Model output discussion - mid-winter

[Frosty.]

1 minute ago, northwestsnow said:

Thats 516 DAM quite a long way SOUTH!!

Really really cold air on that chart..

Indeed, even better than the 522 dam I said, i would be very happy with 516 DAM!

[Glacier Point]

Models seem to be hitting a brick wall after day 10, large scatter developing thereafter

[A Frayed Knot]

1 minute ago, Glacier Point said:

Models seem to be hitting a brick wall after day 10, large scatter developing thereafter

Well i ain't at all bothered with day 10 ' let's get the cold here first and then see what the outcome is ' all looking quite nirvana at the moment

[blizzard81]

2 minutes ago, Glacier Point said:

Models seem to be hitting a brick wall after day 10, large scatter developing thereafter

Are you still airing on a non westerly regime at plus day 10?

 

[feb1991blizzard]

4 minutes ago, Glacier Point said:

Models seem to be hitting a brick wall after day 10, large scatter developing thereafter

It'll take a good turnaround from the D10 Ecm mean chart as it enters the more reliable to avoid more PM outbreaks, if it wasn't for your musings earlier, I would be predicting more of the same until if and when the MJO 7-8 / strat warming combo arrives.

[nick sussex]

News regarding the differences upstream:

From the New Hampshire state forecast:

On Tuesday, another piece of energy will be approaching from the
Great Lakes region. This will trigger cyclogenesis off the
Eastern coastline. 12Z model suite remains in significant
disagreement with the evolution, intensity and track of this
next system. The operational GFS and GFS ensembles remain very
progressive with this system, limiting any intensification and
tracking the system from the southern Maine coast to Nova Scotia
by Wednesday morning. The Canadian model has somewhat more
development of the surface cyclone as it tracks through the Gulf
of Maine. The Euro is the most robust with this system, cutting
off a strong upper level low off the New Jersey coastline. This
allows for rapid cyclogenesis on Thursday as the system track
north towards the northern New England coastline.
 

Until this is resolved treat all the outputs past day 5 with  a degree of scepticism. The detail for the UK and what happens after the initial PM flow is uncertain.

 

 

[Bazray]

27 minutes ago, Man With Beard said:

Many many ECM ensembles take the runner low even further south - increasingly the risk of an M4 SOUTH event

Unlikely, never underestimate the force of the M4 shield!

Edited January 12, 2018 by Bazray

[blizzard81]

1 minute ago, nick sussex said:

News regarding the differences upstream:

From the New Hampshire state forecast:

On Tuesday, another piece of energy will be approaching from the
Great Lakes region. This will trigger cyclogenesis off the
Eastern coastline. 12Z model suite remains in significant
disagreement with the evolution, intensity and track of this
next system. The operational GFS and GFS ensembles remain very
progressive with this system, limiting any intensification and
tracking the system from the southern Maine coast to Nova Scotia
by Wednesday morning. The Canadian model has somewhat more
development of the surface cyclone as it tracks through the Gulf
of Maine. The Euro is the most robust with this system, cutting
off a strong upper level low off the New Jersey coastline. This
allows for rapid cyclogenesis on Thursday as the system track
north towards the northern New England coastline.
 

Until this is resolved treat all the outputs past day 5 with  a degree of scepticism. The detail for the UK and what happens after the initial PM flow is uncertain.

 

 

Thanks for that Nick. However, if there is large uncertainty from day 5, how come the ensembles are tight out to day 10?

[offerman]

5 hours ago, Rollo said:

I would think it would be better not to criticise those who attempt some sort of long range forecasts if you cannot proffer something sensible yourself.

Not a direct personal attack I’m just saying how difficult it is to forecast beyond a few days. It seems futile beyond this. Summer months seem much easier on a slightly longer time period but in winter nature plays havoc and solar activity adds to the complexities too. 

So apologies , I was agreeing with a poster and echoed his thoughts too as to me he made sense in his statement . 

 

 

 

[SMU]

34 minutes ago, Man With Beard said:

Many many ECM ensembles take the runner low even further south - increasingly the risk of an M4 SOUTH event

It will be a similar track to the December runner....

Poss more south as there will be more forcing this time to hold the track further south-

Edited January 12, 2018 by Steve Murr

[SMU]

28 minutes ago, northwestsnow said:

Thats 516 DAM quite a long way SOUTH!!

Really really cold air on that chart..

Those are not thicknesses !!

[northwestsnow]

2 minutes ago, Steve Murr said:

It will be a similar track to the December runner....

Blimey mate dont be saying things like that shaky wont sleep for the next 4 nights...

Its an interesting trend and without wanting to repeat myself i saw Helen with my own eyes and ears talking about potential for snow in the south later next week.

Something for us all to keep an eye on steve- did yoy notice how far south 516 DAM gets nxt week/!!

edit just seen your post, waht do they represent steve?

Edited January 12, 2018 by northwestsnow

[nick sussex]

1 minute ago, blizzard81 said:

Thanks for that Nick. However, if there is large uncertainty from day 5, how come the ensembles are tight out to day 10?

The Euro trough isn't the issue, that has very good agreement and gets locked in because of the Russian high.

The bit in the middle and to the nw is the problem in terms of forecast. You'll see from the crayon job I did earlier how these differences upstream effect any mid Atlantic ridge.

And as you can see from the NH forecast theres a real issue with the GEFS and GFS if they all seem to be having the same progressive upstream pattern.

If they have the wrong set up at T144hrs over the ne USA then you can see how that would effect the subsequent evolutions.

Of course the GFS might be right we don't know yet. That's why I'm urging some caution, I've seen the ECM do this before with phasing and over deepening systems in this manner and if I quote this from the earlier discussion:

However, there is some suggestion of a gradual tilt to the
longwave, enhancing the lower lvl baroclinic zone off the coast,
which may allow for energy transfer in the form of secondary
redevelopment. ECMWF leads the charge here, as it deepens and
tilts the trof more significantly. While this is a typical bias,
it has been most persistent with this thinking.

Given recent ECM episodes I'm reluctant to go with it even though the GFS has a flat bias. Hopefully we can get this resolved tomorrow morning.

[SMU]

3 minutes ago, northwestsnow said:

Blimey mate dont be saying things like that shaky wont sleep for the next 4 nights...

Its an interesting trend and without wanting to repeat myself i saw Helen with my own eyes and ears talking about potential for snow in the south later next week.

Something for us all to keep an eye on steve- did yoy notice how far south 516 DAM gets nxt week/!!

actually double checked the GFS 

it is correct-

the 850-1000 is 1285-1290 which is bit high-

the post runner allignment is better ~ T162

wisespread sub 1290

Edited January 12, 2018 by Steve Murr

[January Snowstorm]

Anyone know how to access the Dam lines for gfs?  Remember the 528 blue and 510 lines? Are they now gone from charts?

[northwestsnow]

Just now, Steve Murr said:

Yes mate sadly it’s not the correct chart-

My bad

Looks cold on my PC though

 

[ANYWEATHER]

Hello folks , Potential next week for two dumpings of snow for southern Uk ,two sliders possible , watch this space......

[comet]

Another rather coldish spell on the way by the looks, with some snow around although not worth going into to much detail at present. Of course further north with elevation it may well be a noteworthy spell of weather to come but certainly no freeze for the majority of us. The forecasted strat warming is now evident in the ecm  Berlin charts and forcing from this MAY  temporarily shorten any colder synoptic pattern we are in as it changes the dynamics and structure of the atmosphere ( it would not be the first time this has happened) but hopefully we will reap bigger benefits from this as we enter February.

[SMU]

3 minutes ago, northwestsnow said:

My bad

Looks cold on my PC though

 

It’s was right- I’ve added the 850-1000 thickness now as well- 

[blizzard81]

3 minutes ago, January Snowstorm said:

Anyone know how to access the Dam lines for gfs?  Remember the 528 blue and 510 lines? Are they now gone from charts?

Go to wetterzentrale top karten. Click the gfs tab and then click mittl.wolken tab. 

[northwestsnow]

1 minute ago, Steve Murr said:

It’s was right- I’ve added the 850-1000 thickness now as well- 

Thanks steve

[bluearmy]

4 minutes ago, January Snowstorm said:

Anyone know how to access the Dam lines for gfs?  Remember the 528 blue and 510 lines? Are they now gone from charts?

On meteociel gfs top right - ISO 0c charts

 

4 minutes ago, northwestsnow said:

My bad

Looks cold on my PC though

 

Those are dam heights at 500hpa.  there is an equation to work out the surface thickness using slp and 0.87 as a multiplier 

Ecm gets down to 520 dam at the surface by day 8 which is very low with slp around 980mb 

 

[MildCarlilse]

4 hours ago, Steve Murr said:

pretty Decent 12Z our to about day 10-

If I lived in any of these locations I would be salivating at the models ( +150 M )

-Lake District

-Yorkshire dales

- western Pennines

- peak district

- Shropshire hills

- Exmoor

- Beacons & Snowdonia

- Sperrin in Ireland-

possibly even the Cotswolds - 

we could see DEEP snow accumulating from when the cold spell starts lasting 7-10 days... 

somewhere is going to get North of 30cm of snow from convective showers followed by frontal Atlantic sliders -

The most snowiest spell for the UK since 2010 ... let’s hope it’s backed up by the North Easterly Post 192....

S

Oh,Scotland missing out???

[bluearmy]

33 minutes ago, Glacier Point said:

Models seem to be hitting a brick wall after day 10, large scatter developing thereafter

Not seen the eps extended struggle as badly as they currently are for consistency for quite a long time 

[bluearmy]

2 minutes ago, MildCarlilse said:

Oh,Scotland missing out???

Definitely not - I think it's just assumed