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phil nw.

Model Output Discussion 01/09/17

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7 minutes ago, jvenge said:

For me, no. I dunno for others. But a block to me is high pressure stationary or slow moving enough that it has the same effect of locking in a pattern. Any form of high pressure somewhere just can't be called a block. 

Of course, I can't see past t240, but I don't imagime that bus parking.

Yes indeed and what precisely is it supposed to be blocking?. If you look closer at the end of the run the 300mb wind is tracking around the high over Greenland and then south over Ireland which actually helps to bring the cooler air to the UK although it is fairly well mixed. But the warmer air to the west isn't that far away so you wouldn't want ridge to weaken and shift a tad east. :shok:

Edited by knocker

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So as fortunate as the ECM 12z with the upstream amplification, it's also very unfortunate with the way that first the weekend storm stalls out for about a day while so far N. (mixes out a lot of the cold air before it can reach us), and second the associated trough drifts just a bit too far east for the slider low to merge with it and turn the flow to between NE and N across the UK and pull that cold air across, rather than drop down to the S. of the UK and produce a dank easterly with spells of rain.

Goes to show it's not just the ingredients you have, but what you do with them!

If the trough was a bit slower moving east, we'd get the merger but the cold would mostly go west of us at least to begin with, so the best upgrade would see the sliding low made faster.

...and that, everyone, is how you sniff at some very interesting weather patterns for late November :shok::laugh:

 

Even with all these issues, the run still finishes with some decent WAA heading between Iceland and Greenland and only a weak trough on the other side of the ridge, which should mean the ridging N of the UK gets at least a small boost, helping to keep that cold airflow in place across the UK.

ecmt850.240.png npsh500.240.png

Such details are just for fun at this range, of course :) 

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2 minutes ago, booferking said:

JMA has colder uppers for weekend so maybe the EC will upgrade 850.

J96-7.gif

J120-7.gif

J144-7.gif

Much colder than EC for 850s..probably faulty :(

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Image issue down to my IPad....apologies for that.  HP to W/ NW and displaced PV to NE.  A great start.  ECM really playing ball, UKMO really playing ball, GFS.... yep I can have you.......Nice entry to winter

 

BFTP

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By T288 the EPS means have the ridge with less amplification and the trough more to south east thus the upper flow backing more north west en route to becoming more zonal. Temps still below average. Still a well organized Siberian vortex and the lobe N.Canada.

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Evening All , So the signal for cold is still there its how the models deal with this age old scenario is the usual problem . Gfs is much sharper with cold across the nation, Ecm is still cold but has a sluggish , messy outlook. At this stage ,no model will be correct , but the Gfs is certainly the pick of the best bunch of outputs for me tonight...:cold:

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1 hour ago, tight isobar said:

Ec12z...very blocky run..

And very amplified indeed..

And as ec-can some time over-ampilfy..

It can also under cook cold/850hpa.

Also on the upside is the mass siberian lobe pv...

All looking v-promising in terms of cold!!!

ECH1-168.gif

Hi mate, still learning so a quick question - what is the significance, in practical terms, of Siberian lobe of the PV? Many thanks :)

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Just now, Paul_1978 said:

Hi mate, still learning so a quick question - what is the significance, in practical terms, of Siberian lobe of the PV? Many thanks :)

the chart you quoted explains it well in picture form. if the vortex is over there, we get more chance of blocking over here. (in simple terms!)

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1 hour ago, Ali1977 said:

Great charts but never really cold enough for snow away from high ground Midlands north, could get better of course!! Just shows how good Nov 2010  must have been to bring that big freeze so early on in the year !!

See my post from yesterday, @Ali1977kind of what I and many others expected. Baby steps with our eyes set firmly on the prize, longer-term. Keep expectations your relatively low, and we might all get what we want. Well, most of us that is who like the seasonal scenes of years past.

Edited by gottolovethisweather

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Maybe this time then !  Looking good for cold from Friday. What I like even more is the general set up after the initial cold plunge. Lots to be happy about and it's still only Autumn.

So far in November the model watching has been more entertaining than the actual weather we have received. (If you like cold)  Maybe that will change soon !      

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5 minutes ago, Paul_1978 said:

Hi mate, still learning so a quick question - what is the significance, in practical terms, of Siberian lobe of the PV? Many thanks :)

Bobbydog summing up in a nutshell.

Eastern side large lobe northern-hemispherical vortex much more in favour of delivering  cold for uk.

Although no certainty.any block forming northwest...aids cold transfer to our shores better than western side lobe'ing.

And any transfer from siberian quarter is always favourable...from this time onwards!

Edited by tight isobar

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10 minutes ago, Summer Sun said:

ECM op and ens in good agreement throughout this evening

graphe_ens3_php.thumb.png.7dbb721fa6c0fc6308c43604c0d27aa9.png

With a cherry on top:D

ECM mean preasure and temps

EDH1-240.GIF?20-0EDH0-240.GIF?20-0

gefs,not as good but i will take it

gensnh-21-1-240.png?12gensnh-21-0-240.png?12

and latest from NOAA,a lot better than yesterday's

610day_03.thumb.gif.52e4d1fe19c0824c7c04c04f81470943.gif814day_03.thumb.gif.e79e80bba3462b36d68cc5d780227a6b.gif

 

Edited by Allseasons-si

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What's interested me is what looked a nailed on west-based -NAO on Saturday has progressed quickly into a more central one. All last week in the back of my mind was the last modelled attempt at the west based -NAO, I think it was 2 years ago, which between D7 and D4 moved east so quickly that we nearly didn't get the northerly at the end of it. I was waiting all last week for something similar to happen, I thought the moment had passed on Saturday but hey presto it's happening. So I wonder if the models have a general tendency to overdo the west based -NAO - perhaps meaning coldies should be excited in the future if they see one!!

Onto the EC ensembles, a slight majority are with the op between T144 and T240 as far as they have a NWly that turns more N or NEly by the end of the period. But not a huge amount of snow on any of the ensembles except for Scotland and N/W hills. If only it were December ;)

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Even at 300hour GEFS mean has an observable deviation from it's normal zonal output, this time with a distinct northerly component for the UK:

gens-21-1-300.png

Normally any deviation from typical weather is washed out at this range.

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I suppose it's not surprising to see some issues with the 850s given how far north the low travels at the weekend; this means a period in which we both see less cold air journeying north and very cold air not journeying west or southwest toward us.

A classic southward adjustment would do very nicely. I know - I'm asking for a lot and it's only early doors! :rolleyes:

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3 minutes ago, Singularity said:

I suppose it's not surprising to see some issues with the 850s given how far north the low travels at the weekend; this means a period in which we both see less cold air journeying north and very cold air not journeying west or southwest toward us.

A classic southward adjustment would do very nicely. I know - I'm asking for a lot and it's only early doors! :rolleyes:

The trouble is, southward adjustments of lows to our NE rarely seem to happen. But I suppose this time could be different!

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As much as we've seen some good outputs I'd like to see the following corrections to the ECM.

ECM1-168.thumb.gif.780faf93598b633016d06081e764a4f4.gifECM1-192.thumb.gif.210aebaf5c716d8b8869642e7e605de5.gif

This would stop the chance of any milder air over the Med daring to show its face!

The only issue I have with the ECM is the shortwave track, although we of course need the amplification initially too much of a good thing could cause issues. Remember here the shortwave can feed those low heights over mainland Europe, we don't want the shortwave dropping south as that pushes a ridge ne ahead of it, you can see on the T192 hrs that little high nosing into southern Europe.

If the shortwave tracks too far to the west this ridge gets pushed in to the UK and theres less chance of some snow on the northern flank with that track too far to the west.

Overall I am happy with the outputs but with this caveat re the trigger shortwave.

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1 hour ago, Steve Murr said:

So back after the ECM that delivers a great run, the ongoing signs from that model are very nice as chunks of the vortex gradually navigate closer & closer Scandi-

The ridging in the atlantic between 168 & 240 does have some moderate agreement from GFS but more importantly has reasonable height profiles over the pole to support that ridge being more prolonged than usual, the flow over the states looks repeatedly amplified so the standard Northerly toppler isn't the immediate form horse - although it will always be in the mix until this ridging & prolonged amplification is down between 72-120

Its very unusual to see an atlantic high ( remember its Atlantic not Greenland ) remain in Situ for more than 24-48 hours before the jet flattens over the top, so net the cold from the East generally stays there-

However on occasion it does get locked in the atlantic- for example Dec 1981-

archivesnh-1981-12-5-0-0.png

archivesnh-1981-12-8-0-0.png

Notice the high was supported with blocking over the pole-

So in a nutshell this new atlantic high keep an eye on what the energy looks like going over the top & whether we can tap some of cold over Scandi-

S

 

Steve...

 

http://www.meteociel.fr/modeles/archives/archives.php?day=31&month=12&year=1961&hour=0&type=ncep&map=0&type=ncep&region=&mode=0

 

 

Another example to set the pulses racing, is this one from the archives.

 

Edited by Midlands Ice Age

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EC mean looks very nice this evening all the way out to day 10- pretty much nothing in the way of zonal muck and ends with the azores high being pulled west with LP over Europe at day 10.

:)

Edited by northwestsnow

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A reasonable start to the 18z GFS pushing the colder air further SE at 72-84

Looking for some potential mild V cold interaction along the wave @96...

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Low off southern Greenland tilting against the developing high reaching from the Azores which is an improvement

gfs-0-108.png

Edited by winterof79

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