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Model output discussion - the beast arrives


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2 minutes ago, chionomaniac said:

For those bamboozled look at the jetstream - It is the returning jet that assists in powering the low - the easterly is a victim of its own success.

GFSOPEU18_87_21.thumb.png.874de513abcf0c30a2a9e54bd5eea070.png

Though from this point the jet is a mess so nothing is sure yet....

Normally in breakdown scenarios the jet moves towards the UK and at that point the models have to juggle where the energy goes.

Thats not the case here, you’re right the jet is a mess!

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Evening Guys  Officially signing off for the winter from my window - still all but 5 inches on the ground - have a great year ! Current   favourite   See

First rule of GFS model watching. Never trust a dartboard low....... But especially in this type of set up.

See you next Saturday then, Steve?

Posted Images

Too many obsessing with the possible breakdown will miss what's happening outside their window this week. Models are rubbish at this range when it comes to the position of a LP when we have cold air over us. Probably won't be entirely resolved in great detail until Wednesday with possible adjustments still possible by then. 

Edited by BlastFromThePastbuzz
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Regarding the Low being discussed for some time now.

5a93401ba318f_ScreenShot2018-02-25at22_59_47.thumb.png.4211c86f6a6ae40c672d6d5e7586639f.png 70hpa

5a93402531c86_ScreenShot2018-02-25at22_59_32.thumb.png.b9b7765432d14c7967c67b89d51e33b6.png 250 hpa

5a93402aaa4a4_ScreenShot2018-02-25at22_59_18.thumb.png.4a4a0728fba3cc04ad35320fd8f0ac78.png 500hpa

5a93403332c24_ScreenShot2018-02-25at22_59_02.thumb.png.b213b97b140979b9d28aefb00f758d35.png 700hpa

5a93403a2f411_ScreenShot2018-02-25at22_58_45.thumb.png.5a3548523bced9eb1c965b8f54c3b535.png 850hpa

5a93404537408_ScreenShot2018-02-25at22_58_29.thumb.png.575958cf8d39dce03954b6ba4878f0f2.pngsea level approx

These screen shots are for the 3rd of March. For me I think the layers of the atmosphere are being modelled as coupled so well, that the low is moving on track with the winds to the north of the overall pattern. I'm imagining it as a really tall funnel of a low pressure system, rather like a tornado (although not as ferocious obviously) that is being side swiped by the East to West winds as it moves Northward. I'm probably bonkers and talking nonsense but its a theory all the same. :shok: 

The earth Null images are based on the GFS output also so obviously there will be differences with regard UKMO / ECM etc.

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4 minutes ago, nick sussex said:

What normally happens is this thread gets quiet as soon as the snow arrives and everyone heads off to the regional threads.

But fear not as I’m threadless I’ll still be here! :D 

 

Surely the south west is nearer you Nick - you are welcome to join us in the nutty SW thread!

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trend on GEFS ensembles is good for us to stay cold. why? the high block moving west is slower on 18z than 12z on 16 of the 20 ensembles putting more pressure on the low to stay further south the 12z themselves were slower than the 6z if trend continues on next couple of runs there will be tipping point when all of sudden that low will disrupt a lot more and send energy east/south east with it being flatter shape with no mild sectors. 

 

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I think there will at least be some trough disruption next weekend as the Ecm 12z showed with the deeper cold air persisting across northern uk before coming back south again..so maybe a brief less cold blip before another reload from the n / ne as I just don't believe how the 18z ends it!!..night all:)

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6 minutes ago, pages said:

trend on GEFS ensembles is good for us to stay cold. why? the high block moving west is slower on 18z than 12z on 16 of the 20 ensembles putting more pressure on the low to stay further south the 12z themselves were slower than the 6z if trend continues on next couple of runs there will be tipping point when all of sudden that low will disrupt a lot more and send energy east/south east with it being flatter shape with no mild sectors. 

 

This is exactly as I see it the low may not even impact us at all and fill in the bay of biscay leaving us in the beasterly. But I’m hoping a middle ground will occur risk reward and all that, stalling in the channel and dumping a metre of snow somewhere along the southern half of the uk starved of snow for so long.

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13 minutes ago, khodds said:

Surely the south west is nearer you Nick - you are welcome to join us in the nutty SW thread!

I have some friends in Cornwall and I’ve already told them to stock up! 

Before any cloud spills in from the low to the sw there could be some big convection in the Channel, so as the flow swings round more to the ese this could drive snow showers we’ll inland .

The stronger flow, warmer waters of the Channel and deep upper cold ! A very good mixture!

 

 

Edited by nick sussex
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Right, a pretty drab operational run there, though we would still get a good snowfall on Thursday night into Friday, a second front moves in, giving us all milder weather eventually. The OP I expect is one of the milder solutions but there are plenty that go down the mild cyclonic path.

However there are still some cold runs there, P10 and P15 would be awesome if either of them verified.

For Friday there is evidence of more trough disruption although on many runs the mild air wins out. Again could easily change.

Overall I reckon 50% of the ensemble members in the GFS still have an atmosphere cold enough for snow down here in the far south come midday Friday compared to 60% from re-examining the ECM ensembles. By Saturday, the picture is no less clear as to whether our cold pool hangs on but the milder solution is still somewhat more likely on face value. More trough disruption could change that. PS anywhere north of the M4 should be cold enough for snow regardless as it stands.

Here is the graph updated anyway.

image.thumb.png.48e8335ed642943493331ef6a3e0ffe1.png

Overall the picture is no less clearer tonight after today's runs. The only thing I can think of is that the incoming low looks deeper.

All to play for, lets hope the pendulum swings further towards cold tomorrow!

Edited by Quicksilver1989
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2 minutes ago, nick sussex said:

I have some friends in Cornwall and I’ve already told them to stock up! 

Before any cloud spills in from the low to the sw there could be some big convection in the Channel, so as the flow swings round more to the ese this could drive snow showers we’ll inland .

 

Excellent! All coming down to nowcasting time. Tumbleweed will be blowing in here tomorrow no doubt. Here’s hoping the 00z runs throw a bit more light on the situation. I’m just hoping that low doesn’t remain in the channel and not even make it to UK shores as has happened in the past.

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Is it me or does that image look like a pair of dodgy french butt cheeks with a serious case of snow diarrhea....lol

South.thumb.png.41aa99c2930e6dc5f066d5237c1ca655.png.3b552182174d35eeb391c4a7ffc3382e.png

2 things of note, firstly the GFS 18z is not a great run for next weekend for southern areas at face value, but does show a northerly/NE incursion later on in the run....hopefully though for snowlovers darn sarf it's off the mark for this weekend, and secondly what's up with NW site, is it the amount of traffic...I couldn;t help feeling jealous, I wish my missus went down as often as the NW servers......I'll fetch me coat....lol

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28 minutes ago, nick sussex said:

Normally in breakdown scenarios the jet moves towards the UK and at that point the models have to juggle where the energy goes.

Thats not the case here, you’re right the jet is a mess!

This is very interesting........

 

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Just a word before my post sets off panic buying ! This isn’t in relation to the low to the sw , that’s far too uncertain at this stage.

Theres a window where the flow turns more ese and this will change the distribution of showers , you do need though sufficient sea track to develop convection.

 

 

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50 minutes ago, nick sussex said:

What normally happens is this thread gets quiet as soon as the snow arrives and everyone heads off to the regional threads.

But fear not as I’m threadless I’ll still be here! :D 

 

Nick, surely by now you are an honorary member of all threads!

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No turning back now, see you on the other side (regionals). Get ready to say adieu to your lawns and daffodil heads ?

S80226-00014676.jpg

Edited by geordiekev
Netweather v4 radar, still my fav for wind vector overlay. Any chance adding them to v7, mods
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1 hour ago, Pembroke Dangler said:

It looks like the low is being pulled from the southern jet heading into Spain and the easterly weaker jet to the north of it. 

I think it will be weaker than projected and further south come the time but it’s a headache that’s for sure.

A5D9458D-D653-4D30-9809-A335EA710498.jpeg

I rarely post here but enjoy the reading

I only look at fax charts and find this one fascinating

Where does the low go from here and what happened to the Scandi heights ?

Expert opinion much appreciated

 

 

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4 minutes ago, Coastal Eddy said:

I rarely post here but enjoy the reading

I only look at fax charts and find this one fascinating

Where does the low go from here and what happened to the Scandi heights ?

Expert opinion much appreciated

 

 

Too me there's only two ways that can go, along the channel coast towards Belgium or west back out into the Atlantic

The Jet (using GFS) is racing through the Med at this time, so its clearly cut off.

It's already crashed into the block to the North and from there that seems the only logical option.

Edited by Dean E
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Rather than start from the point of a preferred outcome, in this situation it’s best to go back to Sherlockian principles. “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.". So, systems always travel west to east, right? Well, not if we have been put in reverse they don’t. Similarly that there is always a southwards movement of such systems as models zero in, well this is already only a two to one bet and, in these circumstances, it’s probably evens.

So, all major models show the first low being sent north and west and this looks to be very likely now. GFS then traps the second low in the orbit of the first one, however, and they perform a slow circular dance whilst sending southerlies our way. Not a done deal in this instance because both UKMO and ECM have the next low escaping and being spun out at what may, or may not be a preferred angle. The further south the better but it all depends on how that second low behaves and when (or if) it escapes out to the east.

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27 minutes ago, Dean E said:

Models not having none of that it seems

GFS for the same day for example

gfsnh-5-96.png?18

I wonder what his source is?

Look at the date stamp -- the chart Paul Williams tweeted was from the 6z Friday run. Things were looking very different in many ways then!

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6 minutes ago, Arctic Hare said:

Look at the date stamp -- the chart Paul Williams tweeted was from the 6z Friday run. Things were looking very different in many ways then!

 Yep. Can we keep tweets in the correct thread please, and posting 2-3 day old tweets isn't ideal anyway!

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1 hour ago, ghoneym said:

For me I think the layers of the atmosphere are being modelled as coupled so well, that the low is moving on track with the winds to the north of the overall pattern. Screenshot_20180226-004055.thumb.png.801185b389ac9f7ea835c2245b5af349.png

Just to emphisise the point I made earlier regarding strat-trop  coupling 

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