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Model output discussion - Post SSW - Will it turn cold?


Message added by Paul

Please only post model discussion in this thread. 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

Thank you!

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Cold - Yes Instability - Yes Prolonged - Yes I just wet myself - Yes!

I quite often agree with your sort of sentiment, as I'm one who opts to look at the most likely solution to fit the signals rather than the preferred one But, equally impartially and with intended

Sorry, I just thought I’d walked into the moans threa.. oh wait. <passes around a big bag of grips> No sooner do we get a cold spell within sight it astonishes me that time and time again some p

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35 minutes ago, Jimmyh said:

it is interesting to read all of the comments on ECM and how if it shows something different it must be followed. I have to admit I am totally confused by this. Correct me if I am wrong but the ecm has flipped more than any other model going into this scenario starting at the weekend in Ernest. if there was a chance of this being delayed or reduced time scale, I very much doubt the super computers at Exeter would have released this statement, otherwise they would be left with egg on their faces, like the bbq summer as an example despite that being a long range forecast.....

Met largely go by MOGREPS we are none the wiser however @essexweather did post lately we used to have IF reveal snippets it’s superior guidance compared to ECM however it too is incorporated. We have a mean like this at day 6! If you’re from Southern England then it should make you ecstatic unless you’re knocks, severe cold looks odds on for south, snowy conditions more uncertain particularly the northern extent.

EF2292E1-1D93-4C6A-8E6C-993837521C54.thumb.png.d6ff7855fc00ee1d4a44144f2c887261.png

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Another tense set of runs coming up,  Arpege and ICON 06z's heading the right way (better ridging/Atlantic profile). 

Remember that regardless of whether or not the 12z's show what we all want (or don't) that this is unlikely to be set in stone this evening. S4lancia's post above is worth taking stock of- run to run variation happens every time. 

I have to say it's been some of the best model watching over the last few weeks,  watching the SSW being forecast and then coming to fruition with a devastating affect on the tropospheric vortex coming - pure synoptic heaven.  Hopefully this beast lands...  It's long overdue. 

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29 minutes ago, bluearmy said:

Looking at the gem ens mean (geps) for next Tuesday (taken from last Monday) and thinking this is a model we should be paying more attention to !!

496CA007-0CFF-44D4-AF85-9387C4CDF7A9.thumb.jpeg.213f284a7c3ea1f816d5ea5be94fbfce.jpeg

Yes and as I posted earlier here is the mean for next Wednesday

gens-0-1-228.png  Just saying:D

gens-0-1-216.png

gens-0-1-216.png

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I know we always say this but due to the high impact this cold spell could have and the fact we're less than a week out, this afternoon's ECM is huge- one of the most important I can think of. If it sings from the GFS hymn sheet, we can be fairly confident of the way this pattern will evolve and if we really will get snowmaggedon! I for one am nervous... 

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3 minutes ago, Deep Snow please said:

We're definitely heading into twitchy toes time with the runs this afternoon, tonight and tomorrow. If we still have no clear pattern by tomorrow night I'd be concerned.

Mmmmm.....possibly, however, most folks are posting charts that are still 7 to 10 days out ( and ramping them up IMO...not there's anything wrong with that...i love a decent cold chart !! )....i'd give it a few more days before you allow your toes to twitch !!

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1 minute ago, ZK099 said:

I know we always say this but due to the high impact this cold spell could have and the fact we're less than a week out, this afternoon's ECM is huge- one of the most important I can think of. If it sings from the GFS hymn sheet, we can be fairly confident of the way this pattern will evolve and if we really will get snowmaggedon! I for one am nervous... 

Firstly we need gfs to stick to its current output lol as that comes out first!!!if it continues with the wintry output on the 12z then i expect ecm to look better this evening!!if not then i expexct madness in this forum and paul is gona have a big job on his hands lol!!

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Afternoon all :)

Late to the discussion party today as I have a life beyond forecast charts, model output and the like.

Last evening, on a rare weekend foray into the thread, I opined we might face a stand-off or trade-off in terms of medium term evolution (I'll leave the agonising over T+72 - T+96 to others) between a short, intense, very cold snowy spell followed by a substantial thaw from the south and a more extended colder but drier period.

The positioning of the controlling Scandinavian HP is vital - too far north and the immediate chances of snow and cold increase but leave us more vulnerable to the Atlantic from the west and south and especially so if we move to a west-based negative NAO. Too far south and while the longevity of cold is likely especially via retrogression to Greenland, there's less chance of snow which is after all what most here want.

So it's a fine balancing act if you want both snow and an extended period of cold making sure we are on the cold side of the east-west trough.

Some extraordinary output over the weekend, any single example of which would have reduced the forum to meltdown in the past four years. As it is, if the uppers are less than -12 it's a downgrade. Incredible.

So where are we going into March with the charts of the first day of spring (allegedly) - starting with ECM 00Z at T+240:

ECM1-240.GIF?19-12

The HP has retrogressed but maintains a strong SE'ly ridge right down to the Bay of Biscay. A light NE'ly flow covers the British Isles with a small disturbance over Holland. 850s of -4 to -8 suggest some wintry precipitation to high ground but the far north west dry and fine. There is colder air to the NE again but the extent to which this can push SW remains to be seen.

GEM 00Z OP at the same time:

gem-0-240.png?00

An intense HP over SE Greenland controls the weather with a ridge ESE across the Faeroes to Scandinavia. LP is over Iberia and in between the British Isles is in a strong E or ENE'ly flow. 850s are -12 over southern England with -16 uppers over Northern France. Any precipitation would be of snow with drifting in the strong winds and a pronounced wind-chill. Much drier over northern Scotland and Ulster though with severe overnight frosts.

GFS 00Z OP at T+240:

gfs-0-240.png

A large anticyclone over Greenland ridges SE toward the British Isles. Between that and LP over the Adriatic and Scandinavia a NNE'ly flow covers the British Isles. 850s generally between -4 and -8 as the coldest air departs south. Some wintry showers to southern and eastern coasts but drier further north and west. The cold weather is on its way out as a ridge pushes up from the south and very soon "normal service" is resumed with a westerly flow and much milder air.

GFS 06Z OP at T+234:

gfs-0-234.png?6

LP is over the Channel and an ESE'ly flow covers the British isles. Cold air remains to the north and west but much milder air is in to the SE but, I suspect, with plenty of rain and showers with snow further north as a transitional frontal band moves north and north-west. Further into FI a broadly Easterly flow remains in place with signs of as renewed pressure rise over Scandinavia at the very end of FI.

GFS 06Z Control at T+240:

gens-0-1-240.png

Signs of a west-based negative NAO and a small LP has spun up from the SW and while currently over the SE of England is going to swing up the east coast with much milder air on its eastern flank while very cold air (850s of -8 to -12) remains to the west over the bulk of England and Wales. Further into FI and it turns milder for all briefly before the winds swing back NE'ly and a new plunge of very cold air looms.

Looking at the T+240 GEFS:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

Some seem to want to bring milder Atlantic air from the SW via the west-based negative NAO, others go for an attack from the south but a lot of members are still very cold at this time. Going further into FI and I note a growing tendency for the GEFS to indicate a flow from the N or NE returning some very cold air across the British Isles.

In summary, another day of extraordinary chart output but little is resolved. GFS seems keen to promote a breakdown at the T+240 stage but they may just be playing the progressive card and indeed signs even within the GEFS suite any milder spell could be quite short-lived. No such issues with ECM and GEM which keep Britain firmly in the cold - both promote retrogression but fans of snow will prefer GEM which has more possibilities than ECM which keeps the stronger anticyclonic influence.

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Just now, K9 said:

Mmmmm.....possibly, however, most folks are posting charts that are still 7 to 10 days out ( and ramping them up IMO...not there's anything wrong with that...i love a decent cold chart !! )....i'd give it a few more days before you allow your toes to twitch !!

Well I think everyone is pretty confident on the synoptic pattern that is about to evolve. The only question is where the high will sit. If the ECM corrects northwards on the next two/three runs I think we can get excited

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1 minute ago, ZK099 said:

Well I think everyone is pretty confident on the synoptic pattern that is about to evolve. The only question is where the high will sit. If the ECM corrects northwards on the next two/three runs I think we can get excited

Fair point...i just like to get to around +96 before i allow a smile to break out...seen far too many 'garden paths' since the olden days of the 'BBC Forum' where it all crashed and burned ( even at +48 TBH !! ) at the last minute....great model outputs though courtesy of the SSW...eyes down for a full house over the next few days !!

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9 minutes ago, Summer Sun said:

I posted it this morning here it is for anyone who's missed it and a comparison with ECM

ukm2.2018022600_168_lant.troplant_prp_fcst.gentracker.thumb.png.373e4a9b2bcf564c8fec9c687b090803.pngfv3e.2018022600_168_lant.troplant_prp_fcst.gentracker.thumb.png.94ae24da13ab5c94487e017c2dd22085.png

 

Does anyone know what the FV3 models output on there is about. I thought they were experimental models to replace FIM AND NOGAPS but not at all sure?

https://ruc.noaa.gov/hfip/tcgen/

They do show similarities to GFS and GEM but I think they may be linked to GFS 

Edited by winterof79
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10 minutes ago, Summer Sun said:

I posted it this morning here it is for anyone who's missed it and a comparison with ECM

ukm2.2018022600_168_lant.troplant_prp_fcst.gentracker.thumb.png.373e4a9b2bcf564c8fec9c687b090803.pngfv3e.2018022600_168_lant.troplant_prp_fcst.gentracker.thumb.png.94ae24da13ab5c94487e017c2dd22085.png

 

I think you have posted FV3 NCP instead of ECM ?

It pains me to say that the ECM is closer:)

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Icon rolling 

at 42hr looks like that shortwave off the NE  Norwegian coast is taking more energy with it and by 6ohr heading more SE than SEE in last run. think the block will end up further West than last run. earlier easterly coming up

icon-0-42.png

icon-0-60.png?19-12

Edited by pages
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1 minute ago, pages said:

Icon rolling 

at 42hr looks like that shortwave off the NE  Norwegian coast is taking more energy with it and by 6ohr heading more SE than SEE in last run. think the block will end up further West than last run. earlier easterly coming up

icon-0-42.png

icon-0-60.png?19-12

brave call at T42 !

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Just a quick observation  as  the MET update mentions an area of snow moving N/E next week presumably from the s/w and the earlier GFS shows a disturbance moving up from the south. This could change on the link as the 12z rolls out.

"There is also the risk of more significant snow pushing northeastwards across southern and some central areas." 

gfs-0-222.png?6

No sign on ECM which makes me side with GFS more so.

ECM1-216.GIF?19-12

 

Edited by winterof79
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