Model output discussion - 20th Feb onwards

[knocker]

1 hour ago, Bring Back1962-63 said:

Final Comment:

So, we have a second consecutive day with a colder trend showing on various indicators. The ECM seems to have picked up on this far more than the other models and it really looks like they are picking up on signals of the likely SSW surface impacts. I have a hunch that we might see some very interesting developments for coldies during the rest of this week. Surely this thread will come to life again? More tomorrow.

I'm having great difficulty in following this unless by cold trend you mean temps a little below average , also I'm puzzled by various indicators. And what are these interesting developments you are hunching about this week?

[blizzard81]

1 minute ago, knocker said:

I'm having great difficulty in following this unless by cold trend you mean temps a little below average , also I'm puzzled by various indicators. And what are these interesting developments you are hunching about this week?

Take a look at the blue control run on the 12z ecm. That will certainly go some way to answering your question.

[damianslaw]

Continue to dip in and out of the forum at present, due to other things..

Well we are a world away from the Nov-Jan base state it appears. High pressure on the scene for the first time since late October.. only slow changes forecast for the rest of the week, with heights gradually moving towards the NW, with a slight northerly component to things by the weekend. Temps close to average away from the NW, cloud amounts difficult to call, indeed SE quarter of the country looks very dull, temps here a bit below average compared to the warm west of Scotland, nothing unusual in this, spring often sees a role reversal of fortunes for the NW before the late spring deluges return..

Longer term - ECM showing the coldest looking charts of the year so far, very cold uppers descending thanks to robust northern blocking heights, and a screaming northerly, indeed think Dec 16 2010! GFS less keen showing a more typical polar maritime airflow, with the atlantic kicking against any build of heights. UKMO looks to be moving towards the ECM scenario though.

Will take a look at the models again tomorrow, see if ECM continues the arctic blast trend.. will begin looking at the models again proper next week.

[knocker]

34 minutes ago, blizzard81 said:

Take a look at the blue control run on the 12z ecm. That will certainly go some way to answering your question.

Actually it doesn't. The ecm run on the whole including the EPS and anomalies do not indicate a cold trend unless you are talking temps just below average. The 'arctic blast' is a possible transient event and even then it's hardly Arctic. I say possible because we also talking ten days hence. There is nothing on all the anomalies including NOAA that indicates a sustained cold period. So what are the various indicators?

I also don't know how one can say the ecm is picking up SSW surface impacts. If it is the GEFS is as well as it's not that different but I'm quite wary of these assumptions as we've had enough torpedos this season to sink the Bismark.

Edited March 14, 2016 by knocker

[damianslaw]

3 minutes ago, knocker said:

Actually it doesn't. The ecm run on the whole including the EPS and anomalies do not indicate a cold trend unless you are talking temps just below average. The 'arctic blast' is a possible transient event and even then it's hardly Arctic. I say possible because we also talking ten days hence. There is nothing on all the anomalies including NOAA that indicates a sustained cold period. So what are the various indicators?

The ECM op for 24 March is showing a very potent arctic blast and it is this that people are mentioning - it would be arctic as well with sub -10 uppers showing, no denying where the isobars are showing from.

Evolution next week will depend on where heights migrate too, indications are westwards which would allow a trough to drop down across Scandinavia - indeed BBC long range forecast just now suggests this could happen with low heights developing to our NE.

Your right it is just one chart and one possible evolution, but a very plausible one.

[feb1991blizzard]

Has anyone got any news on the ECM32 control run yet please?

[knocker]

13 minutes ago, damianslaw said:

The ECM op for 24 March is showing a very potent arctic blast and it is this that people are mentioning - it would be arctic as well with sub -10 uppers showing, no denying where the isobars are showing from.

Evolution next week will depend on where heights migrate too, indications are westwards which would allow a trough to drop down across Scandinavia - indeed BBC long range forecast just now suggests this could happen with low heights developing to our NE.

Your right it is just one chart and one possible evolution, but a very plausible one.

And According to the EPS means the 850mb temp and streamline chart two days later there is a weak ridge over the UK with westerly winds and temps of -3C. One chart at day ten  doesn't constitute a trend in my book. Plus the eps anomalies are not having it.

Okay it's plausible if you say so but not as plausible as a transient northerly IMO.

And the various other indicators?

 

Edited March 14, 2016 by knocker

[weirpig]

certainly will feel a bit nippy if this chart verified

 

 

[Frosty.]

Nice Gfs 18z tonight which shows an Arctic blast as we enter the Easter period with snow in places and widespread frosts.My hope is that the models can build on this and that we do see a potent Arctic blast later next week..and the Ecm 12z in case anyone missed it..Arctic air incoming..

[knocker]

And some nice Easter warmth

[IDO]

I am with Knocker on this one, where this Arctic blast is I cannot see it? No point looking at ECM op D10 charts as they have been promising this for days but it never gets nearer. The GEM and GFS this morning have HP the main influence to D10, and beyond for the latter. Maybe a brief day where the east coast gets a northerly flow.

Flick through the GFS T850 NH chart and see where the cold block is: http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=192&mode=1&carte=1 . IMO you are not going to get any sustained cold from that set up. As for the promised SSW impacting the AO, well there is no sign of HLB'ing yet and are we sure it will go strongly negative? 

Another beautiful day yesterday, 13c when 8c was forecast only the day before, and with the CET heading towards neutral the promised cold March is really not happening. All subject to change of course but until I see consistent signs of an Artic spell I reserve judgement.

 

[knocker]

A quick word  vis last night's EC32 update,

On the 24th the mean anomaly has ridging to the west and the trough over Scandinavia, Ergo upper flow NW, etc, etc.

Within two days the trough has weakened, the ridge has gone replaced by a cool zonal flow and, quite important, The Siberian HP has moved west  into western Russia,

By Friday 1st there is a trough to the west running south with ridging over Scandinavia as the Russian HP continues  to move west. This pattern backs the upper flow to SW with temps around average.

So I'll stick to my stance of last night that there is no evidence of any prolonged cold spell. Just a period of unsettled weather with temps below average once this quiet spell ends.

 

Edited March 15, 2016 by knocker

[Frosty.]

54 minutes ago, knocker said:

 

So I'll stick to my stance of last night that there is no evidence of any prolonged cold spell. 

 

Has anyone said anything about a prolonged cold spell?..I don't think anyone has!

[knocker]

2 minutes ago, Frosty. said:

Has anyone said anything about a prolonged cold spell?..I don't think anyone has!

On this occasion I wasn't commenting on what anyone else has or has not said, merely making an observation.

[knocker]

A quick look at the GEFS anomalies

A familiar story  on the 25th so no comment necessary.

The pattern then quickly becoming less amplified with the Canadian trough shifting east.

By the end of March the trough now central Atlantic with the trough over Scandinavia replaced by slight ridging. Not a million miles away from the EC32.

[KTtom]

I don't think anyone is particularly hoping or expecting any wintry weather to return this late in the season, however what the models do indicate is a continuation of the airflow over the UK originating from a northerly quadrant with high pressure to the west......gardeners beware!

[knocker]

1 minute ago, KTtom said:

I don't think anyone is particularly hoping or expecting any wintry weather to return this late in the season, however what the models do indicate is a continuation of the airflow over the UK originating from a northerly quadrant with high pressure to the west......gardeners beware!

You obviously haven't read some of the posts last night then.

[Paul]

This all has a familiar ring to it. Can we keep it friendly, and model based please.

[Gibby]

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 09:00 ON TUESDAY MAR 15TH 2016

THE CURRENT GENERAL SITUATION  Pressure will remain very high over the UK in the coming days. A weak warm front followed by a cold front will move West across England and Wales tonight and tomorrow.

http://www.wetterzentrale.de/pics/Rtavn001.gif

CURRENT SNOW FORECAST AND FREEZING LEVEL OVER THE UK The freezing level across the UK will remain in the range of 6000-7000ft asl under strong High pressure bit the level may fall to around 5000ft tomorrow behind the cold front moving West. No snowfall is expected across the UK today.

http://www.snow-forecast.com/maps/dynamic/uk

http://www.natice.noaa.gov/pub/ims/ims_gif/DATA/cursnow.gif

MODELS-2 WEEK HEADLINE Mostly dry and bright with some frosts at night. Probably becoming less settled later in the month especially in the North.

THE GFS JET STREAM FORECAST  The Jet Stream remains blocked by a large High to the North and NE of the UK. The result of this is the flow is diverted both South and North of the UK before declining High pressure next week makes for a less defined pattern to the flow yet to be properly determined..

http://www.netweather.tv/index.cgi?action=jetstream

GFS OPERATIONAL The GFS Operational Run today shows High pressure moving slowly West or SW from a point to the NE of the UK over and away to the West and SW of the UK all this time maintaining bright and fresh weather with sunshine at times and little or no rain. then as we move towards Easter a glancing blow at a chilly NW flow could bring a chilly period with a few showers towards the NE before milder SW winds but High pressure close to the South offers some rain in the NW while the South and east of the UK stay largely dry and bright with temperatures near average over the Easter weekend 

GFS CONTROL RUN The theme of the Control Run shows the same High pressure moving West across the UK through the rest of this week and weekend with it's largely fine and settled conditions maintained. then as we move into the run up towards Easter the weather looks like turning more unsettled with some rain at times and a marked chilly day or so under a transient Northerly with some wintry showers in the east before milder air at times encroaches in and over the UK from the Atlantic towards the end of the month.

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

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

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=144&mode=0&carte=0

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=384&mode=0&carte=0

GFS ENSEMBLE DAY 14 DATA  The GFS Clusters today have now endorsed a more definitive pattern to be set up for the UK in 14 days time. Most members follow a Low pressure route now with it's centre somewhere near NW Britain with milder SW winds and rain at times in average temperatures the most likely scenario for the UK in two weeks time.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=372&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

UKMO The UKMO model this morning shows High pressure on the move West and then South to lie across Southern areas by the early days of next week with a milder Westerly flow developing across the North. The weather looks like staying dry and fine for the most parts with a chilly breeze in the South and East dying down by the weekend.

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

THE FAX CHARTS The Fax Charts illustrate the High pressure 's movement West or SW over the North of the UK through the week. With the UK lying on the Southern flank of the High chilly NE winds are shown to drag weak troughs West in the flow at times each bringing increased cloud cover at times and more suppressed temperatures.

http://www.weathercharts.org/ukmomslp.htm#t120

GEM GEM this morning looks very settled too over the next 10 days as High pressure slowly transfers from a position just to the NE of the UK to one just to the SW by next week extending a ridge across Southern Britain. This prevents the earlier projected cold plunge to affect Europe this far west and keeps temperatures respectable throughout the period especially given the increase of Atlantic Westerly flow across the North next week.

http://www.wetterzentrale.de/pics/Rgem2401.gif

NAVGEM NAVGEM too looks very similar to the general theme shown by most output this morning with High pressure moving from a point to the NE to one to the SW of the UK by this time next week with largely fine and settled conditions continuing for all areas in temperatures close to average.

http://www.wetterzentrale.de/pics/Rnvg1681.gif

ECM ECM this morning looks a little isolated as it is the only operational run this morning that still shows a cold Northerly or NW'ly flow across the UK as we move towards Easter though it is somewhat moderated from what was shown yesterday. Nevertheless after another week of fine and quiet weather next week would become chilly and unsettled as Low pressure is steered down from the NW or North with North and NW winds with rain and showers likely by then with snow on hills possible. 

http://www.wetterzentrale.de/pics/Recm2401.gif

ECM 10 DAY MEAN The 240hr mean Chart has moved towards a less cold theme than it showed yesterday at it's 10 day time point as it now shows weaker Low pressure to the East and NE, High pressure well to the SW and a pattern of Westerly winds across the UK with some rain at times over the North. There are still a few members who continue to project a colder Northerly possible though this result has far less support this morning.

http://www.wetterzentrale.de/pics/Reem2401.gif

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS The trend towards a cold and unsettled Easter has been lessened today with a more likely South/North divide looking most popular across the models this morning with the best weather retained in the South for Easter itself.

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKMO & ECM The verification Statistics of GFS, UKMO and ECM show at 24 hours ECM ahead at 99.6 pts with UKMO at 99.5 pts and GFS at 99.4 pts.  At 3 days ECM is leading with 97.5 pts to UKMO's 97.1 pts while GFS lags behind at 96.3 pts. At 5 days ECM leads with 89.9 pts to UKMO at 89.1 pts and GFS at 85.7 pts. Then at 8 Days ECM has the leading spot from GFS with 64.3 pts to 60.0 pts. Finally at Day 10 ECM has regained the lead from GFS with a score of 45.7 pts to 44.8 pts.

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day1_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day3_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day5_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day8_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day10_PMSL_MSL_G2NHX.png

MY THOUGHTS  There are some changes in the output this morning regarding the period around Easter. I'll talk about those in a minute but for now the message is the same as was with High pressure in complete control of the UK weather. High pressure just to the NE is maintaining a chilly NE flow across the South with the best temperatures maintained across Western Scotland. Cloud amounts will vary and could be quite large for a time near the East coast and other areas too for a time tonight and tomorrow as some very weak fronts move West. Then as we move through the weekend prospects remain good with rather less breeze in the South as the High pressure moves slowly West and SW across the North to a position to the West of the UK. Then the general theme looks for the High pressure to slip South towards a point SW of the UK but maintaining a ridge across the South. This is where the differences come into play as the general message from the models appear to be for Westerly winds to take hold across the North perhaps with some rain while the fine weather holds on over the South. If this pattern continues to be shown then Easter could be a good deal milder than was shown yesterday with temperatures nearer to average and less chance of wintry showers. Nevertheless, ECM still shows a chilly theme under North winds up to Good Friday and it looks like this could be maintained for the rest of Easter too with a large blocking High over the Atlantic so all is not lost for those looking for a cold and showery convective period over the long holiday weekend. However, it should be noted that it's 10 day mean chart this morning has taken a step towards the majority of output in suggestion for a less cold Westerly rather than a cold Northerly looking increasingly likely for Easter. I'm sure we will see the picture become much clearer one way or the other in the coming days. 

Next Update Wednesday March 16th 2016 from 09:00

Edited March 15, 2016 by Gibby

[Summer Sun]

GFS 00z looking better for Easter

Possibly a bit more unsettled for the Monday but 3 out of 4 days staying dry aint bad is it?

Temps nothing spectacular but not cold by any means

ECM aint as good though typical BH weekend weather

Edited March 15, 2016 by Summer Sun

[I remember Atlantic 252]

SS not bad, FI so hope of even better, but ECM disagrees, vile FI 

[Singularity]

As usual I can gain a general impression of the model tendencies from looking at the MJO projections; the sharp dive in the mid-to-long range ties in with some westerly momentum being added to the mid-latitudes. The dive being in phase 5 focuses that on the Atlantic, with the emergence of a high pressure belt extended from the Azores into Europe being a favoured outcome. ECM takes longer to send the MJO into the COD and corresponding to that we see a later move towards a more westerly type regime in the EC ens. compared to the GEFS.

This, of course, is taking the models at face value. When the MJO was declining in phases 8/1, the models initially had it heading right for the COD near the 7/8 divide, and this turned out to be about 1 phase too early. If this sort of thing happens again, the flattening of the pattern will arrive later in time - perhaps at the turn of the month. The move to phase 6 would also encourage further mid-latitude blocking near or over the UK, perhaps getting slightly north of us at times.

To this point this is an entirely MJO based outlook.

To expand on this - the stratospheric events may continue to favour cross-polar heights on and off, from the Pacific to Atlantic sides of the Arctic. This brings the risk of mid-latitude blocking linking up from time to time, to bring the UK a blast of air from the high Arctic, and we are seeing this well reflected by the ECM output in particular. A more sustained cold spell is still a threat, but it seems the MJO may just about to enough to prevent that in favour of a more variable regime of temperatures.

[Frosty.]

2 hours ago, knocker said:

You obviously haven't read some of the posts last night then.

The posts last night were describing what the models were showing, what's wrong with that? I know that some of us prefer mild and others cold but if we all posted like robots with no preference for any weather type, this thread would be boring..

[Frank Trough]

if more time were spent discussing the output up to t+144 there would be an awful lot less guff on here. At least that has half a chance of verifying, be it mild, cold, wet, windy, cloudy...

So on that note, up to sunday the latest GFS offers plenty more usable spring weather to enjoy, with an emphasis towards the end of the week of slightly warmer temps more widely if it is on the right lines:

 

 

[Tamara]

As is usual with assessing the overall likely direction of travel of the weather patterns, and how the mid term upper air anomaly charts continue to evolve, we have to contextualise the whole global atmospheric state, of which tropical forcing (MJO) is just one part.

We continue as ever in an El Nino driven high Atmospheric Angular Momentum global pattern, and the Global Wind Oscillation tells us this through its persistent orbit triangles through Nino Phases 5,6,7.

 

However, we are in March and shortening seasonal wavelengths have different implications for hemispheric synoptic patterns to the winter months under this regime.  We see a prominence of mid latitude high pressure instead of a train of depressions, and with the relaxation of polar westerlies, we see blocks able to hold position much better than seen under the turbo charged jet stream of the winter.

Questions have been raised in places on the forum regarding when, or if, we might see a cold blocking response to the SSW.

Generally, in winter-time a low angular momentum state (Nina-like) is prohibitive towards high latitude blocking. This is related to the dominant position of tropical forcing in the Indian Ocean, which tends to promote bolstered sub tropical ridges sitting above the easterly trades across the equator and pushing them northwards into mid latitudes. However, too strong an opposite Nino base state, and in the absence of a compliant weak stratospheric vortex, will promote as we have seen this winter too vigorous a sub tropical Jetstream. (Best winter combination is a slight, moderate Nino, overall, in tandem with a weak unstable stratospheric vortex, -ve QBO and, ideally, weak solar forcing)

However, large changes in seasonal wavelengths as we arrive through March and into April  means a tanking lower AAM state into Nina territory becomes best required to take best advantage of final break-up and warming out of the winter-time stratospheric vortex in terms of potential high latitude blocking product -  and subsequent releasing of cold air from the arctic and advection to mid latitudes. Especially with the QBO now fast transitioning away from its westerly phase.

As posted and anticipated previously, the part that seasonal wavelengths play in terms of the westerly winds bursts across the Pacific that characterise an El Nino, is to slow their eastward progression increasingly through late winter and especially early Spring, and for consequential cooling of the warm waters to accelerate first starting from the eastern most 1.2 region. This trend has been evidenced over the last 6 weeks or more

Although, the strong Nino that has been witnessed through the recent two seasons has been releasing its grip slowly but surely, and there is enough historical evidence to suggest that this trend might accelerate in the coming weeks, there is no sign yet that the atmospheric circulation is going to change significantly - and it is highly likely a Nino atmospheric response will continue at least throughout the Spring and perhaps into early summer too.

With all this in mind, and the tendency for the jet stream to be, mostly, inclined to stay north, we should be cautious about any indicated potency of Spring cold spells. That is not to say that there is no chance of them, but to suggest how they might be inhibited from reaching maximum potential.  We might be reminded here of the potent late March and early April northerlies that occurred in 2008 - such a switch occurring as part of some repeated cold incursions that occurred during that Spring ...under La Nina atmospheric conditions.

      

Torques are large drivers of angular momentum tendency, and they add or take away energy, or wind, from the atmosphere according to whether they are rising or falling.

Frictional torque tendency (which can be seen as a means of measuring jet stream strength) has been negative.

Overall Global Mountain torque budget is positive, supporting high relative AAM

... As the direction of travel of frictional torques usually lead Mountain torques - it is likely that a small -ve North American MT response may be upcoming.  This will likely provoke something of a (temporary) -ve pull on AAM tendency. The effect of this is slow upstream velocity and amplify the pattern there.

However, tropical forcing continues eastward and, with the Nino base state persisting for the time being, we should be cautious of any model forecasts to decrease MJO amplitude too quickly as the MJO heads back towards the Pacific - and this will place a flooring on any attempted drop in AAM. Indeed, track of tropical convective forcing into the Western Pacific should bolster AAM further and ensure yet another GWO orbit through to Phase 5/6

Translating this into synoptic evolution, and unless there is any unforeseen developments to change the atmospheric circulation more significantly, this implies some attempted upstream amplification in response to NA MT (and allied to the warming stratosphere) and this may provide a meridional cold(er) and more unsettled shot from the north to follow the current fine anti-cyclonic spell.. However, against the background patterns as described, this doesn't look, at least at present, to have any sustaining power of potency - and so therefore the sharpness of amplification and depth of cold air advection as depicted on recent ECM operational outputs, may be rather overstated.

A return to High pressure is quite possible, and coldest and most unsettled conditions may be restricted further NW. In the meantime, that part of the world is benefitting from some of the warmer Spring like conditions under our High pressure regime.