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phil nw.

Winter Model Discussion - Cold Hunting -23/12/12

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A new thread ready for the 12z model runs.

Please refer to the relevant threads when posting to help keep model discussion on topic.

Current Model Related Threads:

The winter / cold model output discussion thread (this one) - busy, fast moving, sometimes a bit of a rollercoaster, generally cold orientated, with views from a wide range of people with differing interests, biases and levels of knowledge.

In depth model discussion, analysis and summaries - slower moving, sometimes more technical, straight down the line type model analysis, info and discussion:

http://forum.netweat...-and-summaries/

Model mayhem - all the emotion from looking at the models, rants, ramps, hopes etc

http://forum.netweat...n-ramp-go-nuts/

Let`s hope that a cold New Year spell will start to show up in the model runs soon.

In the meantime I hope you all have a great Christmas.smiliz19.gif

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The London combined ens. graph from the00z runs.

post-2026-0-33101500-1356277710_thumb.gi

shows both operational runs were mild against the main bunch further on.

Let`s hope that that mild trend is reigned in on the 12z runs.

Well will soon see.

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Small improvements in the 12z compared to the 06z; the warmth has some what been delayed and we have the 528 dam line reaching Scotland.

post-17320-0-47980600-1356277948_thumb.p

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Pattern matching is fun, and considering that severe wintry spell started at the end of January we can't write off this winter at this point although it's sorely tempting when you look at the current trends from the gefs and ecm, they are pretty dreadful viewing with a predominantly swly to wly airflow, the thing about the famous winter of 1947 was the duration of the freeze, it went on for something like 6 weeks unbroken before it ended in major flooding as the snow thawed in mid march, the only similarity I can see is the current charts and the flooding which look like persisting well into the new year with fine days few and far between.

post-4783-0-14769200-1356277960_thumb.gi

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Looks quite a bit better at +120, the troughing is negatively tilted rather than positively tilted on the 6Z which shows the models are still having a bit of trouble with the details of the troughing at this range.

gfsnh-0-120.png?12

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As expected at this range T120hrs the 2 main players are around the same location ie.Greenland Vortex and Azores high.

We are unlikely to see any radical change at this early stage.

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Just goes to show how the chart for Christmas Day has backed down from a Northerly shown 48 hours ago, and now that we are in the reliable, a clearer outcome for Christmas Day is emerging. I don't think we will see the double digit temps of the last two or so days. We are looking at temps dropping back below the 10oC mark, and if this chart remains true, then it could well be a washout in the south on Christmas Day, with some heavy showers in Wales as well.

brack1a.gif

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Much better run so far from the 12z with much greater heights over western

north America and subsequently better heights across the Arctic.

Could be a good run in the extended range we will see.

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Hmm, generally a bit more amplification on this run, some decent cold shots for Scotland coming through at times too:

gfsnh-0-216.png?12

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These 3 images from the UKMO run for midday Boxing day-T72hrs are a great example of steep thermal gradient differences across the Atlantic spawning low after low along the boundaries.

post-2026-0-33657300-1356280202_thumb.gipost-2026-0-20512800-1356280218_thumb.gipost-2026-0-19147900-1356280240_thumb.gi

we can see the cold Arctic air oozing south from the vortex over Greenland meeting the tropical sourced air in the Atlantic.Plenty of frontal activity coming this way.

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Ah, merde! Le petit toppleur sans neige! Sacre bleu!

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....well that was a waste of time - sledge well and truly put away - even going to struggle at altitude for ppn.

positively well tropical up here today. smiliz39.gif

GFS goes for this for cold at T+174

post-6879-0-63704100-1356281054_thumb.pn

All the Best...!

Ian

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where is everyone? gfs 12z is better than I expected with some surprise cold shots in FIohmy.png

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where is everyone? gfs 12z is better than I expected with some surprise cold shots in FIohmy.png

FI - exactly Frosty

Pretty much worn out by it all - for the big day at least - not even a sniff and it's all melting on Helvellyn spiteful.gif

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where is everyone? gfs 12z is better than I expected with some surprise cold shots in FIohmy.png

It's pretty gruesome for cold fans to be honest, no end to the zonal conveyor, deep low heights to the NW etc...

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where is everyone? gfs 12z is better than I expected with some surprise cold shots in FIohmy.png

Yes, not certain how far south the cold shots will reach. No point speculating whether the AH will extend north or the Jet push a bit south. This will take time to resolve. Synoptics remain the same:

T384: http://cdn.nwstatic.co.uk/gfsimages/gfs.20121223/12/384/h500slp.png

Z word all the way...

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Im thinking you could give the mo a five day break and the generall set up would be the same.oh well its drink timesorry.gifsorry.gif

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These 3 images from the UKMO run for midday Boxing day-T72hrs are a great example of steep thermal gradient differences across the Atlantic spawning low after low along the boundaries.

post-2026-0-33657300-1356280202_thumb.gipost-2026-0-20512800-1356280218_thumb.gipost-2026-0-19147900-1356280240_thumb.gi

we can see the cold Arctic air oozing south from the vortex over Greenland meeting the tropical sourced air in the Atlantic.Plenty of frontal activity coming this way.

To be honest Phil, this remains the theme once again for the duration of the GFS 12z, bar the brief west or north westerlys that follow as the low clears east ahead of the next incoming low. The sheer number of lows hammering in over the next 10-14 days must surely lead to records being broken for rainfall. With one of the wettest Decembers on record in some places.

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Ha ha, doesn't this just sum things up at the moment...

post-5114-0-77850500-1356282747_thumb.pn

A better run though, maybe something to start building on.

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Ha ha, doesn't this just sum things up at the moment...

post-5114-0-77850500-1356282747_thumb.pn

A better run though, maybe something to start building on.

How is it better? apart from a brief northerly incursion there is nothing on that run that gives hope to cold lovers, infact in the lower resolution part of the run it 'powers' the jet stream up!

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How is it better? apart from a brief northerly incursion there is nothing on that run that gives hope to cold lovers, infact in the lower resolution part of the run it 'powers' the jet stream up!

Better, not good, just better. Signs of a bit more amplification midway through. Nothing special but gotta have hope. As for low res, it's low res...

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Apart from some brief amplication as that deep trough develops in the eastern USA overall another depressing GFS run.

I'd take no notice of any output that tries to take the jet further south whilst we see low heights to the north. As we saw this week, the models have a bias at longer range, then the jet gets pushed north and with it goes the colder uppers.

Unless someone can order more amplification upstream with the PV moving away from our north then I see no way to anything colder.

The strat warming still shows and we can only hope that does the trick, and lets hope the models don't decide to then leave a piece of the PV in the worst possible location!

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Looks like I'm going to get my severe gale fix. Im loving it, but just like hunting for cold, my severe gale hunt may and often does get downgraded, so I promise, I understand the frustration of the coldies.

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