Model output discussion - 20th Feb onwards

[weirpig]

2 minutes ago, fergieweather said:

As usual at this time of year, expect any (less significant falls of) snow by day to either struggle to settle and/or melt at low levels under any insolation. Settling will generally occur readily only at the WBFL elevation or above, but of course still remain a more widespread hazard at night.

Thats fine by me  cold, snow a possibility will settle if the ppv is strong enough  espicially at night. possibly 2 weeks of more seasonal weather.  ill take that 

[Cheshire Freeze]

GFS upping the ante at 144....quite a chart

Not letting me copy and paste the image on my mobile though unfortunately. Better rigidity in pressure rise towards Greenland though.

[bobbydog]

2 minutes ago, CreweCold said:

GFS upping the ante at 144....quite a chart

Not letting me copy and paste the image on my mobile though unfortunately. Better rigidity in pressure rise towards Greenland though.

here you go- 

[bradymk]

55 minutes ago, fergieweather said:

Only points of emphasis I'd add to Gibby's summary are re Fri-Sat:

- sufficient signal still within EC-EPS and MOGREPS to maintain a risk of more developmental outcome with gales/severe gales into SW/S, with attendant risk of heavy rain and lower risk significant snow

- mismatches this morning between WV imagery and model expectations in critical source area for evolution later this week illustrates the low confidence message re how things will unfold: treat deterministic fields by Fri with a due level of doubt. May remain unresolved until short lead time.

6z GFS showing the threat of heavy rain in the south west on Friday...

[bobbydog]

2 minutes ago, bradythemole said:

6z GFS showing the threat of heavy rain in the south west on Friday...

turning to snow saturday....

[SMU]

Morning all

I mentioned the other day the advent of the surface High pressure would support the potential of possible snow & cold, also a few weeks ago I mentioned that as we approach the near time the GFS & subsequently the ensembles usually upgrade the cold as the depth of the airmass is identified -

we are now down to -10c on the ECM & -9c  on the GFS when 2 days ago -7 was the lowest value in the UK-

also the models now swinging to perhaps an ENE flow - sustaining the -7c flow as opposed to the initial ( moreso GFS ) ESE flow mixing out the uppers to -3

do I expect to see snow falling here at sea level in Kent- yes, snowcover probably not - but the local hills maybe !

lots of snow chances seemingly scattered at all angles for all IMBY's....

s

[SMU]

Just to add @ 192 the SE corner after a sustained NE flow is back down to -9c

based on the same rationale - if this run actually varified then near time that may well upgrade to -10 / -12c

s

[Cheshire Freeze]

Interesting to see where we go from here....better alignment of lp and a smidgen of better heights to N at this juncture 

 

At least I solved the mystery of posting charts!

[MR EXTREMES]

31 minutes ago, Snowynorth said:

Just a typical cold spell, nothing unseasonal and nothing noteworthy.

Generally dry throughout the week, pleasant winter sun during the day with harsh frosts overnight. 

Very little in the way of precipitation and for areas where precipitation is greatest (that area of low pressure) it will be of rain. 

Then when the low pulls away and draws in a more easterly flow Europe isn't cold enough so what you'll see is wintry showers a majority of which will be of rain within 30-40 miles of coastal areas in the north, east and south-east.

Europe needs to cool down a lot for anything noteworthy later in the week which I suspect it won't.

 

 

Totally disagree-6 850s from the ne will and can create some great convection and these will be snow.

also feel similarly this spell like feb 2008.

it is true that the Greenland block has been rather over modeled over the past few winters but seems to quickly decline to nothing more than a transition ridge although this time does enough to direct Lows se I'm certain the models will show more interest as we move threw this week.

with snowfall very possible in the south as lows swing through the channel like what's currently happening now.

although the uppers are way to high right now they do go low enough to allow snowfall to be possible north northeast eastern uk and later in the week possible streamers from ne into the se and even southern England as well as lows dragging easterly which might not be cold enough.

i think the northeast flow would most certainly be the coldest outcome 

[fergieweather]

24 minutes ago, bobbydog said:

Ian. your post from yesterday came across to many as good confidence of a protracted period of "below normal" temps for "quite a few weeks". (some people would read that as 'into the freezer for months...')  obviously this is not your personal forecast- its what the longer range models are (were?) showing.

you dont seem so confident today. are the LR models backing away from an extended cold(er) period?

Met Office assessment remains consistent:

- A protracted period of below average temperatures (ie most extended period of such seen for some time) remains key message from longer range output

- Timing of any return to mobility after end of this week remains very uncertain

- However, persistence of any blocking becomes much less pronounced through early March as mean NW flow becomes more dominant in extended range products

- GloSea5 takes us through mid-March on a wetter than average, cyclonic-dominated signal. EC Monthly does likewise, but retaining colder than average conditions

- Further transient blocked periods are possible

- Self-evidently, 'below average' for late Feb-early March must be interpreted relative to normal seasonal trend: so, that does NOT equate to what it would mean in e.g. mid-Jan!! 

- Finally, EC Monthly updates again tonight and the UKMO Seasonal Team will shortly update probabilistic expectations for March-April-May.

 

[Cheshire Freeze]

Completely academic and out at day 10 but that's some deep Scandi troughing. I must say, looks very like the GLOSEA seasonal output it has been advertising for late winter/early spring 

[feb1991blizzard]

12 minutes ago, fergieweather said:

Met Office assessment remains consistent:

- A protracted period of below average temperatures (ie most extended period of such seen for some time) remains key message from longer range output

- Timing of any return to mobility after end of this week remains very uncertain

- However, persistence of any blocking becomes much less pronounced through early March as mean NW flow becomes more dominant in extended range products

- GloSea5 takes us through mid-March on a wetter than average, cyclonic-dominated signal. EC Monthly does likewise, but retaining colder than average conditions

- Further transient blocked periods are possible

- Self-evidently, 'below average' for late Feb-early March must be interpreted relative to normal seasonal trend: so, that does NOT equate to what it would mean in e.g. mid-Jan!! 

- Finally, EC Monthly updates again tonight and the UKMO Seasonal Team will shortly update probabilistic expectations for March-April-May.

 

I don't know why people are interpreting your post any differently from yesterday, the line i've highlighted clearly indicates that its not out of the question at some point that someone could get lucky and get a big dumping (you don't need bitter cold -12c uppers and ice days to get a single snow event) but its obviously less likely more at the end of the season, its just a case of waiting and seeing how it pans out.

 

EDIT : And the stratospheric vortex is getting completely blasted although could have done with that happening a month or 2 earlier.

Edited February 22, 2016 by feb1991blizzard

[feb1991blizzard]

14 minutes ago, CreweCold said:

Completely academic and out at day 10 but that's some deep Scandi troughing. I must say, looks very like the GLOSEA seasonal output it has been advertising for late winter/early spring 

My theory now is that the GLOSEA5 is by far the best LRF model out there, and this would be its biggest achievement yet if that Atlantic / Southern Greenland high / scandi troughing ends up being the mean pattern throughout early spring.

[bobbydog]

16 minutes ago, feb1991blizzard said:

I don't know why people are interpreting your post any differently from yesterday, the line i've highlighted clearly indicates that its not out of the question at some point that someone could get lucky and get a big dumping (you don't need bitter cold -12c uppers and ice days to get a single snow event) but its obviously less likely more at the end of the season, its just a case of waiting and seeing how it pans out.

no- the line you have highlighted "clearly indicates" what one model is showing. i does not suggest anyone will get a "big dumping" 

of course, that could happen at any point but the rest of ian's post, when read in context, did not suggest that at all. this is the problem i was trying to highlight earlier. people read key words or sentences within a post and misinterpret  what is actually being said.

edit- i see you have now highlighted more of ians post since i started typing but the point still stands regarding cherry-picking lines of a post (not necessarily aimed at you)

Edited February 22, 2016 by bobbydog

[Lukesluckybunch]

Would just like to point out,from what the models are showing us,is temps of 5/6c not 2/3,so on that basis are people not getting carried away with this cold spell?

[feb1991blizzard]

1 minute ago, bobbydog said:

no- the line you have highlighted "clearly indicates" what one model is showing. i does not suggest anyone will get a "big dumping" 

of course, that could happen at any point but the rest of ian's post, when read in context, did not suggest that at all. this is the problem i was trying to highlight earlier. people read key words or sentences within a post and misinterpret  what is actually being said.

My post states that a dumping isn't out of the question, probably very unlikely in the south (although not out of the question) but cyclonic weather, with above average precipitation and below average temps at this time of year suggests the North COULD get a dumping

[PolarWarsaw]

As far as I can see/am aware - this is just a bog standard late winter affair, anticyclonic, cold and predominantly dry - with it always worth keeping an eye out on anything that could pop up suddenly or at the last minute and provide a little entertainment. Generally speaking, you get this kind of a spell at some point in virtually any and every late winter, normally between mid feb - mid march as that's when the vortex tends to commonly run out of steam.  It's a chance for a period of frosts and some of the flooded regions of the country to dry up a little bit. If we get ANY snow, then it's a bonus. It will feel colder than it would because the background of this winter - in general has been, supremely mild weather. 

That being said, nobody should be downbeat - it's this kind of setup that does occasionally provide last minute surprises. 

[Snowynorth]

42 minutes ago, emotional rollercoaster said:

Totally disagree-6 850s from the ne will and can create some great convection and these will be snow.

also feel similarly this spell like feb 2008.

it is true that the Greenland block has been rather over modeled over the past few winters but seems to quickly decline to nothing more than a transition ridge although this time does enough to direct Lows se I'm certain the models will show more interest as we move threw this week.

with snowfall very possible in the south as lows swing through the channel like what's currently happening now.

although the uppers are way to high right now they do go low enough to allow snowfall to be possible north northeast eastern uk and later in the week possible streamers from ne into the se and even southern England as well as lows dragging easterly which might not be cold enough.

i think the northeast flow would most certainly be the coldest outcome 

Hi ER

I think you're not understanding the point I'm trying to make.

It is not just the upper air temperatures that defines a cold spell or guarantees snow, it is also vitally important you have other variables favorable down to the surface.

freezing level, dew points and WBT's.

At this time of the year a north easterly or easterly without Europe being pretty cold is completely different to a an east or north easterly during December when Scandanavia and Russia is very cold.

The North Sea temperatures are warmer than average after a relatively mild winter, couple this with not so much cold pooling to the east then you will have significant modification when the air reaches the United Kingdom.

We would need to see much colder pooling to the east and much lower upper 850's for it to bring any significant wintry weather, as a result conditions at the surface would be more favorable, take the freezing level for example.

If we can somehow get a second bit of the cherry albeit with a better flow and Scandanavia/Europe cooling down with some very cold upper 850's the temperature gradient will be much greater with warm SST's which would more than likely lead to convective snow showers in such setup.

At the moment, despite an average of -7 850's  this just won't cut it. 

The perfect setup this time of the year would be a northerly!

 

Edited February 22, 2016 by Snowynorth

[feb1991blizzard]

2 minutes ago, PolarWarsaw said:

As far as I can see/am aware - this is just a bog standard late winter affair, anticyclonic, cold and predominantly dry - with it always worth keeping an eye out on anything that could pop up suddenly or at the last minute and provide a little entertainment. Generally speaking, you get this kind of a spell at some point in virtually any and every late winter, normally between mid feb - mid march as that's when the vortex tends to commonly run out of steam.  It's a chance for a period of frosts and some of the flooded regions of the country to dry up a little bit. If we get ANY snow, then it's a bonus. It will feel colder than it would because the background of this winter - in general has been, supremely mild weather. 

That being said, nobody should be downbeat - it's this kind of setup that does occasionally provide last minute surprises. 

That's exactly my sentiments, its a start to at least have monthly / seasonal models on side.

[stodge]

Morning all

It looks as though the GFS 06Z FI has read Ian's assessment. It's the first OP run I've seen that perpetuates the colder pattern well into March (as distinct from other output this morning which suggested a more settled and milder spell moving into March).

The exact positioning of the LPs as they move through England from NW to SE will be critical in terms of precipitation amounts and types. It seems more probable the SW will see rain with the NE on the colder side of the passing storms. 

 

 

[Kentspur]

6 minutes ago, Snowynorth said:

Hi ER

I think you're not understanding the point I'm trying to make.

It is not just the upper air temperatures that defines a cold spell or guarantees snow, it is also vitally important you have other variables favorable down to the surface.

freezing level, dew points and WBT's.

At this time of the year a north easterly or easterly without Europe being pretty cold is completely different to a an east or north easterly during December when Scandanavia and Russia is very cold.

The North Sea temperatures are warmer than average after a relatively mild winter, couple this with not so much cold pooling to the east then you will have significant modification when the air reaches the United Kingdom.

We would need to see much colder pooling to the east and much lower upper 850's for it to bring any significant wintry weather, as a result conditions at the surface would be more favorable, take the freezing level for example.

If we can somehow get a second bit of the cherry albeit with a better flow and Scandanavia/Europe cooling down with some very cold upper 850's the temperature gradient will be much greater with warm SST's which would more than likely lead to convective snow showers in such setup.

At the moment, despite an average of -7 850's  this just won't cut it. 

The perfect setup this time of the year would be a northerly!

 

But its quite obvious Northerlies are to put it mildly shi*! for most of the areas that still have not seen any of the white stuff since Jan 2013- maybe the same places that have already had the goods will benefit again though, I just hope with an extended period of cold as mentioned by Ian and others, that this will allow us to finally tap into some colder air, in conjunction with a east to northeast flow so that the heavily populated regions further south can get their long awaited rewards!

[feb1991blizzard]

Some of the GEFS members are a stonker and a big upgrade on the 0z.

[Snowynorth]

3 minutes ago, Kentspur said:

But its quite obvious Northerlies are to put it mildly shi*! for most of the areas that still have not seen any of the white stuff since Jan 2013- maybe the same places that have already had the goods will benefit again though, I just hope with an extended period of cold as mentioned by Ian and others, that this will allow us to finally tap into some colder air, in conjunction with a east to northeast flow so that the heavily populated regions further south can get their long awaited rewards!

Purely an example for the time of year. Northerlies have a much better track, if you get a decent feed/flow you will get less modification. You can get some decent features in northerlies still, not mildy sh*t as you said but they don't deliver to southern areas.. 

[feb1991blizzard]

Just now, Snowynorth said:

Purely an example for the time of year. Northerlies have a much better track, if you get a decent feed/flow you will get less modification. You can get some decent features in northerlies still, not mildy sh*t as you said but they don't deliver to southern areas.. 

My favourite setups are cyclonic North Easterlies at this time of year.

[Kentspur]

4 minutes ago, Snowynorth said:

Purely an example for the time of year. Northerlies have a much better track, if you get a decent feed/flow you will get less modification. You can get some decent features in northerlies still, not mildy sh*t as you said but they don't deliver to southern areas.. 

I get that first bit but atleast with a easterly lower due points probable coming from the continent (once its cooled) and much more of the population will have a chance of seeing the goods as there is far less land for precipitation to cross going east to west than from John O Groats to Hastings!

Edited February 22, 2016 by Kentspur