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Model Discussion Thread - short term
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20-11-2011 7:13pm#1Seems we are missing a thread dedicated to the computer models. Think we should start one.
To christen the thread we have a wonderfully mild ECM run showing little in the way of change for the forseeable future with just the odd incursion of cooler air at times with a hint of frost some nights too.
The less said about it the better I think..0
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Seems we are missing a thread dedicated to the computer models. Think we should start one.
To christen the thread we have a wonderfully mild ECM run showing little in the way of change for the forseeable future with just the odd incursion of cooler air at times with a hint of frost some nights too.
The less said about it the better I think..
Hey Darkman2,
Given your reputation as a notorious cold ramper (I refer to recent thread about cold from the 16th November onwards that never materialised), I take it you are being slightly sarcastic in the above post?!
PS - are you finding the current period of very mild weather frustrating? Also, I am looking forward to the times this winter when you post your "warnings"....always entertaining and great to see you back on the boards!
Finally, what are your own views on what winter 2011-2012 holds for Ireland? I associate your posts with the winter season for some reason so would be interested to hear your thoughts on the winter ahead...............
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Hey Darkman2,
Given your reputation as a notorious cold ramper (I refer to recent thread about cold from the 16th November onwards that never materialised), I take it you are being slightly sarcastic in the above post?!
Yeah it's sarcasm.:)
I am not a cold "ramper" btw. I like all sorts of weather. All weather has it's individual moments that I personally enjoy. Still i'd rather see something more interesting then what is currently forecast.
Rampant Jet Stream, Polar Vortex in the wrong place - preferably it (the blues and purples) should really be over Scandinavia and little in the teleconnections to be overjoyed at either because the AO and NAO across the board look like staying in positive territory for the time being reflected in the synoptic charts, high pressure to the South - low pressure to the North.
Hopefully the PV will weaken or move and the Jet Stream will amplify. We need everything to slow down. It's too fast. With the PV anywhere over Greenland and we ain't unlocking the door to cold weather. Hopefully we will eventually get some pressure rise there.
Things can change quickly though as we know. Forecast could be completely different tomorrow.:cool:
Max temperatures of 4 - 6c on Friday with a hard frost Friday night?
P.S derekon for the Winter ahead (i do dislike Winter forecasts btw - others here trust them more then I do) my own opinion is that it will be a cold Winter overall with plenty of ice and snow and that sort of craic but later in the season then last year. Can't see that kind of a major change until well into December at this stage. I am not confident about that. Just a feeling I have about it. MT goes into these forecasts in some detail. My advice would be to take his advice;)
The 18z GFS tonight is not too bad btw. Some encouraging signals early in the run for coldies.
Just an example from the 18z run of what we want to see. High pressure in the Atlantic anchored from Greenland means happy days! (although this is not perfect it's a good sign just to see it)
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A pretty standard and non eventful few days ahead but still a chance of a decent storm on the 25th, tonight's GFS has it tracking north and only really intensifying once it passes Scotland but some runs have had it as far south as southern England so no real agreement as of yet. A glancing blow on the 18z
The Shetland Isles get a real battering on tonight's run though, >78 knot winds
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Just a quick question.
The current GFS Europe run has this 850 temp chart for next Friday:
with this 500-1000 chart:
Just from what I've picked up on here, I've been following the temp charts looking for the -5 to -8 uppers for snow, but someone mentioned that if we're under the 528 line, like on the second chart above, that we'll get snow as well.
Just so I'm clear, do these two charts have to correlate as in -8's and the 528 line, or would those -4 uppers bring us snow because we're under the 528 line?
Just curious, thanks in advance! 0 -
Seems we are missing a thread dedicated to the computer models. Think we should start one.
To christen the thread we have a wonderfully mild ECM run showing little in the way of change for the forseeable future with just the odd incursion of cooler air at times with a hint of frost some nights too.
The less said about it the better I think..
A dream run if it was a summer month - sadly we can't seem to manage such set-ups when their wanted and at this time of year its simply a waste:(0 -
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Strangegravy wrote: »Just a quick question.
The current GFS Europe run has this 850 temp chart for next Friday:
with this 500-1000 chart:
Just from what I've picked up on here, I've been following the temp charts looking for the -5 to -8 uppers for snow, but someone mentioned that if we're under the 528 line, like on the second chart above, that we'll get snow as well.
Just so I'm clear, do these two charts have to correlate as in -8's and the 528 line, or would those -4 uppers bring us snow because we're under the 528 line?
Just curious, thanks in advance!
Good question Strangegravy. But unfortunately neither sub 528 thickness or sub -5 850 uppers or even both together mean precip will fall as snow. They're just kinda two of the basic minimum ingredients to look for.
There's a lot of other variables involved, for example where the air is coming from, over what surface and for how long. In this case (the 25th), with the winds coming in over the Atlantic Ocean for many 100s of miles the atmosphere near sea level will be warmed too much by the water for snow to fall at low altitudes. -4 to -6 850's don't stand a chance, even within the 528 dam line.
An easterly with the same thickness/uppers coming in over cold snow fields of continental europe however could be a different story.0 -
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Good question Strangegravy. But unfortunately neither sub 528 thickness or sub -5 850 uppers or even both together mean precip will fall as snow. They're just kinda two of the basic minimum ingredients to look for.
There's a lot of other variables involved, for example where the air is coming from, over what surface and for how long. In this case (the 25th), with the winds coming in over the Atlantic Ocean for many 100s of miles the atmosphere near sea level will be warmed too much by the water for snow to fall at low altitudes. -4 to -6 850's don't stand a chance, even within the 528 dam line.
An easterly with the same thickness/uppers coming in over cold snow fields of continental europe however could be a different story.
Ah ok... Thanks for clearing that up for me!
I knew it wasn't going to be as straightforward as I was thinking, and just when I thought I was getting an understanding of it all too... 0 -
Yes, that is why for us, the 850-1000 hPa thickness is a more important value to watch. The 500-1000 hPa is a good first guess, as if that's not right in the first place, then snow is pretty unlikely, though freezing rain still is, if there's a sub-zero layer near the surface. 528 dam is a good first guess, but 522 would probably guarantee snow at sea level, regardless of anything else.
The 850-1000 thickness shows the mean temperature of the lowest, i.e. the most important, layer of the atmosphere, where the physics comes into play. You could have a very cold mid and upper atmosphere, with lowish 500-1000 values, and even cold 850 temperatures, but it's the boundary layer that is most affected by modification by surface characteristics, and the one that snow must survive in order to reach us intact.
Have a look at the 850-1000 thickness charts, which are freely available for the GFS and NAE. If we get around 1280 dam or lower, then snow's fairly certain.
One thing to remember though - thickness is related to the average virtual temperature of the layer, which also includes humidity. For the same temperature, a humid layer will have a greater virtual temperature, and hence a greather thickness, than a dry layer. However, the drier the layer, the less chance there is of heavy snowfall. It is therefore a fine balance of looking at several factors at once, which is why things can be so marginal in some cases where some factors would shout snow.0 -
A dream run if it was a summer month - sadly we can't seem to manage such set-ups when their wanted and at this time of year its simply a waste:(
Looks a little bit too much like the default pattern of the last 2 summers which (to me) were basically pure rot, but each too our own I suppose.0 -
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Brief period of colder weather, with small risk of low level sleet in the northwest and north. Moderate risk of sleet 250m asl in the same regions.
Much midler conditions again on Saturday
A similar scenario to Friday is in place for Saturday night/Sunday morn.
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Brief period of colder weather, with small risk of low level sleet in the northwest and north. Moderate risk of sleet 250m asl in the same regions.
I would like to report we had sleet today, and it was as near as damit at sea lvl.
No dont get excited, It was about 4 bits on the windscreen in a hell of shower that lasted 20 mins.
You knoiw the type the wind just blows and the sky turns black.
But still first sleet for the year
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isle of man wrote: »I would like to report we had sleet today, and it was as near as damit at sea lvl.
No dont get excited, It was about 4 bits on the windscreen in a hell of shower that lasted 20 mins.
You knoiw the type the wind just blows and the sky turns black.
But still first sleet for the year
I thought I warned all you IOM shadow feckers never to darken the door of this forum again after what ye did to me last year!!!
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2nd of December seems more likely to show something.
Dew point is just about there for parts of the country.
As is air temp...JUST
As is the precipitation, just about :P
Clutching at straws there but it seems plausible :P
Almost the same lineup for Sunday afternoon/evening too. Other than that, nothing else cropping up for snow potential in the short run.0 -
Should keep an eye on that little shortwave coming in off the Atlantic next week end (represented by that small bulge in the isobars just to the Southwest on the charts below) against a very cold Northwesterly flow. It's actually the polar front which means it's a potential temperature battleground - cold from the north, mild from the south. It will not turn rain into wine but it could turn rain into snow. A potential snow event. The GFS has this possibility aswell. The UKMO shy's away from it ballooning the depth of the depression and consequently the warm sector. The ECM run this evening looks quite good.
That's the sober model. The less sober JMA model prompting quite a wind and rain/sleet/snow event next weekend.
That may not happen of course but it is 144hrs out now and worth keeping an eye on over the next few days. Other then that a short window of wintry showers and frosty nights almost certainly by the end of next weekend into the early days of next week with scope for further upgrades or downgrades.0 -
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On the 18z again we see this nasty looking battleground shortwave next Sunday and I would not be at all suprised if it came off like this to see frontal snow from this setup either ahead or on the back edge of the warm and cold fronts respectively.
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Yeah another really interesting run throughout, strong wind events, a few potential snow events and in general it should throw up some interesting weather much like the past week has
FI is only a few days out though with new lows showing up all over the place. The ensembles are already splitting just three days out so interesting times ahead
Mean 850hPa temps below 0C for the duration of the run as well!
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