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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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96hours away people. Good start to the 18z runs from the Icon...

5A0FC0F6-F5D7-4991-8E38-279B720EEE7D.png

High further north, cold air pool further westward by about 6hrs. Marginally better wind angle. Decent improvements even by 108.

here is 120 on 12 (first chart) vs 18

BE892320-47B6-4140-8641-B5B4C4CEAEE2.png

F30485C1-4E60-4266-9A60-B893550DF201.png

Edited by ITSY
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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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17 minutes ago, Nick L said:

The EC is usually fairly keen to kill off shower activity as it trundles inland. Will be interesting to see the shower activity on the UKV and Euro4 over the coming days.

I would have thought that more strength in the sun as we approach early March may provide enough shallow heating above the ground to support some convective development inland as well - given how steep the lapse rates will be, something the models may not simulate well - through experience of seeing no ppn shown inland by a model but showers still popping up.

 

Edited by Nick F
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2 minutes ago, ITSY said:

96hours away people. Good start to the 18z runs from the Icon...

5A0FC0F6-F5D7-4991-8E38-279B720EEE7D.png

High further north, cold air pool further westward by about 6hrs. Marginally better wind angle. Decent improvements even by 108.

Yes 12z on left 18z on right :good:

iconnh-0-120.thumb.png.4486aa51c2ff278b416a17da6945d517.pngiconnh-0-114.thumb.png.f3d96ebefa66ff6bf3a25b09446d1406.png

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3 minutes ago, Nick F said:

I would have thought that more strength in the sun as we approach early March may provide enough shallow heating above the ground to support some convective development inland as well - given how steep the lapse rates will be, something the models may not simulate well - through experience of seeing no ppn shown inland by a model but showers still popping up.

 

I  thought the lack of moisture would negate the laspe rates , surface thermals ? 

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1 hour ago, Nick L said:

I'll add to this, it will all depend on what the ratio of liquid water to snow ratio these maps are using too. Dry snow will put down about 3 times more than wet snow for the same equivalent of water.

question for you @Nick L 

is there any type of chart/graph that i can look at that will show this or is it a case of now casting

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3 minutes ago, Nick F said:

I would have thought that more strength in the sun as we approach early March may provide enough shallow heating above the ground to support some convective development inland as well - given how steep the lapse rates will be, something the models may not simulate well - through experience of seeing no ppn shown inland by a model but showers still popping up.

 

Yep, already been seeing daytime convection over land in the last week or two, and that's without the aforementioned ridiculous lapse rates. Will certainly be a learning curve for how the models deal with it.

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Just now, moorlander said:

question for you @Nick L 

is there any type of chart/graph that i can look at that will show this or is it a case of now casting

Can't say I know of such a thing unfortunately, if anyone does it would be useful. The figures I quoted are a rough rule of thumb!

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1 minute ago, rory o gorman said:

I thought have thought the lack of moisture would negate the laspe rates , surface thermals ? 

Usually there is enough moisture aloft in our maritime climate to support high based convection with warming from below, even if the continental surface flow has dried out inland from the North Sea.

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2 minutes ago, Nick F said:

I would have thought that more strength in the sun as we approach early March may provide enough shallow heating above the ground to support some convective development inland as well - given how steep the lapse rates will be, something the models may not simulate well - through experience of seeing no ppn shown inland by a model but showers still popping up.

 

Agreed, I can remember a few past examples in which a predicted (by models) dry day was interrupted at least once by those magnificent sort of billowing yet at the same time wispy clouds, leading to a sudden transition at ground level from clear to snowing readily. 

Admittedly some of those may be from my dreams but I assure you it has happened in reality at least once this century :D.

So yes, should be lesson one of global model reading really; don't trust them to handle convective showers.

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7 minutes ago, ITSY said:

96hours away people. Good start to the 18z runs from the Icon...

5A0FC0F6-F5D7-4991-8E38-279B720EEE7D.png

High further north, cold air pool further westward by about 6hrs. Marginally better wind angle. Decent improvements even by 108.

here is 120 on 12 (first chart) vs 18

BE892320-47B6-4140-8641-B5B4C4CEAEE2.png

F30485C1-4E60-4266-9A60-B893550DF201.png

looking very good. Italian low is slightly further north and more energy going it into from the lows in the Atlantic. I think its possible we might see more energy go under.

can you imagine the chaos if there was stronger Italian low increasing the pressure gradient/wind speeds and driving the sub -18 uppers into us.

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1 minute ago, Nick F said:

Usually there is enough moisture aloft in our maritime climate to support high based convection with warming from below, even if the continental surface flow has dried out inland from the North Sea.

0 /15 c spread will be quite interesting to see the the results of LCL ect  .Forecast Soundings will come into reach soon certainly worth a look over. 

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4 minutes ago, pages said:

looking very good. Italian low is slightly further north and more energy going it into from the lows in the Atlantic. I think its possible we might see more energy go under.

can you imagine the chaos if there was stronger Italian low increasing the pressure gradient/wind speeds and driving the sub -18 uppers into us.

Interesting observation - the low in question is actually much further north on the 18 ICON than the 12 GFS, though even by +48 it is slightly further north on the GFS (18z run) this evening. It would certainly accelerate the cold westward by strengthening the mean easterly across Central Europe, which would be no bad thing at all for early cold onset. Just another thing to look out for...

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