General Model Output Discussion

[gottolovethisweather]

Hello,

To me this is already a classic textbook winter, especially for the north, someone said 4 weeks of lying snow, how quickly would 2 feet or more of lying snow melt even if rained on with a therorhetical AT of say 5c. My point, is that the snow cover surely cools the air above and we would need something 546 dam air over us to then claim the breakdown is here and over within 24-48 hrs.

What matters to me is that the only to look for a change is raging zonality and I just dont see that happening for many days/weeks.

Science is not my strong point but experience and watching day to day petterns is how we learn, when and why they go wrong is an issue for the real experts. Unfortunately I agree with Nick Sussex's view past this weekend and people south of the M4 brace yourselves for something special once again.

We all love the weather and 2010 is a special one and the floods, storms and heatwave i think are all in the mix this year, just gut feeling and having divulged some texts on the great winters of past.

Stay safe people, whatever we wish for we can only stand with our backs to it, the weather will do whatever it likes.

STORMBOY

[MP-R]

http://www.wetterzentrale.de/pics/Rtavn2161.html

No Greenie High later on in this run, but instead something more anticyclonic with westerlies. Could be worse but of course all up to change. High pressure nearby to the east and the charts for this coming week look very interesting! Lots to be watching.

[TEITS]

Fasinating watching this battle between the block and the Atlantic with F.I most certainly +72. In my experience of these synoptics the first push from the Atlantic usually results in a stalled front across Wales, W Midlands. What happens with the next push dictates whether it turns milder or remains cold. I would put the odds at 50/50 at the moment.

[Duane S.]

Most break downs are a damp squib for many only a few have been exceptionally wide spread snow events, dont think this break down will go into the record books!!

Yes that's very true and my gut feeling is that it won't amount to anything down here either BS (although that could easily change) but I think that some are going to get an incredible dumping of snow from this breakdown, more even than last week.

With regards to a reload, I think we can all but forget any retrogression to Greenland. I think a renewed block emerging from Scandi may well be on the cards as we get into the last third of the month. In the interim and after the low pressures have come in towards us from the Atlantic, less cold in the south and west (but still below average I suspect). North and East to remain cold for a while longer.

[sandstorm2]

Out to +132 on the GFS 0600 and it looks like it keeps the cold hanging on, the western approaches could be in the firing line, think +72 is FI right now, models are still struggling.

SS2

[NorthernRab]

Yes that's very true and my gut feeling is that it won't amount to anything down here either BS (although that could easily change) but I think that some are going to get an incredible dumping of snow from this breakdown, more even than last week.

With regards to a reload, I think we can all but forget any retrogression to Greenland. I think a renewed block emerging from Scandi may well be on the cards as we get into the last third of the month. In the interim and after the low pressures have come in towards us from the Atlantic, less cold in the south and west (but still below average I suspect). North and East to remain cold for a while longer.

I don't know, the latest GFS is beginning to show signs of the high retrogressing towards Greenland, it's all just down to how the Atlantic behaves.

[snowking]

Im a bit confused this morning with the suggestion that the ECMWF would turn things to sleet/rain across the SW and S first

I'm not going to claim to be an expert here, but dry continental feed there right across the south, which away from maybe the very far SW (cornwall and perhaps devon) should result in dew points conductive of snowfall. If you then take a look at the 850 projections....it actually looks remarkably similar to the snow storm 'that never was' earlier this month, though obviously this time with the embedded cold we need! The coldest uppers actually move in from the NW, so its more eastern areas which would be likely perhaps to see a spell of more sleety stuff for a time?

Excuse my ignorance if ive got the wrong end of the stick

SK

Edited January 9, 2010 by snowking

[gottolovethisweather]

Fasinating watching this battle between the block and the Atlantic with F.I most certainly +72. In my experience of these synoptics the first push from the Atlantic usually results in a stalled front across Wales, W Midlands. What happens with the next push dictates whether it turns milder or remains cold. I would put the odds at 50/50 at the moment.

Thanks TEITS, keep us informed with your odds, I'll go 60/40 in favour with the cold staying, albeit less cold at first. The way I read the latest GFS DP charts is that a slight warming is due around Tuesday and then we're guessing., imho gets colder from the northeast/east again.

Am I right that less cold air over snowcover can't bring us rapid melting unless the atlantic kicks in furiously, can it? and the influence is from the warmer seas.

Whatever, gotta love this weather pattern so far.

Take Care

STORMBOY

[Typhoon John]

I think both the ECM and the GFS are overplaying the strength of the low coming in from the West. I'd expect corrections nearer the event that put it further SW with the High further West. It'll be Sunday night or Monday before we really know what's going to happen.

[nick sussex]

Its no coincidence that the chance of a breakdown/ return to milder weather coincides with a forecast for rising NAO/AO to near zero, rather than being well NEGATIVE.

http://www.cpc.noaa.gov/products/precip/CWlink/pna/nao.mrf.gif

http://www.cpc.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif

If you look at the past weather weve had, its all being with the telleconections being very negative. And for such an exceptional/prolonged cold spell that weve had, these are absolutly esential.

Im not saying a breakdown/mild is inevitable just that a another greeny high or retrogressing towards that area is very unlikly now. I think If we can just hang on to the cold in the form of a scandi type high/ a euro high that streches pretty far north, we may just hold off the atlantic in time for more WAA to be pumped towards greenland increasing the chances of a real block

The chances of huge snowfalls will be increasing next week, but as ever the risk of a breakdown to mild. If I had it my way Id perhaps prefer more of the same, less of a gamble (says a guy who likes a gamble.)

Hopefully the dream scenario will be, heavy snow pushing in from the atlantic, but just as the milder air is about to turn the snow to rain, it gets edged southwards followed by a chilly night and high pressure from the east

NOAA in the USA last night continued to forecast a deeply negative AO so i can't see that much changing overnight.Also there is uncertainty regarding the Pacific Jet as to how far north this will be. This is quite important upstream in western Europe, also how the trough sets up over the eastern USA again will effect western Europe, these variables are likely to lead to model variability especially in the later timeframes. Heres a few quotes from NOAA last night.

THE ARCTIC OSCILLATION IS PREDICTED TO CONTINUE TO BE HIGHLY

NEGATIVE THROUGH THE 6-10 DAY PERIOD, WHICH FAVORS BELOW NORMAL TEMPERATURES IN

THE SOUTHEAST, BUT IF THE SOUTHERN MEAN TROUGH ORIENTS ITSELF OVER TEXAS, AS

THE CANADIAN AND ECMWF MODELS PREDICT, TEMPERATURES MAY AVERAGE CLOSE TO NORMAL

ALONG THE SOUTHERN ATLANTIC SEABOARD

HOWEVER, STRONG EL NINO CONDITIONS ARE CURRENTLY OBSERVED, WHICH FAVORS

A SOUTHWARD DISPLACEMENT OF THE JET, SO THE PROBABILITY OF ABOVE MEDIAN

PRECIPITATION IS ELEVATED SLIGHTLY FARTHER SOUTH OF THE AREA MOST TOOLS

INDICATE. TEMPERATURES IN CALIFORNIA EASTWARD TO THE CENTRAL AND SOUTHERN

ROCKY MOUNTAINS ARE UNCERTIAN SINCE THEY ALSO DEPEND ON THE ORIENTATION OF THE

PACIFIC JET. NEAR NORMAL TEMPERATURES APPEAR MOST LIKELY AT THIS TIME, HOWEVER

THE CHANCES OF BELOW NORMAL TEMPERATURES INCREASE MARKEDLY IF THE JET SETS UP

FARTHER SOUTH THAN MODELS CURRENTLY INDICATE

[MR EXTREMES]

i noticed a good little post from another talented forecaster brickfield on tec model thread.

intresting someone posted a rise in nao from the first bit i read this is not the case,

this could be part of the problem with model outputs being rather messy possibly because there is a growing trend.

still hard to say what the outcome will be as no forecast futher out is 100%.

but im convinced there juice still in the tank for cold outlook.

i do think a warm up is on the cards but i also think a reload is possible 60/40 on a reload.

but its a case of the next couple of days hopefull a clearer picture with so much cold air i dont think its a case of low moving in from the southwest with rain mild,

more like snow to rain and i dont think it will get any futher than north hampshire.

although a thaw looks like in the south end of next week,

i think cold will push back and win out the alantic has no strength to dominate cold has.

intresting stuff indeed very exciting.:wacko:

Edited January 9, 2010 by badboy657

[Paul T]

In My view;

75% -

From Tues 12th; Low after low until a proper zonal SW setup is in place. There will be some ''initally heavy snow, turning to rain/sleet later'' set-ups, and at times the midlands could have some heavy falls. This will gradually be balsted away and the cold spell long forgotten by the 20th. Then possibley colder from 26-27thJan onwards.

25% -

Low after low approaches the Uk, weakens and tends to want to drop to the south. The first will be centred over England, the second dropping into France/Spain even. Widespread snow from the first for the midlands, and also from the second, with heavy rain for S/SW. Temps in South back to normal, up north still cold. The cold gradually pushes back in to all areas from the 20th and a weak eastern flow, into a possible Northerly later in month.

I haven't a clue what planet the Met are on to forecast heavy snow on wednesday in the Devon and Cornwall , I think they've gone into Weather warning overload to avoid bad press (as the news-reporter on itv on Thursday night tried to highlight - incorrectly in my opinion).

I would say the chance of heavy snow over Cornwall and Devon (barring the moors) is close to 5%. You may as well start puttng out warnings for earthquakes.

Edited January 9, 2010 by Paul T

[pyrotech]

In My view;

75% -

From Tues 12th; Low after low until a proper zonal SW setup is in place. There will be some ''initally heavy snow, turning to rain/sleet later'' set-ups, and at times the midlands could have some heavy falls. This will gradually be balsted away and the cold spell long forgotten by the 20th. Then possibley colder from 26-27thJan onwards.

25% -

Low after low approaches the Uk, weakens and tends to want to drop to the south. The first will be centred over England, the second dropping into France/Spain even. Widespread snow from the first for the midlands, and also from the second, with heavy rain for S/SW. Temps in South back to normal, up north still cold. The cold gradually pushes back in to all areas from the 20th and a weak eastern flow, into a possible Northerly later in month.

I haven't a clue what planet the Met are on to forecast heavy snow on wednesday in the Devon and Cornwall , I think they've gone into Weather warning overload to avoid bad press (as the news-reporter on itv on Thursday night tried to highlight - incorrectly in my opinion).

I would say the chance of heavy snow over Cornwall and Devon (barring the moors) is close to 5%. You may as well start puttng out warnings for earthquakes.

reason is low is expected further south and later Wednesday and into Thursday sleet and rain expected into sw especially at near coasts. We have dense cold air over the UK and continental Europe. Will be very marginal but further north even worse conditions. This is similar to the set up last year that stranded motorists in the SW and made breaking news.

[Methuselah]

Don't get too disheartened by talk of incoming zonality...IMO, what the models are tending towards, is a classic 1960s-style attack from the SW?? I can still recall some monumental 12hr blizzards ahead of such breakdowns. Like many folks though, I can probably recall the blizzards better than I can the following rain??

[Glacier Point]

Long range guidance tools (GEM and GFS ensemble mean) suggest the upper low to be maintained well to our west ejecting energy SE between ridges over Scandinavia and southern Iberia:

http://raleighwx.easternuswx.com/models/cmcensemble/00zCMCENS11-15day500mbHeightAnomalyNH.gif

http://raleighwx.easternuswx.com/models/gfsensemble/00zENS11-15day500mbHeightAnomalyNH.gif

That's death by a thousand cuts to the cold pattern. Trouble is, by the time we get to the 50th cut, we may well have seen the atmosphere progress towards a signal for the ridge over Scandinavia back further west and north.

The global wind oscillation phase 4 solution for a weak (negatively tilted) trough attempting to work over the UK continues to look like the best solution for me, that's unlikley to shift the surface cold rapidly and opens up the potential for a very worrying national situation next week w/r/t grit. The trend for attempted attacks #1 and possibly #2 looks southward on each successive run.

[Duane S.]

i noticed a good little post from another talented forecaster brickfield on tec model thread.

intresting someone posted a rise in nao from the first bit i read this is not the case,

this could be part of the problem with model outputs being rather messy possibly because there is a growing trend.

still hard to say what the outcome will be as no forecast futher out is 100%.

but im convinced there juice still in the tank for cold outlook.

i do think a warm up is on the cards but i also think a reload is possible 60/40 on a reload.

but its a case of the next couple of days hopefull a clearer picture with so much cold air i dont think its a case of low moving in from the southwest with rain mild,

more like snow to rain and i dont think it will get any futher than north hampshire.

although a thaw looks like in the south end of next week,

i think cold will push back and win out the alantic has no strength to dominate cold has.

intresting stuff indeed very exciting.

Yes I agree, Brickfielder is right up there with GP. Looking at the NAO ensembles, I see no clear indication of it going positive any time in the future so with that in mind, all to play for in the medium term I would suggest. AO also showing it has no desire to move to any sort of positive state, with most members hinting at another decline in about a week's time (and that's from an already deeply negative state).

At the end of the day, there is not a lot of strengh in the Northern arm to indicate any sort of steamrollering in, it is going to take at least two shots and then, does the Atlantic have the reinforcements to sustain it??

I also think that the low will be less deep and as a consequence end up tracking further south then a lot of charts would have us believe. Mild(er) it will be down here in a week's time but not a lot and what happens next???

Edited January 9, 2010 by s4lancia

[Cecil Hogmanay Melchett]

Long range guidance tools (GEM and GFS ensemble mean) suggest the upper low to be maintained well to our west ejecting energy SE between ridges over Scandinavia and southern Iberia:

http://raleighwx.easternuswx.com/models/cmcensemble/00zCMCENS11-15day500mbHeightAnomalyNH.gif

http://raleighwx.easternuswx.com/models/gfsensemble/00zENS11-15day500mbHeightAnomalyNH.gif

That's death by a thousand cuts to the cold pattern. Trouble is, by the time we get to the 50th cut, we may well have seen the atmosphere progress towards a signal for the ridge over Scandinavia back further west and north.

The global wind oscillation phase 4 solution for a weak (negatively tilted) trough attempting to work over the UK continues to look like the best solution for me, that's unlikley to shift the surface cold rapidly and opens up the potential for a very worrying national situation next week w/r/t grit. The trend for attempted attacks #1 and possibly #2 looks southward on each successive run.

Thanks GP, hopefully the trough will not be strong enough to force the block to our NE to far SE.The further south the trough and its energy the better.Not keen on ecm this morning at all,it wants to destroy the block very quickly!!

[Turnedoutniceagain]

Don't get too disheartened by talk of incoming zonality...IMO, what the models are tending towards, is a classic 1960s-style attack from the SW?? I can still recall some monumental 12hr blizzards ahead of such breakdowns. Like many folks though, I can probably recall the blizzards better than I can the following rain??

That's pretty much how i see it Pete. SW hits cold pool - bingo !!

[Paul T]

Oh yes, i can see the slight potential, but every chart update is programming the first low to be very progressive into the uk, thus rising temps in the south west, and the next low, which i do believe may travel up the channel/over france, will drop heavy precipitation on areas that have just had the dense cold removed from the first low, therefore not recreating the feb 6th event, but the event just before Christmas....Rain, with sleet/snow on its leading edge.

Still hoping for more though, and next week has potential to cause very snowy problems as i said, but I think that the momentum is beginning to pick up pace in support of much milder conditions.

Anyhow, im off to look forward to my light snow flurry tomorrow at 7:46am.

Paul

[Harsh Climate]

NOAA in the USA last night continued to forecast a deeply negative AO so i can't see that much changing overnight.Also there is uncertainty regarding the Pacific Jet as to how far north this will be. This is quite important upstream in western Europe, also how the trough sets up over the eastern USA again will effect western Europe, these variables are likely to lead to model variability especially in the later timeframes. Heres a few quotes from NOAA last night.

THE ARCTIC OSCILLATION IS PREDICTED TO CONTINUE TO BE HIGHLY

NEGATIVE THROUGH THE 6-10 DAY PERIOD, WHICH FAVORS BELOW NORMAL TEMPERATURES IN

THE SOUTHEAST, BUT IF THE SOUTHERN MEAN TROUGH ORIENTS ITSELF OVER TEXAS, AS

THE CANADIAN AND ECMWF MODELS PREDICT, TEMPERATURES MAY AVERAGE CLOSE TO NORMAL

ALONG THE SOUTHERN ATLANTIC SEABOARD

HOWEVER, STRONG EL NINO CONDITIONS ARE CURRENTLY OBSERVED, WHICH FAVORS

A SOUTHWARD DISPLACEMENT OF THE JET, SO THE PROBABILITY OF ABOVE MEDIAN

PRECIPITATION IS ELEVATED SLIGHTLY FARTHER SOUTH OF THE AREA MOST TOOLS

INDICATE. TEMPERATURES IN CALIFORNIA EASTWARD TO THE CENTRAL AND SOUTHERN

ROCKY MOUNTAINS ARE UNCERTIAN SINCE THEY ALSO DEPEND ON THE ORIENTATION OF THE

PACIFIC JET. NEAR NORMAL TEMPERATURES APPEAR MOST LIKELY AT THIS TIME, HOWEVER

THE CHANCES OF BELOW NORMAL TEMPERATURES INCREASE MARKEDLY IF THE JET SETS UP

FARTHER SOUTH THAN MODELS CURRENTLY INDICATE

Thanks for that.

Interesting though, the whole of USA is set to warm up next week, with an ever increasing zonal flow

http://www.wetterzentrale.de/pics/Rnamavn242.png

http://www.wetterzentrale.de/pics/Rnamavn1622.png

I think if this happens the upstream telleconections should head towards positive, and all that cold heading out of the eastern seaboard perhaps towards greenland shouls decrease the chance of a pressure rise towards greenland.

Like you say though, if expert talk on the latest gfs/some other models, is that some of the ways there predicting this set-up should be dismissed, then this goes pretty much out of the window lol...

I think a painfully slow brakdown to less cold conditions is most likely with zonality not quite pushing through the UK, but with our blocking high not being too favourable for a return to much colder weather

[The PIT]

The GFS 060z is going for a brief breakdown this Tuesday although the thaw only looks like reaching the far South West. Worth watching and it'll be interesting too see whether Frontal Snow delivers or not and how far North it does actually push.

Could also be a threat of freezing rain which would be great fun without grit.

Edited January 9, 2010 by The PIT

[Paul]

I think it's important not to read too much into the 850hpa temperature charts as we move into next week as they don't show the cold we have at the surface across the UK..

For instance 850hpa temperatures for Wednesday midday:

Compare that to the 850-1000 thickness which gives a much better indicator of the temperature closer to the surface:

[Frosty.]

Another very cold 6z run with the scandi high not showing signs of sinking due to low pressure to the south propping it up which should just allow the E'ly or SE'ly winds to continue with snow flurries into the east & northeast but with complications as low pressure tracks east to the south of the uk, eventually the flow turns back into the east. More heavy snow next week seems likely with no thaw according to this run but the euros do still indicate a less cold trend so it's all very much in the balance at the moment.

[TEITS]

The ensembles sum up the situation perfectly at the moment.

http://charts.netweather.tv/ensimages/ens.20100109/06/prmslCambridgeshire.png

As you can see high pressure remains close by with the mean at 1020mb.

My view is we're going to remain cold with the flow alternating between SSE/SE/ESE,ly. I can also see a big snow event for Wales/W Midlands/parts of the SW because this is the usual locations that see a stalling front. Beyond next week and at the moment I cannot see any movemenr of our HP to Greenland but instead LP systems continue to track underneath our block keeping much of the UK cold with only the SW possibly turning milder. However with these LP systems tracking underneath the block to the E there is always the chance of retrogression. I just can't see it happening this week.

Whatever happens in future model output will not change the fact that this winter will be remembered for many years. Hard to believe its only the 9th Jan!

I will finally add that the snow event this weekend into monday could be significant. This isn't due to the intensity of the snow but the sheer persistance of it. The heavier snow in the SE will move further N and affect central regions as the flow changes from a ENEly to a E,ly. I feel Monday is going to be an extreme day for much of E Anglia/Midlands/Wales/N England.

Edited January 9, 2010 by THE EYE IN THE SKY

[johnny1972]

I think it's important not to read too much into the 850hpa temperature charts as we move into next week as they don't show the cold we have at the surface across the UK..

For instance 850hpa temperatures for Wednesday midday:

Compare that to the 850-1000 thickness which gives a much better indicator of the temperature closer to the surface:

Paul

The second chart im not that familiar with despite seeing it posted numerous times. The 1310 over NI what exactly does that mean?