Winter Model Discussion 12Z 22/1/13 onwards.

[Summer Sun]

After a very unsettled week GFS again as per yesterday morning build's pressure later this week bringing us some welcome settled weather

For those wanting a return to cold weather a spell of high pressure may be needed because once it drifts into the Atlantic it eventually allows a cold flow to develop

Edited January 27, 2013 by Gavin.

[TEITS]

Having had another look at the models here are the important dates for me.

2nd Feb

A shortlived N,ly which has good support from the models.

http://modeles.meteo...-21-1-144.png?0

3rd Feb - 6th.

Return of W,lys.

http://modeles.meteo...-21-1-216.png?0

7th Feb - 8th.

A N,ly developing as we see LP moving SE into Europe with blocking becoming established.

9th Feb to 15th.

Welcome back winter with a potentially bitter N/NE/E,ly.

Edited January 27, 2013 by THE EYE IN THE SKY

[Summer Sun]

UKMO isn't as quick as GFS but you can see high pressure edging closer at t144

[Ian Brown]

Verynice GFS FI this morning,ecm quite the opposite with a hideous profile to the north west.

Im not sure i can remember a winter in recent times with an almost constant PV in place over Greenland from Nov right through to Feb,really the weather gods must have it in for us as you can bet your bottom dollar there will be some great blocking up there come spring!

HD if you want a reminder of similar profiles look back to the middle years of the last decade, the late 90s and the late 80s.

We are playing a medium to longer game for now and there is, if the teleconnections are to be believed, a good chance that we will see those low heights retreat West to allow pressure build to the NW though thus far this winter it hasn't happened as parts of the PV have remained in the wrong place with the NAO therefore refusing to go negative.

[Bobby]

All of the models show a Wly Atlantic flow out to day 10 at the moment with wind and rain at times with signs the jet will be nudging N as pressure builds from the S. Because of the high pressure strong to the south it looks hard to get an undercut some talked about.it will be hard to get out of a westerly Atlantic flow until at least day 10 I would say, then the ridge could flatten or advect North to introduce colder weather but that's deep FI at the moment.

[cooling climate]

As predicted the growing trend for a much more amplified pattern to emerge as we head into

February with northerly blocking and a east/northeasterly airflow for the UK and Europe.

How cold well it is far to early for specifics like that yet but a true beast from the east is certainly

on the cards down the line.

The strat warming is certainly the cause of the amplified pattern ahead and I would hazard a guess

that the MJO, GWO, GLAMM etc a by product of this.

Exciting times are not far off for winter weather lovers again but my main interest is weather the real

beast from the east will show its hand although we are probably several days to early still for such a

pattern to manifest itself into the model runs.

Again the GFS 06z run starting to look very interesting at t168 and it is very interesting to see that

it is actually the Siberian vortex that is moving across the pole to Canada building a large powerful

vortex there while segments of the canada vortex in the lower latitudes are cutting further south

into Europe hopefully building a large cold pool there which will be advected westward by the building

heights to the north.

[The Northern Ramper]

HD if you want a reminder of similar profiles look back to the middle years of the last decade, the late 90s and the late 80s.

We are playing a medium to longer game for now and there is, if the teleconnections are to be believed, a good chance that we will see those low heights retreat West to allow pressure build to the NW though thus far this winter it hasn't happened as parts of the PV have remained in the wrong place with the NAO therefore refusing to go negative.

Fair point Ian, lets hope this is third time lucky this winter.

[Ice Day]

Here we go at 216. Heights climbing towards Greenland

[Ice Day]

All goes pear shaped at the end of the run............still, at least we can console ourselves that it's only the 6z!!!!

[Nick F]

All goes pear shaped at the end of the run............still, at least we can console ourselves that it's only the 6z!!!!

Unfortunately that deep vortex over NE Canada, with its associated deep cold air, continues to power a strong jet across the Atlantic - which doesn't really help maintain the amplification that brings the N/NW'erly next weekend.

At least the ECM ens H500 mean suggests a deep trough being carved out over Europe, which suggests flow from the W or NW. We just need to see greater amplification work downstream to take advantage of this signal for troughing over Europe. Certainly no indication this morning for a Bartlett high bringing endless mild SW'erlies. But no signs of a sustained cold spell returning either.

Edited January 27, 2013 by Nick F

[Frosty.]

Unfortunately that deep vortex over NE Canada, with its associated deep cold air, continues to power a strong jet across the Atlantic - which doesn't really help maintain the amplification that brings the N/NW'erly next weekend.

At least the ECM ens H500 mean suggests a deep trough being carved out over Europe, which suggests flow from the W or NW. We just need to see greater amplification work downstream to take advantage of this signal for troughing over Europe. Certainly no indication this morning for a Bartlett high bringing endless mild SW'erlies. But no signs of a sustained cold spell returning either.

I suspect that will change when the next downwelling phase impacts and we start to see those gfs 00z deep FI charts pushing towards a much closer timeframe. I'm very encouraged by what BFTP has said and RJS's latest thoughts that the most severe wintry spell is still on course next month.

[legritter]

Some very good signs today in the modells for a return of cold ,but we need to wait patiently for another 2 runs or so from ECM and UK met . It will be a nervouse time as we all cast an eye down to our south ,west at the azores high ,Sorry didnt mean to swear but you all know what i mean .get high pressure near us and then wait for mother nature to do the rest ,although of course she does the lot anyhow .but as of now very interesting modell watching and plenty of action on the weather front . if we dont get a full on cold spell it could become very interesting at the end of this week as cold air floods south with perhaps some embedded disturbances .i dont think winter is anywhere near finished yet and if you look at northern hemisphere its way from boring at the moment .catch up with you all after tonights runs ,i will put the drinks on ice ,

[TEITS]

. But no signs of a sustained cold spell returning either.

Strongly disagree with this.

If you look at the overall trend of the ensembles i.e GEFS/ECM rather than just a few operationals then you will see a clear signal towards a sustained cold spell developing around the dates I said earlier.

[bluearmy]

Unfortunately that deep vortex over NE Canada, with its associated deep cold air, continues to power a strong jet across the Atlantic - which doesn't really help maintain the amplification that brings the N/NW'erly next weekend.

At least the ECM ens H500 mean suggests a deep trough being carved out over Europe, which suggests flow from the W or NW. We just need to see greater amplification work downstream to take advantage of this signal for troughing over Europe. Certainly no indication this morning for a Bartlett high bringing endless mild SW'erlies. But no signs of a sustained cold spell returning either.

at the moment, the current extended naefs shows a similarity with the first half december. worth taking a look at the charts for that fortnight to see what we might be expecting to see. if you recall, the first half december ran several degrees below average - the depressions tending to run nw/se to our east which is not the best direction for sustained snowfall as it allows pm sectors in the flow. early days yet for the pattern to be set two weeks away and if the general forecast anomolys verfiy, we can expect a few tweaks which could either work to a more/less or less wintry scenario.

[BLAST FROM THE PAST]

Its going to be one of those weeks IMO re model output. I think we'll see some stonkers and stinkers showing in the t200+ timeframe, but I'll be looking for decent more prevalent signs come end of the week. I think general consensus will be that 6-10 days will be absorbed by the milder mobile pattern and nothing interesting cold wise until say 4/5 Feb...and then only an interest as the proposed pattern emerges. There is no 'immedaite' return so I anticipate that there'll be posts with isloated chart frames being posted to show that the Atlantic is charge, jet too strong, no Greeny heights etc etc but we have to ride through this period, that is set

BFTP

[Frosty.]

Its going to be one of those weeks IMO re model output. I think we'll see some stonkers and stinkers showing in the t200+ timeframe, but I'll be looking for decent more prevalent signs come end of the week. I think general consensus will be that 6-10 days will be absorbed by the milder mobile pattern and nothing interesting cold wise until say 4/5 Feb...and then only an interest as the proposed pattern emerges. There is no 'immedaite' return so I anticipate that there'll be posts with isloated chart frames being posted to show that the Atlantic is charge, jet too strong, no Greeny heights etc etc but we have to ride through this period, that is set

BFTP

At least it looks colder later in the week into next weekend with frosts returning and wintry showers, maybe even some heavy snow showers briefly for the far north. then a bit more settled with overnight frosts mixed with changeable zonal and then potential for a severe wintry spell towards mid feb.

[Polar Maritime]

A very realistic post BFTP, with all the expert's calling Feb to be the month for cold, there will be some very interesting model watching to come over the next week or so, exiting times ahead. FI at t120hr imo.

As Frosty says a cool down to more average temps towards the end of the week, after this mild blip !

Edited January 27, 2013 by Polar Maritime

[cooling climate]

Unfortunately that deep vortex over NE Canada, with its associated deep cold air, continues to power a strong jet across the Atlantic - which doesn't really help maintain the amplification that brings the N/NW'erly next weekend.

At least the ECM ens H500 mean suggests a deep trough being carved out over Europe, which suggests flow from the W or NW. We just need to see greater amplification work downstream to take advantage of this signal for troughing over Europe. Certainly no indication this morning for a Bartlett high bringing endless mild SW'erlies. But no signs of a sustained cold spell returning either.

Plenty of indicators say otherwise. I would even say the coldest weather of the winter is still to come.

Even the 06z run is picking up on the growing trend now in fact I think it is the first 06z run to do so.

[Summer Sun]

The 06z shows a brief cold shot but it doesn't last long

Like I said yesterday the longer the high pressure just to the SW of the UK hangs around its going to be hard to get sustained cold unless it shifts right out into the Atlantic (like it does briefly at t240) this is what happens a few days later

Edited January 27, 2013 by Gavin.

[Methuselah]

Unfortunately that deep vortex over NE Canada, with its associated deep cold air, continues to power a strong jet across the Atlantic - which doesn't really help maintain the amplification that brings the N/NW'erly next weekend.

At least the ECM ens H500 mean suggests a deep trough being carved out over Europe, which suggests flow from the W or NW. We just need to see greater amplification work downstream to take advantage of this signal for troughing over Europe. Certainly no indication this morning for a Bartlett high bringing endless mild SW'erlies. But no signs of a sustained cold spell returning either.

Would agree with that, Nick, for the time being! IMO, the most positive thing in the models is the projected shape of the PV; in that it clearly doesn't indicate raging long-term zonality...

Initially - I think - the first thing to look for might be LPs sinking SE into Europe? And, for that, I reckon that JH's upper-height anomalies may give a better advance warning than the synoptics guessed-at by FI?

[Frosty.]

Plenty of indicators say otherwise. I would even say the coldest weather of the winter is still to come.

Even the 06z run is picking up on the growing trend now in fact I think it is the first 06z run to do so.

Since Nick is an expert, it's hard to argue too much with his view on things but yes, there are signs of change already appearing as you and teits have said and they should continue to grow and grow in the next 7-10 days.

[london-snow]

We always new that there was going to be a more milder spell for this coming week the change has happened and will be a further 5-7 days before we see a possible change which brings us up to the 3rd of feb.

However i think that some will be suprised in the way that i feel that a quick change to much colder weather will happen. I am not looking at 10th - 15th of next month for cold to take hold i am and always have been thinking the key dates for a return to colder weather is going to be around the 4th - 7th as per my conversation with crew cold a few days back.

So a breif warm up over the coming days but as we move into the weekend the atlantic loseing steam and sending what ever features south. With a attack from the north east to take hold from the 4th onwards.

[Summer Sun]

Certainly a downward trend from the ensembles (albeit with lots of scatter as you would expect at this range) notice how much drier it becomes from the 7th (5th in Aberdeen) that would suggest to me a cooler settled spell

Edited January 27, 2013 by Gavin.

[Thundery wintry showers]

It will be a standard Atlantic onslaught this week- sunshine and blustery showers for many today, then grey, drizzly and mild (especially warm in southern Britain) on Monday and Tuesday with a tropical maritime regime, but then brighter and more showery weather returning from Wednesday onwards with temperatures falling closer to average. Winds will be strong throughout the week and much of Scotland may be hit by gales on Wednesday.

A 24-36 hour northerly "toppler" is likely this weekend and the models currently disagree slightly on how potent it will be. The ECMWF version is, to my mind, a bit more potent and long-lasting than the GFS version and may bring wintry showers a fair way inland in the north and east, though with lying snow likely to be restricted mainly to low-lying parts of NE Scotland and higher ground further south:

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

Don't expect anything substantial or sustained though- this is pretty much a bog-standard toppler.

Longer-term signals are indicating a mid-Atlantic block, which leaves us open to more short-lived north-westerlies with wintry showers in the north, though we would need a general rise of pressure to the N/NW to bring any advance on topplers.

[mulzy]

Unfortunately that deep vortex over NE Canada, with its associated deep cold air, continues to power a strong jet across the Atlantic - which doesn't really help maintain the amplification that brings the N/NW'erly next weekend.

At least the ECM ens H500 mean suggests a deep trough being carved out over Europe, which suggests flow from the W or NW. We just need to see greater amplification work downstream to take advantage of this signal for troughing over Europe. Certainly no indication this morning for a Bartlett high bringing endless mild SW'erlies. But no signs of a sustained cold spell returning either.

There is very little chance of sustained cold within 8 days, but that chance does increase as we head into FI. The issue is as ever going to be the placement of any PV fragments, the jet and high lattitude blocking. Colder than average in the medium term seems likely, but a "big freeze" looks unlikely at this stage according to NWP. This may change over the next few days - interesting model watching times at least.

Edited January 27, 2013 by mulzy