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phil nw.

Model Output Discussions 12z 30/11/16

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ALL_emean_phase_full.gif UW144-21.GIF?04-17

UKMO stands out in avoiding MJO phase 2 activity, which is more in line with the low-frequency tropical mode, and lo and behold, its 12z run is primed at day 6 for a ridge to build in from the southwest in much the same way that it did on the 12z GEM run of yesterday, though perhaps not quite as extensively with a westerly flow hanging on for Scotland at least. Or so I see it - the compact low SW of Greenland is a tricky one to resolve the impacts of as it's nothing like as deep or expansive as GFS has it.

Now I must stress - this prospective build of heights from the southwest is a potential positive IF we see further amplification down the line - and well beyond what GFS stubbornly chooses to run with. The 12z looks like it must be one of the variations that don't propagate the MJO signal. The GEFS have at least made some progress in showing a move to phase 3, but then the mean goes back the wrong way again for reasons I struggle to conceive. 

It's tough putting together an outlook for the 8-14 day period this evening; it could quite possibly be a very long way away from recent GFS output or even the ECM 00z, but the ensembles related to both are at least starting to explore the potential more effectively so we're not sailing as blindly as we were a couple of days ago.

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24 minutes ago, igloo said:

the UKMO at 144h aint to bad with slim heights to our north its atleast better than the GFS which is as flat as a pancake

As does GFS but to a lesser extent. It looks fruitless to me unless by some Christmas miracle we deserve one! We can build stronger +ve heights to hold back the nastiness. 

image.jpegimage.jpeg

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I suspect we are going to go back to the usual GFS / ECM differences over the coming few runs, the former as often the case ramping the atlantic into gear on a flat trajectory and doing very odd things around the 300hr mark, the latter showing far more amplification and more keen to show ridge development to our NE. UKMO more than likely to side closer to ECM than GFS..in the 120-144hr timeframe. Very much back to normal service resumed I suspect. What tends to happen when a more zonal flow is in ascendency is for sudden short term developments to throw spanners in the work, and the models very often GFS has to backtrack.

The PV/ polar / strat profile isn't conducive to full on atlantic attack at the moment, and with two lobes of the PV in the position they are in, there is every chance for ridge development to settle inbetween and this will be a place somewhere between Iceland and N Scandi as we  move through the middle part of the month - trough disruption could very easily be the order of the day. With this is mind, I fully expect the GFS runs over the next 2/3 days to continue to show zonal flat pattern - until such developments enter a more reliable timeframe. Advice for those who don't like looking at a flat atlantic pattern, better refrain from viewing GFS charts in the next 2/3 days, and perhaps come back about Thursday. 

 

 

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Big old high centred over Scotland on the 06z parallel run. Looks like this could be what the meto are predicting! 

gfs-0-384.png

Edited by Seasonality

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10 minutes ago, Ali1977 said:

we know it's going to be warmer for a week or so it's a case for looking beyond this and anything beyond this is FI 

Spot on Ali, we know the mild spell is going to last around a week, give or take a little so of course any glimmers of cold potential are going to be in low res but I'm still anticipating a more seasonal second half of december with a return of frost and fog and then hopefully deeper cold will pop up near christmas or new year.:santa-emoji:

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To me the interest in the ENS is getting closer, plenty at day 9 now...

such as

IMG_3701.PNG

 

IMG_3702.PNG

IMG_3703.PNG

IMG_3704.PNG

IMG_3705.PNG

Edited by Ali1977

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18 minutes ago, Ed Stone said:

That was some GFS...I'd be clutching at straws if I could find any!:D

That's the spirit Ed, a sense of humour is vital after a run like that:D

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7 minutes ago, knocker said:

Actually it's not "yet another" as one of the possibilities of arriving at a position with HP to the north has already been mooted. It involves, eventually. the main Atlantic trough deconstructing with more of the energy tracking south east and cut off upper lows thus formed phasing with the trough to the east and so so setting up a low pressure area to the south whilst at the same severing the Azores surge north conduit and thus setting up high pressure cell to the north. :)

 

oh ok didnt realise it was that straight forward

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1 minute ago, swfc said:

oh ok didnt realise it was that straight forward

I was thinking the same thing..what could possibly go wrong:D

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Just now, feb1991blizzard said:

12z GEFS - Oh Yes boy.!!!

They are better, but i made the point earlier, we seem to be CONSTANTLY getting the mild, or mildest ops...

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Just now, northwestsnow said:

They are better, but i made the point earlier, we seem to be CONSTANTLY getting the mild, or mildest ops...

Don't worry about ops and controls at the 16 day range, look at ops and controls past about 288 as an individual Ens member - still better to have them on board but just like any other piece of the jigsaw.

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1 minute ago, northwestsnow said:

They are better, but i made the point earlier, we seem to be CONSTANTLY getting the mild, or mildest ops...

And tomorrow they will be different again

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When looking out beyond day 5, consistency is so so important if we are to make a serious forecast of it. Whether that be from consistent operational runs or a consistent trend in the ensembles, and at the moment we are lacking a clear signal in the mid term.

So although following the ops right through into FI is what this thread is about, we need to remember they are pretty useless beyond the obvious days 3/4/5 unless their is a clear and strong signal.

 

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Huge improvement on the GEfS ensembles! Some quality output for decent cold 

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UW144-21.GIF?04-17  gfs-0-144.png?12

@knocker I admit the difference in spatial extent is not as vast as I initially inferred (I was looking at the GFS on the NetWeather viewer which made it look like a bigger difference) but GFS has a near-955 mb low when UKMO has a near-970 mb low and that's a notable difference for the strength of the feature while in that position i.e. having made it that far east.

With the weaker low I believe there's more chance of the low near Iceland 'escaping' the one S of Greenland, allowing heights to nose up in between as the overall wave pattern progresses east. So we see a UK ridge - like what the 12z GEM did yesterday.

I'm prepared for the fact I could be wrong though - http://ruc.noaa.gov/hfip/tcgen/ will provide the answer when the D7 uploads. Not sure what time it does so on that site.

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MT8_Aberdeen_ens.png

Good to see the (Aberdeen) ensembles showing some colder options.  In fact c50% of the members have a Greenland/Iceland/Scandi high scenario leading to cold at the end of the run.  Of the others there are 3 that are close but no cigar.  It's the consistency between those outcomes that drive the cold that is interesting, with heights ridging to the North. Some very interesting model watching to come.

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23 minutes ago, Ali1977 said:

To me the interest in the ENS is getting closer, plenty at day 9 now...

such as

IMG_3701.PNG

 

IMG_3702.PNG

IMG_3703.PNG

IMG_3704.PNG

IMG_3705.PNG

Yes, another tantalising tease from the GEFS. Every single one seems split 50/50 between blocking and zonal at the moment. I am more and more convinced we are about to see another instance of amplification ... but what will it look like? Still thinking the UK high is the middle ground here.

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A steady drop in the 850's later next week with Christmas week still showing the chance of at least starting cold / chilly

gefsens850London0.png

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about 7 flatliners or near flatliners at the end of the run.

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