Model Output Discussion 1200 hrs 15/11/14

[bluearmy]

Actually, having viewed the control, I'd give the op solution one more chance tomorrow morning before dismissing it.

[nick sussex]

Just in, at last the very latest on the pattern over the USA  from New York state forecast by NCEP:

 

This includes all the evening outputs including the ECM and was updated at 9.09pm UK time:

 

I'm happy to report that the GFS has been dumped as the GEFS regardless of what happens downstream is more amplified and supports at least the troughing over the USA:

 

UNCERTAINTY IN THE FORECAST INCREASES FOR THE MID TO LATE WEEK AS
MODELS DIFFER IN THE INTERACTION OF SHORTWAVE ENERGY ROTATING AROUND
A CLOSED POLAR LOW NW OF HUDSON BAY AND ITS INTERACTION WITH
NORTHERN STREAM ENERGY. THE CMC/ECMWF AND ASSOCIATED ENSEMBLES ARE
AGGRESSIVE WITH THIS INTERACTION...PIVOTING A PHASED AND STRONG
SHORTWAVE THROUGH THE NORTHEAST WED NIGHT. THE GFS IS TAME WITH THIS
INTERACTIONS AND SIGNALING A PRACTICALLY FLAT UPPER FLOW...WHILE
THE GEFS DEPICTS A MORE AMPLIFIED SHORTWAVE PASSAGE LIKE CMC/ECMWF
ENSEMBLES. HAVE LEANED TOWARDS THE MORE AMPLIFIED FLOW AS DEPICTED
BY THE ENSEMBLE MEANS.

 

This doesn't mean that a northerly or ne is a definite because there are other issues with the GEFS to the north but at least it gives this a bit more chance. We still need to see the GFS and GFS P however start moving in their operational runs given the divergence begins well within T144hrs.

[chionomaniac]

Actually, having viewed the control, I'd give the op solution one more chance tomorrow morning before dismissing it.

I think it is all to do with the jet stream split in the short term in the Atlantic. A small change here and we get a big change later on.

 

 

 

GFS

 

ECM

 

 

For me the best sign is that the models are splitting flow here - a trend that I expect to see continue throughout the winter with more energy south than last winter.

[Ali1977]

I would like to see some better looking charts from the GFS in the medium term, good charts at day 15 mean nothing. Now if in about 30 mins the 8/9 day charts look good I'll sleep happy.

[knocker]

But on the other side of the pond. Oh.

 

Michael Ventrice â€@MJVentrice 

For Winter lovers: latest ECMWF week 4 forecast shows western N. American ridge. Would force cold air down o/the U.S.

Edited November 28, 2014 by knocker

[bluearmy]

But on the other side of the pond. Oh.

 

Michael Ventrice â€@MJVentrice 

For Winter lovers: latest ECMWF week 4 forecast shows western N. American ridge. Would force cold air down o/the U.S.

 

have to say that chart leaves me a tad confused knocks. it certainly isnt the ens mean but it could be the control. if the control for week 4 then it may as well be my six year old drawing it!

[damianslaw]

As ever it remains an uncertain outlook, as others have said much depends on the position and strength of energy into the Jetstream and how amplified the flow over eastern N America becomes. As per usual, GFS less keen on amplification and sending energy into the southern arm of the jet, ECM much more so.

 

Everything feels a bit ineffectual at the moment full of lacklustre..

 

I remain confident we will see a trigger in the not too distant future shaking us out of the non-descriptness benign conditions of recent weeks.. Perhaps give the models another a week before this trigger signal is latched onto, the trigger from the NW....

[fergieweather]

Just for info: UKMO have modified 12z GM (versus raw/unmodified output seen on public websites) to make ridging more prominent out towards E/SE towards T+132, preferring the GFS 12z solution into that timeframe (and equally preferring as signalled in earlier UKMO-GM run).

[Grimsby Snow Lover]

Just for info: UKMO have modified 12z GM (versus raw/unmodified output seen on public websites) to make ridging more prominent out towards E/SE towards T+132, preferring the GFS 12z solution into that timeframe (and equally preferring as signalled in earlier UKMO-GM run).

What exactly does that mean? I'm still learning all the technical jargon. Thanks

Edited November 28, 2014 by Grimsby Snow Lover

[nick sussex]

Just for info: UKMO have modified 12z GM (versus raw/unmodified output seen on public websites) to make ridging more prominent out towards E/SE towards T+132, preferring the GFS 12z solution into that timeframe (and equally preferring as signalled in earlier UKMO-GM run).

Interesting so UKMO prefer GFS over western Europe but NCEP prefer GEFS/ECM/GEM ensemble means for the USA.

[fromey]

Interesting so UKMO prefer GFS over western Europe but NCEP prefer GEFS/ECM/GEM ensemble means for the USA.

Sorrys mods for this but is that good or bad for a cool down for us

Fromey

[Nick F]

Interesting 12z ECMWF H500 ens mean/anomaly chart at t+360 someone kindly posted on a US forum, shows -ve heights over Greenland diminshing, +ve height anomaly over Scandi and UK while there's a -ve height anomaly over SW Europe,/western Med - kind of heading into a -NAO territory.

 

And not the same chart as Knocker posted!

 

Although there's signs of the AO going into slightly -ve territory, been a while since we had signs of a -ve NAO. Really need to relax those low heights over Greenland/Iceland to take the energy out of the northern arm of the jet.

Edited November 28, 2014 by Nick F

[Barry12]

Sorrys mods for this but is that good or bad for a cool down for us

Fromey

Bad.

[bluearmy]

Sorrys mods for this but is that good or bad for a cool down for us

Fromey

 

look at the 12z gfs op run at that timeframe. tbh, as the action is upstream at T132, its a bit irrelevant. exeter dont need to get involved post day 5 at the moment.

[legritter]

Plenty of interest today in the models especially towards the further outlook .great to see the ECM Showing some colder options but we need them showing tomorrow [please ECM ] Well will the GFS Twins give us some cold charts tonight ,all in all plenty to cheer about ,but we must not base any thoughts of proper cold on a couple of runs ,if its out there i think it will be a slow process ,

[johnholmes]

Amidst all the hype and hope this chart shows what is most likely the pattern out to day 10 in my view

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

the 8-14 is below

http://www.cpc.noaa.gov/products/predictions/814day/500mb.php

I have been studying these charts daily for over 3 years and there is nothing YET that would suggest within the 14 day time scale that any deep cold is going to affect the UK. No doubt some will disagree but I would like an explanation of how this would occur. An honest question folks.

Until the main trough on the chart, that from nw Greenland down across the far eastern states moves, be it east of west, then no marked NW flow can occur into the UK at 500mb. Nothing in the anomaly charts to me suggests this is going to happen within 14 days or so.

The MJO is currently in phase 3 which seems to equate to 

http://www.americanwx.com/raleighwx/MJO/MJO/DecemberPhase3all500mb.gif

pretty much a flattish ridge from N Ameica across the Atlantic into nw Europe.

 

The GFS forecast for the MJO takes it through 4-5-6-7-8, by which time it is close to the origin and often small amplitudes give little guidance of how the 500mb pattern might show. If we take a mean of 6 and 7 with decent amplitude, phase 6 shown

http://www.americanwx.com/raleighwx/MJO/MJO/DecemberPhase6all500mb.gif

This would suggest some kind of 500mb ridge west of the UK with only the slightest -ve anomaly east of the country. This is perhaps what some of you are inferring in some of the posts. Again I would suggest that after 14 days then the probability is currently about 20-25%. Obviously this might change over the coming days in which case it would be relected by a consistent change in the anomaly charts. We have to wait and see in my view if this does happen. I do believe that any initial cold outbreak is going to come from west and not east.

[Yarmy]

But on the other side of the pond. Oh.

 

Michael Ventrice â€@MJVentrice 

For Winter lovers: latest ECMWF week 4 forecast shows western N. American ridge. Would force cold air down o/the U.S.

And only 500 hours away! To be fair, it looks like a strong Atlantic struggling against a stubborn Sceuro block. Where have we seen that before?

[nick sussex]

The GFS 18hrs is flat and similar to the 12hrs, the GFS P now goes in another direction from its earlier 12hrs by building pressure ne, it looks quite cold with a slack continental flow for a time.

 

The GFS's haven't read the NCEP script and so we'll see whose right and wrong tomorrow, quite a big test here for the outputs, we've seen the ECM do some weird things at T168hrs onwards over the last few weeks however this is the first time that theres a big divergence within T144hrs so one model is going to look very silly tomorrow morning.

 

This is also a possible pointer to the new GFS P , will it have a flat upstream bias like the old GFS?

[bluearmy]

Interesting 12z ECMWF H500 ens mean/anomaly chart at t+360 someone kindly posted on a US forum, shows -ve heights over Greenland diminshing, +ve height anomaly over Scandi and UK while there's a -ve height anomaly over SW Europe,/western Med - kind of heading into a -NAO territory.

 

And not the same chart as Knocker posted!

 

Although there's signs of the AO going into slightly -ve territory, been a while since we had signs of a -ve NAO. Really need to relax those low heights over Greenland/Iceland to take the energy out of the northern arm of the jet.

 

i think the upstream story over the next week or two will be around the split jetstream, both across and upstream off n america, and when the models will get a good handle on it. the back end of the ecm ens show the southern arm getting the upper hand off the eastern seaboard. (as may be expected once the deep cold is lost in ne canada)

Edited November 28, 2014 by bluearmy

[Nick F]

And here comes the amplification upstream:

 

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=276&mode=0&carte=1

 

Followed by a northerly of sorts, re-occuring theme across the models? 06z, 12z and now 18z GFS albeit earlier this time.

[knocker]

have to say that chart leaves me a tad confused knocks. it certainly isnt the ens mean but it could be the control. if the control for week 4 then it may as well be my six year old drawing it!

 

I assumed it was the HR of the EC32 but I don't know that.

[Captain Shortwave]

I think the next week/fortnight could be rather frustrating. The polar pattern is in such a state where a little over-amplification by the models in the 7 day + range could result in a lot of cold looking charts. At this moment I'm still feeling it is too early, though a polar maritime or even Arctic blast could not be ruled out.

I think it's best to hang in there and hold on for dear life as I suspect it will a question of when, not if cold weather arrives.

 

The CFS and JMA monthlies are fairly similar in their evolution, week 1 is settled, week 2 sees heights decline before low pressure pushes through the UK during weeks 3 and 4. Worth pointing out that low pressure in this case is generally on a South east trajectory towards central Europe with a strong ridge in the western Atlantic and slightly higher than normal heights over the pole.

[phil nw.]

Having looked at all of today's runs the common theme is mid-latitude heights around the UK/W.Europe for the next week to 10 days at least.

The jet flow splitting out in the Atlantic keeping enough energy under the block to prevent the high sinking but at the same time the northern arm keeping any ridging north temporary.

There will be small variations in the surface features but that seems to me to be the overall set up going forward.

 

After the brief warm up it does look like a colder outlook next week as we get some injections of PM air coming south through the coming days.

Not much rain around and increasing risk of night frosts if the high settles over the UK.If it does we could see some freezing fog too so some Wintry conditions quite possible,just not the snowy kind.

There's plenty of deep cold out east but no sign of it coming this way yet.

 

The ECM op was a cracker but the mean outputs on both runs show this a long shot with the main part of the pv spread across our side of the pole between Canada/Greenland and Siberia.

Edited November 28, 2014 by phil nw.

[knocker]

And here comes the amplification upstream:

 

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=276&mode=0&carte=1

 

Followed by a northerly of sorts, re-occuring theme across the models? 06z, 12z and now 18z GFS albeit earlier this time.

 

Am I reading this correctly Nick? The amplification shows up quite well on the dynamic tropopause potential temperature chart. Of course it's better to run the sequence.

Chart courtesy weatherbell

[Cloud 10]

Ridiculous differences between the day 7 ECM 12z and the 18z GFS P,may as well be day 77!

 

ecm..  gfsp..