Model Output Discussion 12z 30/11/2012

[IDO]

I've run through the GEFS ensembles and it's a real struggle to find an ensemble member worse for cold prospects post 168hrs than the op run. Infact there is a remarkably strong signal for Iceland/Greenland height rises 10 days + in those ensembles. The one caveat being it's a looooong way out. It's around about a 60/40 split in favour of cold prospects week 2 +. It's an all or nothing situation in light of what I can see......either a raging +NAO & vortex energy around Greenland or the complete opposite.

http://modeles.meteociel.fr/modeles/gens/graphe_ens3.php?x=306&ext=1&y=141&run=12&ville=Londres&runpara=0

The op certainly one of the milder options with some support, but minimal. Very little sign of precipitation apart from Monday, with the mean barely registering.

At the end of the run the 850s mean around -2.5c with very few members going for lower than -5c. Cool/cold outlook from the GFS with no sign of widespread snow or bitter cold. It looks like a hiatus, as bits of the puzzle are pushed into place; still going for the last week to ten days of December for the potential for the UK.

[Weathizard]

ECM goes for lower pressure over Iceland, relatively good agreement on positioning of the low but the west side of the Atlantic looks quite different

[SMU]

The storm chaser your following will be wrong-

The tropical wave is already initialised at T0 on the ECM & goes on to develop over 72 hours or so-

Its developing because of the jet streak & strong thermal gradient across its centre-

http://www.meteociel...CH0-72.GIF?30-0 Some 15 degrees or so across it.

T 120 ECM

http://www.meteociel...H1-120.GIF?30-0

slider low over iceland to move SE- this will ensure the tropical wave moves ESE- not ENE towards the UK

S

Edited November 30, 2012 by Steve Murr

[chris55]

I'm liking the ECM 120

[london-snow]

Exeter's latest thoughts into the trend period. Nothing surprising in the broad scheme of things:

"Good model agreement now for a cold, cyclonic northerly spell at the beginning of this period, with

the low latitude depression looking less likely to affect the UK than was the case a few days ago.

Thereafter, an emerging signal now for a build of pressure within the cold airmass later next week,

which is rather different from that offered by the models recently, and is tentatively followed for

now. The longevity and evolution of this ridging is then subject to very large spread within and

between EPS suites. MOGREPS-15 favours this to transfer into Europe with a more southerly type

becoming established (albeit often with cold continental influence), which opposes EC EPS signal

for retrogression and a renenwed risk of a northerly outbreak. In either case, the probabilities

favour a colder-than-average theme which is consistent with EC monthly output."

Should we be concerned about that pattern emerging which may scupper the chances of cold in and throughout December? I have been very encouraged thus far for a cold & possibly snowy December. But it just seems to me despite having the background signals in our favor to receive a cold & possibly snowy December throughout the uk things may not go our way. Granted we are seeing cold wintry conditions in the uk now and snow for some northern parts of the uk. But you have to ask yourself ' Cold but uneventful days but the further north you go you may see some snow ' a typical winter pattern?

I do hope some don't think i am bordering on imby territory because i am not. It just seems despite all the signals pointing to cold or very cold in December we may not get the luck we need countrywide.

[Iceaxecrampon]

GFS very close to a huge snow event for those in the south,

http://www.wetterzen...s/Rtavn1442.png

http://www.wetterzen...s/Rtavn1441.png

What happens to this Little cut off Low could be very interesting, We need it to hold and push energy southwards (like GFS) rather than just filling/disrupting (like UKMO) One to watch and the slightly unusual nature of the set up may give the models some headaches.

Last weeks charts?

Ian

[Zakos]

ECM at 120 markedly better than the GFS.

GFS

ECM

#

*Sigh* you never learn do you GFS.

Edited November 30, 2012 by Zakos

[fergieweather]

Should we be concerned about that pattern emerging which may scupper the chances of cold in and throughout December? I have been very encouraged thus far for a cold & possibly snowy December.

Many of my punters wouldn't be at all "concerned" if the winter was average / non-descript and I don't subscribe to any bias, either way... but who knows!

[Hammer]

From National Hurricane Centre in US.

A BROAD AREA OF LOW PRESSURE HAS FORMED OVER THE CENTRAL ATLANTIC

OCEAN ABOUT 1300 MILES EAST-NORTHEAST OF THE LEEWARD ISLANDS AND IS

PRODUCING DISORGANIZED SHOWERS AND THUNDERSTORMS. SOME DEVELOPMENT

OF THIS LOW IS POSSIBLE OVER THE NEXT COUPLE OF DAYS AS IT MOVES

GENERALLY TO THE NORTH AT 10 TO 15 MPH. THIS SYSTEM HAS A LOW

CHANCE...20 PERCENT...OF BECOMING A TROPICAL OR SUBTROPICAL CYCLONE

DURING THE NEXT 48 HOURS.

[chris55]

Last weeks charts?

Ian

No

[January Snowstorm]

ECM looks mighty fine at 144hrs

We could be back in the freezer very soon

Models have been disgracefully poor of late, all 3 of them!! (poor as in not having a clue)

Of course our own GP never lost the faith..

Edited November 30, 2012 by January Snowstorm

[SMU]

http://www.meteociel.fr/modeles/ecmwf/runs/2012113012/ECH1-144.GIF?30-0

A crazy chart!! slider moves through as a band of possible sleet & snow-

High builds to the north- a bit flat- surface high also over scandi.

S

[SouthPennine88]

Should we be concerned about that pattern emerging which may scupper the chances of cold in and throughout December? I have been very encouraged thus far for a cold & possibly snowy December. But it just seems to me despite having the background signals in our favor to receive a cold & possibly snowy December throughout the uk things may not go our way. Granted we are seeing cold wintry conditions in the uk now and snow for some northern parts of the uk. But you have to ask yourself ' Cold but uneventful days but the further north you go you may see some snow ' a typical winter pattern?

I do hope some don't think i am bordering on imby territory because i am not. It just seems despite all the signals pointing to cold or very cold in December we may not get the luck we need countrywide.

I fully understand this view, however we have to understand that the models so far don't even go up to half way through December!

We can't ask for cold right through, sometimes there has to be a let up ... but the models at the moment of course don't run as far as beyond mid month. Hence, we are already slap bang in the middle of -4 nights and +2 days ... so what more can you ask for except from a nice little snap to kick the season off?

[Eskimo]

Last weeks charts?

Ian

Always look to the left hand corner, it says 30th of November

[bobbydog]

ECM looks mighty fine at 144hrs

We could be back in the freezer very soon

Models have been disgracefully poor of late, all 3 of them!! (poor as in not having a clue)

Of course our own GP never lost the faith..

have the models been poor? or have the weather patterns been so chaotic lately, that the models have been simply churning out the vast array of possibilites?.......

[Cheshire Freeze]

ECM looks mighty fine at 144hrs

We could be back in the freezer very soon

Models have been disgracefully poor of late, all 3 of them!! (poor as in not having a clue)

Of course our own GP never lost the faith..

Yes, modelling has seemingly been poor but that also means that even if this ECM run goes on to show the next ice age,it's got the same chance of verifying as the GFS 12z!

Remember,don't get suckered in until 72-96 hrs out.

[chris55]

ECM 144 on Wetter, do those little kinks represent a front?

[TEITS]

Very difficult to make a prediction at the moment. I've looked at the SLP ensembles across Europe and overall I would say in the longer term HP is likely to remain in charge across the UK rather than LP.

Looking at the ensembles the SLP mean is lower in the Med than in Scandinavia. The SLP GEFS mean across the UK is relatively high (1020mb) but around Iceland we have alot of scatter.

So despite the uncertainities with the synoptics, high pressure around the UK will always mean cold temps at this time of year regardless of the upper temps. As for snowfall and to be honest its impossible at the moment to say until we know where HP will be situated in the longer term. I agree with CH a Greenland HP is looking very unlikely at the moment.

[Frosty.]

Models have been disgracefully poor of late, all 3 of them!! (poor as in not having a clue)

No they haven't, they have been trying to get to grips with a pattern that is alien to them with the weather coming towards us from the northeast rather than the south and west as is usual. Slowly but surely they are getting there.

Edited November 30, 2012 by Frosty039

[chionomaniac]

Right ECM T+168 where did it go? Hands up - who's nicked the slider?

Edited November 30, 2012 by chionomaniac

[SMU]

http://www.meteociel.fr/modeles/ecmwf/runs/2012113012/ECH1-168.GIF?30-0

[Tom Jarvis]

The storm chaser your following will be wrong-

The tropical wave is already initialised at T0 on the ECM & goes on to develop over 72 hours or so-

Its developing because of the jet streak & strong thermal gradient across its centre-

http://www.meteociel...CH0-72.GIF?30-0 Some 15 degrees or so across it.

T 120 ECM

http://www.meteociel...H1-120.GIF?30-0

slider low over iceland to move SE- this will ensure the tropical wave moves ESE- not ENE towards the UK

S

Thanks Steve

[chris55]

I don't think the models have been poor, it's just that we are in a more difficult period of forecasting than a Zonal flow would be. Post 96/120 is always less certain but in this situation it's even more open to changes.

[Snowy Easterlies]

ECM at 120 markedly better than the GFS.

GFS

ECM

#

*Sigh* you never learn do you GFS.

can you explain to me why the GFS is wrong and the ECM is right at T120 ?

[Stuie]

Interesting when this band of rain moves in from the west on Monday and what it will exactly fall as.