Model Output Discussion 29th December - Into mid-Winter.

[johnholmes]

This type of weather pattern is where one needs to look at the B Isles weather map, whichever one you favour, (there are several), look for minor wind variations, slight pressure falls in areas where otherwise the barometer is rising, winds backing with time, convective clouds increasing along perhaps with upper clouds. These are minor troughs which develop, and it is rare that at leas a couple will not occur through a 48 hour period. The effect is the make inland areas more prone to a wintry shower when perhaps least expected. Usually the forecast will pick them up, at least mentioning the probability of one or more. They are NOT Polar Lows. These will show up on both visual and infra red satellite shots or movie loops, (the Icelandic one is a good one to watch, pretty much for any weather type)

good luck folks

Edited January 9, 2017 by johnholmes

[Nick F]

Well, certainly a window for snow to fall almost anywhere on Thursday and Friday, though before then across the hills of Scotland from as early as Wednesday morning before increasingly across the north and west later on Wednesday.

However, weekend onwards looks like a case of high pressure taking over and creating an inversion with some chilly days and cold frosty nights before eventually milder air encroaches across the NW then filtering further SE with time next week the most likely case IMO.

Looking further ahead, although some deride such signals / teleconnections, GFS and ECMWF are keen to take the MJO into phase 1 after mid-month, GFS quite amplified, so we may hopefully a greater chance of amplification in the upper flow in the second half of the month.

Couple this more favourable movement of MJO, which increases likelihood of colder weather, the zonal winds at 10 hPa are forecast to ease off and even reverse, which may have ramifications for late winter PV if it continues in such a manner

So some positives for more opportunities for the rest of winter in perhaps seeing another and hopefully better chance at a cold spell with some snow. As so far, the MJO has been weak and strat rather strong to support much amplification north of ridges at more favourable higher latittudes over our side of the N Hemisphere.

Edited January 9, 2017 by Nick F

[feb1991blizzard]

Just the very slightest suggestion that things could be looking up for February, theres a pretty strong warming underway at the top of the strat with a vortex displacement (that may become favourably located), not sure if there's a decent East Asian MT event underway or whether its just the GFS off on one,

http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2017010912&var=TMP&lev=1mb&hour=384

[Summer Sun]

NOAA

NOAA

PREFERENCE: 12Z GFS/NAM AND 00Z ECMWF

BLEND CONFIDENCE: AVERAGE

A STRONG SHORTWAVE FROM THE CENTRAL PACIFIC RACES INTO THE EASTERN PACIFIC BY TUESDAY UNDER CUTTING THE WEAKENING UPPER LOW FEATURE. THIS WILL DIRECT DEEP MOISTURE FLUX AND ANOTHER BOUT OF FLOODING CONCERNS FOR N CA LATE TUESDAY INTO WED. THE ECMWF IS SLIGHTLY FASTER IN THE MID-LEVELS COMPARED TO THE NAM/GFS THOUGH THE NAM/GFS ARE A BIT MORE VERTICALLY STACKED THAN THE ECWMF...THE OVERALL SPREAD IS MILD BETWEEN THE SOLUTIONS. THE 00Z CMC BECOMES QUITE ROBUST WITH SOME INCREASED FEED BACK AS IT NEARS THE COAST AND BLOSSOMS A VERY DEEP SURFACE REFLECTION TO MAKE IT A BIT LESS DESIRABLE.

THE UKMET HAS QUITE A FEW MID-LEVEL BINARY INTERACTIONS THAT LEAD IT TO BE WELL OUT OF PHASE EVENTUALLY BECOMING 180 DEGREES OUT OF PHASE BY THE END OF THE FORECAST PERIOD. AS SUCH A BLEND OF THE 12Z GFS/NAM AND 00Z ECMWF SEEMS PRUDENT WEIGHTING TOWARD THE MORE CONSISTENT GFS SOLUTION. NOTE: SHORTWAVE ENERGY FROM THIS WAVE CROSSES THE CENTRAL ROCKIES LATE WED INTO THURSDAY AND PLAYS A SIGNIFICANT ROLE IN SPREAD ACROSS THE GREAT LAKES AS IT PHASES WITH NORTHERN STREAM ENERGY...PLEASE SEE TWO SECTIONS ABOVE FOR THOSE DETAILS. REMAINING NORTHEAST TROF ENERGY SWINGING THROUGH THE WEST THURSDAY

___________________________________________________________________________________________________________________________________________________________________________________________

PREFERENCE: 12Z GFS AND 00Z ECMWF/CMC

BLEND CONFIDENCE: AVERAGE

WESTERN EXTENSION OF SHORTWAVE ENERGY IN THE DIGGING NORTHERN STREAM WEST OF THE COASTAL RANGE CAN BE SEEN BREAKING OFF NEAR HAIDA GWAII CURRENTLY. THERE IS FAIR MODEL AGREEMENT THAT THIS ENERGY WILL CONSOLIDATE AND LINGER OFFSHORE AS THE OVERALL LARGE SCALE TROF CONTINUES TO BREAK DOWN TUES/WED. EVENTUALLY...THE VAST MAJORITY OF GLOBAL GUIDANCE AND ENSEMBLE MEMBERS DRAW THE WAVE SOUTH AND EAST TOWARD THE WEST COAST THURSDAY AS THE BASE OF THE LARGER SCALE TROF. THE MAIN EXCEPTION IS THE UKMET WHICH SHOWING A BIT MORE STRENGTH IS INFLUENCED BY THE MEAN TROF LESS AND BREAKS OFF INTO A DEEP CONCENTRIC CLOSED LOW WELL OFFSHORE.

UNFORTUNATELY THIS PLACES THE UKMET 180 DEGREES OUT OF PHASE WITH ALL BUT MAY ONE ECMWF MEMBER WITHIN THE ENSEMBLE PLOT. THE ENSEMBLE SUITE AS A WHOLE SHOWS QUITE A BIT OF VARIATION OF THE STRENGTH OF THE TROF ON THURSDAY THOUGH THE OVERALL TIMING IS FAIRLY WELL AGREED UPON PROVIDING SOME CONFIDENCE IN THE PATTERN AS A WHOLE THOUGH NOT NECESSARILY ONE RUN OVER ANOTHER. THE 12Z NAM HOWEVER DOES HAVE A GREATER OVERALL POSITIVE TILT DUE TO NORTHERN DIFFERENCES (SEE TWO SECTIONS ABOVE) THIS LEADS THIS FEATURE/BASE OF THE TROF TO BE A BIT SLOW AND BROADER COMPARED TO THE REST OF THE GUIDANCE. AS SUCH A PREFERENCE TOWARD THE 12Z GFS AND 00Z ECMWF/CMC SEEMS PRUDENT AT THIS TIME.

Edited January 9, 2017 by Summer Sun

[IDO]

Looking at the period before the UK/Euro high sinks which includes D9 we see the the control and op at the opposite ends of the spectrum. The control looks the best case scenario, the op the worse:

op control mean

The mean a mish mash of the two probably the safest bet at the moment.

[Seasonality]

7 minutes ago, Summer Sun said:

NOAA

PREFERENCE: 12Z GFS/NAM AND 00Z ECMWF

BLEND CONFIDENCE: AVERAGE

A STRONG SHORTWAVE FROM THE CENTRAL PACIFIC RACES INTO THE EASTERN PACIFIC BY TUESDAY UNDER CUTTING THE WEAKENING UPPER LOW FEATURE. THIS WILL DIRECT DEEP MOISTURE FLUX AND ANOTHER BOUT OF FLOODING CONCERNS FOR N CA LATE TUESDAY INTO WED. THE ECMWF IS SLIGHTLY FASTER IN THE MID-LEVELS COMPARED TO THE NAM/GFS THOUGH THE NAM/GFS ARE A BIT MORE VERTICALLY STACKED THAN THE ECWMF...THE OVERALL SPREAD IS MILD BETWEEN THE SOLUTIONS. THE 00Z CMC BECOMES QUITE ROBUST WITH SOME INCREASED FEED BACK AS IT NEARS THE COAST AND BLOSSOMS A VERY DEEP SURFACE REFLECTION TO MAKE IT A BIT LESS DESIRABLE.

THE UKMET HAS QUITE A FEW MID-LEVEL BINARY INTERACTIONS THAT LEAD IT TO BE WELL OUT OF PHASE EVENTUALLY BECOMING 180 DEGREES OUT OF PHASE BY THE END OF THE FORECAST PERIOD. AS SUCH A BLEND OF THE 12Z GFS/NAM AND 00Z ECMWF SEEMS PRUDENT WEIGHTING TOWARD THE MORE CONSISTENT GFS SOLUTION. NOTE: SHORTWAVE ENERGY FROM THIS WAVE CROSSES THE CENTRAL ROCKIES LATE WED INTO THURSDAY AND PLAYS A SIGNIFICANT ROLE IN SPREAD ACROSS THE GREAT LAKES AS IT PHASES WITH NORTHERN STREAM ENERGY...PLEASE SEE TWO SECTIONS ABOVE FOR THOSE DETAILS. REMAINING NORTHEAST TROF ENERGY SWINGING THROUGH THE WEST THURSDAY

Excellent advice for North American weather enthusiasts. But how would it influence outcomes in Europe though? (Genuine question!)

[nick sussex]

So the UKMO has dropped its morning output and looks more similar to the ECM 00hrs. The GFS continues on its merry way with its shortwawe obsession in the Atlantic.

The one noticeable difference is we're seeing a bit more waviness over the USA and this is developing that more amplified high exiting Canada. So you may ask why is this important? Well it means that rather than the elongated PV wanting to send a pile of energy eastwards this waviness, that's amplitude but just sounds more creative! lol helps to hold some of that back so essentially you get bit more ne movement rather than easterly between T144hrs and T192hrs.

Now we don't get much out of that because the GFS has already started an uphill climb from its less than exciting earlier stages.

Theres still an annoying shortwave showing on the UKMO, this in effect stops a better ridge developing between T120hrs and T144hrs although thankfully it doesn't have the shortwave love in that the GFS has.

So what does this mean going forward, if you believe the GFS then at best probably some surface cold towards the se, the UKMO a better chance of getting any surface cold further ne and then with a similar waviness upstream after that perhaps some easterly towards more southern areas especially.

That leaves us waiting for the ECM, we want more waves upstream  and less shortwave issues!

 

Edited January 9, 2017 by nick sussex

[Radiating Dendrite]

3 minutes ago, Seasonality said:

Excellent advice for North American weather enthusiasts. But how would it influence outcomes in Europe though? (Genuine question!)

Because what happens upstream in the US has significant ramifications for what then follows on over the UK.

[Radiating Dendrite]

3 minutes ago, Seasonality said:

Excellent advice for North American weather enthusiasts. But how would it influence outcomes in Europe though? (Genuine question!)

Because what happens upstream in the US has significant ramifications for what then follows on over the UK.

[beng]

42 minutes ago, Nick F said:

Can't see any trough disruption to the west myself? The trough looks too positively tilted for disruption. Looks like the ridge over the UK may nose further east like GFS though.

Seems to be a general theme for the GFS over last several runs and UKMO over last few runs for the Azores high to ridge in after the cold NWly later this week, and for many parts to become dry and cool and frosty at night, while the NW is prone to a milder SWly flow with Atlantic fronts bringing rain.

The Azores high ridging NE is no good for getting a Scandi high and easterly when there's so much jet energy piling NE between Iceland and Scotland anyway.

00z ECM was trending down a similar route, so perhaps finally we will have some agreement this evening in the medium range unless 12z ECM wants to make more of high pressure to the NE.

Trough disruption might be the wrong term, but if you look closely some of the energy is heading south with yes a fair chunk going NE, more going South than GFS. I didn't suggest a scandi high was on the cards from that, but I do think you end up with a cold block to the East and a continental flow of sorts into parts of the UK. Hopefully someone will post that 168h chart so where can see how it turns out :-)

[Seasonality]

1 minute ago, Radiating Dendrite said:

Because what happens upstream in the US has significant ramifications for what then follows on over the UK.

I do know that, looking for a little more specific analysis! Do you have an idea what the NOAA update could mean for Europe?

Edited January 9, 2017 by Seasonality

[weirpig]

1 minute ago, Radiating Dendrite said:

Because what happens upstream in the US has significant ramifications for what then follows on over the UK.

Yes we know that but an explanation of the ramifications for our isle would be appreciated 

[chris55]

UKMO @72 interesting for those in the south :0

Also the UKMO has moved towards the ECM keeping that Atlantic feature to the west of the ridge although not quite as amplified. Whereas GFS pushes it through flattening things. This will influence the potential easterly type flow that "could" develop.

For me UKMO and GFS are chalk and cheese at 144, with the UKMO far more conducive to the easterly type evolution (more like the ECM)

 UKMO ridging to Norway!

GFS flatter..ridging into Germany!

[Seasonality]

1 minute ago, weirpig said:

Yes we know that but an explanation of the ramifications for our isle would be appreciated 

Exactly, anybody? We'd really appreciate it. @Summer Sun you posted it so you must have an idea of its implications? @Radiating Dendrite any ideas?

[nick sussex]

Just now, Seasonality said:

I do know that, looking for a little more specific analysis!

You've seen the NCEP discussion and the bit about the large spread towards the Great Lakes. This plays a big role downstream with the type of ridge we'll see in the Atlantic. The differences you can see between the GFS and UKMO are a direct result of how they handle the shortwave energy from the Pacific and how it phases, when etc with low pressure over the ne of Canada. I've probably bored everyone to tears by now with my constant rambling about that Pacific shortwave energy but the models are making a complete mess of modelling that interaction over the ne USA and that's why we're seeing the difficulties in getting agreement between the outputs.

[Frosty.]

Whatever happens from the weekend onwards, even southern uk is likely to have snow showers scattered around later this week and feeling bitterly cold with frosty / icy nights so at least most of us should see some snow, for many of us it will be the first snow of the winter. For Scotland, yellow be aware warnings are already showing with significant drifting snow expected above 200m during wed / thurs & fri...so for some of us this upcoming cold snap looks quite potent.

[radiohead]

8 minutes ago, weirpig said:

Yes we know that but an explanation of the ramifications for our isle would be appreciated 

It helps to look at the Northern Hemisphere view on Meteociel, then picking a timeframe (say 168) and then go backwards through the run. You'll see the features that influence our weather can often be traced back to the atmosphere on the other side of the Atlantic.

Edited January 9, 2017 by radiohead

[Summer Sun]

 

[Singularity]

As perhaps the most peculiar period of model watching in recent history continues, let's all take a break and admire a cherry-picked GEFS which actually has a tremendous amount in common with the control run:

  

It's one of the few runs that don't just fire that more northern shortwave low straight on east. 

One can find a hybrid example as well, but it's more of an uphill struggle to get the easterly:

 

There is also the option of diving the more northern feature sharply enough that a ridge can build over the top - but you get a big warm sector crossing most of the UK:

 


Isn't it nice when you disregard the GFS operational run? 

[chris55]

11 minutes ago, nick sussex said:

You've seen the NCEP discussion and the bit about the large spread towards the Great Lakes. This plays a big role downstream with the type of ridge we'll see in the Atlantic. The differences you can see between the GFS and UKMO are a direct result of how they handle the shortwave energy from the Pacific and how it phases, when etc with low pressure over the ne of Canada. I've probably bored everyone to tears by now with my constant rambling about that Pacific shortwave energy but the models are making a complete mess of modelling that interaction over the ne USA and that's why we're seeing the difficulties in getting agreement between the outputs.

Its an interesting debate, and it's kind of "chicken and the egg".

Two considerations,

Firstly is it really east to west influence all the way round the globe? Can a local development in our area retrograde and influence the pattern back west?

And secondly if our longitude synopticly develops in a certain way from a local driving force, will that ultimately have a consequence directly to our east...and so on....and so on.... until it eventually feeds back to our patch from the west?

Im no scientist so its more of a digression from me, but interesting I think.

[bluearmy]

the most 'scandi ridge' gefs suite yet and if that's where we go (even a supressed one,)  then I hope some of you will doff your caps to the ecm op.

in the meantime, plenty of uncertainty to keep us glued to each run and suite

[swfc]

After following the ups and downs of the lastv5-7 days what i have noticed that every model shows promise after the 7 day mark.It then eventually drops the idea and so far this winter leaves a mlb or euro heigths.Im not moaning but everything keeps getting pushed back and a couple of posts earlier mentioned the pacific ridging and pressure coming of the esb could bring hope in feb.Maybe thats possible and may happen but looking at the pv and our old euro slug im not so sure.The 2-3 day cold snap coming up from the nw giving snow showers is really just normal winter fair but i guess after this winters efforts so far its better than nothing.Heres hoping the 12z ecm throws up a great run !!!

[Summer Sun]

 

[karyo]

14 minutes ago, Summer Sun said:

 

Exactly! I had a laugh at work this morning as some colleagues read the newspapers and though that we are going to get the severe cold that is affecting much of Europe!

[beefy201]

Sorry Mods I know it's in wrong place but any chance of an upcoming cold snap thread