February1978

GFS following ECM in developing high pressure around day 10, even if it is somewhat transient. Grounds for optimism?

10.0C and 94mm please Miserable first few days, mild and wet start, high minima, hope for a springlike spell later

*Stormforce~beka* Completely agree. I'm north of Basingstoke, we've had 950mm in 9 months, way more than in a normal year (750mm). Lacking in sunshine too. Easter doesn't look like helping that....but there is time for that to improve - current GFS looks slightly better.

Difficult, anything could happen, cold or mild, wet or dry. On current outputs, the value has to be on the colder and drier side - so 6.8c and 68mm please......... I don't like going cold side though!

Gowon dry is good for me!

Meanwhile, this will be the 8th wetter-than-average month running on EWP. The last drier month was June (though you could say August and January were 'average'). How unusual would this be?

Beyond the next day or so outputs are still poor – and no real cold anywhere near for at least a week plus. We are only just about still in play, and probably need a favourable SSW to help out. Meanwhile 15mm rain at 5c here…… what if……..

andymusic hopefully they are right, anyone seen the UKMO 12z yet?

Lukesluckybunch Afraid so - that low leaks away northwestwards again on GFS and opens the door to the Sahara

Good to see a southward trend of the models, much better for longevity through February. Meanwhile, whilst we’re all wondering where the ‘snow line’ is going to be on Thursday, it’s worth remembering that in these global models 50-100 miles is quite a small distance - but for us it could be a huge deal. Expect ‘small’ changes right until the end & enjoy the ride……!

Nick2373 Cold at Day 16-18!

5.3c & 94mm please

GFS could get fun/interesting here..... (about time too!)

Agreed, will it ever be possible to model these small scale features at more than a handful of days? There will always be an error in the initial state, whether it’s instrument error, lack of coverage in certain parts of the atmosphere, topology or the like and that’s before any physics assumptions are made. Due to the chaotic nature of meteorology, there is often not a ‘steady state solution’ & errors grow, irrespective of how fine the resolution or accurate the dynamical equations are. Rubbish in, rubbish out……..so I think NWP will always struggle beyond a few days. On a slightly different tack - the (off-the-) scale of EAMT anomaly highlighted in Tamara’s post is really something - must surely have an impact in due course….?

@sebastiaan1973 Party? More like a wake for winters past at the moment...! At least we get to dry out for a bit

ECM keeps it away from the south coast on 12z (except Cornwall) on this one. But watching brief until it happens as you and saintkip say........

I agree with this, 50 miles is not far in NWP, would make a massive difference to us. I've seen rain extend quite a bit further north than forecast in this type of set-up before. That said, there is pretty good consensus between the models for it to stay at coast or south.

The Bermuda Triangle ..... or Birmingham Triangle? Where snow disappears.......

ECM at 120 hrs - attempt at WAA off Eastern Seaboard? Definitely looks a bit different / more blocky

...and the pressure of the Greenland High has largest uncertainties/differences.....

As someone also in a similar scientific software business, I agree with the sentiment of this. Initial conditions are a big thing in my opinion. In an inherently chaotic system, if you don't get the initial state correct you won't get an accurate answer. Rubbish in ---> rubbish out. Areas lacking data are at altitude, over the oceans and near the poles where there are no humans to record and report data, so satellite and aircraft data are used I believe. Then you have the solution method which always has a truncation error and probably has efficiencies to make sure it is a) robust and b) quick enough to reach a solution. Developers make compromises/assumptions which always have impacts in due course. For example, mountainous areas will be a problem - how do you model the boundaries there? You can't directly model each feature (mountain), it's too small a part of the domain, but they are important for (eg) torque as discussed at length by others previously – how do we know we are accurate enough? All numerical models have inherent assumptions and weaknesses, much of the skill of those using them is to understand where those limitations are. It has been really fascinating to see the experts here comment on the output, what they trust and what they don't. We're in one of those spells where they are not convinced by the outputs they are seeing and giving their opinions, much respect for them sharing their knowledge from me – thanks! Apologies if this is slightly off piste, but it is relatively quiet…. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5008639

As someone also in a similar scientific software business, I agree with the sentiment of this. Initial conditions are a big thing in my opinion. In an inherently chaotic system, if you don't get the initial state correct you won't get an accurate answer. Rubbish in ---> rubbish out. Areas lacking data are at altitude, over the oceans and near the poles where there are no humans to record and report data, so satellite and aircraft data are used I believe. Then you have the solution method which always has a truncation error and probably has efficiencies to make sure it is a) robust and b) quick enough to reach a solution. Developers make compromises/assumptions which always have impacts in due course. For example, mountainous areas will be a problem - how do you model the boundaries there? You can't directly model each feature (mountain), it's too small a part of the domain, but they are important for (eg) torque as discussed at length by others previously – how do we know we are accurate enough? All numerical models have inherent assumptions and weaknesses, much of the skill of those using them is to understand where those limitations are. It has been really fascinating to see the experts here comment on the output, what they trust and what they don't. We're in one of those spells where they are not convinced by the outputs they are seeing and giving their opinions, much respect for them sharing their knowledge from me – thanks! Apologies if this is slightly off piste, but it is relatively quiet….

I think it's model fatigue...! Pub run is great, could be lots of snow possibilities for all later

An astonishing event which I was lucky enough to witness in Taunton. About 40cm level snow plus huge drifting. Hopefully someone gets a pasting like that & tonight's GFS!

As you might guess from my ‘name’ it is for me too. I was a 9 year old in Taunton, and it was not well forecast if I remember correctly. It started Saturday lunchtime, continued all day and by the morning there was level snow probably 40-50cm and drifts the same height of the garden fence. Because it was not expected, people were stuck visiting friends, in pubs and so on. There was a story that people stuck in the local pub only dug themselves out when the beer and food ran out a few days later An extraordinary few days, but mild set in pretty quickly and much of the snow had gone by the following weekend.