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Model output discussion - here comes the beast!


Message added by Paul

Please only post model discussion in this thread 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

We also have a special post SSW cold spell discussion open here:
https://www.netweather.tv/forum/topic/89358-ssw-related-cold-spell-will-it-wont-it/

Thank you!

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Early guidance forewarning of next weeks weather was issued earlier on, and this has been further enhanced with extended outlooks in bulletins. AFAIK (comms not being my area) public agencies and majo

Come on those looking for the breadown before the major cold and snow has begun You will be very lucky if that is the correct word to see this in ANY winter in the rest of your lives I would sugg

Microscale detail absorbing an awful lot of attention on here, when in reality it is a waste of emotion. The macroscale pattern is now fixed - it will not change significantly now for the start of nex

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1 minute ago, TEITS said:

My tip for newcomers to this forum who want to know if its going to snow is this.

Step 1 ignore most precipitation charts on the ECM/UKMO/GFS.

Step 2 When the period of interest is within 48hrs then use the model below. This has always been my preferred choice.

http://expert-images.images-weatheronline.com/daten/proficharts/en/euro4/2018/02/21/basis00/ukuk/pslv/18022300_2100.gif

Step 3 When the day of interest arrives, which at the moment appears to be Monday, then head over to the regional threads where everyone will be following the radar/Sat. Personally I am going to be purchasing the NW radar but I shall be waiting till Sunday as I don't want to jinx the cold spell!

Some good advice there, to expand on your link here's the main link to the precipitation charts that I also tend to look at 48 hours in advance:

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=nae&MODELLTYP=1&BASE=-&VAR=prty&HH=6&ZOOM=0&ARCHIV=0&RES=0&WMO=

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6 minutes ago, bluearmy said:

Hang on a minute - the ecm op isn’t a one off single run

the latest op has folllowed the fastest growing ens cluster from yesterday’s two runs which became the largest cluster by day 8.

it still shows as a cluster in the spreads this morning and will shortly be clear how large it is. 

To claim it’s an odd run without support is to be an ostrich !

 

What do you mean by fastest-growing cluster 

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1 minute ago, bluearmy said:

It was cluster 2 on the 00z suite around 25% and cluster 1 at 43% on the 12z 

Looking at the mean BA, I would expect the cluster to be significant but probably less than 43%.  Hoped to be proved wrong!

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Just now, mulzy said:

Looking at the mean BA, I would expect the cluster to be significant but probably less than 43%.  Hoped to be proved wrong!

Agree with you - u less there is a larger number of clusters this morning in the 6/8 day period 

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If the clusters are changing so much, doesn’t it show that they are also pretty volatile in this setup also?

The only thing that seems certain to me at the moment is we are going to see a significant cool down from Sunday into next week. 

Edited by karlos1983
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Just now, frosty ground said:

So it had most support of all the clusters then.

This morning’s ec op evolution day 7/8 was the most likely if you just take the previous run eps clusters as best guidance (which I don’t btw)  

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1 minute ago, karlos1983 said:

If the clusters are changing so much, doesn’t it show that they are also pretty volatile in this setup also?

 

Trends in the mid term karlos - you have to get from the easterly to the nor’easter. How will that evolve??

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6 minutes ago, bluearmy said:

It was cluster 2 on the 00z suite around 25% and cluster 1 at 43% on the 12z 

Apologies as I'm sure you would have already mentioned this but is ECM out on its own with this one or is it getting some support from the other models as well ? If so does it appear to be a growing trend ? 

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5 minutes ago, Youcan'tbecirrus said:

Thanks for the explanation Dan. To help us complete novices out, can you briefly explain please in layman's terms what you mean by thicknesses and high lapse rates.  

I'm not an expert by any means, but have a decent enough general understanding.

High/steep lapse rates - high rate of change (decrease) in temperature as you travel upwards through the atmosphere. So with relatively warm sst's over the North Sea (e.g 6c) and 850 temps of, lets say, -12c. That gradient between relatively warm water and very cold temperatures at the 850 layer of the atmosphere creates instability which will spark off shower activity. If the 850 temps were only -4c for example, then the lapse rates would not be as steep which would result in less instability and less shower activity. 

In terms of thicknesses, someone more experienced can explain this to you, however thickness is a measure of how cold/warm a layer of the atmosphere is. The lower thicknesses are better for snow prospects.

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4 minutes ago, Youcan'tbecirrus said:

Apologies as I'm sure you would have already mentioned this but is ECM out on its own with this one or is it getting some support from the other models as well ? If so does it appear to be a growing trend ? 

Op ecm was a mild run from its ensemble pack I doubt it will verify at all how it is showing,so don’t panic

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2 minutes ago, danm said:

I'm not an expert by any means, but have a decent enough general understanding.

High/steep lapse rates - high rate of change (decrease) in temperature as you travel upwards through the atmosphere. So with relatively warm sst's over the North Sea (e.g 6c) and 850 temps of, lets say, -12c. That gradient between relatively warm water and very cold temperatures at the 850 layer of the atmosphere creates instability which will spark off shower activity. If the 850 temps were only -4c for example, then the lapse rates would not be as steep which would result in less instability and less shower activity. 

In terms of thicknesses, someone more experienced can explain this to you, however thickness is a measure of how cold/warm a layer of the atmosphere is. The lower thicknesses are better for snow prospects.

Many thanks Dan. If I am understanding correctly then, with regards precipitation, in the coming days we shouldn't be looking so much at what there is on the near continent as any precipitation will be determined by the high/steep lapse rates & sst's over the north sea ie in this instance, the low countries might see very little snowfall whereas we "could" see more and therefore the references to lake effect snow.        

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just a point to note, on the GFS, the high is not further north, its pretty much in exactly the same position. its actually slightly weaker so everything is 'pulled in' which allows the low heights and cold 850's to be slightly further north. 

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The one thing I have noticed is the high is becoming harder and harder to cut off, as soon as we get towards day 5 the cut off becomes much less clean, the high has become progressively saggier over the last few days.

Bit of a slack easterly if you ask me, yes it's being fussy but I want the holy grail:diablo:

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