Model Output Discussion 4th Dec.2013-12z onwards.

[nick sussex]

A poor lower resolution GFS with the PV reforming into one blob to the north. It's imperative with this set up that you get that lobe of higher pressure into the Arctic to stop that from happening like the ECM at T240hrs. If you don't have that lifting out of low heights into Greenland then you lose some of the forcing to edge the jet further south.

 

In the higher resolution we see a deepening low running east/ne from the base of the trough, always a possibility with this set up, there could be some wet snow on the northern flank of that as it runs into the North Sea if it verifies.

Edited December 14, 2013 by nick sussex

[Costa Del Fal]

A poor lower resolution GFS with the PV reforming into one blob to the north. It's imperative with this set up that you get that lobe of higher pressure into the Arctic to stop that from happening like the ECM at T240hrs. If you don't have that lifting out of low heights into Greenland then you lose some of the forcing to edge the jet further south.

 

In the higher resolution we see a deepening low running east/ne from the base of the trough, always a possibility with this set up, there could be some wet snow on the northern flank of that as it runs into the North Sea if it verifies.

FI is seriously windy however. Very deep low after very deep low. Now I know the GFS likes to go a bit crazy but these are some of the most unsettled charts I have seen in a long time. Very unstable. Could be one of the wettest and windiest Christmas for some time.

[nick sussex]

FI is seriously windy however. Very deep low after very deep low. Now I know the GFS likes to go a bit crazy but these are some of the most unsettled charts I have seen in a long time. Very unstable. Could be one of the wettest and windiest Christmas for some time.

Yes pretty dismal all round. Lets hope for a change towards the New Year. Interesting that the GFS develops some more notable strat warming towards the end of the lower resolution. If I remember last winter although the lower resolution in terms of surface patterns is often all over the place these warmings have a much better chance of surviving.

[Purga]

purga, to help the less informed on here, can you link to the occasions over the past few winters where that pattern has prevailed for six weeks on the back of a v cold canada?

 

the mean trough approaches as we reach xmas.  now here's the only question that really matters - will it get into w europe for more than a day or two ? if it does, then we, sitting above the PFJ will get cold enough to see some snowfall between xmas and new year, especially in the north of the uk.  the extended ens output has, until now, indicated that the next ridge will soon be along to reset the general sw/ne flow.

BA, as you well know, there hasn't been a similar type of pattern with such depth and strength 'in the past few winters' but there have been plenty of examples pre 2007 which i am sure you are aware of!

[bluearmy]

BA, as you well know, there hasn't been a similar type of pattern with such depth and strength 'in the past few winters' but there have been plenty of examples pre 2007 which i am sure you are aware of!

Indeed - but we're now 'post modern winter' ! lets come back in six weeks and have a look this one. Edited December 14, 2013 by bluearmy

[Panayiotis]

A bit windy! This would be similar to the Jude storm if it verified!

Edited December 14, 2013 by Panayiotis

[radiohead]

A bit windy! This would be similar to the Jude storm if it verified!

 

A similar path, but it would be stronger. For comparison :

 

[Panayiotis]

The high res NASA is coming out now and shows a nice WNW developing for the 19th with -6C uppers coming over the UK. That flow should have some heavy showers some of which maybe wintry even at lower levels especially in heavier bursts however moving quickly.

Edited December 15, 2013 by Panayiotis

[Mucka]

UKMO now adding support to the idea of a storm 18th/19th, no doubt the MetO will be watching this closely but no warnings as yet.

 

UKMO/GFS

 

 

Looks as though showers could turn wintry for a time on Thursday, perhaps even down to low levels in the North.

 

There after the usual pattern in a zonal set up of transient conditions fluctuating between dry, wet and windy, cool and showery - rinse and repeat.

Let's hope GFS has this FI chart wrong as well (It does of course)

.

Edited December 15, 2013 by Mucka

[Chris W]

Hi all. 

 

Hope you are all well and that this weekend's wind/rain is not posing too many problems.  I will be returning to the UK and landing on Thursday at 3pm GMT, at which time the GFS would welcome me with this:

 

 

That being a snapshot the jet does look set to dive quite far south whilst remaining strong with the PV edging over the north west of the UK.  Very likely (potentially stating the rather obvious) to my mind to be very windy and wet, and potentially wintry.  Certainly not dull in the lead-up to Christmas Day.

Edited December 15, 2013 by Chris W

[Iceberg]

General themes remain consistant with small differences this morning.

Well tracked low pressures most notably for around the 19th and again for around the 26th. The exact timing and intensity differ however the theme of the 19th being particularly windy for the NW with a stronger band of winds moving across the country and the the low for around the 26th being more south.

The low of the 19th being more likely to happen (obviously) but the low around boxing day maybe being more problematical due to the holiday timing and what i think will be more uncertainty with development.

Its fair to point out that the range of solutions re development are from a slack rain producer to a 930mb monster crossing england.

 

Another point of note is the rainfal which again is being well progged now with 50-130mm for western and southern area over the next 5 days and 80-200mm between now and the 28th.

Cold is much less certain and although there remains a few members going for more widespread cold(10% maybe), its really limited to the pm shots.

any pattern change is certainly after christmas, with a possibility from the models that as we move into Jan a more normal less steroid pumped atlantic is in the offering.

[Frosty.]

Interesting christmas period coming up, the Gfs 00z shows cold air and continued unsettled conditions with a higher risk of wintry ppn with rain turning to sleet and wet snow, then icing over at night.

[YorkshireLiving]

Don't think I have seen such a wide range of option as after the 20 th the GFS at the moment does not know which way to go, ... a sign of possible major change? 

[Frosty.]

Ecm 00z op run shows a brief lull in the very unsettled weather for the south and southeast developing during the early part of the new working week with a slight pressure rise but it continues generally wet & windier further north and west with persistent rain followed by squally showers, wintry on hills. From around midweek onwards it's back to widespread gales and heavy rain alternating with colder, showery weather, it's a very undulating pattern with occasional weak atlantic ridging but the jet is fast and furious, fueled by the very cold air spilling out of the eastern US and shows no sign of slowing down, cold enough at times for snow on hills, especially in the north and overnight frosts during the brief quieter interludes.

Edited December 15, 2013 by Frosty.

[Mr Frost]

A pretty bonkers December so far here - numerous air/ground frosts, couple days of severe gales, three days of falling snow, one day were the temperature was 14 degrees and a thunderstorm last night. Really exciting last 15 days being a lover of all types of weather.

Just checked the latest Metoffice update for my location - Outlook for Tuesday to Thursday:

Sunny spells and showers on Tuesday, mainly north and west, then windy with outbreaks of rain on Wednesday. Turning much colder with snow showers and severe gales on Thursday.

Issued at: 0400 on Sun 15 Dec 2013

The weather just keeps giving it seems!

Looks a bit nasty on Thursday! Definitely one to keep an eye on.

[pdiddy]

Don't think I have seen such a wide range of option as after the 20 th the GFS at the moment does not know which way to go, ... a sign of possible major change? 

I think the pattern is similar, but the timing of the low/ridge/low varies by member, hence the spread.  I would be looking for grouping of flatter lines for pattern change

[Iceberg]

Don't think I have seen such a wide range of option as after the 20 th the GFS at the moment does not know which way to go, ... a sign of possible major change? 

 

I think one the main things to draw from the ENS (as above) is how few of them go for any kind of high pressure and none really go for strong high pressure.

So no signal for settled conditions or any kind of euro high really effecting is for the rest of the year.!

 

This isn't a bad thing btw as it generally indicates a more southerly jet when you get these kinds of ENS.

[Gibby]

Good morning. Here is the report on today's midnight outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Sunday December 15th 2013.

 

All models continue to show a very changeable and often windy period over the next week with winds strong and from the SW for much of the time with a notable exception on Tuesday when winds will be much lighter and temperatures as a result less mild for a time. From soon after midweek all models show a particularly deep Low to the North of Scotland carry gale or severe gale SW or West winds across the UK with a band of squally rain followed by sunshine and squally showers through Thursday and Friday with some wintry showers over the hills in the North.

 

GFS then takes us through next weekend with a spell of milder and windy weather again with rain at times move swiftly NE across all areas in turn followed by slightly colder and showery weather once more as another Low moves East to the North of Scotland, and so the pattern continues over the Christmas period and in the run up to the New year. It may become very stormy over the latter part of Christmas and in the days that follow as intense depressions cross the heart of Britain with potential for storm force gusts giving local damage for a time. In additions the model shows rather colder conditions generally late on with some snowfall reaching low levels briefly in the North and the hills of the South too in the showery periods behind the depressions.

 

UKMO shows next weekend with Low pressure over Iceland and a broad, mild and strong SW flow across Britain with gales for many and spells of rain in all areas, especially but not exclusively in the North and West.

 

GEM today shows a mild weekend too next weekend as a broad SW flow carries troughs NE and delivers rain to all at times with temperatures well up to average if not above across the South for a time. Later the weather turns potentially stormy and somewhat colder towards Christmas with rain and gales alternating with wintry showers over Christmas itself.

 

NAVGEM also shows relatively mild weather next weekend but with a very strong SW wind with gales and rain at times for all as troughs pass over quickly in the flow. Some slightly colder and more showery weather could affect the North at times.

 

ECM maintains a very changeable run up to Christmas with rain at times with strong winds and relatively mild weather for much of the time though the risk of short polar maritime incursions of air with wintry showers increases across the North at least as we move towards and over Christmas where wintry showers could occur as a result.

 

The GFS Ensembles this morning show compact agreement in temperature values at the 850 level very close to the long term average for the forseeable future. This indicates the odds of a white Christmas in any one place away from high ground is extremely remote with most places seeing rain and strong winds the main factors of the weather with average surface temperatures with little in the way of frost.

 

The Jet Stream continues to blow very strongly in a NE direction over the Atlantic and the UK currently in a somewhat sine wave pattern as Low pressure ebbs and flows towards the UK. Later the flow changes it's orientation to a more West to East flow which carries it deeper into Europe and allows the chance of polar maritime air to dig deeper down across the UK in Week 2.

 

In Summary the pattern remains locked as it is now for some considerable time. With deep Low pressure out to the North and NW there will be frequent bands of rain and strong winds for all with copious amounts of rain in places probably giving flooding issues in places before the end of the year. With winds never straying far from a West or SW direction there will be a lot of mild weather, especially across the South with little in the way of frost. However, incursions of cold polar maritime air will waft over Britain at times behind exiting depressions and this could deliver some upland snowfall at times especially later in the period. All in all though it's wind and rain that will make any weather headlines over the Christmas period rather than widespread disruption from snowfall with no real sign of a change in weather pattern in sight this side of the New Year.

[Frosty.]

The GEFS 00z mean shows the very unsettled spell persisting right through the christmas / new year period with the PFJ to the south of the uk, however, early in the period, a slight rise in pressure across the south / se looks like bringing a brief window of fine and calmer weather with an overnight frost or two, continuing more unsettled and windier the further north and west you are, by midweek or soon after the lower heights to the north west swing further south and east with more severe gales and heavy rain interspersed with clearer, colder and showery spells. The christmas period looks rather colder with a strong westerly flow of polar origins and as the gfs 00z op run shows, there could be complications as atlantic lows bump into the colder air across the uk with a risk of snow in places.

[Frosty.]

The Ecm 00z ensemble mean shows a few relatively milder interludes but always with colder air from the north atlantic / polar regions sweeping in from the west / nw...it's a recurring theme until the PFJ is eventually forced further south by deeper lowering heights to the north west and those milder incursions stop with a generally rather colder and strong broadly westerly flow which mainly consists of polar maritime air and an increasing chance of wintry ppn with snow on hills and occasionally wet snow further south becomes more of a risk, along with icy patches /  night frosts.

[IDO]

As many of us highlighted when this zonal signal was picked up as trumping the Euro high we warned that this could be a long term driver. Not from any great insight, just from experience of the pattern type. Well the GFS now goes out till the end of the month and it is a zonal fest all the way through. I know some posters like this, so enjoy.

 

The T384 (normal caveats) mean: 

 

PV over Greenland, weak mean polar ridge, the Pacific heights dampened by a powerful jet on the other side of the NH, and with the real cold on the east/west axis, little to suggest on current output of anything cold and wintry even for early January.

 

At the end of FI the UK trough has good support now from the ens, led from a few days ago by the Control and op: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=384

 

So a NW/SE jet with possibly most of the UK on the cold side. Tentative signs this could be a medium term flow, though tempered at times by the AH attempted ridging before another LP system is ejected off the Greenland Vortex to restore that NW/SE flow. The control is close to this scenario...

 

...allowing a more meridional flow downstream with maybe the Russian high pumping up that weak cross polar ridge. Not sure that will drag in any cold uppers due to the cold being mixed out as it crosses the Atlantic, but it might keep us in a below average slack trough, with potential for colder spells.

 

Christmas Day is now on GEM & ECM.

 

GFS:  GEM:  ECM: 

 

Possibly a horrible day for travel, though early days.

[YorkshireLiving]

I think one the main things to draw from the ENS (as above) is how few of them go for any kind of high pressure and none really go for strong high pressure.

So no signal for settled conditions or any kind of euro high really effecting is for the rest of the year.!

 

This isn't a bad thing btw as it generally indicates a more southerly jet when you get these kinds of ENS.

Thank you for the guidance on these matters I am very interested by the knowledge that you impart I will spend a bit more time comparing ENS with the charts. 

[johnholmes]

the charts below give what will probably be a pretty accurate idea of what the upper air pattern will be over the Christmas period, not mild most of the time, and not calm most of the time!

 

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Edited December 15, 2013 by johnholmes

[ANYWEATHER]

the charts below give what will probably be a pretty accurate idea of what the upper air pattern will be over the Christmas period, not mild most of the time, and not calm most of the time!

 

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Indeed John. Just scanning through the models the Atlantic is in overdrive for the foreseeable future, with some potentially stormy periods between now and Christmas and including the holiday period. The temperatures look like alternating very swiftly between colder and milder spells, so even though conditions are not conducive to nationwide Wintry conditions, some snow will be around, perhaps giving a surprise snowfall here and there. !  But rain and wind will be the biggest likely newsmaker during the days ahead.....

Edited December 15, 2013 by ANYWEATHER

[Summer Sun]

GEM's take on the deep low for Thursday

 

 

UKMO

 

 

GFS

 

 

ECM

 

 

All models agree on a deep low for Thursday its just a case now of whether we get any downgrades and the final position of it

Edited December 15, 2013 by Summer Sun