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Paul

Model output discussion - 16th Nov onwards

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I see the ECM has another re-load for next week with another northerly.

 

If you look upstream there are big differences between it and the other models,in the state discussions by NCEP we should take note of this:

 

VERY LITTLE CHANGE TO FORECAST GIVEN CONTINUED DISPARITY AMONGST

THE MAJOR MEDIUM RANGE MODELS AT THE 00Z RUN. HANDLING OF

SIGNIFICANT NORTHERN STREAM HIGH AMPLITUDE TROF AND SFC LOW

REDEVELOPMENT OVER THE WEEKEND INTO MONDAY NEXT REMAINS IN

QUESTION.

 

The ECM develops a much deeper low over central Canada at T144hrs and also has another more amplified system ahead of this, these culminate at T168hrs by  phasing and helping to build the ridge to the east by means of WAA.

 

Its quite a complicated set up over the eastern USA and western Atlantic so I'd be cautious about getting too excited about another northerly.

 

A positive in terms of the ECM is in relation to its performance over the last week, both the UKMO and GFS originally were too flat, however we tend to find that the middle ground solution ends up being the way to go.

 

We should have agreement this evening as the differences start as early as T120hrs over the USA and Canada.

 

I know those NCEP guys like their jargon, but ...'SIGNIFICANT NORTHERN STREAM HIGH AMPLITUDE TROF AND SFC LOW REDEVELOPMENT'?

 

TROF (trough?), SFC?  :cc_confused:

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Looks to me like a trough/front sliding down the country, very very similar to 30th January 2003 when East Midlands, East Anglia and even as far as Hampshire and west London got blanketed unexpectedly by snow.

And north kent - we got slammed that day and it was the first time I heard thunder snow. Good times.

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I am really sorry to be a pain but this is like hieroglyphics to me in places - can anyone more attuned to this language / jargon put it in simple terms?  I get some of it but then I lose it.... 

 

(The post from the NCEP team)

Edited by P-M

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ECM Op didn't have much support this morning within its own ensembles but the 06z GFS offers a little encouragement this may be a trend rather than a blip.

I think there is a good chance we will see something more benign from ECM this evening but if it sticks to its guns then all bets are off.

 

ensemble-tt6-london.gif

 

Very hard to pick out an early December pattern from what we have to go on though perhaps a deep trough to our North bringing wet and windy weather is the current favourite but this would not preclude any wintriness, especially for the North if we can keep lower heights over Northern/central Europe - this would also allow the prospect for MLB to set up once more and we have seen that the models are not keen to revert to a typical Dec zonal pattern in FI so plenty to keep us guessing and interested as we descend into Winter proper.

 

We are getting nearer to our weekend cold snap but not quite close enough to put the finer detail on it.

Thus far it seems ppn most likely NW and NE in the form of showers, though the further West the more likely it will fall as rain or sleet, and that risk extending further South through Saturday into Sunday morning but even very small changes to the NH pattern can mean large differences locally so it won't be until Thursday any real detail will start taking shape.

 

It will be a bonus if we see any of the white stuff falling in November let alone settling at low levels so fingers crossed on that and the models firming up on a "double dip" Northerly. :cold: (where did the snow icon go - did it get overused :laugh: )

Edited by Mucka

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ECM Op didn't have much support this morning within its own ensembles but the 06z GFS offers a little encouragement this may be a trend rather than a blip.

I think there is a good chance we will see something more benign from ECM this evening but if it sticks to its guns then all bets are off.

 

ensemble-tt6-london.gif

 

Very hard to pick out an early December pattern from what we have to go on though perhaps a deep trough to our North bringing wet and windy weather is the current favourite but this would not preclude any wintriness, especially for the North if we can keep lower heights over Northern/central Europe - this would also allow the prospect for MLB to set up once more and we have seen that the models are not keen to revert to a typical Dec zonal pattern in FI so plenty to keep us guessing and interested as we descend into Winter proper.

 

We are getting nearer to our weekend cold snap but not quite close enough to put the finer detail on it.

Thus far it seems ppn most likely NW and NE in the form of showers, though the further West the more likely it will fall as rain or sleet, and that risk extending further South through Saturday into Sunday morning but even very small changes to the NH pattern can mean large differences locally so it won't be until Thursday any real detail will start taking shape.

 

It will be a bonus if we see any of the white stuff falling in November let alone settling at low levels so fingers crossed on that and the models firming up on a "double dip" Northerly. :cold: (where did the snow icon go - did it get overused :laugh: )

 

Would have thought the other way round given the warmer uppers further east, or are you thinking along the coast? 

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Would have thought the other way round given the warmer uppers further east, or are you thinking along the coast? 

 

I know warm sectors are currently programmed to be further East but the breeze will come in off the Atlantic so yes certainly near the coast but also a bit further inland. 

I'm not going to get too married to that opinion right now though and it may well be different come the time.

 

 

GFS 12z almost develops a channel low

 

gfs-0-78.png?12gfs-2-84.png?12

Edited by Mucka

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Looks like a slight upgrade to me, WAA into Greenland slightly stronger which moves things ever so slightly west resulting in a stronger and slightly colder Northerly.

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Looks like a slight upgrade to me, WAA into Greenland slightly stronger which moves things ever so slightly west resulting in a stronger and slightly colder Northerly.

 

WAA up the Eastern flank of the trough and a NE flow as opposed to a NW flow at day 5 as with GFS 06z. 

Plenty of wiggle room yet in how this is finally resolved.

 

gfsnh-0-126.png?12

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I'll be interested to see how much snow is deposited in NE Scotland during Saturday morning as that feature runs down the North Sea - I imagine heavy snow showers will merge to give a more prolonged period of snow with winds increasing too. It look a relatively 'cold core' low too, normally these lows contain less cold air turning snow more to rain at low levels

Edited by Zerouali lives

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I'll be interested to see how much snow is deposited in NE Scotland during Saturday morning as that feature runs down the North Sea - I imagine heavy snow showers will merge to give a more prolonged period of snow with winds increasing too. It look a relatively 'cold core' low too, normally these lows contain less cold air turning snow more to rain at low levels

 

This appears to be it's maximum depth on the current run, but I'm never sure exactly how accurate these are, and it'll change. If I see any snow actually falling it'll be a bonus for Nov, if it settles, even better.

 

132-780UK.GIF?17-12

Edited by Ravelin

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I know those NCEP guys like their jargon, but ...'SIGNIFICANT NORTHERN STREAM HIGH AMPLITUDE TROF AND SFC LOW REDEVELOPMENT'?

 

TROF (trough?), SFC?  :cc_confused:

 

you have to remember it written for other forecasters to read for guidance on producing their forecasts. A bit like the senior man summary at Exeter which we do not see.

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Looks like 'reloads' are the theme of the day.....

 

gfsnh-0-204.png?12

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Similar to this mornings ECM run, 12z GFS also giving the potential for another cold shot later on next week with the high in the atlantic rebuilding and pushing north again. Possible scandi high aswell to finish the run with hints in recent ECM ensembles too of height rises to our North East.

 

No scandi high in the end but high in atlantic building north once again to finish....

Edited by bradythemole

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I know those NCEP guys like their jargon, but ...'SIGNIFICANT NORTHERN STREAM HIGH AMPLITUDE TROF AND SFC LOW REDEVELOPMENT'?

 

TROF (trough?), SFC?  :cc_confused:

 

"Significant Northern Jetstream,high amplitude trough and surface low redevelopment"

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"Significant Northern Jetstream,high amplitude trough and surface low redevelopment"

 

 

Surface! Of course, SFC=surface. :good:

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Looks like 'reloads' are the theme of the day.....

 

gfsnh-0-204.png?12

Most interesting theme to me on this chart is the northward push of the pacific ridge towards Alaska and how that will effect the jet through North America? and whether this will force the North Atlantic ridge in the same direction?

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Most interesting theme to me on this chart is the northward push of the pacific ridge towards Alaska and how that will effect the jet through North America? and whether this will force the North Atlantic ridge in the same direction?

 

That Alaskan high sticks around right until the end of the run, heading way up towards the pole. North Atlantic ridge gets flattened somewhat along the way. At the end of the run we end up with this, but not until after another northerly burst as that low that ends up over Europe has headed down the East coast of the UK...

 

gfsnh-0-384.png?12

Edited by Ravelin

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Afternoon all :)

 

Well, plenty of excitement from the GFS 12Z OP output I would imagine. Beyond this weekend's shenanigans, we have a more disturbed outlook from the middle of next weekj as the trough sets up NW-SE through the British Isles. 

 

http://modeles.meteociel.fr/modeles/gfs/runs/2015111712/gfsnh-0-228.png?12

 

That would be about the best of it from a cold perspective. The PV remains far from organised in comparison to last year at this time:

 

http://modeles.meteociel.fr/modeles/gfs/archives/gfsnh-2014112712-0-6.png?12

 

All of that said, it wouldn't be unusual to have a milder more zonal episode in early December before a more "seasonal" spell mid month.

 

Interesting times...

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Well, a very thought provoking performance from the GFS 12z, especially on the back of this morning's ECM op. The GFS has lows diving well down into Europe, helping to sustain heights to our north east. We haven't seen much of that over the last 2 or 3 winters. We just need to see something similar from tonight's ECM.

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Taking into account the wind chill it will feel absolutely bitter

 

90-290UK.GIF?17-1296-290UK.GIF?17-12

 

Anyone out late Saturday night / early hours of Sunday better wrap up well still a raw wind by Sunday afternoon

 

108-290UK.GIF?17-12120-290UK.GIF?17-12

 

:cold: :cold: :cold:

Edited by Summer Sun

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Would it be fair to say that, by this stage, the upstream patterns for the weekend and immediate aftermath ought be be somewhat more "in focus" than they were a day or so ago?  In other words, if the ECM agrees with the GFS 12z, we might reasonably anticipate the predicted broad-brush pattern to emerge as shown?

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Well, a very thought provoking performance from the GFS 12z, especially on the back of this morning's ECM op. The GFS has lows diving well down into Europe, helping to sustain heights to our north east. We haven't seen much of that over the last 2 or 3 winters. We just need to see something similar from tonight's ECM.

 

I think we did last winter at the end of January when the PV slackened its grip briefly. The problem was there was no height rise to the east so the Atlantic crashed back in.

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ECM going with forming an Icelandic low again at 120h so may repeat the double dip Northerly of this mornings run depending on the track.

 

ECH1-120.GIF?17-0

 

Very close to UKMO by 144h

 

ECH1-144.GIFUN144-21.GIF

Edited by Mucka

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