Model Discussion - January 17th

[leicesternosnowzone]

The medium term gfs charts (t100-t180) look reasonable with the -5 850hpa line reaching down into southern england. In fact right out to t192-204 at the end of the high res part of the run the prospects of snow/wintry weather look reasonable particularly for scotland and norhtern england. The gfs then shows a very deep (below 950mb) low pressure system in the north atlantic at around t228 and this brings in a more zonal and warmer SW winds for the uk. However the low is probably being overcooked by gfs so i would suggest the later parts of FI are unlikely to come off (even though they look quite good for coldies).

Overall in the near term next week COULD bring some colder conditions and possibly snow for some if the synoptics pan out as shown on 00z gfs.

[winterof79]

Energy going south

http://www.wetterzen.../Rtavn21614.png

AH pulled North eventually links with the siberian high if i see it correctly

http://www.wetterzen...s/Rtavn2161.png

Interesting,lets see if its on the 12zs.The ridging starts around the 180 mark.All in FI but first time i have seen low heights over the med holding our displaced high

http://www.wetterzen...s/Rtavn3361.png not exactly a raging easterly flow though.

Edited January 18, 2012 by winterof79

[Duane S.]

The 00z's scream potential but on the whole, despite most showing significant changes in the vortex, a more southerly jetstream and much better amplification somehow none really manage to thrust us into a cold scenario. This is worrying as now we are finally starting to see models reflect other signals better but are we about to see us sat in the warm sector of a west based -NAO?? Now that would be about right!

Not downbeat though as changes are happening and a lot will change plus we have all of Feb to get through yet). Two charts from the GFS and ECM ops that are rather interesting for different reasons ('FI' or not)...

Edited January 18, 2012 by s4lancia

[bluearmy]

the trend in the modelling continues to be energy sinking south over the next 10 days. upstream patterns continue to tease although most modelling wants to drop vortex energy back into the greenland area (prob staying west). not convinced of that. will be looking to see if the ecm ens are clustering cold beyond day 10. otherwise, the stand off between the ens and the 32 dayer will continue. at lest we appear to be headed in the right general direction with the mean jet sinking south of the uk and some trough disruption being picked up.

[weather_it_will]

Big change in GFS 00Z this morning with LP pushing SE from the Atlantic from T96 which disturbs the HP to the south of the UK by T144.

LP systems north of Scotland and north Europe are then pivoted by HP pushing north from SE Europe.

In the low resolution HP forms over Scandi bringing in an easterly flow over the UK, which falls into what the Meto think could happen.

Interesting model watching to come.

[warrenb]

I thkn we are clearly seeing the PV being destroyed, and then it is anybodies guess (including the models), we a right in the middle of another Strat warming at the moment, which will affect the trop in about 7-10 days time.

[If Wishes made Weather]

ECM 00z now showing a highly disrupted PV by t240.

[Radiating Dendrite]

Big change in GFS 00Z this morning with LP pushing SE from the Atlantic from T96 which disturbs the HP to the south of the UK by T144.

LP systems north of Scotland and north Europe are then pivoted by HP pushing north from SE Europe.

In the low resolution HP forms over Scandi bringing in an easterly flow over the UK, which falls into what the Meto think could happen.

Interesting model watching to come.

Shame the Easterly brings zero cold uppers!

Since it is in the low res we all know it will not happen quite like that.

As others have said, the PV is now looking like it is finally going to go down in the 12th round!

I am still concerned about where any of its little lobes may still be placed after this. Could be a very interesting day of model watching today!

Edited January 18, 2012 by Radiating Dendrite

[BLAST FROM THE PAST]

A knife edge and volatile period is upon us. Very much improved picture in short term BUT models still don't go full hog as we approach and enter low res. This may suggest that it could indeed still go either way. However, positives are that the huge Arctic Russian HP exists and the Atlantic ridge is very much developing ad responding to the signal. Now we may see more consistency develop shorter term BUT I suspect not so post T144 yet.

BFTP

[nick sussex]

Shame the Easterly brings zero cold uppers!

Since it is in the low res we all know it will not happen quite like that.

As others have said, the PV is now looking like it is finally going to go down in the 12th round!

I am still concerned about where any of its little lobes may still be placed after this. Could be a very interesting day of model watching today!

Yes those mini PV segments can be a right pain and we certainly don't want to see one of those set up shop in sw Greenland.

There looks to be agreement growing for troughing over the UK and then from there much depends on what happens to the NAO, in terms of whether its a west or east based negative NAO.

You can't get better agreement for troughing over the UK at 168hrs by the ECM ensemble maps:

http://www.ecmwf.int...t!2009112700!!/

Its a shame we couldn't have seen the pattern retrogress now its down to shredded nerves for cold lovers as we wait to see where that trough goes.

The ECM ensembles will be telling today as they might give a suggestion as to where that trough will go after 168hrs.

Edited January 18, 2012 by nick sussex

[Radiating Dendrite]

Yes those mini PV segments can be a right pain and we certainly don't want to see one of those set up shop in sw Greenland.

There looks to be agreement growing for troughing over the UK and then from there much depends on what happens to the NAO, in terms of whether its a west or east based negative NAO.

You can't get better agreement for troughing over the UK at 168hrs by the ECM ensemble maps:

http://www.ecmwf.int...t!2009112700!!/

Its a shame we couldn't have seen the pattern retrogress now its down to shredded nerves for cold lovers as we wait to see where that trough goes.

In terms of west and east based NAO, what does a decent east based one look like since that is what we are after?

I know last year was one example, but even that was slightly marginal was it not?

[shedhead]

A knife edge and volatile period is upon us. Very much improved picture in short term BUT models still don't go full hog as we approach and enter low res. This may suggest that it could indeed still go either way. However, positives are that the huge Arctic Russian HP exists and the Atlantic ridge is very much developing ad responding to the signal. Now we may see more consistency develop shorter term BUT I suspect not so post T144 yet.

BFTP

Agreed, but talk about pulling teeth!! The overall pattern does look a lot more condusive to cold on the big two this morning, but UKMO appear much less keen to play ball at 144hrs, with the next system already kicking up a ridge across the UK. However, it it went out to T+192hrs it would probably be more in line. I think the best we can now hope for is the effects of any pattern change to be felt across the last few days of Jan, giving us about 5 weeks overall to redress the hitherto mild balance.

Edited January 18, 2012 by shedhead

[Cecil Hogmanay Melchett]

Maybe im in a grouchy mood as we are back to the current winter default pattern of grey skies/ dzizzle here again this morning but im just not seeing much in the way of cold this morning.

GFS ens look zonal.ecm operational is pretty much positive NAO right through with maybe a neutral for a short while thrown in but its still pretty uninspiring to say the least imo.

[TEITS]

As I thought yesterday the ECM extended mean is continuing to drop.

http://www.knmi.nl/exp/pluim/vijftiendaagse/Data/15DAAGSE_06260_NWT.png

Will add the mere mention of a western based NAO should be banned lol. I would prefer mild SW,lys than that scenario because in my opinion its one of the most frustrating weather patterns.

[nick sussex]

In terms of west and east based NAO, what does a decent east based one look like since that is what we are after?

I know last year was one example, but even that was slightly marginal was it not?

Eastern based ones vary but this is a good example:

As Dave just mentioned western based negative NAO,they make me want to throw the laptop out of the window as all the cold heads into the Atlantic!

I'm trawling through the archives to find a good example of a west based one.

Edited January 18, 2012 by nick sussex

[nick sussex]

Low confidence in the upstream pattern from NOAA:

USED THE 00Z/18 ECMWF FOR THE PRELIMINARY FRONTS AND PRESSURES FOR

DAYS 3 THROUGH 5...THEN THE 12Z/17 ECENS MEAN FOR DAYS 6 AND 7.

ALL THE DETERMINISTIC MODELS HAVE BEEN MARKED BY POOR RUN-TO-RUN

CONTINUITY OVER THE PAST FEW CYCLES...WITH THE ECMWF THE MOST

STABLE OF THE LOT. STILL...EVEN IT SEEMS TO BE STRUGGLING WITH

THE UPCOMING PATTERN...WITH ITS DAY 6 AND 7 SOLUTION DIFFERENT

ENOUGH FROM ITS PAST TWO RUNS TO SINK CONFIDENCE IN ITS DETAILS.

WHILE NOT THE BEST MATCH...THE 00Z/18 GEFS MEAN AND 12Z/17 ECENS

MEAN AT LEAST POINT TOWARD A PLAUSIBLE MIDDLE GROUND AMONG THE

DISPARATE DETERMINISTIC OPTIONS. NEEDLESS TO SAY...CONFIDENCE IS

LOW FOR THIS PRELIMINARY FORECAST.

[Weathizard]

Liking this run a lot more, less of a cold shot over the weekend but pressure 8mb higher over Greenie + more Greens over eastern side, Russian High better placed, vortex less powerful. Still think this will probably end in Zonal though.

[feb1991blizzard]

In terms of west and east based NAO, what does a decent east based one look like since that is what we are after?

I know last year was one example, but even that was slightly marginal was it not?

Ive got this horrible feeling we could have a good example of a west based NAO in 10-14 days time on one of the analysis charts, those troughs in FI look to be stalling before they reach us, we desperately need one to dig south and east.

[feb1991blizzard]

ECM 00z now showing a highly disrupted PV by t240.

Agreed, i dont think the PV disrupting enough is now in much doubt, to be honest, especially after METO update, its where any heights manage to set up thats the key.

Edited January 18, 2012 by feb1991blizzard

[Tim Bland]

Something odd with the 6z....There appears to be a patch of green appearing over Greenland...Not seen that for a while, surely it can't be high pressure

Edited January 18, 2012 by Tim Bland

[TEITS]

Ive got this horrible feeling we could have a good example of a west based NAO in 10-14 days time on one of the analysis charts, those troughs in FI look to be stalling before they reach us, we desperately need one to dig south and east.

I wouldn't worry too much about a W based NAO just yet. I still recall Dec 2010 and the heated arguments when the ECM modelled the trough too far W. I remember this because myself and Nick S were accused of being biased towards the E/SE. Thankfully eventually the ECM modelled the trough over the UK.

Quiet a difference on the 06Z run although I did mention the uncertainity last night on the 18Z ensembles.

[geoffw]

is this a west based -NAO on the 06z?

[feb1991blizzard]

I wouldn't worry too much about a W based NAO just yet. I still recall Dec 2010 and the heated arguments when the ECM modelled the trough too far W. I remember this because myself and Nick S were accused of being biased towards the E/SE. Thankfully eventually the ECM modelled the trough over the UK.

Quiet a difference on the 06Z run although I did mention the uncertainity last night on the 18Z ensembles.

Yes, i remember that well, i had only just joined the forum, i remember being confident of the cold spell but was worried from an IMBY perspective about PPN, and it turned out i was right to be,

Looking at the 6z, looking okay for a PM blast for the North West, but what happens after that, i still cant see any sign of lower heights digging into europe, and that could be the hardest hurdle to overcome, it will be interesting to see what the Met office make of it, i cant see them coming off the fence today, however its unusual for a forecast like the one yesterday remaining in the 6-15 day range for very long.

[Severe Siberian icy blast]

Snow fest anyone?

I no i no i shouldnt do that as it prob wont come off but quite clearly there is obvious signs of a pattern change aloft which is a breath of fresh of air.

[john mac]

is this a west based -NAO on the 06z?

It could be seen as that but IMo opinion and as dave said its too far out to determin that atm. Tghe models are really struggling with the pattern change so all to play for.