228 replies to this topic

[warrenb]

Trend is my friend, PV further west on every run now. Starts off over Greenland and is now firmly in N Canada. Trough digging in closer to us each run with a good NW/SE tilt to it.

[swilliam]

Osbourne One-Nil, on 17 January 2012 - 16:25 , said:

Just a suggestion, but when people comment on some aspect of a chart, like PV much further west, etc,could they also perhaps give a quick summary as to what that means in terms of what might result?

The result is that the jet stream is less strong and more amplified.




This measns that the the LP is more likley to go SE and the Azores high dissappear off as seen in the later frames.

Edited by swilliam, 17 January 2012 - 16:30 .

[sn0wman]

swilliam, on 17 January 2012 - 16:30 , said:

The result is that the jet stream is less strong and more amplified.

gfsnh-2012011712-5-24.png

This measns that the the LP is more likley to go
SE and the Azores high dissappear off as seen in the later frames.

gfsnh-2012011712-0-168.png

Sorry for my ignorance, but could you tell me where the PV is on this chart and also, how do
you tell it apart from other low pressure systems? Thanks.

Edited by sn0wman, 17 January 2012 - 16:34 .

[Grimsby Snow Lover]

sn0wman, on 17 January 2012 - 16:33 , said:

Sorry for my ignorance, but could you tell me where the PV is on this chart and also, how do
you tell it apart from other low pressure systems? Thanks.

I personally look for those very dark blues and purples over the Pole. As far as I can tell that is the Polar vortex

[Tim Bland]

Low pressure next week further south on GFS 12Z. Looking at the PV it is weakening and as that lobe from Greenland ejects SE there is scope for higer pressure over Greenland. In the short term this means cool zonal with snow for higher areas in the north. Longer term it increases our chances of a Northerly outbreak IMO. Jetstream is also pushed well South of the UK.

Attached Thumbnails

• 
• 
• 

Edited by Tim Bland, 17 January 2012 - 16:38 .

[danm]

Chalk and cheese comparing the GFS 12z with the 6z at t174.

12z:


6z:



Azores high backing west, ridging slowly towards Greeny, Russian high ridging westwards towards the Arctic/Svalbard, PV further west, trough digging SE through the UK. If the trough continues to dig SE'wards, and the Azores high continues to back west and north, then it could show an interesting solution in the medium term with many more options for cold and snowy weather.

Edited by danm, 17 January 2012 - 16:35 .

[Radiating Dendrite]

sn0wman, on 17 January 2012 - 16:33 , said:

Sorry for my ignorance, but could you tell me where the PV is on this chart and also, how do
you tell it apart from other low pressure systems? Thanks.

The PV is the area with low damn values.

Basically the Purple areas.

Edited by Radiating Dendrite, 17 January 2012 - 16:36 .

[danm]

The only problem at t186 is that pesky low exiting Newfoundland. It prevents the Azores high from properly ridging up towards Greeny and as a result the Azores high starts to get pushed south and flatten out slightly. But a better run so far.

GFS @ t186:

[mulzy]

UKMO pretty zonal - no significant height rises around Greenland.

http://www.meteociel...=120&carte=1021

http://www.meteociel...=144&carte=1021

[Grimsby Snow Lover]

sn0wman, on 17 January 2012 - 16:33 , said:

Sorry for my ignorance, but could you tell me where the PV is on this chart and also, how do
you tell it apart from other low pressure systems? Thanks.

Just to add to my previous reply these two charts from last December show how the PV can get dislodged from Greenland and affect areas much further south, including us. Note the dark blue/purple colours.

http://www.wetterzen...00120101216.gif December 16th 2010
http://www.wetterzen...00120101217.gif December 17th 2010

Edited by Grimsby Snow Lover, 17 January 2012 - 16:42 .

[swilliam]

The low res part has blown up that low to the West of us so probably best to ignore the rest of this run.

Edited by swilliam, 17 January 2012 - 16:42 .

[danm]

Post t192 it goes tits up as the low exiting newfoundland blows up, flattens the pattern and resets into a more zonal flow. The signs up till then were encouraging for medium term prospects and the evolution of the GFS run all depends on the track of that low leaving Newfoundland at t168.

[Tim Bland]

High over Russia is at 1056MB and spreading further west. Unfortunately the lows to our NW and PV is still raging so we are stuck in the middle.

Attached Thumbnails

• 

[happy days]

Not much to like in the 12z runs is there.
Little amplification,strong jet.
Back to square 1,i rather think so.

[Radiating Dendrite]

As has been said many times before, anything in the low-res is best ignored.

Up until that point the signs were encouraging.

As is always the case, the GFS blows up lows in the low-res part and flattens the pattern.

[Radiating Dendrite]

happy days, on 17 January 2012 - 16:45 , said:

Not much to like in the 12z runs is there.
Little amplification,strong jet.
Back to square 1,i rather think so.

Not sure where you are getting that from.

The jet was much better positioned in the hi-res run compared to the 6z with better amplification.

The canadian high is also seen to be continuing its development which is a good sign and the PV was shifted further west yet again.

It went wrong in FI, but the GFS always flattens the pattern in FI.

[ukpaul]

GFS very disappointing, building blocks are being put in place but only leading to relentless zonality (and not even of the cold sort). If it is getting the signals then either the competing ones are much stronger or we are in the wrong place pretty much every time to benefit, we should be seeing a change now in output according to changes in NAO, PV etc. but none of this seems to cut any ice (literally!)

[happy days]

Radiating Dendrite, on 17 January 2012 - 16:48 , said:

Not sure where you are getting that from.

The jet was much better positioned in the hi-res run compared to the 6z with better amplification.

The canadian high is also seen to be continuing its development which is a good sign and the PV was shifted further west yet again.

It went wrong in FI, but the GFS always flattens the pattern in FI.

Well looking at the jet stream charts was enough for me just a contiunation of what we have seen all winter is what im seeing on the 12zgfs.
Not sure ukmo looks all that mind blowing either.

[Buzzit]

Radiating Dendrite, on 17 January 2012 - 16:46 , said:

As has been said many times before, anything in the low-res is best ignored.
Up until that point the signs were encouraging.
As is always the case, the GFS blows up lows in the low-res part and flattens the pattern.

Agreed. i was encouraged that up to +96 there was very little difference between 6z and 12z if not slightly better in the 12z. Quite a variation in FI at times when looking at the jetstream which I find interesting, I see further hints of a NW, SE tilt when excluding the FI mega lows.

[Radiating Dendrite]

ukpaul, on 17 January 2012 - 16:49 , said:

GFS very disappointing, building blocks are being put in place but only leading to relentless zonality (and not even of the cold sort). If it is getting the signals then either the competing ones are much stronger or we are in the wrong place pretty much every time to benefit, we should be seeing a change now in output according to changes in NAO, PV etc. but none of this seems to cut any ice (literally!)

BUT IT WENT WRONG IN THE LOW-RES PART OF THE RUN.

I am sorry, but people are still treating the post 180 period as gospel.

What does the GFS nearly always do to lows in the low-res part of the run..............answers on a postcard!

One clue.....bomb.