chris55
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Posts posted by chris55
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5 hours ago, RainAllNight said:
Do cold temps feel colder if the dew points are even lower?
Its essentially just dryer air.
The dew point is the stage where the air can no longer hold the moisture so it relents and the moisture gathers on solids, like dew on the grass.
In my experience cold dry air often feels less cold than more humid cold air.
Moisture conducts heat more readily than air, meaning a cold damp day feels colder than a day when the air is dry, but the temp is lower.
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Smattering of snow here in Eastington this morning.
cold and very Icy 
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3 hours ago, TSNWK said:
this 100% under -6 uppers within a trough from the north it really is case of waiting for " pop-up's " with the broader pattern..
polar low territory? Can’t remember the exact parameters for a true polar low to develop but looks possible.
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3 hours ago, Battleground Snow said:
Reminds me of xmas day 2004, snow shower late on the day gave a nice seasonal dusting in parts of Gloucestershire
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1 hour ago, Ali1977 said:
This looks like another good snow event
Maybe the midlands south has the best chance
Could be an epic snow event on this run
Bank that Ali
This December so far has shaped up to be the best for cold and snow we have seen for many years.
If we could get another fall over xmas that’d just be the icing on the cake.-
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Nothing falling from the sky in Stroud this morning even though the radar shows the front well over is!
Must be lots of sublimation (evaporation) as the moisture takes the cold out of the air so to speak.
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Be sad to see all the snow melt. Today is the first day I can here a drip drip. So that’s pretty much a week of lying snow which is very rare for here!
Been a memorable spell in Stroud and surrounding areas.
Sunday
Monday
Wednesday
And this little guy…..who’s time is up
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Xmas weekend into Boxing Day looks to have the potential for a battleground snow event somewhere in the U.K.
Lots to get through yet mind!
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Already down to -5 at Fairford! -7 at Benson.
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3 minutes ago, Benny123 said:
That’s a big temperature contrast upstream..
Hopefully that’ll drive some WAA into the Artic due to the lack of zonal flow generally
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2 minutes ago, blizzard81 said:
I think the yanks would laugh at that statement
Coldest night in England since 2010 last night.
-11c
That’s remarkable for central U.K.
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4 minutes ago, Ali1977 said:
WAA up through the Atlantic, trough clearing , and heading for a awesome day 10 - as in Xmas day
The Trop PV is shredded. U.K. winter still on the cards.
Easterly the form horse into new year IMO.
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2 minutes ago, blizzard81 said:
And don't forget.... Brutal cold for the US - AGAIN! No flip flop modelling for them.
Don’t forget the “brutal cold” outside right now for the U.K…..
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1 minute ago, Captain Shortwave said:
If it wasn’t for the past week or so, this chart would be potentially rage inducing…
Extensive Arctic blocking, dominant trough to our north east. Yet we end up with south westerlies thanks to that wedge of heights near Greenland that steers areas of low pressure in the worst way possible.
It would only be ‘rage inducing’ if it verified…… long way to go yet.
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16 minutes ago, Mike Poole said:
Yes, they just calculate an initial T0 condition (which is not straightforward as the data is not all taken at the same time) and then simulate physics. The wealth of human knowledge about the weather may influence which physics to code in the models and to how good an approximation, but the models don’t pattern match historic states of the atmosphere or anything like that.
Yes but surely the foundations for the algorithm is set from past knowledge and events. Even though, once that instruction is initiated it just processes the data.
What im getting at is basically if we were in a standard zonal flow with a big trop PV over Canada the modelling would be a little more straightforward
for what reasons that would be is up for debate.
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51 minutes ago, Mike Poole said:
Why the uncertainty? Well, it isn’t because it is a rare setup per se, because the models have no knowledge of history at all, they just get our best knowledge of the T0 conditions.
Are you sure about that Mike? Surely the model Algorithm has historic data dialled into the code? It would seem unthinkable these computers wouldn’t use the wealth of past data to predict new events?
Absolutely genuine question here. Done a bit of Googling but didn’t have time to read through all the articles.
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These ensembles are to far apart for any confidence in the forecast, some very cold runs in there (London)
p1 and p 6 the two extremes - coldest and mildest for xmas eve.
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P23 the coldest option for day 7
p22 the mildest for day 7
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Surely these super computer have a “average” bias locked into their algorithms?
With the NH profile as it, and with the constant chopping and changing with each operational, and to some extent the ensembles, I would think we need to be really careful if we are trying to make forecasts beyond the 4/5 day period.
Plenty to get though in the shorter term before we can be confident in the mid term
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Lots of scatter on the ensembles.
Op on the less cold side for London
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Just popped outside with a cuppa to check temp and seen two very clear and bright shooting stars streak through the crisp and ultra clear night sky! Was amazing!
Googled it and it’s the Geminid meteor shower and it peaks tonight. So if you outside have a look
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Just look at how the NH profile is causing big swings in the mid term, for the U.K. at least!
The one line brigade on here need to be a little more pragmatic throughout the day IMO.
Still could go anywhere over xmas TBH but we gotta see the pattern for what it is and factor that into our analysis (which most do.)
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15 minutes ago, Cleeve Hill said:
Try and get up there tomorrow. Sun will be out. The sky cleared this afternoon up here, explains why it’s gonna be a v cold night
I prob will, was meant to be on site this week but all cancelled due to the weather (suits me !) so off again tomorrow. Some alpine conditions I’m thinking
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Model discussion highlights
in Forecast Model Discussion
Posted
Its essentially just dryer air.
The dew point is the stage where the air can no longer hold the moisture so it relents and the moisture gathers on solids, like dew on the grass.
In my experience cold dry air often feels less cold than more humid cold air.
Moisture conducts heat more readily than air, meaning a cold damp day feels colder than a day when the air is dry, but the temp is lower.
Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4799672