Model Output Discussion - 19th - 25th December

[chionomaniac]

For those wanting to see an end to the Increased strength polar vortex this winter the straws to clutch have gotten a whole lot bigger this morning. More news in the strat thread later!

[bluearmy]

For those wanting to see an end to the Increased strength polar vortex this winter the straws to clutch have gotten a whole lot bigger this morning. More news in the strat thread later!

Looks like a displacement SSW ed? If so, would a relocation of the vortex towards Siberia be likely if we get propagation? also, the nwp seems to have a pretty fast response looking at the trend on gfs at t384?

[Snowmad79]

Looking at the runs for this morning, I don't think a proper bartlett looks like a straight forward bet and no prolonged Swerly flow. Looks rather fluid to me and quite changeable with some cold air filtering down from the north at times.

I mean the models look to me to have more of a tendency of building HP back west of UK rather than maintaining it to the SE. Even the attempt at Euro high later on in the ECM run looks shabby to me, like it would just be blasted well out the way. On the ECM only 2 actual frames (T120 & 144) have HP centered to the SE, the rest of the frames have it either west or east of us.

Also, If you look at the 850hpa temps they alternate from cold(ish) to mild(er) but are not fixed one way or the other.

However, if you think the GFS output is more credible then maybe you could call a bartlett but personally I find that difficult to believe after seeing the GFS op going back to being the loner at the top end of the cluster and one of the warmest ensemble members. I'd still say the GFS control run is performing better than the operational becuaue it seems to follow the mean way better than the over the top operational has been doing (and for a long while now too).

For those wanting to see an end to the Increased strength polar vortex this winter the straws to clutch have gotten a whole lot bigger this morning. More news in the strat thread later!

I shall be looking forward to reading that later, for sure.

Edited December 21, 2011 by Snow Time 79

[Great Plum]

Such a tease C!!

Despite the 0z GFS op being one of the milder in the suite, the ensembles paint a gradually cooling picture...

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

[Snowmad79]

Such a tease C!!

Despite the 0z GFS op being one of the milder in the suite, the ensembles paint a gradually cooling picture...

http://www.netweathe...;type=ens;sess=

GFS Operational is erratic to say the least!

[Great Plum]

GFS Operational is erratic to say the least!

Indeed. I think this is often the case if an SSW is forecast... I don't know if this would be reflected in the models yet, however...

[Frosty.]

The models look like they will reset to the pattern we have had for most of the last 3 or 4 weeks with a mix of mild, cool and cold zoneality but the next few days will be very mild and springlike, much as november was a very springlike month and came out as the second warmest november in meteorological history no less, daffodills are already in full bloom in some parts of the uk (swaying in the balmy mild swly breezes) and trees are budding, the birds think it's spring already! and 12-14c today and tomorrow will feel more like early april! it does look colder on friday with temps dropping back to 7c and a slight frost to begin xmas eve but then turning milder again.

Edited December 21, 2011 by Polar_ Low

[nick sussex]

If this doesn't slow the jet down nothing will!

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/temps.gif

Great news from the stratosphere forecasts this morning, thats still about 9 days out though and could change so best keep our feet on the ground.

This would be very unusual in that these sudden warmings rarely happen this early into the winter.

[Frosty.]

If this doesn't slow the jet down nothing will! http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/temps.gif Great news from the stratosphere forecasts this morning, thats still about 9 days out though and could change so best keep our feet on the ground. This would be very unusual in that these sudden warmings rarely happen this early into the winter.

We must remember though that this may not benefit the uk if the blocking develops in the wrong place, strat warming is no miracle cure but it does help of course, I seem to remember there was a big strat warming event last feb and yet it turned out to be a fairly mild month.

[winterof79]

Morning all.Does anyone have a link to the ECMWF ensemble graphs,i have lost the link.Many thanks.

[nick sussex]

We must remember though that this may not benefit the uk if the blocking develops in the wrong place, strat warming is no miracle cure but it does help of course, I seem to remember there was a big strat warming event last feb and yet it turned out to be a fairly mild month.

Yes I've often stressed this, this is not a guarantee for colder weather but just gives a better chance for some northern blocking, we then have to hope that this sets up in the right place.

In terms of any warming last February this was minimal compared to whats shown today by the ECM strat forecasts, when I looked at todays forecast I thought someone from net weather had infiltrated the ECM computer!

Morning all.Does anyone have a link to the ECMWF ensemble graphs,i have lost the link.Many thanks.

Here you go ECM ensemble maps upto 168hrs:

http://wekuw.met.fu-...cmwf1/temps.gif

Extended ECM ensembles for De Bilt:

http://www.weerplaza...?type=eps_pluim

Edited December 21, 2011 by nick sussex

[Frosty.]

Yes I've often stressed this, this is not a guarantee for colder weather but just gives a better chance for some northern blocking, we then have to hope that this sets up in the right place. In terms of any warming last February this was minimal compared to whats shown today by the ECM strat forecasts, when I looked at todays forecast I thought someone from net weather had infiltrated the ECM computer!

It's potentially great news nick and it will be fascinating how this impacts on the models in the coming weeks, there is nothing worse than looking at charts with mild swly winds as the next few days show.

[Iceberg]

All though an ssw is not a guarantee of cold weather the models and ens have been showing signs that the Ssw if it where to happen would help blocking to form on the right places and the Mods indicating that the Pc will move eastwards

The indications are good but it will be after Christmas that we really know

(null)

[nick sussex]

It's potentially great news nick and it will be fascinating how this impacts on the models in the coming weeks, there is nothing worse than looking at charts with mild swly winds as the next few days show.

I agree , at least if this strat warming holds up we can view the output with less stress! the background signals mean that we might see a change into January but I don't want to talk this up too much until we see at least the first stage in removing the PV verify, this is just a forecast at the moment so we should bear this in mind.

[Isolated Frost]

I would say the outlook does look Tm dominated with some sunshine most likely for the south-east, with temperatures above average, and precipitation below average, but with the highlands seeing rather high rainfall, melting lots of snow i'd think; it's setups like what's projected that thaw a lot of snow in hilly, northern places.

However with that (potential/possible) ssw, I can probably say the 85' evolution TWS had shown is rather more possible now, but of course we're probably talking first cooler blast come mid-jan.

I'd also wage a bet that with an increasingly blocked atlantic and distorted ridge with a prominence of arctic highs rather than >1050mb greenland highs, a more continental route to our first cold is more likely.

[chionomaniac]

Looks like a displacement SSW ed? If so, would a relocation of the vortex towards Siberia be likely if we get propagation? also, the nwp seems to have a pretty fast response looking at the trend on gfs at t384?

What is interesting about that, and I noticed it a lot last year with the splits, is that the output would get the end result right but not have a clue how to get there! I wonder will this happen again.

[Summer Sun]

Too far out to take very seriously but..........

http://www.wetterzentrale.de/pics/Rtavn3481.png

http://www.wetterzentrale.de/pics/Rtavn3721.png

http://www.wetterzentrale.de/pics/Rtavn3841.png

Mayne some hope for coldies in the new year after a nice mild christmas.

[MisfitDog3]

Interesting developments and I particularly like the far end of the gfs run though as likely to come off as me winning the lottery before the end of 2011! With an upper atmosphere warming event on the cards the next few days are going to produce some interesting FI runs I suspect....just before my wife's Xmas lunch gives me some interesting runs...(boom boom!)

[winterof79]

Yes I've often stressed this, this is not a guarantee for colder weather but just gives a better chance for some northern blocking, we then have to hope that this sets up in the right place.

In terms of any warming last February this was minimal compared to whats shown today by the ECM strat forecasts, when I looked at todays forecast I thought someone from net weather had infiltrated the ECM computer!

Here you go ECM ensemble maps upto 168hrs:

http://wekuw.met.fu-...cmwf1/temps.gif

Extended ECM ensembles for De Bilt:

http://www.weerplaza...?type=eps_pluim

Many thanks Nick

[Frosty.]

just before my wife's Xmas lunch gives me some interesting runs...(boom boom!)

maybe you should cook it then

the models are probably going to start looking a lot different as we go into the new year as the effects of downwelling from the potentially huge strat warming phase begins to impact, so maybe IB's forecast of prolonged bartletts and weeks of swly mush will be in short supply through jan and feb, a mild christmas is now certain but all bets are off from early jan.

[snow drift]

maybe you should cook it then

the models are probably going to start looking a lot different as we go into the new year as the effects of downwelling from the potentially huge strat warming phase begins to impact, so maybe IB's forecast of prolonged bartletts and weeks of swly mush will be in short supply through jan and feb, a mild christmas is now certain but all bets are off from early jan.

I may well be wrong here but the change shown on models showing the warming are for 10 days time. Does it not take 8 plus days for this to then affect lower down. If so then the earliest impact would be from the 8th onwards, if indeed it does have an affect.

Please feel free to correct if I am wrong as this is an area that I have little knowledge but I am trying to learn all the time.

[ITSY]

It will be interesting to see what late GFS FI does - will it sustain the developing arctic high seen on the 00z (which would tie in with the strat. Warming forecast) or change? I agree with the post above, I think it's not till post Christmas we should start seeing some, if any, cold forecast

[phil nw.]

I may well be wrong here but the change shown on models showing the warming are for 10 days time. Does it not take 8 plus days for this to then affect lower down. If so then the earliest impact would be from the 8th onwards, if indeed it does have an affect.

Please feel free to correct if I am wrong as this is an area that I have little knowledge but I am trying to learn all the time.

Yes a sensible view Snow Drift re.. Strato.Warming.

As Chiono,myself and others have said,there`s no certainty for cold in the UK,although obviously any weakening of the vortex increases our chances.

The main thing is any changes are not going to be quick so as encouraging as it is can we please concentate on what the models are now showing and centre discussions around that please.

Any questions or points re. the forecasted Strato. warming are better posted in that thread.

[IDO]

It will be interesting to see what late GFS FI does - will it sustain the developing arctic high seen on the 00z (which would tie in with the strat. Warming forecast) or change? I agree with the post above, I think it's not till post Christmas we should start seeing some, if any, cold forecast

"The Lord giveth and then taketh away"

The last two GFS were a surprise but 06Z is back on track with HP influenced weather and any attempts for the cold sinking south sent packing.

[Glacier Point]

Some very subtle indications on show within the modelling suggesting an intermittent weakening of the polar westerlies.

The last two GFS operationals (didn't see the 18z) have come up with attempted cut off lows in the Atlantic (t168 and again around t300) as a result of an amplification in the longwave pattern over North America. The 00z GFS ensemble suite picked these as well and generally trend the mean ridge back further west and north-west with a resulting better organised trough digging to our east.

However, the westerlies soon returned and prevented any blocking structures form taking shape in the ops and a fair reflection of the current state of play - ridges being shunted intowards western Europe from the mid Atlantic with the trough coming and going to our east. Worth looking out for as trend to fill this 'downtime' until the modelling takes us into the New Year.