Model Output Discussion 1st January 2014-06z onwards.

[Dunmurry Hedgehog]

another pdf on the elusive probability using 500mb anomaly charts

 

update on 500mb anomaly charts 2 jan.pdf

I suspect that this will sound crazy with a very powerful PV sat over Eastern Canada/Western Greenland directing a series of lows across the Atlantic straight at us for weeks now, but it looks to me from your 500 mb charts that the pattern whilst being similar has moved between 5 & 10 degrees west. Do you think that this retrogression will be maintained, and if so, how much of a further correction would be needed to bring cold to our neck of the woods? Thanks in advance.

[nick sussex]

POSSIBLE MAJOR UPSTREAM DEVELOPMENT!!!

 

Okay a bit theatrical but everyone knows what I'm like by now!

 

For those who read my earlier NOAA update they had not used either the GFS 12hrs or NAM 12hrs because they were viewed as being too progressive and flat with the initial development of the low.

 

The latest NAM has made a  shift in the depth of the low aswell as its track, it only goes upto 84hrs but below is the 12hrs to Monday 00hrs:

 

 

Followed by the 18hrs to the same time:

 

 

And the GFS 12hrs to the same time:

 

 

You can see the GFS is much further east and a lot shallower. Lets hope that the NAM is a good sign before the GFS 18hrs run comes out, hopefully that makes a similar shift.

 

We want the low to run as far inland as possible so certainly the latest NAM looks nice.

 

NOAA expected a track and deepening through the eastern Great Lakes so the NAM does support that.

Edited January 2, 2014 by nick sussex

[pdiddy]

The MO are not forecasting a wintry 2nd half of Jan though Frosty....their latest output simply suggests it's a possibility, not a given, so things have to be kept in context here imo. 

 

UK Outlook for Friday 17 Jan 2014 to Friday 31 Jan 2014:

Current indications point towards unsettled conditions persisting through mid-January. Some signals are emerging suggesting that the weather may undergo a change later this month allowing colder conditions to then become increasingly likely. This would increase the risk of some wintry conditions developing during the second half of January. A change to a colder weather type would also increase the potential for more settled conditions leaving a lower risk of wet and windy spells than has recently been the case.

Issued at: 1600 on Thu 2 Jan 2014

The whole point of forecasting is calculating future events, so nothing can be "a given", either cold or mild options.  The MetO mention it, one assumes, because there is a chance of it happening?  That's what needs to be in context, surely?

[TSNWK]

POSSIBLE MAJOR UPSTREAM DEVELOPMENT!!!

 

Okay a bit theatrical but everyone knows what I'm like by now!

 

For those who read my earlier NOAA update they had not used either the GFS 12hrs or NAM 12hrs because they were viewed as being too progressive and flat with the initial development of the low.

 

The latest NAM has made a  shift in the depth of the low aswell as its track, it only goes upto 84hrs but below is the 12hrs to Monday 00hrs:

 

nam_namer_084_850_temp_mslp_precip.gif

 

Followed by the 18hrs to the same time:

 

nam_namer_078_850_temp_mslp_precip.gif

 

And the GFS 12hrs to the same time:

 

gfs_namer_084_850_temp_mslp_precip.gif

 

You can see the GFS is much further east and a lot shallower. Lets hope that the NAM is a good sign before the GFS 18hrs run comes out, hopefully that makes a similar shift.

 

We want the low to run as far inland as possible so certainly the latest NAM looks nice.

 

NOAA expected a track and deepening through the eastern Great Lakes so the NAM does support that.

Many thanks for the update nick.. However after spending the last few days watching these upstream developments which seemed to have gone our way we are still being scuppered by those pesky European heights..

[nick sussex]

Many thanks for the update nick.. However after spending the last few days watching these upstream developments which seemed to have gone our way we are still being scuppered by those pesky European heights..

You're welcome, the sticking point is western Europe with the limpet troughing filling but not going anywhere over the UK, to combat that we need to see high pressure to the north further sw to cut off phasing with the PV for as long as possible, the PV also needs to be corrected westwards.

 

We need to buy as much time as possible so really need the inland runner over the eastern USA, lets just hope that the GFS does a similar shift as the NAM, that still might not be enough but will be a start at least.

[fergieweather]

 

Ian may have different information shaky but the 12z NMM model doesn't indicate any snow for lower levels.

A couple of images for Sat am just to give a basic idea

 

prec.pngdews.png

 

Dewpoints above 0c except over some mountainous areas Scottish highlands for example.

Snow risk maps just to show this probability.

Recent runs shifted it further north - e.g. Welsh uplands; Peak District etc. Very PPN intensity dependant anyway. In any event it's wholly surpassed by far greater forecast concerns / priorities right now, of the watery variety.

[shaky]

Recent runs shifted it further north - e.g. Welsh uplands; Peak District etc. Very PPN intensity dependant anyway. In any event it's wholly surpassed by far greater forecast concerns / priorities right now, of the watery variety.

oh damn ian that update is like a knife to the heart!!never mind we can only hope!!

[damianslaw]

UKMO at 144 hours showing strong height development north of Scandinavia in the region of Svalbard which would be a significant pattern change over the polar regions. There is a strong likelihood of the longwave trough becoming unstuck over the country and eventually squeezed out by a combination of heights building both to the south and northeast aided by an ever weakening polar vortex. Such developments would tie in with the Meto forecast of possible colder conditions during the second half of the month.

 

In the meantime we have some further damaging weather ahead, but I'm a firm believer that mother nature has a habit of balancing things out to achieve equilibrium state- with this in mind don't be surprised to see what has been an exceptionally volatile period come to a crashing end quite suddenly - but may take a couple of weeks yet.

[Grimsby Snow Lover]

oh damn ian that update is like a knife to the heart!!never mind we can only hope!!

...hope indeed that nobody gets killed or injured when the next batch of storms arrive later tonight. Here on the East coast we are still rebuilding sea defences from the severity of the weather. Edited January 2, 2014 by Grimsby Snow Lover

[Iceni]

With the GEFS 12z mean turning significantly colder during the second half of the run, it's not surprising to see perturbations as lovely as this small sample, P1 is a stonker....as is P20  I would have that right now if it was offered to me..it sure would feel like winter has arrived!

 

There is a God!

[Polar Maritime]

oh damn ian that update is like a knife to the heart!!never mind we can only hope!!

 

No it's not 

 

Can only see it being confined to the highest peaks anyway i would think, 400m+

Edited January 2, 2014 by Polar Maritime

[SMU]

Mr Sussex- 18z GFS has shifted a way back north with the low-

 

expect the GFS to more or less look like the ECM / UKMO at 132 tonight- which is where FI starts....

 

S

[fergieweather]

 

...hope indeed that nobody gets killed or injured when the next batch of storms arrive later tonight. Here on the East coast we are still rebuilding sea defences from the severity of the weather.

We have grave concerns for tomorrow here in SW and that includes into the afternoon/eve. Gotta dash - cheers for now.

[shaky]

No it's not 

 

Can only see it being confined to the highest peaks anyway i would think, 400m+

fax charts looked quiet promising though for snow across the midlands and east anglia with the 528 dam line across those areas!!and everything was shown to be further south and not across the peak district and wales!!

[Newberryone]

As highlighted by many, recent runs of the Ecm looking far less amplified again. Dare I even say the chart for Sun Jan 12th has all the signs of a zonal reset. Those far fetch southwesterly winds not looking great for coldies 

[cheshire snow]

fax charts looked quiet promising though for snow across the midlands and east anglia with the 528 dam line across those areas!!and everything was shown to be further south and not across the peak district and wales!!

 

 A very much blink and you would miss it affair though,as the next batch of wind/rain sweep in

 

 C.S

[Gaz1985]

GFS showing possible snow for the Pennines and Scottish Southern Uplands late Saturday into Sunday. Possibly the Lakes too.

 

 

Edited January 2, 2014 by Gaz1985

[Tim Bland]

Depressing to see Northern Norway, Sweeden & Finland with possitive uppers in mid winter

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=138&code=0&mode=1

[BLAST FROM THE PAST]

18z 'should' be another step forward methinks.  The movement and shape of the LP moving up into Canada will lessen any eastward incursion allowing cold air from our north to invade.  We shall see

 

BFTP

[Mucka]

Mr Sussex- 18z GFS has shifted a way back north with the low-

 

expect the GFS to more or less look like the ECM / UKMO at 132 tonight- which is where FI starts....

 

S

 

Except with GFS where FI starts at T48 apparently.

Slightly better upstream with that low and ridge but worse with regards the Arctic high. 

[Timmytour]

My impression of the 18z Gfs so far is that it looks a lot more exciting for prospects of eventual cold if you run it backwards!

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2014010218/gfsnh-0-168.png?18

 

Lol- & away we go with the GFS..

S

[Grimsby Snow Lover]

My impression of the 18z Gfs so far is that it looks a lot more exciting for prospects of eventual cold if you run it backwards!

I was thinking the same thing!! That would be a very cold NE wind wouldn't it.

[shaky]

http://modeles.meteociel.fr/modeles/gfs/runs/2014010218/gfsnh-0-168.png?18 Lol- & away we go with the GFS..S

steve do you think the models will show the atlantic undercut that arctic block tomorrow?or what are the chances of that happening?

[Mucka]

Two improvements on this run, one out West and one to the South. Makes me wonder what it would of looked like if it had modelled the Arctic high as the other models.

I hope more of its ensembles are now onboard with the Atlantic ridge and cut off heights to our North.