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Polar Maritime

Model Output Discussion 29th December - Into mid-Winter.

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I have to say though, that UKMO 12z is one of the strangest looking runs I've ever seen. I suppose the lower resolution can lead to some odd moments such as the shape of the low across Greenland at +96 and the lack of an intense core SW of Greenland such as all other models have.

I've not had time to read back over all the comments on the 12z so far but in case it hasn't been posted already, JMA and GEM only add to the confusion by producing a ridge on a par with the 00z ECM:

J84-21.GIF?10-12 gem-0-84.png?12

I believe this model is showing that the approaching trough could still turn out to be slower and further south.

GEM goes on to perform the switch-back jet approach rather than slicing a low through the UK this weekend.

gem-0-156.png?12

So it would not be surprising to see ECM remain along similar lines with its 12z effort.

The run then quickly slackens off - and it does still seem that the odds are in favour of a generally slack easterly with fairly feeble convection away from the east and perhaps south coasts, but you never know, the Euro low could end up closer to our shores.

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3 minutes ago, Dominic Carey said:

So do we bin GFS after a certain point?

Beyond day 4 it can show more of a bias to a flatter pattern putting more emphasis on energy into the northern arm of the jet.If it is wrong early on then the later pattern can look completely different compared to other models.This can flatten a possible Scandi high into a Euro high.Not saying it's wrong all the time but it is something we become aware of after following the models for a time.This is more noticeable now where we don't have a straightforward zonal pattern. 

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By 192 you would be very hard pressed to find any kind of Easterly flow within GFS ensembles, just a couple or so.

That said, a couple of days ago you would of been very hard pressed to see any building a ridge. 

If we do get something closer to ECM this will have been a very poor spell for the GFS model.

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13 minutes ago, pyrotech said:

Thing is Nick, as many long timers on here have seen time and time again its the same story with GFS

It showed this cold spell at 15 days, run with it then it dropped it and went for a new route and something completely different only to slowly return to it again late on .

How many times have we seen the GFS find the correct trend and drop it when ECM comes into timeframe and the GFS slowly try to catch the ECM up again.

 

Well its a bit like model musical chairs! I know we like to use the GFS as a piñata sometimes but all models have good and bad spells. I'm very interested to see what the ECM has to say, so far its wanted the cleanest evolution to the easterly. At this point we still don't know what the correct solution might be.

The NCEP diagnostic discussion:

CYCLONIC FLOW/SHORTWAVES SINKING ACROSS NORTHERN PLAINS
ASSOCIATED FLAT SURFACE WAVE ACROSS GREAT LAKES EARLY THURS
SURFACE WAVE CURVING THROUGH THE CANADIAN PRAIRIES EARLY THURSDAY

SO OVERALL...THE 00Z ECMWF APPEARS TO BE THE BEST FIT OVERALL TO
THE PREFERENCE AT ALL FORECAST HOURS...BUT THERE ARE TIMES THE 00Z
CMC/12Z GFS AND 00Z UKMET LOOK REASONABLE. CONFIDENCE IS ONLY
AVERAGE GIVEN MODEST CHANGES FROM RUN TO RUN AND MODERATE ENSEMBLE
SPREAD.
 

This was the subject of all that drama with the upstream pattern in that area and the knock on effect into the Atlantic.
 

Edited by nick sussex

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Superb set of charts today so many options good, bad, ugly.. 

My favourite of course would be the ecm with its love affair with cold.  (no bad thing)  we await in anticipation for the next run from the ecm this evening.. 

Although don't know why we are focusing so much attention past Saturday we got the best wintry spell knocking on our door for years tomorrow.. 

Ohhhhhhh snow. 

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12 minutes ago, phil nw. said:

Beyond day 4 it can show more of a bias to a flatter pattern putting more emphasis on energy into the northern arm of the jet.If it is wrong early on then the later pattern can look completely different compared to other models.This can flatten a possible Scandi high into a Euro high.Not saying it's wrong all the time but it is something we become aware of after following the models for a time.This is more noticeable now where we don't have a straightforward zonal pattern. 

FWIW, I always think the GFS is better at picking-out a return to zonality before the other NWP models, but, as you say, is often reluctant to show cold weather and tends to blast cold Eurasian airmasses from the map as soon as any energy leaves the eastern seaboard of the US.

Edited by chrisbell-nottheweatherman
Correcting typo.

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3 minutes ago, chrisbell-nottheweatherman said:

FWIW, I always think the GFS is better at picking-out a return to zonality before the other NWP models, but, as you say, is often reluctant to show cold weather and tends to blast cold Eurasian airmasses from the map as soon as any energy leaves the eastern seaboard of the US.

That's because it always does it and zonality is our default weather pattern 

 

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UKMO and GFS fairly similar at T144. It's more of a question how much energy goes to the north sinking the high. The GFS solution would probably leave us with grey skies and drizzle. yuk.

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Massive Ecm coming up, it's been another dramatic day so far and I honestly can't remember a better looking ecm than this morning but could it reach those dizzy heights again?.. this is a test for the ecm, it's led us (coldies) up the garden path countless times but hopefully not this time!

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11 minutes ago, radiohead said:

12Z shows heavy snow with 85-90 km/h gusts there at 66 hours. -5 to -7 windchill. Very wintry! If that happens....

66-289UK.GIF?10-1266-779UK.GIF?10-12

I hope that doesn't clash with a spring tide. That has tidal surge written all over it. Full moon the day before as well.

Edited by Ian Suffolk

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5 minutes ago, Frosty. said:

Massive Ecm coming up, it's been another dramatic day so far and I honestly can't remember a better looking ecm than this morning but could it reach those dizzy heights again?.. this is a test for the ecm, it's led us (coldies) up the garden path countless times but hopefully not this time!

Why is it a "massive" ECM coming up? Whatever the ECM shows mean very little regarding the possible easterly because of the timeframe but the signal for some sort of continental flow is increasing. The GFS does seem to be closer to the mark of trying to flatten the pattern initially(the UKMO at 96 hours threatens to show this) but looks like as per usual its too progressive to bringing the Atlantic in.

So it could be a case of a brief milder period for some before turning colder again? Although the further East you are, the more likely the cold air might hang on however if this mornings ECM is right then only the far North West will see a brief milder period and the majority of the UK will stay in the cold air throughout. Will be interesting what tonights ECM brings but its nothing decesive either way.

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1 minute ago, Ian Suffolk said:

I hope that doesn't clash with a spring tide. That has tidal surge written all over it.

Hi Ian, i have been watching developments since last week.

Yes it will coincide with high spring tides, serious flooding to be expected if this happens

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8 minutes ago, nick sussex said:

Thanks Tamara

I was trying to think back to a similar type scenario. OMG now I feel even older if that was 2012, the years are flying by! That spell saw some incredibly cold air down here, even further north in Bordeaux parts of the river started freezing over.

Yes, I see the similarity too ... why I've been looking out the thermals. :cold:

Heavy snow followed by a two week freeze and -17C overnight as the coldest. It's great but our house is not well enough insulated for that on a prolonged basis.

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8 minutes ago, Ian Suffolk said:

I hope that doesn't clash with a spring tide. That has tidal surge written all over it. Full moon the day before as well.

East coast (Hull) has spring tide at 6am.

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Just now, phil nw. said:

As Nick S posted above the main 2 can both have their good and bad spells.We have observed the ECM's tendency to inflate ridges days 8-10 sometimes- which of course can increase expectations,re cold.

It's not easy this model viewing sometimes.that's why we need to view all the outputs,ens,clusters and anomalies,means to arrive at the most likely outlook.

 

 

Agreed; just as the GFS likes to underplay blocking and push aside cold airmasses unrealistically rapidly, I've come to learn that the ECM can overplay blocking at longer range.  I do, however, think that, in much the same way that the GFS can often pick up on renewed zonality at longer range, the ECM can do the same with blocking.

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12Z ECM follows the 12Z HIRLAM, shows that little low embedded in the flow at 48 hours...

ECU1-48.GIF?10-0

Edited by radiohead

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12z EURO4 doesn't give the southerners much optimism with regards to snowfall on Thursday.  All the wrong side of marginal really;

17011212_1012 (1).gif

17011212_1012 (2).gif

17011212_1012 (3).gif

17011212_1012.gif

 

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It's interesting to see almost 8000 people currently watching the ECM at Meteociel

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Regarding Thursday and potential snow for south, ECM doesn't have the colder air as far south as GFS for midday. 

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