Winter Model Discussion 18Z 5/2/13 onwards.

[ForeverPomeroysnow]

Just to show how it will be down to now casting - we have been issued a weather warning for snow today out of nowhere!!

[nick sussex]

The forecast for snow at the weekend isn't as complex as would be the case with a normal slider low, its unlikely its going to be an all snow event so its a rain turning to snow.

The GFS has the largest warm sector, the ECM less so but still could go that way, the UKMO makes little of the low and clears it quickly into mainland Europe so thats a rain turning to snow followed by snow showers for the east and se.

[Ryan Dutch Weatherman]

Look Cma 00z , snow for most part.

Than Look ECMWF 00z Ensemble s , no any evidence at all for strong Atantik.

[Simonl]

No you are right. Today's output suggests the SE is the only place in England (barring Cornwall) to miss out on the snow. Sleet at best, probably cold rain. Higher ground may get a bit. Still could change though.

I hope so. We are the most 'snow starved'. That would be absolutely TYPICAL. The areas that have had plenty getting more.

The low needs to go further south...

[Gibby]

Good morning. Here is the report of the 00z output from GFS, UKMO, GEM and ECM for today Thursday February 7th 2013.

All models show a weak front moving into the UK today and becoming slow moving at the same time as dying in situ over Western Britain tomorrow. After a cold and frosty start with still the odd wintry shower in extreme Eastern Coasts the day will steadily become cloudy with outbreaks of mostly light rain moving in from the West through the day. This may fall as snow on higher hills, especially in the North. Winds will be lighter than recently. The rain and sleet will continue overnight and into tomorrow before dying out leaving a legacy of cloud and rather benign conditions still under rather cold air. Saturday could well be a dry and brighter day with some sunshine as a ridge moves across from the West with frost possible overnight. On Sunday all models show a much more active frontal system edge in from the West with an attendant developing depression sliding down over the UK towards Southern Britain and into NW Europe over Sunday and Monday.

GFS then shows the Low close to Southeast Britain for several days in the early part of next week with cold NE winds wrapping around the feature. Sunday will become wet for many with heavy rain turning to snow over the hills later, a trend that continues over Monday and Tuesday with possibly disruptive snow in places before drier weather edges in from the NW by midweek as a strong ridge of High pressure takes control with snow being replaced by a cold and frosty spell with some daytime sunshine towards the end of next week. High pressure remains in control for some time then with further frost at night while the far North see weak troughs brushing over the top of High pressure bringing a little rain or sleet. Through FI today Low pressure regains control as Low pressure moves East across the UK bringing rain or sleet at times and further snow on the hills at times in continuing temperatures that are often below the seasonal average.

The GFS Ensembles show a rather cold picture with the operational run above being one of the milder members at times. The average for the run remains below the long term mean, at least in the South. Rainfall amounts will peak at this weekends and early next weeks Low before drier conditions take over.

The Jet Stream still flows down from the North on the Eastern flank of its ridging around the Azores anticyclone. The flow does break up at the weekend before realigning itself still blowing from a NW or North direction down over the UK around the seemingly permanent Azores High in a weeks time. The flow continues to track Eastwards at low latitudes over Southern Europe throughout the next week.

UKMO shows the weekend Low over East Anglia at midnight on Monday with a cold Northerly or NE flow developing on the Northern flank of the SE moving depression. With most areas having endured a wet and breezy Sunday rain would turn to snow as we move through the overnight period and into Monday itself as it clears steadily away SE through the day. As we then move towards midweek the weather remains cold and with a NE flow in the South especially some snow showers would be likely, especially on Tuesday before things settle down though staying cold from the NE by Wednesday.

GEM today keeps the axis of the SE moving Low further to the SW with more areas seeing significant snow as early as Sunday before it too pulls the Low away into Europe leaving a legacy of cloud and lessening wintr conditions through the early days of next week. By midweek a ridge is shown crossing from the West with unsettled, less cold but windy and wet conditions taking control over all of the UK well before next weekend.

ECM shows a disrupting trough sliding across Southern England on Sunday developing a deepening depression over the English Channel with an increasingly cold and wintry NE or East flow setting up over the UK. Most areas will see a spell of heavy rain on Sunday with the rain steadily turning to snow late in the day and overnight on Sunday. With the Low pressure similar to GFS reluctant to pull away on Tuesday further sleet and snow could cause disruption to many Southern and Eastern areas in particular before the Low finally pulls away SE over Wednesday leaving a cold and raw NE flow over the South with snow showers near the East Coast while the North becomes dry and cold with overnight frost as a ridge moves in from the NW. This ridge then holds ground over the Uk for a day or two before the close of the run sees an Atlantic front bring rain in from the West preceded by snow for upland areas with NW winds and showers following to the West. This would usher in less cold but far from mild weather.

In Summary today there is still much indecision about the path and the depth of the feature bringing the potential wintry conditions early next week. It looks increasingly likely that we will all have to endure a spell of heavy cold rain on Sunday before cold air engages the feature fully later on Sunday, overnight and into Monday turning rain to snow and potentially causing some disruption to travel on Monday, particularly if the more persistent feature clings on close to the SE like GFS and ECM suggests. UKMO and GEM bit pull the Low away quicker to the SE allowing High pressure to collapse SE over the UK before milder air attempts to regain control over the UK as the block to the NE is possibly pushed further back to the East. A week is a long time in these type of winter synoptic situations so expect some more surprises over the coming days towards or away from milder solutions.

[TEITS]

Morning all.

Little has changed from my post last night. The trend in the medium range continues to suggest we remain cold rather than the mild Atlantic returning. Here are the latest means at +240 from the GEFS & ECM.

If we look at the upper temps the GFS Op was much milder than the mean throughout the run including this weekend.

http://cdn.nwstatic.co.uk/ensimages/ens.20130207/00/t850Cambridgeshire.png

As for this weekend and to be honest I can't be bothered to go into detail because I know it will change. We shall see differences even +24hrs prior to the event and the exact detail will change on the NAE with every run once we are only 24hrs away. This will be a rain turning to snow event but locations such as the Peak District could see an all snow event. We do have the potential to see big snow event though because it appears a combination of the depth of the LP and how slow it is clearing the UK means alot of precip could fall. Very exciting to watch unfold over the next few days.

[Frosty.]

The models are looking very wintry for sun/mon/tues especially from the Ecm 00z which also keeps the entrenched cold until the end of next week, the gfs 00z also brings a lot of snow across the uk but next week eventually turns less cold, the ecm is much better. Towards the end of the ecm, things go a bit pear shaped but focus on the next week, i'm sure that the longer range will end up improving the chances of a strengthening cold block and not allow the atlantic to slowly gain the upper hand. The first half of next week looks potentially bitterly cold with strong ENEly winds and lots of persistent snow and also snow showers for n and e areas with widespread severe frosts and several ice days. The next few days are the relatively less cold calm before the snowstorm

[craigore]

GFS opp is a nightmare run for the SE. ECM would be very good and with meto I'd imagine a middle ground. Can't see the uppers on meto after 72 hours so hard to tell though.

Bitter experience suggests to me that it will be a cold and wet weekend Imby sadly. Essex, Kent and parts of Suffolk may well be in for a good soaking whereas west and north of London could see mostly snow. I just think we may be too near the low pressure cell to benefit from the colder air feeding into the system.

That said, long time to go yet and the charts are mixed in terms of who gets rain / snow etc. I'd recommend expecting rain though and regarding anything else as a bonus in our part of the world.

Jason

What about the following Easterly, will that not produce for the south east{convection, snow showers }???

[Ryan Dutch Weatherman]

Ec ensemble at 240 , still no strong atlantik , not at all.

Who is saying that for the ECMWF ?. who is playing the ambassador from EC 00z.?

En who or wat or it is seeing rain in this chart from the ECMWF 00z ?

It is complete a potential snowbomb.

Take it or leave it.

Edited February 7, 2013 by Coast

[Cecil Hogmanay Melchett]

You know i cant help but feel excited and disappointed by the 0z runs.Some places will get a good dumping sun/mon which is great (and i dont care who or where just happy for those that dp)but such a great profile to the North east is probably going to count for nothing come thursday as the colder uppers just get swept east by that damn Atlantic profile,there is just no let up in that conveyor of lp's,i honestly dont think i have seen anything like it before !

[Blizzardof82]

I've not seen anyone claim it is settled tbh. This is the model discussion thread however and the talk is about what is shown in the models is it not?

For my part I can't believe people post in the model thread saying that they can't believe that people are discussing the models :-)

All very strange IMHO.

Jason

Point taken but people moaning and groaning that they will have all rain event when nothing is settled yet is a tad silly, my take on the model output is there will be corrections west leading up to Sunday. I don't really have anything I can back that up with just a hunch and views on past events.

[snowking]

En who or wat or it is seeing rain in this chart from the ECMWF 00z ?

It is complete a potential snowbomb.

Take it or leave it.

The rain is clear to see Ryan as the system is running in to some slightly less cold air...it's not until we see the system slide towards the near continent at present that we pull in the colder dew points and the wet bulb freezing level will drop

To be honest it's rather pointless is speculating at this range as to what may/may not happen, you would hope this is the sort of situation that high resolution modelling was made for (though even this will likely struggle). It will be interesting to get some views from Ian regarding the UKV take on things nearer the time.

For now we have to accept that Sunday is still too far away to call...the interesting development is the length of time the GFS/ECM hold this system to our SE, though it must be remembered that the last couple of low pressure systems hemave been handled best by the UKMO inside 120 hours, with both the ECM and GFS over-deepening them (and as a result overestimating the northern latitude they would reach)

SK

Edited February 7, 2013 by snowking

[Ryan Dutch Weatherman]

Bom 12z , end after the snow bom slide low your east coastal area will be pounded with snow shouers , from the the Noord to the south,.

Clear to ass ? Rain with -8 at 850 Hp ? I see all Britisch expert agree with me.

End you see clear as ass rain , you make me lough.

Edited February 7, 2013 by Coast

[Jason M]

What about the following Easterly, will that not produce for the south east{convection, snow showers }???

Possibly, but it depends on so many things. Often in these situations you don't get a 'clean' back edge to the weather system. This could be especially true here as the low takes a long time to clear. Any overhang of cloud will prevent convection. If your living in, E England or Norfolk i'd wager you will see snow showers for a time. Essex / Kent and SE generally might not be so favoured. If we get a clean back edge to the system the Kent mob may be into streamer territory.

Its only my interpretation and others will see blizzards etc in the charts so take your pick at this juncture. Also, this is all a long way out still, and tbh the GFS opp was probably the worst case scenario as far as the SE is concerned. Given that what is shown now will no doubt change there is some comfort to be drawn from seeing the worst case being shown now .

I noted some comments on one of the weather forcasts this morning about record warmth in Eastern Europe. This sums up the irony of the situation really and in part explains why we are struggling to retain cold uppers next week when synoptically the pattern looks fine in our neck of the woods.

Jason

[snowking]

You know i cant help but feel excited and disappointed by the 0z runs.Some places will get a good dumping sun/mon which is great (and i dont care who or where just happy for those that dp)but such a great profile to the North east is probably going to count for nothing come thursday as the colder uppers just get swept east by that damn Atlantic profile,there is just no let up in that conveyor of lp's,i honestly dont think i have seen anything like it before !

HD - I would agree to a certain extent with that prognosis

What I would suggest though is to remember that up until Tuesday, the overwhelming consensus from models - extended ECM ensembles included in that - was for a gradually less cold and more Atlantic regime by Monday (as evidenced by Ian F's post detailing the medium range Exeter thoughts, with the MOGREPS having been heading in that direction too). Now we are talking Thursday. And what's the main reason that we were initially looking at Monday? A refusal of LP to undercut an HP to our east that was clearly underestimated in strength.

That's not a guarantee of a repeat performance, but it's just worth bearing in mind anything beyond even 120hrs remains extremely uncertain! There are 360 degrees on a compass, and I wouldn't like to hazard a guess as to which of those directions the flow will be from come Thursday at this range!

SK

Edited February 7, 2013 by snowking

[That ECM]

Clear to ass ? Rain with -8 at 850 Hp ? I see all Britisch expert agree with me.

End you see clear as ass rain , you make me lough.

Enjoy your posts and certainly could not reply in any other language. Just can't get allo allo out of my head when I read your posts. I know it's set in a different country and please take it in the good humour it is meant.

[snowking]

Clear to ass ? Rain with -8 at 850 Hp ? I see all Britisch expert agree with me.

End you see clear as ass rain , you make me lough.

Apologies for typo (I am on my phone) - it should have said see (and I need to learn to read!)

Ryan it can rain with uppers at -10c if there's a warmer layer at the surface boundary - equally it can snow with 850's at 0c.

Nobody is disputing it would likely turn to snow, it's just likely on current face value output to be rain initially

SK

Edited February 7, 2013 by snowking

[Cecil Hogmanay Melchett]

sunday monday is VERY complex! It will most certainly be a nowcast for different regions and altitudes,the good news is that we do have some pretty cold air over us and have for a few days,but the track of the low(s)will change a few miles before sunday and that will be the difference between tears of joy and tears of sadness for many of us.

[Ryan Dutch Weatherman]

Look the pluim for my country Netherlands noord.

Wenn there was a strong Atlantik like some people here say , than why i do see different.

Becouse i dont live pacific , i live near Brittain , if there was strong atlantik , my country EPS would also notice that.

[Summer Sun]

ECM is sticking to its guns on the 00z run looks like a change maybe on the way later next week as we finally loose the cold air with the Atlantic trying to push in

UKMO, GFS and ECM are not far away at t144

Fairly decent agreement even at this range

[Timmytour]

Gavin....i think it's just the ECM being typical....being too progressive with the Atlantic as always

Edited February 7, 2013 by Timmytour

[Ryan Dutch Weatherman]

Apologies for typo (I am on my phone) - it should have said see (and I need to learn to read!)

Ryan it can rain with uppers at -10c if there's a warmer layer at the surface boundary - equally it can snow with 850's at 0c.

Nobody is disputing it would likely turn to snow, it's just likely on current face value output to be rain initially

SK

Yes yes , but i said also it will turn over snow .\.

End look your wind direction .

Look the douwpunt.

Look the tickniss of the cold dam.

End its also cold at low level.

Why are you stribbeling.

Even the highest resolution model WRF 10 km.

Is saying possible 20 cm snow or more , WRF say that ,. If you angry for the HIGHEST short term resolution model the most accuraat for this range , than go fight with them.

[Liam J]

What about before we get to that stage Gavin? We still have divergence within T72-T96 so until we get this crucial time frame nailed then looking at the outcome and where we go by the end of next week is rather pointless?

[snowking]

Incidentally, the GFS operational remains far out of touch with its ensemble suite (along with that of the GEM) in terms of its NAO/AO outlook:

Extended ensemble outputs continue to favour any stronger heights to be focused around the Greenland locale:

Medium range outlooks remains uncertain, and I suspect we may end up just on the wrong side of the Atlantic vs Eastern block, but as GP as alluded to over the past few days, the 11-15 day signal seems even stronger at present

SK

[london-snow]

ECM is sticking to its guns on the 00z run looks like a change maybe on the way later next week as we finally loose the cold air with the Atlantic trying to push in

UKMO, GFS and ECM are not far away at t144

Fairly decent agreement even at this range

& what are those ensembles suguesting this morning about the atlantic moving in around that period?