Model Output Discussion 1st Nov.2013

[Cloud 10]

A selection of eye candy from the 18z gefs. 

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-1-1-264.png?18

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-4-1-300.png?18

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-10-1-216.png?18

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-13-1-288.png?18

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-16-1-300.png?18

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-17-1-264.png?18

 

http://modeles.meteociel.fr/modeles/gens/run/gensnh-20-1-252.png?18

 

 

 

[Gaz1985]

Except from the snow that could fall in Scotland, even to lower levels, which is considerable given the time of year.

 

Edit: Indeed, even the chart you've posted shows -7'C uppers over Scotland with -10'C uppers brushing the northern coast, which under high pressure could easily lead to day time maxes some 6'C or so below average, I would call this really rather wintry as opposed to not being "remotely" wintry.

 

Indeed, for most of the country (where people live) south of the -7c line it looks rather benign I would say. Big differences from Glasgow southwards compared with north of that and in lightish winds it won't feel that bad, pressure gradiant looks rather tame nationwide. 

 

 

Edited November 13, 2013 by Gaz1985

[NorthernRab]

Indeed, for most of the country (where people live) south of the -7c line it looks rather benign I would say. Big differences from Glasgow southwards compared with north of that and in lightish winds it won't feel that bad, pressure gradiant looks rather tame nationwide. 

 

 

I think we'd best get the next week out of the way, which looks interesting and varied with some both Atlantic systems, frosty nights and some snow, before getting our hopes too high for any settled spell of weather. The chart in question is nearly 240 hours away and has very little chance of verifying

[SMU]

The first real siter from the UKMO this morning and its a very good run at 144

Very cold air aloft hitting NI & Scotland, in the region of -6/-7 with deeper cold waiting in the wings-

Of note is the NNE advection up the western side of greenland- it isnt perfect as its positively tilted but none the less a lot more solid than the shakey GFS which quite frankly is all over the show again.....

Eyes down on the ECM

S

Also of note on the UKMO is the tentative rise in polar heights at 144

A semi split flow divided by 2 tenuous linked ridges of high pressure!

[The PIT]

Well the FI could spell still there this morning still well out of the reliable time frame so no guarantee it will survive without any major changes, downgrades and the very rare upgrade. So be wary of running out for the snow shovel yet. Despite that there's fairly good agreement between the GFS at 132 and yesterdays ECM at T144 allowing the different time runs which is a good sign.

The deep FI cold blast has been swept out on the midnight run as GFS indicates a more active Atlantic. Next run it maybe all high pressure such is the nature of deep FI.

[shaky]

The first real siter from the UKMO this morning and its a very good run at 144Very cold air aloft hitting NI & Scotland, in the region of -6/-7 with deeper cold waiting in the wings-Of note is the NNE advection up the western side of greenland- it isnt perfect as its positively tilted but none the less a lot more solid than the shakey GFS which quite frankly is all over the show again.....Eyes down on the ECMSAlso of note on the UKMO is the tentative rise in polar heights at 144A semi split flow divided by 2 tenuous linked ridges of high pressure!

the ecm is just amazing steve!!more like to your standard mate!!Edit:gfs looking better aswell in high resolution.it then goes all stupid and loses the plot!! Edited November 13, 2013 by shaky

[AWD]

A couple of rather teasing 240hr charts;

Certainly enough to keep me interested for the foreseeable!

[That ECM]

At t144 all three major models show pressure building to west/ north west allowing a northerly flow. The UKMO has more of a split PV at this time but all are of a similar theme. There after the GFS is keen to flatten the pressure to west/ north west where as ECM has hit holding firm and if anything moving a little nearer to Greenland. SM I think, believes this is more likely but we will have to see more runs to see.

Encouraging to see the UKMO this morning in particular. So a flood of of cold air from the north. Will the pressure get flattened or will it hold firm?

For my money it will hold. Why, low heights over Italy and GFS has a habit of sending to much energy down but the biggest reason for me is the UKMO northern profile at t144 and the look of the PV. If there were further output it would be reasonable to see pressure moving north west.

In saying all that, what do I know, like most on here, we are trying to be forecasters and get a handle on a very interesting but hugely complicated subject.

Edited November 13, 2013 by That ECM

[bluearmy]

Yesterdays 12z ecm ens for london were trending cool/cold and the average/mild runs were dropping out somewhat. (days 11 to 15)

I wonder if this theme can continue. Certainly some impressively chilly clusters becoming apparent.

[garbagebags]

Looking nice across all models this morning both for cold snap next week, and generally long range PV stuff too (technical term).

[Severe Siberian icy blast]

Once again the PV dismantled. This one is ECM 240z , but a definite trend developing , this is obviously tropospheric led , and it's brilliant to see that even with a cold vortex with no MMW we can stil get cold , and indeed still get a disturbed vortex , despite all the signals going against this .

Know one saw this coming , yes we knew the pacific would cause some amplification , but not to have the knock on affect it's having , there is a clear signal for a reload after the initial blast , with the vortex under pressure from both ends , I think in general the models have been excellent in picking this up , with an obvious developing tripole over the last month which points to a -NAO suddenly Decembers looking a million miles away from people's thoughts two weeks ago, along with the pole going -AO in the next 10 days or so . . . . Role on December . . .

[Severe Siberian icy blast]

Yesterdays 12z ecm ens for london were trending cool/cold and the average/mild runs were dropping out somewhat. (days 11 to 15) I wonder if this theme can continue. Certainly some impressively chilly clusters becoming apparent.

Not sure about the ECM ens as the there not out yet but look at the gfs ens , a few runs in there going into the very cold territory after the initial blast. To me there is a clear signal pointing to a possible cold December now

[radiohead]

Whether we get a second bite at the cold cherry remains to be seen and is still deep in FI, but looking at the GFS ensembles this cold spell looks like lasting around 48 hours, with the air clearly becoming less cold on the 20th.

 

Edited November 13, 2013 by radiohead

[Frosty.]

Models are firming up now on a much colder spell through next week with widespread sharp frosts and sleet & snow showers, especially in the north, then the second half of next week is very uncertain, atlantic high pressure could drift over the top of the uk and bring calm, frosty and foggy weather or the high could pull westwards into mid atlantic with a reload blast of arctic air screaming south. I think we will soon be entering a cycle of increasingly cold reloads from the northwest / north / northeast separated by brief settled interludes.

Edited November 13, 2013 by Frosty.

[BLAST FROM THE PAST]

UKMO and ECM certainly on the same platform, GFS starts similar then in FI flattens it out.  As we are still talking target period t120

 

 

 

ECM

 

 

GFS

 

 

All looks well for this set up to start.  Its what follows is the key. Eyes down 

 

 

BFTP

[Man With Beard]

Looking good for a colder snap on UKMO/ECM, possible snow for areas favoured by north-west winds (southern areas will need a few extra variables - fronts with no warm sectors coinciding with the peak of the cold). Of even more interest to me is FI on ECM - really, really cold to the north and if a GH can inflate at the same time, a set-up which might bring this our way. Long way off but one to keep an eye on.

Edited November 13, 2013 by rjbw

[Wayneywoo]

Would be interesting to see what the model verification stats are. Can somebody post them please?

[johnholmes]

from the technical thread

 

Apologies but its looking like I am not going to be able to do the detailed look at the lead up to the change on the anomaly charts that in turn predicted the colder spell of weather for about 5 daysfrom now.

 

In brief the anomaly charts, the 3 I use, plus NAEFS, all show the colder weather with an upper ridge west/NW of the UK and lower heights NE-SE of the UK taking hold from about 144h and keeping this out to 240h. Beyond that and the 'signal' for this pattern begins to look less reliable but 10 days is a long way off. What follows beyond that will be clearer in say 3-5 days time. It is possible that the colder type may last, once it starts, to about the end of November. beyond that is outside my ability to make sensible comment.

As always the detail on how cold, dry or not so dry and what falls from the sky is something the shorter term synoptic patterns are for-watch the Fax charts as a good guide to how these matters may develop and Exeter and ECMWF for T+72 down and GFS if it fits the other two models.

 

and in answer to the model stats question this link for the northern hemisphere, SM did have a link for the Euro area last winter?

http://www.emc.ncep.noaa.gov/gmb/STATS/STATS.html

Edited November 13, 2013 by johnholmes

[Cecil Hogmanay Melchett]

Pick of the big 3 at 144h is UKMO in my opinion.

 

Its becoming likely parts of Scotland and westward facing coasts with some altitude across NW Britian will see some snow as we head through next week as a cold NW wind picks up.

As i stated yesterday though the Irish sea will certainly modify the depth of cold and as mentioned altitude will play a part.

 

Jury still out longer term although interestingly the GEFS have trended colder.

Interesting model watching at present.

[Yarmy]

Would be interesting to see what the model verification stats are. Can somebody post them please?

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/

 

One example...

 

[Purga]

A brief Northerly and then back to rampant zonality according to GFS 0z

 

 

 

ECMF showing similar but a brief NE'ly at 240hrs

 

 

Plus point though is the low heights developing over Europe.

[Cecil Hogmanay Melchett]

A brief Northerly and then back to rampant zonality according to GFS 0z

 

 

 

ECMF showing similar but a brief NE'ly at 240hrs

 

 

Plus point though is the low heights developing over Europe.

GFS 0Z looks to be one of the milder options in its suite so im dismissing it for now.

ECM is for my money still not great at 240hrs,i still say the NH profile will not be allowing a Greeny high moving forward from that chart.I could see a 'UK high'developing which at that time of year would probably be cold.

However,little point discussing 240h charts at depth as they will almost certainly look different come the time.

[shedhead]

Well the trend from the overnight models is a colder one from this time next week, but the detail is clearly yer to be nailed, as is the longevity of any particular spell. Probably also worth pointing out it's still only November, so expecting much in the way of snowfall away from hilly areas and the far north might leave some rather disappointed, but if cold rain floats your boat a treat may well be in store. 

[draztik]

According to the GFS ensembles the snow risk for my native Belfast has risen to 65% on the 19th. Can only imagine its greater in parts of Scotland.

As for the medium term, the ensembles point to a below average setup, especially for central England.

Temp anomaly days 10-15 [GEFS 0Z]

Edited November 13, 2013 by draztik

[garbagebags]

I think "rampant zonality" is a bit harsh, sure the cold will dissapear but all the FI charts are producing anything but rampant zonality.