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

[Yorlum11]

 

Nice ENS!

[phil nw.]

Interesting to see how the London ens.temp graph has dropped in 72hrs,just comparing the 00z runs from the 4th Jan.to todays 00z runs.

as always when looking a few days ahead it's all about trends rather than run to run detail.If looking for a cold spell that may well extend into a longer period those are going the right way.

[bluearmy]

2 minutes ago, phil nw. said:

Interesting to see how the London ens.temp graph has dropped in 72hrs,just comparing the 00z runs from the 4th Jan.to todays 00z runs.

as always when looking a few days ahead it's all about trends rather than run to run detail.If looking for a cold spell that may well extend into a longer period those are going the right way.

always fun to see the scale adjusted to take account of the 'murr run'

[phil nw.]

1 minute ago, bluearmy said:

always fun to see the scale adjusted to take account of the 'murr run'

Yes Nick they are pretty cold aren't they.I should have pointed out that the mean now is running close to 0C rather than 5C of the 4th!

[Fozfoster]

33 minutes ago, Yorlum11 said:

 

Nice ENS!

Look at that spike on the 17th. ;-)

[Pennine Ten Foot Drifts]

It seems to me that now we have an 'exceptional cold spell' in relatively recent memory, ('09/10), I think we're almost in danger of spoiling this upcoming cold spell by over-comparison. I meant to post last night, but a long day at work leading to 'snooze on the couch syndrome' put paid to that. However, whilst any notable country wide cold remains beyond the truly reliable it seems to me that all we can say at this stage is that a build of pressure in the N.Atlantic/Greenland region is looking pretty likely from the middle of next week, with lower pressure over Scandi/Europe, which leads to significantly lower temperatures than we've been used to.

But, from what I'm seeing i certainly don't see the kind of country-wide snowfall we had in '09/10 being repeated. The reason I say this is that, taking the 00z ECM as an example, at T120 it shows this:

And the GFS 00z at T144:

To me these remind me of previous cold spells where precipitation is either fairly limited, or marginal for lowland areas further south than Scotland. And as the GH develops and the troughs fill, coinciding with arrival of genuinely colder temps precipitation starts to die off, leading to ppt charts like this, which we've seen many times in this kind of set up:

 Now I know that the general rule is 'get the cold in first' etc etc, and that we shouldn't trust the GFS ppt charts, but I disagree to a certain extent in that they certainly give a flavour of likely ppt patterns for a given set-up, and to me right now this set-up suggests a few things:

1. The 'real deal' cold is still beyond the reliable time frame, so there are still ample opportunities for subtle near term changes to have significant consequences for better or worse in terms of the extent and depth of the cold we will end up experiencing

2. If we do get the deep cold, it doesn't look to me, at least as is currently being modelled, that there will be many 'dumpings' associated with it, certainly not for more lowland southern Britain anyway.

3. It certainly doesn't look to me like '09/10 MKII !

[Alexis]

.

Edited January 7, 2016 by Alexis
-

[P-M]

8 minutes ago, Alexis said:

You will never get a chart like this modelled accurately until nearer the time though. The above chart, which dumped more snow on Manchester than during the famous spell later in the year, was forecast to just bring a bit of snow to the east coast a few days before.

 

Sorry mods can you delete thought I was still in the discussion thread!

Edited January 7, 2016 by P-M

[snowmadchrisuk]

27 minutes ago, Pennine Ten Foot Drifts said:

It seems to me that now we have an 'exceptional cold spell' in relatively recent memory, ('09/10), I think we're almost in danger of spoiling this upcoming cold spell by over-comparison. I meant to post last night, but a long day at work leading to 'snooze on the couch syndrome' put paid to that. However, whilst any notable country wide cold remains beyond the truly reliable it seems to me that all we can say at this stage is that a build of pressure in the N.Atlantic/Greenland region is looking pretty likely from the middle of next week, with lower pressure over Scandi/Europe, which leads to significantly lower temperatures than we've been used to.

But, from what I'm seeing i certainly don't see the kind of country-wide snowfall we had in '09/10 being repeated. The reason I say this is that, taking the 00z ECM as an example, at T120 it shows this:

And the GFS 00z at T144:

To me these remind me of previous cold spells where precipitation is either fairly limited, or marginal for lowland areas further south than Scotland. And as the GH develops and the troughs fill, coinciding with arrival of genuinely colder temps precipitation starts to die off, leading to ppt charts like this, which we've seen many times in this kind of set up:

 Now I know that the general rule is 'get the cold in first' etc etc, and that we shouldn't trust the GFS ppt charts, but I disagree to a certain extent in that they certainly give a flavour of likely ppt patterns for a given set-up, and to me right now this set-up suggests a few things:

1. The 'real deal' cold is still beyond the reliable time frame, so there are still ample opportunities for subtle near term changes to have significant consequences for better or worse in terms of the extent and depth of the cold we will end up experiencing

2. If we do get the deep cold, it doesn't look to me, at least as is currently being modelled, that there will be many 'dumpings' associated with it, certainly not for more lowland southern Britain anyway.

3. It certainly doesn't look to me like '09/10 MKII !

yeah but in these situations , features do usually seem to turn up at the last minute , such as secondary lows creeping down the irish sea , polar lows in the north sea , or even lows originating from the azores bumping into the cold air from the SW . as wella s the confection potential with the rather higher than normal ssts .... I never take ppn charts serious out of 48 hrs ... 

[Geordiesnow]

Got to say, if this very slow low pressure system does turn out accurate(and you would have to say if it is, then the GFS has got this detail more spot on than the UKMO/ECM) then I'm afraid it will be the wet stuff yet again in the headlines instead of the white stuff, looks quite windy also. 

[karlos1983]

1 minute ago, Geordiesnow said:

Got to say, if this very slow low pressure system does turn out accurate(and you would have to say if it is, then the GFS has got this detail more spot on than the UKMO/ECM) then I'm afraid it will be the wet stuff yet again in the headlines instead of the white stuff, looks quite windy also. 

which one Geordie out of interest? the Azores?

[Ali1977]

Better WAA on this run so far

[karlos1983]

ok we have the link up between Atlantic High and Greenland.

steady as she goes..

[mountain shadow]

4 hours ago, Geordiesnow said:

Got to say, if this very slow low pressure system does turn out accurate(and you would have to say if it is, then the GFS has got this detail more spot on than the UKMO/ECM) then I'm afraid it will be the wet stuff yet again in the headlines instead of the white stuff, looks quite windy also. 

A chart with an explanation would help. No idea what your referring to.

[Orpingtoniceagedec10]

Sorry. Bit of a newbie, what does WAA mean?  

[ALL ABOARD]

As i have mentioned previously the arctic high is once again more robust !! slight upgrade so far for me 

 

 

 

Comparison for the same time! almost 10mb in difference  

Edited January 7, 2016 by ALL ABOARD

[Geordiesnow]

3 minutes ago, karlos1983 said:

which one Geordie out of interest? the Azores?

No, the trigger low, yesterday Euro runs had this shifting eastwards quicker than the GFS runs where it was very slow moving but the UKMO in particular has now moved to the GFS solution whilst the GFS has stuck to its guns of it being slow moving and delaying the opening of the floodgates. I was hoping after viewing last nights 18Z run that the UKMO/ECM was right in having this low pressure system further eastwards as not only it will open the floodgates sooner, it will also remove most of the rainfall but sadly this looks like not being the case now and the weekends forecast just look miserable and wet in places where we don't need the rainfall yet again. 

[knocker]

Just now, Orpingtoniceagedec10 said:

Sorry. Bit of a newbie, what does WAA mean?  

Warm air advection. But that post is about as useful as a chocolate fireguard.

[karlos1983]

4 minutes ago, Orpingtoniceagedec10 said:

Sorry. Bit of a newbie, what does WAA mean?  

Warm Air Advection

 

Basically warm air being pumped into the Arctic, which will aid the Heights in that region

 

Edited January 7, 2016 by karlos1983

[Light Without Heat]

http://forecast.weather.gov/glossary.php?word=WAA

[Ali1977]

1 minute ago, knocker said:

Warm air advection. But that post is about as useful as a chocolate fireguard.

Cheers Knocker - you enjoying these cold charts by the way?

Edited January 7, 2016 by Ali1977

[NorthernRab]

2 minutes ago, Orpingtoniceagedec10 said:

Sorry. Bit of a newbie, what does WAA mean?  

You see the faint dotted line beneath the term? Scroll over it and it reveals its meaning. A lot of the acronyms / shorthand version of terms on here have this feature. Handy that you asked that so that everyone else who's relatively new here or doesn't tune in too often will know this from now on whenever they see one of these cryptic terms!

Edited January 7, 2016 by NorthernRab

[Light Without Heat]

2 minutes ago, Orpingtoniceagedec10 said:

Sorry. Bit of a newbie, what does WAA mean?  

Warm Air Advection

[That ECM]

T126 and that is a chart many would bank.

[Gazza H]

3 minutes ago, Orpingtoniceagedec10 said:

Sorry. Bit of a newbie, what does WAA mean?  

Hover your cursor over any of the words underlined as you see with WAA and a text box will show up with the meaning