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Paul

Model output discussion - 16th Nov onwards

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Cold indeed, and that is unlikely to change but the detail will, the GFS looks a dog dinner with the amount of shortwaves that are in there. There does seem to be a trend emerging that any height rises towards Greenland won't last and the Northerly will probably topple but how quick this will happen will of course be a question that will remain unanswered for now. 

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With the added wind chill it realy will feel raw this weekend.

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Oh dear, what a mess....attempted Greenland height rises and strong Euro heights

 

gfsnh-0-360.png?18

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Oh dear, what a mess....attempted Greenland height rises and strong Euro heights

 

gfsnh-0-360.png?18

Pretty organised vortex there to be fair too. Would doubt future frames would have much interest around Greenland if there were some. Still, deep into FI I won't be concerned for now.

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Pretty organised vortex there to be fair too. Would doubt future frames would have much interest around Greenland if there were some. Still, deep into FI I won't be concerned for now.

 

Being completely honest, today has been a bit of a low in terms of any split vortex trend- the trend we saw yesterday. I'm not in panic mode for now but I do get the feeling that if we fail to hop on the feedback loop now, we could be waiting a long time to see another opportunity.

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This morning'd gfs still on track for a cold weekend. Certainly some potential for snow on Saturday perhaps more inclined to the west and east but the detail will have to wait a couple of days. Pointless speculating now.

Charts weatherbell

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A rough overview of the latest EC32 update

 

Starting Wednesday 25th. Strong HP Siberia and GOA with a trough N. America with trough Scandinavia into Europe and ridging to the west in the Atlantic. Thus the UK in a more NW flow as the cold northerly ingress is cut off at the beginning of the week.

 

The pattern changes quite rapidly over the next few days up to the 30th with the HP GOA dissolving and LP northern Canada and associated trough eastern N. America and Greenland/Iceland appearing. Downstream we have weak ridging to the SW of the UK and no trough to the east. Ergo a more zonal westerly flow over the UK with temps around average.

 

Move on another week to the 7th and now there is a trough Alaska, a non existent Siberian high and a trough Iceland down over the UK. Thus still an unsettled period of weather with the flow from the westerly quadrant and temps around average.

 

This scenario with the trough becoming established in the eastern Atlantic remains in place until the 18th December.

 

Summary.

 

Post the cold snap a rather benign zonal westerly sets in with the HP to the W/SW becoming fairly influential in bringing temps nearer the average but for the last ten/eleven days or so with the upper trough in close attendance the weather becomes much more unsettled.

 

Of course given how this is an exceptional year much could change but one can only  call it as one sees it.

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Somehow the ECM plucks a repeat performance out of the locker - T168-T216 see yet another northerly behind a trough from the NW. Well it was the first onto this weekend's cold snap ... will have to wait to see if has got cold snap no.2 correct as well!

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Blimey hardly any posts this morning!!for a minute i actually thought this weeks northerly had been completely cancelled lol!!!this evenings runs are gona be interesting reason being one thing i have noticed is the 12z runs have been more amplified in general than the 00z runs for some reason i dont know!!!

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ECM snatches victory from the jaws of defeat thanks to that Eastern Canadian trough giving us a quick follow on cold snap. Difficult to be sure where we would go from that position if it were to verify. My money would be on PM airmass for a bit followed by a window of opportunity for further height rises to our NW thereafter. All pie in the sky though as much to be resolved before we get there.

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Somehow the ECM plucks a repeat performance out of the locker - T168-T216 see yet another northerly behind a trough from the NW. Well it was the first onto this weekend's cold snap ... will have to wait to see if has got cold snap no.2 correct as well!

I believe GFS was on to it first, showing height rises to NW,  whilst ECM has performed better overall, verification wise

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For those interesting, the delayed GEFS (ensembles) upgrade (and it's a pretty major upgrade) will be going live on 2nd December according to NCEP. 

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Four days on from previous post here I will once again look at the NH Jetstream profiles as currently forecast by the GFS 00z on 17th November. This is the present picture, globally.

 

 

post-7183-0-27448300-1447747208_thumb.pn

 

Moving on just 18hrs you can see why there might be some concern over Barney (UK's second named storm this Autumn/Winter season) judging by the deep kink in that Jet profile right on our shores at this timeframe.

 

post-7183-0-15075700-1447747426_thumb.pn

 

The wind speeds and Barbs chart replicated below at t+18hrs shows the potential by this timeframe for some damaging gusts being around by then. Other forum members will provide better details on this aspect elsewhere within this forum, I'm sure.

 

post-7183-0-05121800-1447747902_thumb.pn

 

 

Right, onto the period of more interest for most in here, this chart from my post four days ago shows the anticipated NH Jetstream profile for midnight on Friday 20th November.

 

post-7183-0-28609300-1447748033_thumb.pn

 

Here is the reality as predicted by the GFS run overnight now at t+72 hours for Friday 20th November.

 

post-7183-0-10994000-1447748664_thumb.pn

 

The key differences to that forecast previously are a stronger more active Jet profile over mainland North America as highlighted. There is also a slightly different appearance to the anticipated Jet profile for our neck of the woods but all this results in is a delayed start to the colder air incursion. By late Friday and more appropriately into the weekend period it will have well and truly arrived over all parts of the UK.

 

By Monday we were previously expected to see this NH Jet profile.

 

post-7183-0-19764200-1447748811_thumb.pn

 

Now the overnight runs predict the following by 23rd November 0000hrs.

 

post-7183-0-72513300-1447749062_thumb.pn

 

Even at this range, this is some 144hrs away which is a long time Meteorologically speaking and the key changes from the post from 4 days ago are over the North American continent, once again showing a more active Jet than previously. Also, over us the NH Jet profile is not as ferocious as hoped so this might suggest more of a colder blip than a potent polar blast. As for the "why, when and wherefores" regarding any snowfall predictions, I'd leave them in the back of your mind until later this coming Thursday at least in part due to more pressing issues occuring in the more immediate forecast which will potentially have ramifications on the outlook as well.

 

It is a bit pointless looking beyond D6 but if I were to look to D10 (0000hrs on Friday 27th November) it currently states the following regarding the NH Jet profile. This appears to show a continuation of things as per where we are now, so a return to Westerly flows and occasional passing depressions but hopefully not as ferocious or worryingly wet as the current ones. The most active part of the Jet appears to be over the Pacific regions by this time. I imagine this will have an impact on our shores come early December but just how it will affect us I will leave to others to ponder.

 

post-7183-0-74545300-1447750041_thumb.pn

 

Now, just a couple of GEFS ensembles, Aberdeenshire and Warwickshire as per my previous post.

 

Aberdeen precipitation forecasts show a generally unsettled picture once again (perhaps lessening in terms of impact by D7 onwards) with the wintry potential (as indicated by the 850s spreads enclosed) especially apparent through the period from late on Friday through to early hours of the following Monday.

 

post-7183-0-54951700-1447750450_thumb.pnpost-7183-0-95710300-1447750456_thumb.pn

 

 

Warwickshire precipitation forecasts show a slightly less unsettled picture than further North with the wintry potential more likely through the period from start of Saturday through to the very early hours of the following Monday.

 

post-7183-0-35923400-1447750738_thumb.pnpost-7183-0-65651500-1447750749_thumb.pn

 

All in all, a fascinating spell of proper Winter-like weather coming to our little island's shores from Friday onwards. The potency and longevity of which is open to question but by next Tuesday I believe it will have passed us all by. Even then, for those coldies amongst us, in which category I include myself, we can safely say we never expect to see those dizzy tropical-like maximum temperatures of 17c and 18c until the coming Spring season. Good riddance to you and Hello Wintry weather.

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The snow row for Saturday on the London GFS ens is up-to 12 now out of 23

 

gefsens850london0.png?cb=61

 

Aberdeen is up-to 20 now for the 21st so a high chance of snow based on this run

 

gefsens850aberdeen0.png?cb=61

 

Inverness is at 19 for the 21st

 

gefsens850inverness0.png?cb=61

 

A bit further south Liverpool and Newcastle are on 18 for the 21st

 

gefsens850newcastle0.png?cb=61gefsens850liverpool0.png?cb=61

 

So based on this run anywhere from Liverpool north has a good chance of seeing some snow this weekend further south the chance is lower but for high ground you never know

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For those interesting, the delayed GEFS (ensembles) upgrade (and it's a pretty major upgrade) will be going live on 2nd December according to NCEP.

Ha!

I thought they went live last month!

I've been taking the GEFS seriously for weeks!

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Since it's been mentioned but nobody has posted the charts, here's the ECM's attempt at a brief reload...

 

ECH1-216.GIF?17-12

 

ECH0-216.GIF?17-12

 

And now onto the 6z GFS, to see what that brings us.

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Ha!

I thought they went live last month!

I've been taking the GEFS seriously for weeks!

 

It was all set to go live but got pulled at the last minute as it wasn't signed off by the director apparently. 

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Looking at that last chart this morning from UKMO, its appears to be close to ECM output. Could produce a reload of a more direct Arctic attack for a time. We have to close look at the low pressure development in that time span between Iceland and Greenland. The UKMO shows this formation in the latter stages of their latest model run in that region of interest and more importantly with a associated upper trough. This low should deepen in The Norwegian Sea and allow a flood gate of Arctic air for a short time. Beyond that, who knows what can develop , but an interest end to the month for weather watches. Glad to see some snow heading my way ( Eastern Alps )  this weekend. Getting excited now.

 C

 

post-3489-0-42981300-1447754678_thumb.gi

 

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Morning all

Awsome ECM today - I think It was mentioned about the low cutting across the pole for reload :)

GFS out to 114... Building the canadian ridge northwards same as ECM

Reload is coming :)

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Reload!!

 

h500slp.png

 

h500slp.png

 

h500slp.png

 

h500slp.png

 

:D

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GFS 06Z - not a million miles from the ECM, but I'm guessing this one is cold rather than wintry, away from northern hills.

 

gfs-0-222.png?6

 

Interesting trends though, I haven't seen any output get the Azores High back into Europe - as long as it stays there and the jet doesn't fire up too much, there's always the risk of a short northerly outbreak.

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The 6z GFS shows colder -11 850's push into Scotland for the weekend, With a higher Snow risk further South. Detail all subject to change of course..

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