Model Discussion Thread - 15th Jan

[bobbydog]

very little difference between the 00z and the 06z up to 120hrs. i'm sure the experts will pick out the subtleties though

[Harsh Climate]

Just look how close we are to an easterly feed, so close but yet so far! Note everyone going on about the PV over greenland being the killer at the moment, what we have is it over the far south east of greenland, if it was over the centre of greenland we might actually have a shot of an easterly of some sort as there would be just enough room for the high over scandinavia to push far enough west.

Edited January 16, 2012 by Harsh Climate

[weathe20]

06z looks like a repeat of the 00z. Infact less cold in the west, just a fleeting period of cold for western areas.

[Southender]

Visible westward shift of the PV and HP at the mid-range.

Better.

[Harsh Climate]

A lot better, look how much closer we are to an easterly feed compared to the 00z, if only that PV to the south east of greenland could be further north west.

[Buzz]

I believe it's been pointed out before, but there is no point in comparing runs from one model at different times of the day, especially when this comes to the GFS. So DON'T compare the 0z run to the 06z run, etc.

You should compare the previous day's 0z run to the current day's 0z run, etc.

And as Steve Murr has often pointed out, the most 'reliable' GFS run is the 12z

[TEITS]

06z looks like a repeat of the 00z. Infact less cold in the west, just a fleeting period of cold for western areas.

The 0Z, 06Z are chalk and cheese. The GFS is really struggling with regards to the positioning of the block to our NE. If the block is much further W you then have the potential of undercutting resulting in an E,ly.

I shouldn't be surprised because this pattern used to cause forecasting headaches in the 1980s and it seems 30yrs on and nothings changed!

[Harsh Climate]

Though if we got an easterly here it could be one of those annoying set-ups where we get sleet/rain showers rather than snow, look at those warm uppers pushing around the low into eastern europe

[TEITS]

Amazing difference at +144.

Look at the positioning of the block to our NE on the UKMO and then compare with the GFS, ECM.

http://www.wetterzentrale.de/pics/Rukm1441.gif

http://www.wetterzentrale.de/pics/Recm1441.gif

http://www.wetterzentrale.de/pics/Rtavn1441.png

The 06Z is much closer to the ECM compared to the UKMO, 0Z GFS.

Key points are:

1. How far S will the trough push into S Europe.

2. How far W will the block to our NE ridge W.

This makes all the difference beyond +144.

[Harsh Climate]

Rather than looking for an easterly maybe we should be looking for depressions bumping up against the high but not quite breaking through, delivering heavy snow to central parts??

Edited January 16, 2012 by Harsh Climate

[john mac]

6z is nearly but not quite in the later part of the high res

[Zakos]

The beast from the east is approaching on the 06z.... Yes, we should not get hopes up, but I think the russian high is going to win the battle, its simply too strong. And look how much the PV has been downrgraded. Its area and thus is effect on our weather has been masively reduced.

[TEITS]

Latest NOGAPS backs last nights GEFS 18Z ensembles.

If you want a forecast for the next 10 days then don't ask me!

[john mac]

Not even going to bother looking at the low res of the GFS6z as it will change.

[Zakos]

For what must be the 20th time now, as soon as the low res output starts, the russian high randomly disappears, and builds back the PV. Gfs simply pushing the default button! This is not going to happen! I have a theory as to why their is such model divergence. Perhaps the stratospheric warming is affecting them. Also, it is clear from all models that there is a strong signal for a block to our NE. But, there is great uncertainty as to when it will form, how strong it will be, and also how powerful the PV will be during this time. Until the block actually forms, model watching is going to be a pain.

[Tom Montalbano]

The 0Z, 06Z are chalk and cheese. The GFS is really struggling with regards to the positioning of the block to our NE. If the block is much further W you then have the potential of undercutting resulting in an E,ly.

I shouldn't be surprised because this pattern used to cause forecasting headaches in the 1980s and it seems 30yrs on and nothings changed!

Models really struggling around t120, if not before, as heights in the GIN corridor (between Greenland, Iceland and Norway) lift out.

The area becomes up for grabs as the models grapple with Atlantic influence v high pressure to our NE, as we're on the same longtitude, the final solution will have major implications for the UK. As TEITS states GFS00z and 06z poles apart.

As I type 06z showing some nice WAA shooting up to Svarlbard, with trough disrupting to our west, with possible undercut coming bit further on.

Everything still on a knife edge. Expect more model drama today.

Regards,

Tom

Undercut, perhaps not! LOL

Edited January 16, 2012 by TomSE20

[Southender]

Not that it really matters. But the end of the 6z GFS is super. The PV finally moves away from Greenland and heights build. With an attack from the E/NE inbound. Signs of an Omega actually!

Edited January 16, 2012 by Shrimper

[ICETAB]

Does anyone have a link to the latest ECM ensembles?

[Paul_1978]

Not even going to bother looking at the low res of the GFS6z as it will change.

Wise words. The doesn't look that different to 25th Jan 1984, but currently with less cold uppers.

[Just Below Zero]

Does anyone have a link to the latest ECM ensembles?

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

Try that IT]

[Tom Montalbano]

Re comparing runs from day to day, I'm sure this is a considerably better run than yesterdays 06z, although rated the worst of the 4 daily runs, the trend perhaps is more important. Again will be interesting to see where this sits amongst the ensemble members.

These are some mean charts for the ECM 00z. Mean meaning average rather than awesome!

http://www.wetterzentrale.de/pics/Reem961.gif

http://www.wetterzentrale.de/pics/Reem1201.gif

http://www.wetterzentrale.de/pics/Reem1441.gif

http://www.wetterzentrale.de/pics/Reem1681.gif

http://www.wetterzentrale.de/pics/Reem1921.gif

Regards,

Tom.

[Tom Montalbano]

ECM pressure spread in chart form highlights the area between Greenland and Norway that the models are really struggling with, around t120/t144.

Regards,

Tom

[lightningst]

novice here only started looking at these forums and the charts a few weeks ago! could someone tell me how the ensemble graphs are worked out? whats the difference between the control and the operational? i am loving the cold at the minute and really hope the ecm charts are right! we need a cold spell with some snow here in hull but apart from last year we hardly ever get it bad unless its from the east.

[Matty M]

The ECM Ensembles are very much behind a return to a northwest/westerly flow for all by T144hrs, this does not preclude

the possibility of a link to Greenland thereafter.

[OldMetMan]

Also, it is clear from all models that there is a strong signal for a block to our NE. But, there is great uncertainty as to when it will form, how strong it will be, and also how powerful the PV will be during this time. Until the block actually forms, model watching is going to be a pain.

Quite agree. The output beyond 120H is becoming increasingly erratic.The GFS still insists on basically keeping the mobile theme going in the medium- to long-term but for the medium term in particular, both the ECM and GFS just look plain wrong to me.

I'd agree that the shift from a SW to NW jet direction looks plausible up until around 120H, but beyond that we have the ECM and GFS developing new LP up near S Greenland and I think what happens after this is crucial and seems to be where the models are having trouble.

From a purely historical perspective, given the forecast situation at 120H, I would suggest that the new LP I mention above would more likely spiral down SE to join the low complex over Europe, introducing a NE flow as the Russian HP extends westward, possible linking to building HP in mid-Atlantic.For this to happen, there has to be a more decisive long wave amplification over the US and Canada. There are a few tentative signs of this happening now with the E Pacific showing increasing troughing and the jet energy heading on a more NE course in the mid-US, heading up into Canada. You can see this process happening on the WV satellite.

I keep banging on about the jet location and strength upstream from the UK and by creating a N Hemisphere animation of the last week or so, I can see there seem to be clear signs of long wave amplification, together with a gradual weakening of the polar jet into the NW US and Canada, and a stronger sub-tropical stream heading across Mexico and the southern States. All this suggests to me a gradual slowing down of the mid-latitude mobility across the US/Canada into the Atlantic, with most of the jet energy at sub-tropical latitudes. In other words, some mid-latitude blocking from the US to Europe in some form.

All conjecture I know but I sense an overall gradual transition to LP over the Mediterranean and HP building to the NE to NW.

We shall see how the models handle it within the next 2-3 days.