General Model Output Discussion

[kold weather]

Well the 06z is quite the stunner!

If that came off a sub 0C month really would be in grasp for the first time in a long but of course thats probably something of an extreme run, even for this winter!

Saying that the control run of the ECM may well evolve rather similarly...

Edited January 7, 2010 by kold weather

[Thundery wintry showers]

im abit bemused, both the ecm and gfs suggest a more southeasterly next week with the retreat of the 528 dam line any milder uppers, surely this gradual evolution will lead to less cold weather before the atlantic eventually wins out.

Wishful thinking again (understandable, but no better than when the cold/snow lovers look for cold and snow that isn't really there). I think the higher uppers will result in a slight warm-up in the north, particularly near the east coast where there may be some sleety precipitation about next week, causing some pretty unpleasant icy conditions underfoot (cue reassurances of "at least it will be milder", i.e. slush and ice is supposed to be preferable to soft fluffy snow).

But in the south, the warmer uppers will coincide with increasingly south-easterly winds and so mean temperatures might climb up to around freezing, but it will stay cold with chances for further snowfalls. The freezing rain events in the likes of January 1987 were caused by uppers of near 0C- here we're talking around -5C, so freezing rain should be less widespread than on that occasion.

A breakdown is quite possible at around T+240 but if the main thrust of the jet continues to stay south, the attacks from the Atlantic may break through only temporarily, and maybe affect only the west and south, and be followed by more easterly winds. There is certainly a sign that the Atlantic will strengthen, but no sign that it will definitely break through with enough "oomph" to deliver a spell of mild, moist south-westerly winds. The main change is that the easterlies next week are more likely to be mainly dry and cloudy with the odd light shower, as opposed to the sunshine and snow showers that our easterlies have reliably delivered so far this winter.

[Optimus Prime]

I guess the main threat are the low pressure systems just tracking underneath the high pressure rather then toppling it? With pressure set to rise over Greenland after a brief blip, I can only see that as the solution at present.

It's -4.2c currently, I want the mild air back.

[Derp Patrol]

This is quite amazing.. still no sign of a breakdown for quite a while.. but somehow I feel we will have to pay for this.. and this summer is going to be Atlantic dominated like the last 3!

[sandstorm2]

Another very cold outlook from the charts, offering virtually no end to the freeze, is the unthinkable possible? are we ready to get rid of the monkey on our backs that is 1947, 63 etc, and replace it with 2010.

SS2

[timgriff99]

Im still very confused as to where Sundays predicted snowfall and the warnings attatched to it have any merit ,because looking at it the fax chart it basically shows a weak front along the southern half of England and thats about it, I personally cant see how that would produce much if any snow let alone widespread snow.....Am I missing something??

Also, the position of the 528DAM suggests that the southern part of the UK may experience rain/ sleet only. Can anyone varify this?

[bluearmy]

Also, the position of the 528DAM suggests that the southern part of the UK may experience rain/ sleet only. Can anyone varify this?

IN CAPITALS AS SO MANY CANNOT READ WHAT HAS BEEN POSTED BEFORE.

FORGET THICKNESSES IN THE CURRENT SET UP. A CONTINENTAL FLOW DOES NOT REQUIRE THICKNESSES BELOW 528 DAM FOR SNOWFALL. JOHN HOLMES REPEATEDLY POSTS A LINK TO THE NETWEATHER 'WILL IT SNOW' INFO.

with the flow being brisk, even the coastal areas could be ok for snow on this.

[pyrotech]

Also, the position of the 528DAM suggests that the southern part of the UK may experience rain/ sleet only. Can anyone varify this?

528 dam is only one thing needed, cold continental air stream, cold lower level temps can help, just like 528 dam line does not mean definite snow.

Sorry Bluearmy i was a bit slower than you !

But your 100% correct

Edited January 7, 2010 by pyrotech

[leroys35]

IN CAPITALS AS SO MANY CANNOT READ WHAT HAS BEEN POSTED BEFORE.

FORGET THICKNESSES IN THE CURRENT SET UP. A CONTINENTAL FLOW DOES NOT REQUIRE THICKNESSES BELOW 528 DAM FOR SNOWFALL. JOHN HOLMES REPEATEDLY POSTS A LINK TO THE NETWEATHER 'WILL IT SNOW' INFO.

with the flow being brisk, even the coastal areas could be ok for snow on this.

breakdown according to the ggem blocking charts day 11 to 15 any one else got a opinion

[sandstorm2]

The GEM is showing a 1055mb anticyclone over Southern Norway, these things are not shifted easily.

SS2

breakdown according to the ggem blocking charts day 11 to 15 any one else got a opinion

Could you give me a link to these charts please, I thought the GEM only went out to 10 days.

SS2

[Iceberg]

IN CAPITALS AS SO MANY CANNOT READ WHAT HAS BEEN POSTED BEFORE.

FORGET THICKNESSES IN THE CURRENT SET UP. A CONTINENTAL FLOW DOES NOT REQUIRE THICKNESSES BELOW 528 DAM FOR SNOWFALL. JOHN HOLMES REPEATEDLY POSTS A LINK TO THE NETWEATHER 'WILL IT SNOW' INFO.

with the flow being brisk, even the coastal areas could be ok for snow on this.

But rather than shouting, it's probably worth saying why they don't matter.

When you have a contiental feed, the precip tends be shallower and the air dryer. For this reason 1000-500 thicknesses are much less important than the shallower closer to the ground 1000-850 thickness which looks to be around the 128 mark which is easily snow producing rather than rain. You also have more boundary layer modification(to colder) from a continental set up.

This is one of the reasons why more moisture is picked up and deposited over southern england during this kind of easterly set up, as per the METO's thoughts for sun-tues.

[leroys35]

The GEM is showing a 1055mb anticyclone over Southern Norway, these things are not shifted easily.

SS2

Could you give me a link to these charts please, I thought the GEM only went out to 10 days.

SS2

click on the 384 chart its the ggem anolamy chart ggem ensemble images not sure of the proper link

[Totoro]

But rather than shouting, it's probably worth saying why they don't matter.

When you have a contiental feed, the precip tends be shallower and the air dryer. For this reason 1000-500 thicknesses are much less important than the shallower closer to the ground 1000-850 thickness which looks to be around the 128 mark which is easily snow producing rather than rain. You also have more boundary layer modification(to colder) from a continental set up.

This is one of the reasons why more moisture is picked up and deposited over southern england during this kind of easterly set up, as per the METO's thoughts for sun-tues.

That's most helpful, thanks.

But that's for precipitation from an easterly direction - what happens when we have the forecast borderline thicknesses AND precipitation approaching from the West or South West but still with low level cold air from the continent - wouldn't that give freezing rain or drizzle?

Edited January 7, 2010 by Totoro

[Frosty.]

WOW the 6z has surprised me, usually the trash run of the daily gfs cycle but on this occasion is an upgrade on the 00z with a reload scandi high even more severe looking than next week! actually, next week's easterly seems less cold looking with less blues but obviously with a flow over the frozen near continent it will be v.cold at the surface through next week although just with scattered snow flurries compared to the heavy snow showers expected this weekend across southern britain with strong E'ly winds bringing blizzard conditions and drifting plus a high wind chill factor, it may ease a bit next week but remain very cold, this is turning into an epic cold spell and if it lasts much longer will surpass the winter of 1981-82.

Edited January 7, 2010 by Frosty039

[mushymanrob]

It's not a weak front, the hollow symbols indiciate an upper cold front.

"Upper fronts represent the boundaries between air masses at levels above the surface. For instance, the passage of an upper warm front may bring warmer air at an altitude of 10,000 ft, without bringing a change of air mass at the surface." - Met O

all the same, has it any potency? will it result in precipitation? because i agree with 'anyweather', im not so sure theres any real potential for much snow.

in feb 86 i had a month of bitter easterlies and here in derby we had no snow. the upcoming predicted charts are similar and to me its looking cold and dry.

[Weather-history]

.

in feb 86 i had a month of bitter easterlies and here in derby we had no snow. the upcoming predicted charts are similar and to me its looking cold and dry.

Interestingly Manchester recorded 21 days of falling sleet/snow during that month.

[Frosty.]

in feb 86 i had a month of bitter easterlies and here in derby we had no snow. the upcoming predicted charts are similar and to me its looking cold and dry.

There were plenty of snow flurries in the feb 1986 spell and next week looks similar to that for southern & eastern britain at least according to the 00z & 06z output.

[fear sneachta]

Do the models support a milder breakdown from the southwest? Will the south of Ireland and the southwest of England see some milder weather creep in on Monday and Tuesday?

Edited January 7, 2010 by fear sneachta

[Iceberg]

The models don't support a breakdown of any description.

The 00Z ECM Ensembles taken as a whole keep the cold ongoing, The Mean Ensemble max temp for London out to the 21st of Jan is just 3C.

A pocket of slightly warmer 850's look like creeping into the high, but ground temps remain cold. After this the guidance looks to suggest another cold splurge.

Looking at the weekend, ECM 00Z is keen on bringing in maybe 5-10cm over the SW, GFS less keen taken accumulations to 3 or 4cm by Monday morning and higher upto 8-10cm in the east.

METO seems to suggest a bit of both hence the METO advisories for the sun/mon period across most of the country south of Birmingham.

[Nick F]

Do the models support a milder breakdown from the southwest? Will the south of Ireland (if I'm allowed mention Ireland) and the southwest of England see some milder weather creep in on Monday and Tuesday?

Quite a few of the GEFS members go for a low pressure attack from to the SW at some point in the medium range, but whether the attack introduces milder air remains a little uncertain. GFS is often too keen to bring in milder air from the SW, though 06z GFS shows a continuation of a cold feed off the near continent later next week, so any precipitation that moves up from the S or SW would most likely fall as snow inland, and this seems most likely outcome than a mild breakdown from the SW across Sern UK.

Btw, I have updated my blog covering today, tomorrow and the weekend:

http://forum.netweather.tv/topic/59644-new-year-cold-spell/page__gopid__1716970entry1716970

[MR EXTREMES]

well the met office warnings extended to mondays aswell with a large part of england and wales in the early warning zone.

the out also suggests a continued cold so alot of people that are sugggest that surface coild will have an impact could well be right.

gp also seems keep on suggesting some runs for mild are far to progressive which i think they are its after the weekend where thing get even more intresting since lastnight for some reason i feel more confident that the cold could well hold on.

whether a reload is possible im unsure but by saturday where no for sure,

i would not be suprised to see reload maybe straw clutching and maybe selfish but id love to see 2010 match 63 although unlikely.

overall met office are there selfs reluctant to remove cold quickly and as has been mentioned its very cold right now so even a little below average would still be exciting.

[fear sneachta]

Quite a few of the GEFS members go for a low pressure attack from to the SW at some point in the medium range, but whether the attack introduces milder air remains a little uncertain. GFS is often too keen to bring in milder air from the SW, though 06z GFS shows a continuation of a cold feed off the near continent later next week, so any precipitation that moves up from the S or SW would most likely fall as snow inland, and this seems most likely outcome than a mild breakdown from the SW across Sern UK.

Btw, I have updated my blog covering today, tomorrow and the weekend:

http://forum.netweat...0entry1716970

Thanks Nick.

Edited January 7, 2010 by fear sneachta

[snowmadchrisuk]

Out until Sunday Morning it has to be noted that the UKMO precipitation charts do not bring any snow showers inland at all apart from Southern Scotland. GFS shows something of a frequant Snow shower day for the Midlands on Saturday but the UKMO is having non of it , which one will be right ?

My thought's on GFS would be that the Snow falling Sun/Mon/Tue would be of Snow inland and maybe turning a bit Sleety at the End of the Week before a reload of cold into next weekend. The charts look very much like Feb 91 in terms of precipitation with the High feeding constant Snow showers into Central and Southern uk and getting deeper and deeper.

[Nick F]

Out until Sunday Morning it has to be noted that the UKMO precipitation charts do not bring any snow showers inland at all apart from Southern Scotland. GFS shows something of a frequant Snow shower day for the Midlands on Saturday but the UKMO is having non of it , which one will be right ?

My thought's on GFS would be that the Snow falling Sun/Mon/Tue would be of Snow inland and maybe turning a bit Sleety at the End of the Week before a reload of cold into next weekend. The charts look very much like Feb 91 in terms of precipitation with the High feeding constant Snow showers into Central and Southern uk and getting deeper and deeper.

I think you are probably refering to the UKMO global model and their precipitation charts, this model is quite low in resolution, so won't pick out showers that feed inland. 06z NAE model, which is higher res, shows precip feeding inland to the midlands as early as tomorrow evening as a trough moves in off the N Sea on the developing easterly flow. GFS shows showers filtering inland to Midlands on Saturday.

[anvilhead]

most probable outlook to me looks like a continuation of high pressure to the north, southerly jet and low pressure over europe from the early to mid term, with a lobe of the pv over to our far NE possibly being in place for a relead/reinforcement of the cold flow come the middle of the month, with another NE'ly ... I would wager trough disruption not an attack from the atlantic, and the repeating waa involved to pull the high back towards greenland and open the floodgates again from the east wouldnt be too much of a suprise the way this winters going. I dont really see a mild/cold battle developing in the SW - maybe im missing something there

Crazy spell of weather ...