Winter Model Discussion 18Z 19/2/13 onwards.

[johnholmes]

I've always thought 1st day of spring was March 21st

meteorological spring has always been 1 March,

other variations abound of which 21 March seems the most popular

[nick sussex]

not another query

meteorological spring has always been 1 March,

other variations abound of which 21 March seems the most popular

Yes I think its one of those Americanisms that spread across regarding spring.Personally I think its totally illogical given that use meaning winter would be starting on the 21st December!

Going back to the models the pattern for cold lovers in GFS FI is still too far west but at this timeframe still plenty of room for changes.

[SMU]

GFS Regionals on cycle V ECM

http://www.emc.ncep....tml4x/acz5.html

GFS 00z clearly the best but still poor-

http://www.emc.ncep....00x.region.html now if look at the regionals- the 00z performs strongly in the pacific & asia which is wheres it strength is-

However Europe, Atlantic its not the best & falls behind some of the other runs vis a vie- its elevated position near the top is driven by its performance in other areas of the globe within 20-80N.

If there was ECM regionals there would be significant difference across Europe & atlantic- proved time & time again this winter.

S

Edited February 21, 2013 by Paul
Original comment you were responding to has been removed.

[R.P. McMurphy]

From what I've seen over the past few days ANYTHING could happen past +120hrs...

GFS 12z is again teasing us again with its perfect Greenland block. One thing we can be more confident on, nothing average is appearing on the models at this juncture.

SM

The models seem all over the place at the moment - one minute its spring all the way and the next (current) its showing smomegeddon for North England, especially the North West and down the Western side of England & the Midlands. Albeit a bit marginal for the SE. Winter would certainly go out with a bang for those areas should this come off.

Chance: 25%

[Ian Brown]

the gfs anomaly charts do not agree with the op run, although the ecm does trend towards it. until these charts agree there must be considerable doubt over this fi northerly.

http://www.meteo.psu...0z/hgtcomp.html

I think it is still a fair way off and the NWP is dealing with margins that can't be determined at this range, though I think your Atlantic wind and rain is becoming less likely if we look at how the models are trending.

[Panayiotis]

This is the ECM 00z and GFS 12z side by side at 240hrs:

GFS has a more pronounced Greenland high, whereas the ECM has it just below Greenland. One thing for sure though is the movement of part of the PV to N Europe and with this we could see the spawning lows move south driving in a northerly wind (what we call a polar low), GFS and ECM both show this. However on the ECM the PV that has moved holds deeper thickness values l and uppers than the GFS. The GFS weakens the PV and therefore the thickness values and uppers are not as deep as the ECM. We want the PV to be deep to the north of us (like the ECM) because if we get a polar low/northerly the uppers there will be a greater area of deeper uppers to tap into therefore chance of us getting snow is greater.

I wonder if the ECM 12z :

1)Has a better ridge/Greenland high at 240hrs?

2)Keeps the strength of the PV that's to the north of us like the 00z was showing?

Edited February 21, 2013 by Panayiotis

[bluearmy]

Rob - that anomoly is from the 00z op run. I guess you need to compare that 4 day mean with the noon run in an hour when it is out. Presumably gfs ops may not be consistent in the 6/10 day timeframe. 'Hold the front page'!

[LomondSnowstorm]

Rob - that anomoly is from the 00z op run. I guess you need to compare that 4 day mean with the noon run in an hour when it is out. Presumably gfs ops may not be consistent in the 6/10 day timeframe. 'Hold the front page'!

6-10 day anomaly is very unlikely to show a typical height anomaly for a northerly anyway because, on the GFS at least, we still have the mid latitude heights dominating up to day 8. so this only really reflects the fact that the ECM was a bit more progressive with the pattern change than the GFS:

[SMU]

http://www.meteociel.fr/modeles/ecmwf/runs/2013022112/ECH1-120.GIF?21-0

ECM retrograde signal very strong now with the high filling gap & retrograding West-

The question isnt 'is a Northerly coming' its how far south does the cold get across the UK as the upper high over europe may build just enough to hold the cold towards Scotland.

S

[Cloud 10]

ECM has the northerly teed up and pointing for the UK,how far down the fairway can it hit?

[nick sussex]

So close and yet so far, some brutal cold to the north but the ECM is reluctant to take it south with a messy looking set up.

Really have my doubts re the detail of this run though, in terms of trend its a bit of a stalemate, move the pattern further se and you could make a case for some outlandish March temperatures, as it is its looking a bit frustrating.

Still this far out anything could happen.

[mountain shadow]

No potent northerly on the ECM but a watered down version with a West based -NAO.

A below average start to March looks odds on with pressure low to the south west.

[mushymanrob]

Rob - that anomoly is from the 00z op run. I guess you need to compare that 4 day mean with the noon run in an hour when it is out. Presumably gfs ops may not be consistent in the 6/10 day timeframe. 'Hold the front page'!

yeah i know, and i know it might catch up with the op. on the other hand the op might be overstating the possibilities. atm its fi anyway. if we get it then so be it.

[Panayiotis]

Interesting ECM 12z lots of cold options with the Atlantic blocked by high pressure:

1)The low to the SW of Greenland could move SE putting us in a cold NW flow and with the PV close by, uppers will be cold. 25%

2)The low to the SW could could take a NE route putting us in a cold NE flow and again with the PV close by, uppers will be cold. 35%

3)Further lows spawning out of the PV to the north, possibly giving us a polar low. 30%

4) The high over the Atlantic moving over us putting us in a dry but cold northerly flow. 10%

Cold start to March nonetheless, however how cold or how snowy is obviously up to debate considering the timeframe.

[Gibby]

Good evening. Here is the report of tonight's 12z output from GFS, UKMO and ECM for today Thursday February 21st 2013.

All models show a settled spell of weather continuing over the UK for some considerable time as High pressure persists to the North or NE of the UK. A cold and raw East wind will continue to blow across the South and West of the UK over the following two to three days. A lot of low Stratocumulus cloud will be trapped under the cold dry air over the UK giving snow grains or light snow showers at times in exposure to the NE, like Eastern Coasts and hills though even here only small amounts are expected. The first few days of next week sees little change in the overall pattern though the biting NE wind will decrease in the South by Monday and the coldest conditions will temper over the UK the further we progress towards midweek.

GFS then shows High pressure slowly weakening over the UK next week but the weather stays fine and dry for many with some sunshine by day and frosty nights. Eventually pressure falls from the North with unsettled weather gradually developing first in the North and more generally later as Low pressure develops over the UK with rain and showers for all in much increased and moister winds. Though milder than currently some hill snow is likely in the North and over the hills. The run ends with rather chilly and unsettled conditions continuing as Low pressure spirals around the West of the UK with rain and strong winds at times.

The GFS Ensembles tonight show the current cold uppers lasting for two or three more days before a steep if temporary rise early next week takes hold. The rest of the run shows a further colder dip in 10 days or so with the usual spaghetti mixture at the end. Rainfall amounts will increase towards the end of the run.

The Jet Stream continues to flow in two arms, one well to the North of the UK and one well to the South. A temporary link is made from the Southern arm to the Northern arm towards the middle of next week before the pattern reverts to a similar shape to that currently.

UKMO for the middle of next week shows a large High pressure anchored close to Eastern Scotland and NE England with a much slacker NE flow over the South by then. All areas will remain on the cold side, especially at night as further sharp frosts are to be expected but with less wind and somewhat more sunshine possible daytime's should gradually feel less cold, especially in the South.

ECM shows High pressure over Northern Britain too at the middle of next week before it loses it's identity leaving slack winds over the UK with fine and dry weather continuing with variable cloud cover. Frosts at night would still be commonplace and daytime's too could still be on the cold side of average though less cold than currently. Later in it's run Low pressure is centred near the Azores and High pressure over Canada with Low pressure over the Norwegian Sea. An attempted Northerly does largely fail though there is sufficient instability set up over the UK for some rainfall to develop towards the end of the run and with rather cold conditions still likely some snow could fall over higher ground.

In Summary the weather looks like remaining High pressure influenced over the coming week or so with any changes to the overall pattern not expected until after that point. That means very cold and frosty weather through the next 4-5 days with a lot of cloud and some small snowfalls possible in the East. With time as the High both slips further South and loses it's strength the coldest temperatures will be tempered as the cold air mixes out with milder uppers in the circulation of the High. Nevertheless it still looks more likely to stay on the cold side of average for many beyond next week with slack winds and large amounts of cloud together with the chance of rain and hill snow suppressing temperatures rather than the usual milder Atlantic winds or sunshine.

[mushymanrob]

I think it is still a fair way off and the NWP is dealing with margins that can't be determined at this range, though I think your Atlantic wind and rain is becoming less likely if we look at how the models are trending.

my atlantic wind and rain? sorry ive not mentioned that in relation to the anomaly charts i posted. they show either northwesterlies or easterlies. yeah the op,s though have shunted back anything milder.

[Stu_London]

One crumb of comfort is that the GFS does model Northerlies well. Encouraged to see the operational taking the route of some of the colder ensembles we have been seeing

[weather eater]

http://www.meteociel...H1-120.GIF?21-0

ECM retrograde signal very strong now with the high filling gap & retrograding West-

The question isnt 'is a Northerly coming' its how far south does the cold get across the UK as the upper high over europe may build just enough to hold the cold towards Scotland.

S

Despite some recent runs suggesting the cold getting further south I think the cold held further north is still the most likely outcome but it’s far from a foregone conclusion and no doubt it’s going throw up some other options over the coming days thus, keeping the thread buzzing for a while longer. Synoptics may not have delivered for everyone this winter but it’s made interesting watching every month, better than Bartlett’s or months of zonality.

[Purga]

I think it is still a fair way off and the NWP is dealing with margins that can't be determined at this range, though I think your Atlantic wind and rain is becoming less likely if we look at how the models are trending.

Indeed and as highlighted by the ever cold trendung ENS

Even more marked further north (Aberdeen)

In particular the T2's are far from mild for the foreseeable.

[winterof79]

So close and yet so far, some brutal cold to the north but the ECM is reluctant to take it south with a messy looking set up.

Really have my doubts re the detail of this run though, in terms of trend its a bit of a stalemate, move the pattern further se and you could make a case for some outlandish March temperatures, as it is its looking a bit frustrating.

Still this far out anything could happen.

Looks fine for the northern half of the Uk to me

http://www.meteociel.fr/modeles/ecmwf/runs/2013022112/ECM0-240.GIF?21-0

Long way off though.

[Derecho]

Some consistent signals in the output recently with a theme of retrogression towards Greenland. Interestingly in recent runs this has become stronger. The GFS 12Z for example shows a Very strong Greenland high with higher thicknesses (High pressure covered in yellows on Wetterzentrale instead of the blues and Greens... and pressure around 1050mb still) although this run still has a rather West -NAO

Whether we see a west based -NAO or East based is the big question. Given the overwhelming amount of mild Marches in the past 25 years people could be forgiven for underestimating how cold early March can be BUT we have some of the coldest uppers I have seen for the past 5 years at least in the arctic. Now would be a good time to tap into a northerly.

Providing that regression takes place even a west based -NAO( Although not too much), it would still provide something wintry, however if we get an east based negative NAO we could well see a very notable cold spell for the time of year. However a long way to go yet before that is decided.

Good trends though.

Edited February 21, 2013 by Quicksilver1989

[nick sussex]

Looks fine for the northern half of the Uk to me

http://www.meteociel...M0-240.GIF?21-0

Long way off though.

Theres little margin for error and that shortwave that gets involved from the nw makes things very complicated.With heights dropping to the north any cold won't be sustained, you need those low heights further east and a stronger push south.

The best operational run tonight is the JMA at 192hrs, that looks like a clean transition, and the blocking there looks better aligned to drive the cold south.

At this timeframe the models have leeway to move things further south and east, so it may yet get more interesting especially for Scotland/Northern Ireland and northern areas.

[Altohumorous]

A very cold northerly associated with a strong high pressure around Greenland at the end of february/very start of march has been quite a frequent occurrence over the years, right through the long run of mild winter years at least, if my memory is not fooling me.

[bluearmy]

ian - if you read this, can you give the peeps at exeter a nudge. they have forgotten to issue the T72 FAX !!

[lord stratus]

One crumb of comfort is that the GFS does model Northerlies well. Encouraged to see the operational taking the route of some of the colder ensembles we have been seeing

I have to laugh at some of these posts promoting northerlies. They never deliver any potent cold as there is too much modification. It all looks great when viewed on the charts but in all honesty if the northerly eye candy verified it would feel tropical compared to the current easterlies that we are having which has hardly been given a mention!