CloudyBay
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Posts posted by CloudyBay
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Is anyone following the situation on the M62? Sounds like a terrible night for those caught up in it.
Whether you had as much snow as you wished for or not, at least be thankful that you're in a warm bed this evening!Live reporting here:
https://www.manchestereveningnews.co.uk/news/greater-manchester-news/m62-shut-today-weather-winds-14353566-
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19 minutes ago, Sn0wmad79 said:
Anyone got radar latest? Latest suggest ppn is still.pushing north towards Manc area
I think that's all for just about all of us in the region, at least until the sun rises.
The red arrows on the image show the current wind direction, but not its intensity.
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Well, if this contraption is to be believed (and I'm not sure how much faith to place in models like this) then it looks like Lancashire and everywhere further south in the region will get some snow in the next few hours. Then there's a bank of showers on the far west of that active front, currently around The Wash, that could possibly dump snow into Cumbria later tonight.
http://meteoradar.co.uk/expected-rainfall#
And then it all wheels away towards Ireland.
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9 minutes ago, Darren Bown said:
Is anyone around Manchester airport? I’m assuming all is ok there - I’ve got to head there for a meeting later.
I was near there earlier this morning. The main roads were fine and flights seemed to be going in and out.
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8 hours ago, Tracy Flick said:
NWP is traditionally purely Newtonian physics (no historical data use), but some companies are trying Artificial Intelligence ('Neural Networks', the self-learning way).
How I see these 2 approaches:
Using pure Newtonian physics (which is the traditional MetO way): In the case of fluid dynamics, the balance of forces and the conservation of momentum, energy and mass are expressed through Navier-Stokes partial differential equations (mass, energy and momentum are conserved in everything, even car crashes... read about Newton's Laws for more). But these NS equations are difficult to 'solve' both numerically and analytically... in fact we don't even know how to generally prove that physical solutions exist to them at all. The best we can do is therefore create a simplified version of the NS equations and then use computational techniques such as 'finite difference methods' (see Wikipedia) to solve the many partial differential equations simultaneously: these iterate the evolution over increments of time and space (the space increments are the grid spacings that are often referred to.) The starting point (t=0) is observed data combined with reanalysis data. Obviously smaller increments of time and space give better results but are more computationally expensive.
These Newtonian NWP models should in theory be fine with unusual atmospheric states because the laws of physics are still always true... however, the approximations introduced by the physicists and programmers may mean that accuracy is only guaranteed for certain ranges of atmospheric states. By making observations of unusual states we can test the validity of these approximations and improve them if necessary.
An example: If there's an experimental observation such as eg 'high sea surface temperatures in an ocean leads to warmer summers' , this will 1st be checked for good statistically correlation. Then this will be checked on the computer model to see if the simulation output matches the experimental observation. If it does, great, but if not it means something is either lacking from the code or something is in error in the code. Then the possible sources of error are identified eg maybe evaporation needs to be modelled less simplistically, so they will try that. This will mean increasing the complexity of the approximate partial differential equations, or adding new ones.
Nonlinear systems (eg the atmosphere) require exponential increases in computing power for linear increases in forecasting accuracy... I suspect there is therefore probably no real desire anymore to simply improve results by buying better computers because the forecasting improvement is increasingly tiny for each extra dollar spent. It is surely instead more efficient to improve the formulation of the differential equations that have to be simultaneously solved... a question that could be asked is eg "how can I better model turbulence on the edges on tropical storms?" ... answering this question will lead to modifications of the set of partial differential equations.
GFS I think uses finite difference methods to solve the partial diff equations but they want to advance to finite volume methods. ECMWF use spectral methods... these involve writing the solution as a sum of basis functions as is done in Fourier analysis.
The AI Neural Network way:
Some private companies are it seems now trying to somewhat blindly get forecast results using Artificial Intelligence. See https://blogs.microsoft.com/ai/hows-the-weather-using-artificial-intelligence-for-better-answers/
Basically this method I think (or at least one possible implementation) uses historic observations with known outcomes to 'train' the software. Then given enough training it should be able spot patterns and give a correct output (the forecast).
This is similar to spectral methods in that we are trying to find weights to give to each element of a set of functions... BUT this time the desired weighting on a function is evolved towards using nothing but historic observations as a guide, whereas the ECMWF find the weights by 'simply' plugging the sets of functions into the partial differential equations.
For an introduction to weather with neural networks and practising using it yourself: https://www.amazon.co.uk/Neural-Network-Programming-Java-Souza/dp/178588090X
As computing power increases AI might become more important in forecasting, BUT weather has sensitivity to initial conditions so perfect AI forecasting can surely only be achieved with an infinite amount of training data(!)... that's to say AI methods must have at least the same fundamental limitation as classical physics methods. I suspect that it is with unusual atmospheric states that AI will seriously struggle.
Maybe combining AI and traditional NWP in some way is a way some might go in the future.
TLDR of my take: AI uses purely historic weather observations, whereas traditional NWP uses purely Newton's Laws of physics, with approximations.
I'm sure someone at the MetO is playing with AI but they surely aren't using it yet.
This is fascinating, thank you.
So is it the case that the AI system would look at a given weather situation and all the inputs this entails, and then construct a probability-based forecast? (So to put it very crudely, if input 'x' has, 9 times out of 10, produced output 'y,' the prediction will therefore be 'y'. Obviously the real model would have to balance huge quantities of such outputs.)
And is AI really purely based on historic data? Surely a system could also improve on its own accuracy by comparing its earlier forecasts to the actual weather that then occurred. So real time weather data could inform two sets of modelling, retrospective and predictive...
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48 minutes ago, Nizzer said:
I'm actually quite disgusted by some of the comments in this and the other thread over the last couple of pages. From calling out the more knowledgeable posters because the models have changed slightly, by people who add nothing to the forum at all, to people moaning about an apparent southern bias which is absolute nonsense.
No-one who posts in the MOD thread, or any other thread for that matter, is under any obligation to post for everyone elses convenience! Last time I checked, the Model thread was not a 'weather forecasting thread'!
The problem is, you're dealing with complex and ambiguous weather forecasts and the interaction of these with complex and real human beings. Yes, it's frustrating and yes a great deal of nonsense is propagated by people who should know better, but also remember the real gems here who add so much value to all of our knowledge about weather.
Nothing is perfect.-
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35 minutes ago, Hotspur61 said:
Yeah it was an interesting one with "coldie" Tomasz.Looks like snow showers starting midday onwards on Monday and Monday-Weds looks like showers will become widespread with some prolonged snowfall although he did stress some areas will get more than others(graphics showed some could get 20cms+ while others 3cms or less.Friday could be a possible blizzard for Southern Britain but did stress alot of uncertainty.Whilst models as i write this post have much of South in milder air by end of week the BBC graphics didnt indicate this but Friday is so far away in met terms we wont i feel know until Tuesday night how far North this low pressure will go.I am just looking forward to the next 48-72 hrs unfold and then take it from there.Lets just enjoy this epic cold for the time of year and hope this ST cold snap turns into a cold spell and this time next week we will still be enjoying it
Is this the forecast you mean? https://www.bbc.co.uk/weather/features/43184987
If so, it's indeed interesting to see how much uncertainty is still being placed on the scenario from Thursday onwards, but that the the risks of blizzards into next weekend are now being emphasised.
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25 minutes ago, snowbob said:
I think everyone is just now staring at the screen in disbelief.
we are so used to watching model runs from 300 hours get closer and closer then a shortwave will kill the cold.
or watching a 24hour cold easterly or northerly or even a north westerly get watered down to marginal sleet fest. watching our 2cm of slush drip drip dripping away.
this last week has been amazing
0z upgrading on its 6z then 12z totally amazing model watching.
i have been a member on this site since 2009 and haven’t seen anything like this.
this really I believe will not be seen to this level for a good 30 odd years.
some posters on this thread (you know who you are) in my opinion should actually be getting paid for their skills
i.e @chionomaniac , @Steve Murr, @nick sussex, @Nick F
Amazing analysis and tell it how it is and what to look for
keep up the good work fellas
and let’s all enjoy this
Yes, I want to echo those sentiments. Lurking here as I often do, it is amazing how much one can learn from some of the people here. I really appreciate the time and careful thought that so many people put in - I'm sure I'm not the only one who reads and learns so much but rarely comments. The combined pool of knowledge and experience here really is a good thing.
Right, onto the models. The latest GFS model seems to show quite a lot of instability ploughing into southeastern UK from early Friday onwards, that low pressure blob and so on. My unashamedly newbie question is - to what extent is this a low-resolution prediction of an actual weather event, and to what extent is it merely the result of the amplification of noise further down the line of a very complex forecast with lots of variables?
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Just now, I Cumbria Marra I said:
heavy too woooohooooo baby, snow day and sledging tomoz
Shouldn't you update your signature measurements?!?
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7 minutes ago, Bury88 said:
Another huge gigantic let down as per , don’t know why we bother.
I say to all those who feel this way - don't give up hoping! One day, sooner or later, you will wake up and be knee-deep in snow outside. When it does eventually happen it will be all the more sweet and memorable because of all the let-downs.
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Here's a live cam if you want to see that Mersey streamer hit land. Looks like it's quite stormy there!
https://www.everymanplayhouse.com/about-us/webcam
North west regional discussion
in Regional
Posted · Edited by CloudyBay
I think that there's a chance that once the sun starts to warm things up tomorrow morning then we could see the remaining southern bands gain enough energy to keep going north for a little further. At least that's my interpretation of the rationale behind the weather warnings further into the north west for tomorrow.
Having said that, I didn't see any forecasts predict the intensity of the wind in this region tonight, it is certainly disruptive and it's full-on blowing to the west directly. So who knows.