Model Output Discussion - 05/01/2016 18z onwards

[weather eater]

How often does the UKMO or the GEM trump the GFS in these sorts of situations, not very often unfortunately. Tonight's ECM will be an enlightening, If it follows the GEM and UKMO then there is a chance that they, not the GFS has the right signal. if not then we will just have to hope that the GFS at least changes tack on its mid-range projections, otherwise its back to the blow torch.

Edited January 9, 2016 by Polar Maritime
To move discussion on..

[IPredictASnowStorm]

5 minutes ago, Earnest Easterly* said:

Marginal for the S I take it but you're incorrect. 

You kinda need that to be a higher risk for snow to have a good chance for it to happen .. Thanks for Showing me them i didn't see that there was a risk 

Edited January 9, 2016 by IPredictASnowStorm

[peborant]

In la la land there is a trended northerly that would attack Europe toward the end of the run, maybe that is a reload for the future. Who said January was going to be like December? There is still a lot of winter to go, at least up here we can start feeling a difference -even though it has rained at 2C today which is never great and cold has been certainly downgraded and delayed but seems pretty settled on being here for Wednesday, Thursday from the folk south of Manchester. Roll on frosts and snow!

[karlos1983]

If the ECM throws out a different solution, then I think it's even more obvious that none of us can have much clue of what is going to happen past the point that they are all in agreement, be it +24, +48 or +0. Just because the GFS is consistent in it's theme, for me does not mean it is correct.

[A.J]

12 minutes ago, IPredictASnowStorm said:

 

just out of curiosity why do you (and others for that matter) post precip charts for T120+ and ramp and/or moan about them?......they are never to be taken at face value and are only the very roughest of guides....in my experience even the hi-res precip charts from T0-T48 are fickle to say the least....As John Holmes has stated many many times over the years, snow forecasting is very difficult, akin to finding a piece of hay in a stack of needles!

[IPredictASnowStorm]

Most of the lying Snow is high Ground So if it does snow in low levels its gonna be the wet snow that doesn't lay  

[Singularity]

A new idea from UKMO tonight, or perhaps not as GEM may have been there this morning? Anyway, look at how the shortwave south of Greenland scoots over to merge with the UK trough:

This is a crucial development that opens the door for another attempt to build that ridge. Some GEFS members attempt this but the det. is having none of it. 

I think this illustrates just how unlucky the route that GFS keeps coming up with is - one where the shortwave from our trough on Tuesday makes too much progress west, and then the one from the U.S. trough makes far too little progress east. The odds of that particular outcome must be pretty low, even accounting for 'Sod's Law'...

ECM this morning was also different with the shortwave, choosing to absorb it back into the U.S. trough. This outcome means less breakage of the ridge after the Tuesday debacle, but does have the effect of angling the jet more SW-NE than S-N on the western side of the ridge, resulting in it being shoved east over the following days.

This is the funny thing about MJO composites when the MJO is moving at high amplitude from one phase to the next - the extent to which the hemispheric patterns follow suit depends on how much mobility there is in the system. For a time it looked like we'd see low enough mobility for the pattern to get stuck in a phase 7 state but that's been dropped now in favour of trying to shuffle the cards and build something resembling phase 1 perhaps. Ideally, that happens with the key modification of a -ve AO persisting in the Arctic but the models have really trended away from that over the past 48 hours too.

Best case scenario at the mo looks to be a mid-Atlantic ridge getting a good way poleward and then 'leaning' so that it extends NE and becomes more of a Scandi ridge ('Murr Sausage' variety perhaps?) as low heights encroach on Greenland. The ECM 00z det. wasn't poleward enough with the initial ridge for that, but the 12z det. of yesterday was a decent effort. Something to watch as we'll surely get a bit of luck sometime soon, especially once we reach GP's 'torpedo landing period' which is just a couple of days beyond the end of the latest ECM det. runs - though we've not had an update from him in a number of days unless I've missed it?

 

All the 12z GFS det. can be used for is to see how bad having that shortwave off the U.S. trough linger in the way of the ridge can be for keeping the cold air in place beyond Friday. Longer term it's still doing that crazy MJO thing while the other models either have a descent into COD or in the case of ECM progression to phase 1/2 before fizzling out. That last option remains the most logical to my eyes (i.e. agreeing with most of the expert contributors on here).

 

 

[Lampostwatcher]

http://www.wetterzentrale.de/pics/Rukm1201.html this is good for snow even down south 

[Alexis]

The last 2 GFS runs have been mild outliers to some degree or another. Until we see where it lies in the ensembles there is every chance it could be the third 'unreliable' run on the trot.

[chionomaniac]

Where does all this talk of 'phasing energy' come from? I bet it is not in any meteorological books - certainly not in any that I have read. No one seems to put up the jet stream charts anymore and they have far more relevance than any talk of phasing.

The differences between the GEM and GFS at T+144 are all to do with the jet stream strength, direction, and split and nothing to do with energy phasing with each other. To demonstrate at T+72 the jet stream on the GFS is still taking a northerly route, and even though the 'bridge' between the northerly and southerly arms isn't great at source - it still exists.

 

However, by T+ 144 the GFS has forecast that the jet stream has crossed this bridge isolated like an ox bow lake leaving the ridge to eventually collapse as shown here:

And hence the Atlantic comes straight for the UK. One would need to see enough of the jet head north still whilst diverting a significant portion south to maintain the ridge.

Quite simply the UKMO plays out this scenario and is nothing to do with the term energy phasing which is bandied around here and does not really mean anything. ( Occasionally two separate depressions can become phased with each other but this is different)

( And don't get me started on shortwaves !)

Edited January 9, 2016 by chionomaniac

[Harsh Climate]

Still huge uncertainty regarding next weeks cold spell.

 

Just looking at the GFS esembles and quite frankly the gfs doesn't have a clue! As early as 120h we have esemble members showing, heavy snow over southern england (channel low), heavy snow moving west to east across northern england, rain turning to snow in east and south east england, rain for all, dry... Anything could happen.

 

Riculous.

Edited January 9, 2016 by Harsh Climate

[Frosty.]

I agree the Gfs 12z could be a mild outlier in FI, I wasn't expecting to see this lurking in the woodshed

[karlos1983]

Looking at the GFS Purbs, there is support for the UKMO at +144

GFS Purbs here from +144 follow link and click through for yourself http://www.meteociel.fr/modeles/gefs_cartes.php?ech=144&code=17&mode=0&carte=1 

 

[Ali1977]

GFS in extreme FI would go on to be something special - however not much chance of being correct at 120 so beyond 384 would be a minor miracle 

[Harsh Climate]

Some very nice essemble members (144h)

 

1

3

4

7

9

17

18

19

20

 .

 

 

Edited January 9, 2016 by Harsh Climate

[Catacol]

5 minutes ago, chionomaniac said:

The differences between the GEM and GFS at T+144 are all to do with the jet stream strength, direction, and split

Is this therefore the end of the chicken and the egg debate on the jet?! I thought that the jury was still out as to whether the jet was cause or effect...

[IDO]

Good support from the GEFS at T108 for that shortwave spoiler to cut off the Atlantic ridge with the Greenland heights. There was minority support this morning, that grew via the 06z and now it is 66% support and that includes the Control. 

What that shortwave spoiler that phases energy between the US trough and the Scand trough does is provide a geateway for the jet to travel west to east via the quickest route. The jet's route is dictated by the shortwave phasing not the other way round IMO (re Chino's post), though it is a chicken and egg conundrum if you think about it too hard!

[Mucka]

GFS ensembles

Looking through GFS ensemble suite the majority want to make more of shortwave energy coming up from the SW from the Azores low which phases with the trough over the UK. Solutions range from wet windy with a deepening low to cold and snowy if it develops less and stays to the South. Everything in between is also modeled, wintry mix of rain/sleet/snow. Thursday is shaping up to be a very interesting day if GFS is correct as UKMO barely registers the shortwave and it has no impact. The situation is further complicated by the Greenland shortwave moving SE and likely to phase in with the UK trough at around the same time as any energy moving up from the SW. Very complex and not surprising the models are struggling.

Overall the ensembles are moving toward the Op but it still does not have majority support. UKMO type solutions are still there as are some ECM type solutions.

At times like these I'm glad I don't do forecasts but I would say there is a reasonable chance of widespread snow event for England before any transition away from the cold. This will most likely occur around the 14th but depending on which way the output goes thereafter as there could be further opportunities later.

At 192 there is about a 50/50 split between keeping an amplified pattern or something more Westerly based.

Edited January 9, 2016 by Mucka

[doctor32]

Just now, Harsh Climate said:

Some very nice essemble members (144h)

 

 

 

That is quite a few to suggest the ukmo may well be on right track with gem and possibly ecm when it arrives

[Daniel*]

7 minutes ago, ajpoolshark said:

just out of curiosity why do you (and others for that matter) post precip charts for T120+ and ramp and/or moan about them?......they are never to be taken at face value and are only the very roughest of guides....in my experience even the hi-res precip charts from T0-T48 are fickle to say the least....As John Holmes has stated many many times over the years, snow forecasting is very difficult, akin to finding a piece of hay in a stack of needles!

I just wished to exemplify the GFS 12z run was not snowless, what could be on the table, apparently there's a 30% Prob of widespread snowfall on that particular day into Friday thus it is far from madness. The channel low feature has been shown quite consistently over the last few days just grazing the far S. The mist should disperse early next week regarding snow prospects ect.

[Connor Bailey Degnan]

Anything could still happen after 96hrs, i think the ecm will jump on board with the UKMO and GEM. GFS always trys to bring in the atlantic to quick.

[Mucka]

GFS short ensembles SE England. Note the ppn spike on the 14th which will be as a result of shortwave energy moving up from the SW and down from the NW as previously posted.

[nick sussex]

All this talk of phasing! lol In terms of what NCEP thought of this mornings ECM 00hrs, not a lot in terms of later next week.

IMO you can have phasing lows and phasing jet streams but I agree with Chiono re phasing energy. The irritation he has with shortwaves is probably down to me! lol As these often pop up in my posts however if its good enough for NCEP its good enough for me!

In terms of the upstream pattern the issue is north/south jet stream interaction( phasing)! or not. A lengthy look at this in the NCEP outlook.

BETWEEN DAYS 4 AND 6...THE DETERMINISTIC GUIDANCE BEGINS TO DIFFER WITH RESPECT TO THE CHARACTER OF THE PACIFIC FLOW...ITS SHORTWAVE DETAILS ENTERING THE WEST COAST ... CONTINENTAL DIVIDE AND SOUTHERN ROCKIES. EAST OF THE DIVIDE AND ACROSS SOUTHEAST CANADA...THE DETERMINISTIC GUIDANCE OFFERS A MYRIAD OF SOLUTIONS FOR THE UPPER-LEVEL TROUGH AND FLOW TRANSITION FOR THE GREAT LAKES...GULF COAST AND NORTHEAST. AND THE 9/00Z ECMWF OFFERS THE BIGGEST RUN-TO-RUN 'CHANGE' OF THE 4 PRIMARY MODEL GUIDANCE PACKAGES (GFS/CANADIAN/UKMET INCLUDED). FOR NOW...BEST WAY TO DESCRIBE THE DIFFERENCES AND IMPLICATIONS/CONCERNS HEADING INTO DAY 6--- PHASING OR LACK-THERE-OF --- BETWEEN UPPER-LEVEL NORTHERN AND SOUTHERN JET AXES. THE 9/00Z DETERMINISTIC GFS/CANADIAN/ECMWF DO A DECENT JOB WITH THE NATURE OF THE SOUTHERN STREAM FLOW (THE SUBTROPICAL JET) IN THE WESTERN GULF OF MEXICO AND NORTHERN CENTRAL MEXICO---BUT THE 9/00Z ECMWF ESPECIALLY...MAINTAINS A MUCH WEAKER NORTHERN STREAM WESTERLY 250MB SOLUTION ALONG THE ENTIRE STRETCH OF CANADIAN BORDER. AND ALTHOUGH ---

THE NORTHERN STREAM APPEARS TO HOLD THE KEY TO THE LATTER HALF OF THIS MEDIUM RANGE PERIOD---WITH PHASED JET OR SPLIT-FLOW (SEPARATED JET STREAMS)--- DETERMINING THE OUTCOME OF BROAD AND DEEP COLD ADVECTION AND SENSIBLE WEATHER EAST OF THE DIVIDE AND DOWNSTREAM OF THE MISSISSIPPI RIVER---USING THE 9/00Z ECMWF DETERMINISTIC SOLUTION FOR DETAILS (CERTAINLY BEYOND DAY 4) SEEMS TO BE THE MORE QUESTIONABLE OUTCOME DURING THIS WEST-TO-EAST MID-LEVEL FLOW TRANSITION.

You'll note this mornings ECM phased a southern stream low with the PV lobe over the ne USA, this is the issue for NCEP.

We'll see soon whether the ECM will stick to its guns or not.

[Liam J]

ARPEGE bringing blizzards to higher ground in Scotland at T72, maybe even to lower levels away from the coasts. 

[karlos1983]

4 minutes ago, Mucka said:

GFS short ensembles SE England. Note the ppn spike on the 14th which will be as a result of shortwave energy moving up from the SW and down from the NW as previously posted.

OP as expected an outlier from 15th/16th onward