7c
So snow is out of the question right now but around midday we should start to see those numbers fall.
I will monitor dew points and report when they drop significantly and sustained
They along with temperature 2m will drop in heavier precipitation which until closer to the 0c for dew points is useless.
I suspect Beacons around midday for snow at height, Tredegar etc around 3/4pm Cardiff 6/7pm
i hope I'm late on all those and comes earlier
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13 minutes ago, Fujita scale said:
Ten mins ago i gave temperature details here at my location
Was 9.5 C
Now 9.3 C
Dewpoint was -0.4c
Now -1c
So cold air moving in nicely
Thats a dew point i would love to see at this time tomorrow
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4 minutes ago, Fujita scale said:
Yes the graphic on the left is - but I have circled the Wales link - there is nothing by the side of it if you look - but the graphics for the other days show it should have the snowflake icon indicating a warning !
You mean like this?
Change day on maps and then it will appear so highlight second map
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9.5c here in Cardiff
dew point minus 0.4c
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1 hour ago, Iceaxecrampon said:
Thanks - yes I agree looking at it from your point of view.
It's just my perception through experience of what is considered "dry"
Here is something for our friends in North West (Cumbria)
Like models show snow is likely, but not with potential of disruption in the South
That potential in the south also comes with possibility of a no event so seems you have the safer option
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1 minute ago, Iceaxecrampon said:
Class.
How marginal has this turned out...! - coupled with near coastal position non event on the cards.
Even Cumbria is dry....
Will see.
That does not show Cumbria as dry
That shows Cumbria as not in a warning area, Warnings are done on two objectives
The risk and likelihood
It shows that snowfall in Cumbria for that time is lower risk and with it the effect on snowfall effect on people and infrastructure.
Its also subject to change as slight alterations in wind direction can change the warnings even as late as hour before.
Precipitation from showers is likely to be dying as it moves southwards towards that region but as looking at the models that by no means a certainty as if winds moved slightly more west convection from North sea would enhance them
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3 minutes ago, beatpete said:
unlikely i'd say but... http://www.bbc.co.uk/news/uk-wales-38576207 and my house would have to be in the no snow gap!
Unstable air mass
Cumulonimbus embedded clouds and warm seas ( 11c - 8c)
This will cause convection and instability
The thunder snow is just a thunderstorm with snow falling due to temperature instead of rain.
Why is this important for us?
This leads to enhanced precipitation rates
Each rain/sleet/snow drop brings a little parcel of air with it and even as melting on its journey down it cools the air further and further down.
This evaporative cooling is obviously enhanced as precipitation rates increase.
The added thing is any lighting can look stunning and can often appear to have a pink tint to it.
So if this feature moves far enough North and in my opinion it would need to become a full small low with circular feature to really drag in cold air.We could see some significant snow heads of valleys etc. Another area of risk is lower Gwent valleys.
Now for very South Wales its same old story
"areas below M4 likely to see sleet and snow with settled snow above that area
Now that can change if we get full circle of pressure as winds would become Northerly as it moves thru dragging colder temps from mid Wales.
I suspect if it happened as shown Cardiff would see snow falling for a short time around 5pm but it would be too little and too late
We need that low to completely form The dew points right now are too high near the Bristol channel coast
Lots to play for and this could easily become a significant event with snow fall capturing out commuters returning to the valleys from the Capitol"
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Just for you Andy
Pen y fan 2nd jan 2017
I took the easy way up
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Model Output Discussion - cold spell to end Autumn
in Forecast Model Discussion
Posted
The current spell of cold weather was influenced by MJO being in Phase 6 and 7 in late October
Early November we moved into CoD
We are now in Phase 4 and that should lead to a more positive NAO in 15 - 20 days time
The best news is we head into phase 6 i hope in 7 days time and that makes the end of month more interesting (i hope)
So where does that leave the models, they have contrasting signals for next week, The MJO effects of CoD and then the negative AO and possibly NAO.
Unfortunately i feel the NAO will end up being pretty flat and edge towards positive but we have other factors mixed into the fight too.
Solar minimum (heading towards) and ENSO leaning towards weak La Nina
I am very positive about an interesting winter ahead but for now its looking likely to be Wintry showers in prone places and frost for next week. Then something more mobile and then towards Xmas ( if we can get MJO into phase 6 -7 something wintry and more interesting.
It can take 28 days to get influence on strat above the pole from phase 6 so it all takes a bit of time.
One area of interest is the transition from a blocked pattern to a more mobile pattern and around 12 - 15 days after we moved from CoD into phase 4 that is where will be and that has opportunities albeit temporary. That takes us to 9th - 15th December for transition time.