FI Charts ( T120+ onwards) Winter 2020 **READ MOD NOTE IN FIRST POST**

Downwelling well under way I’d say and 3 biggies in broad agreement- omg must remain calm. (Flippin Iberia)

BLIZZARD7 wrote: »

A potentially historic cold spell showing across the model output this morning, caution needed due to it being well into FI still, but key developments are in the 120-144hr time frame at the moment... the SSW might just be doing it's job.

Kermit must have given that mass

BLIZZARD7 wrote: »

A potentially historic cold spell showing across the model output this morning, caution needed due to it being well into FI still, but key developments are in the 120-144hr time frame at the moment... the SSW might just be doing it's job.

Billcarson could get his long awaited cold second half of January

The rollercoaster rages on.

John Hutton wrote: »

As a layman, can I ask a sincere question. There are lots of (exciting/scary depending on your perspective) charts posted, immediately followed by a consensus opinion that the charts do not mean much at all and probably won't materialise. If this is the case, what is the point of these charts if they never/rarely materialise?

I'm not having a go at anyone here, obviously they have a point in the context of this thread and for discussion etc, but I mean why are they made in the first place?

Others can give a more scientifically detailed explanation, but essentially, for several reasons, each day forward from your starting point adds a little more inaccuracy to the charts, and this accelerates exponentially once you reach day five and beyond. So in other words, the charts for later today are probably extremely accurate, for tomorrow are probably very accurate, for Wednesday are probably still quite accurate but slipping a lot, for Thursday are only fairly accurate and for Friday are a bit of a long shot. From Friday and beyond, you're into "anybody's guess" territory.

However, because these models are run several times per day (four times for the GFS, twice for the ECM and UKMO), you can start to build a better picture of what might be coming down the line by taking several runs in a row of all the models and trying to spot trends.

The reason most of us are cautioning that FI models should be considered highly hypothetical right now specifically, is because of the ongoing stratospheric event. Detailed stratospheric modelling is a relatively new science for these models and we have seen time and time again that when there is a large amount of uncertainty regarding developments high up in the atmosphere, the charts which are directly relevant to our weather tend to reflect that and swing wildly from one potential conclusion to another every time the models are run. This tends to continue until events transpiring in the stratosphere are "locked in" and the models can be more certain as to their effects closer to the surface.

To summarise, essentially, all of these charts are theoretical possibilities of what might happen a week or two from now. And each specific event is directly connected to other events around the world. When you look at a chart which is fifteen days away, it's a valid possibility of what the weather might do - but if you change one little variable on say day ten - for example, if a high pressure system which is expected to move away from its current location instead stays where it is - then the chart for day fifteen, which assumed that this feature would stay where it was, will be completely written off as a solution. But we can't know that until we get to day ten and see if the HP system does indeed move.

So essentially, these models are interesting for talking about the theoretical possibilities as to what might happen with our weather, but they must be considered only as potential outcomes among dozens of other possibilities. Until we have major improvements in (a) computing power, and (b) the amount of data we're able to collect about the current state of the weather at any given moment, model accuracy will continue to decline with each day you move away from your starting point in time. Thus, at the moment, charts with a timestamp of more than 120 hours (some would say 144 these days but the consensus is still that 120 is the gold standard) should be regarded as possibilities, but possibilities among many, many others.

Lads, what links do youse use to view the chats ?
There are so many charts on each of the models that I have no idea which is which... thanks