Model Output Discussion - 16th Jan 12z onwards - Smile While You Post!

[karlos1983]

Not according to the latest NMM (6z), where there is still snow forecast for southern areas from the small hours of Wednesday until that evening (and has been on each of the previous 4 runs): http://www.meteociel.fr/modeles/wrfnmm.php?ech=3&mode=1&map=5

 

Kind of ties in with Euro4 as well. await the 12z with much anticipation 

 

You need to adjust your time-frames as the first is for midnight and the second is for midday pm.

   deleted, back to admiring from a distance for me

 

That said, it does back west at any rate.

Edited January 19, 2015 by karlos1983

[Snowy L]

Ddaytime maximums one degree cooler tomorrow across most of N. England and the midlands. Not much but could make all the difference for many areas...

 

Edit: Looks like the 2nd front catches up to the first one earlier (and therefore further west), over the Irish Sea, allowing cooler uppers to mix into the now-combined fronts.

Edited January 19, 2015 by Snowy L

[The Enforcer]

So, 06z GFS says ok for snow away from the SW of England as the occluded frontal system slides SE across the UK.

 

42_20.gif48_20.gif54_20.gif60_20.gif

 

Nevertheless, don't assume it will pan out like that, the picture is complicated across the south by a developing shallow surface low along the trough axis across SW England early Wednesday ... GFS drops the low SE into NW France, whilst ECMWF and UKMO move the low east through the Channel/far S of England.

 

So Weds snow potential for the more marginal south (S of Midlands) will depend on:

 

 1. Models factoring in some mixing as the frontal system arrives with strengthening flow to increase surface temps. But if they do not have the degree of accuracy yet with the angle of approach of the fronts nor development of that low along the front across the SW early Weds, this will ultimately have an affect on the wind direction ... i.e. a more backing the flow as per ECMWF low moving east along Channel as opposed to a more onshore flow with GFS dropping the low into France. This can make a big difference to some areas being on the  wrong side of marginal for snow (onshore milder flow from S or SW) or right side of marginal (calm conditions or backing flow tapping into cold pool to the north or east).

 

2. How the stagnating cold pool across the UK recovers temp-wise during daytime today and Tuesday. Sub-zero temps over the next few nights under clear spells, a ridge of high pressure building in today combined with areas of cloud from decaying fronts trapping cold air at the surface ..., may lead to models perhaps over-estimating daytime temps over next few days.

 

3. If it's still a marginal knife-edge snow/rain situation in some areas (particularly south of the M4)  - will the precip be heavy enough to allow evaporative cooling to lower the snow level? ECMWF precip looks light, though surface temps look reasonable, GFS a little heavier.

 

Ultimately, nowcasting will be the best way of determining which side of marginal certain areas will be for snow/rain

I can see that certainly point 1 would be modeled correctly by T+6 and maybe point 3. I had been wondering about point 2, which must be the hardest element for the models to get right even at the closest possible range. For instance, I have been forecast an overnight minimum of -3 the last two nights, yet we have only managed -1.3 and -0.7C, respectively, with no sign of frost in the morning. I am feeling that tonight needs to be much colder to put this area in the best position possible. Although my location is north of the M4, the results for snowfall are usually as if it is actually 50 miles further south in these type of situations.

Edited January 19, 2015 by The Enforcer

[Catacol]

I must admit that sometimes I do wonder.

For the last two days we have been looking at possible cold weather extending and becoming more established via most models.

Today the models change, whilst believing and understanding Ian F,s expert input in here, even the MO cannot always be right.

I have understood and learnt many different aspects and inputs from the more professional people on here,  in which my understanding has greatly increased since being here.

The bottom line is I have learnt that each model has the last few hours readings put in, this can in times of extra chaos in the atmosphere, can  well change today's output and more especially the next few days.

I expect that by the end of this week the outputs may well be totally different, because the starting data is likely to run a different course, mainly due to conditions changing across different parts of the world.

 

I agree... but today the runs are a bit deflating I must admit. We've had 2 tough winters down here in the south if hunting for cold/frost/ice and snow is your thing! The MetO are getting very good at predicting things... and while I'm sure, somewhere in the future, there will be an error out there somewhere in one of their medium term forecasts I'm afraid my heart has rather sunk at reading IF today talking of strong confidence now on a return to mobility in the foreseeable and out to February too.

 

Hey ho. Perhaps February can deliver. It has done so before... and I am out of the country for a week starting 12th Feb so you can almost bet that Somerset will be hit by a blizzard somewhere around Valentine's Day!

Edited January 19, 2015 by Catacol_Highlander

[Mark Bayley]

GFS 12z downgrades Tuesday/Wednesdays snow and hastens the Atlantic's return on Friday. Midlands north would still get a covering of snow, although most likely a few cm's. 

 

Edited January 19, 2015 by Mark Bayley

[Captain Shortwave]

Day 4 charts

GFS

UKMO

Both models pushing fronts through the UK, mainly of rain, this will clear to leave a clearer weekend with frosty nights again. Wintry showers in the north west.

Before this, a wintry mix of precipitation will push in tomorrow (snow accumulating mainly on the hills, though some will fall to low levels). Also the risk of showers in the south east tomorrow and the north east on Thursday, again a little snow is possible.

Edited January 19, 2015 by Captain shortwave

[carinthian]

That latest GFS(12z) chart for next Sunday is one of the most depressing oF the season for you guys. I just do not know what to say, a two bit cold spell then a gentle mild waft from way down south takes over again. What do you have to do to get a proper easterly in place ? Could come in February but another week passes by all to readily.

C

Edited January 19, 2015 by carinthian

[karlos1983]

This chart doesn't even make sense to me, High pressure on top of High pressure in the Atlantic?

Edited January 19, 2015 by karlos1983

[sunnijim]

That latest GFS(12z) chart for next Sunday is one of the most depressing oF the season for you guys. I just do not know what to say, a two bit cold spell then a gentle mild waft from way down south takes over again. What do you have to do to get a proper easterly in place ? Could come in February but another week passes by all to readily.C

very true! The biggest problem for any interesting weather prospects ( and i include wild and wet zonal in this) as i love all extreme weather types, has been the strength of the Azores High.

Since October it has either diverted Low pressure systems to the North of Scotland ,or a rinse and repeat of what we see progged for Sunday,a strong ridge from the SW across Southern England.

[Gibby]

This chart doesn't even make sense to me, High pressure on top of High pressure in the Atlantic?

There would be a weak front separating them linked to the main Low to the North.

[The Weather Dragon]

That latest GFS(12z) chart for next Sunday is one of the most depressing oF the season for you guys. I just do not know what to say, a two bit cold spell then a gentle mild waft from way down south takes over again. What do you have to do to get a proper easterly in place ? Could come in February but another week passes by all to readily.

 

Getting rid of the PV over Greenland & Shifting the Azores High Westwards would help - no sign of that happening soon

We need to be more realistic and less biased regarding model output - whatever it shows & stop straw clutching which unfairly raises expectations

[igloo]

its going to be a bit of a shock here and others with temps currently -4c with 6 inches of snow lying to +8c this time next week but theres always the GFS fl charts to view over the next few weeks at least another year where the PV doesnt look like it wants to give in

 

[carinthian]

I see as the models have switched to less cold the deafening silence has returned.

All cold weather fans exhausted and let down again, I think, including me. Really feel sorry you all guys, but the latest UKMO and GFS model brings an end this weekend for any prolonged cold spell over much of Europe. Remarkably, snowless so far over much of lowland Europe, following on from last winter.

[karlos1983]

There would be a weak front separating them linked to the main Low to the North.

 

Ah ok, cheers Gibby for the reply! 

[Gibby]

very true! The biggest problem for any interesting weather prospects ( and i include wild and wet zonal in this) as i love all extreme weather types, has been the strength of the Azores High.

Since October it has either diverted Low pressure systems to the North of Scotland ,or a rinse and repeat of what we see progged for Sunday,a strong ridge from the SW across Southern England.

I have been banging on about this all season and despite some colder synotics over the last few days it remains a thorn in the side and if things verify as shown is once more the death nail to what would otherwise of been a decent cold spell.

[frosty ground]

its going to be a bit of a shock here and others with temps currently -4c with 6 inches of snow lying to +8c this time next week but theres always the GFS fl charts to view over the next few weeks at least another year where the PV doesnt look like it wants to give in

 

And a day later it's on it's way out as the westerly ragime starts alternating from south to north to south to north ........

[carinthian]

very true! The biggest problem for any interesting weather prospects ( and i include wild and wet zonal in this) as i love all extreme weather types, has been the strength of the Azores High.

Since October it has either diverted Low pressure systems to the North of Scotland ,or a rinse and repeat of what we see progged for Sunday,a strong ridge from the SW across Southern England.

Yep, the Azores high seems to be the dominant feature this winter,. As expected some short cold spells , but that has always been in the Met Office longer term forecasts.

C

[warrenb]

All cold weather fans exhausted and let down again, I think, including me. Really feel sorry you all guys, but the latest UKMO and GFS model brings an end this weekend for any prolonged cold spell over much of Europe. Remarkably, snowless so far over much of lowland Europe, following on from last winter.

Well as my friends in the Netherlands called last winter, basically the year without a winter, looks like they can have another one. Not that bothered personally. Still, maybe if the vortex drifts over to Siberia, we may get something from that, but that should start to show soon in the ENS towards the end of the runs.

[mountain shadow]

I have been banging on about this all season and despite some colder synotics over the last few days it remains a thorn in the side and if things verify as shown is once more the death nail to what would otherwise of been a decent cold spell.

The Azores High is a semi permanent High though, it will only move to higher latitudes if the PV is weak around Souther Greenland. The positive markers at the start of the Winter were for a SSW and with the OPI/SAI etc the signs were good. The reality is somewhat different with the heart of Winter likely to see South Westerlies for a while this weekend and next week to be replaced by a return to mobile westerlies.

[Severe Siberian icy blast]

Hemispherically speaking though we still have enough to keep us interested , still potential sliders , and always good to see high pressure separating the 2 vortex sisters . As long as that's the case it always leaves the door open to southerly tracking low pressure systems .

[Paul]

Just a reminder - if you want to have a moan about the current output, this isn't the thread for it, so please head over to the banter and moans thread

 

https://forum.netweather.tv/topic/81281-model-banter-moans-and-ramps-autumnwinter-201415/

[The Weather Dragon]

The lesson learned is that for nationwide cold snowy weather we need solid high latitude blocking - without it would be marginal for the majority of lowland areas especially towards the South - this type of blocking doesn't occur very often - and the models and indicators certainly aren't showing any signs of this soon !

[carinthian]

Well as my friends in the Netherlands called last winter, basically the year without a winter, looks like they can have another one. Not that bothered personally. Still, maybe if the vortex drifts over to Siberia, we may get something from that, but that should start to show soon in the ENS towards the end of the runs.

No winter ice skating on the canals again, but still time yet for a February freeze. Some of the best cold spells in Europe have come in February and lets hope the model charts can flip again towards that scenario, but the bigger pictures does not look too encouraging, but a bit better than last winter !

C

[Summer Sun]

And a day later it's on it's way out as the westerly ragime starts alternating from south to north to south to north ........

 

Yeah looks like 2 days with temperatures around 6c to 10c for England and Wales

 

 

Then afterwards they gradually lower down to around mid single figures

 

 

Whats noticeable is northern parts of Scotland never warm up with temperatures never getting much above 2 or 3c

[pages]

The Azores High is a semi permanent High though, it will only move to higher latitudes if the PV is weak around Souther Greenland. The positive markers at the start of the Winter were for a SSW and with the OPI/SAI etc the signs were good. The reality is somewhat different with the heart of Winter likely to see South Westerlies for a while this weekend and next week to be replaced by a return to mobile westerlies.

I don't think it will be for long.

I think we will start to see over the next couple of days, some good runs around 240hr.