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Paul

Winter Model Discussion - The Hunt For Cold - 12th Dec

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Here we go with a new thread - please take the time to post into the relevant model related thread before posting - posts in to this thread need to be model related (and saying things like 'I hope the models do x' doesn't count - that would need to be posted into the mayhem thread!)

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:

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

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

Also, a quick plug - we have a new toy available on the site - the UK's first social radar with live weather related tweets included on the map too:

http://www.netweathe...ion=radar;sess=

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(The free version is live now, the Netweather Extra version will be online tomorrow)

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Oh dear.....

12z says no way back to cold for the foreseeable. Siberian high sinking and Azores combining to bring zonal awfulness. Looks bleak

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Hardly 'zonal' is it really, the low pressures barely reach our shores

No, but the pattern by T180 would deliver zonal. Lets split the difference. Cyclonic and southerly to southwesterly.

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Oh dear.....

12z says no way back to cold for the foreseeable. Siberian high sinking and Azores combining to bring zonal awfulness. Looks bleak

The charts are NOT showing 'zonal'.

And it's not mild either.

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Increasing indication of a the formation of a EuroHigh on the 12z.

Which translated into more reasoned language means FI on the 12z run is showing a ridge of high pressure over Europe for a period of a few days.

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av-2478.jpg?_r=0 Posted by Glacier Point on 05 December 2012 - 11:38 in Model Forum Archive

To add to the positively cold vibe going on....

The trend for vortex shift towards Siberia gathers apace. This should assist in retrogressing the ridge over Scandinavia towards Greenland in the extended range. GEFS mean hight anomalies depicting an amplification of the North Pacific ridge which teleconnects to height rises over southern Greenland.

The only complicating factor remains the modelling of a cut off section of the pv over NE Siberia and its movement across the North Pacific.

this is what he posted about the pv moving to siberia and the hieghts moving to greenland the last sentence i dont understand but we r starting to see link up between scandi and greenland in the model output and maybe it will upgrade

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Anyone wanting to see cold this side of Christmas is going be disappointed once more, the models are just not showing much potential this side of the big day at the moment. However, the best chance of some cold periods look like coming from the Polar front jet bringing some lows to the south of the UK with snaps of north easterly winds. For me, this is the only way I can see cold this side of Christmas at the moment and if we can get some lows to move south eastwards, this can sometimes bring some surprise snowfalls to the UK. Average to slightly below avg temperatures for the foreseeable future with periods of wet and windy weather looks the story however rainfall does not look quite as bad as initially thought. More amplification will help but it just isn't looking like happening at the moment. That being said, I still feel huge potential after the new year.

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The charts are NOT showing 'zonal'.

And it's not mild either.

I live in dorset and the majority of the day times temps are 12c = MILD.

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The charts are NOT showing 'zonal'.

And it's not mild either.

I would call it semi zonal cool/mild cyclonic, a hybrid

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The charts are NOT showing 'zonal'.

And it's not mild either.

Faux zonal/cyclonic. Not mild initially, 13c Christmas Eve in a raging south westerly. Hope that's very wrong.

There is nothing positive in the 12Z for cold, perhaps te ensembles will ride to the rescue.

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Which translated into more reasoned language means FI on the 12z run is showing a ridge of high pressure over Europe for a period of a few days.

Huh? I simply stated that the 12z is showing strong indications for high pressure formation over Europe which on this run sets in from around 120hrs through to 300hrs + so a week or more. Yes you can term it FI if you wish,but it a model discussion thread after all.

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av-2478.jpg?_r=0 Posted by Glacier Point on 06 December 2012 - 08:47 in Model Forum Archive

As if NWP didn't have enough on its plate with the disturbance to the PV, MJO forecasts consolidating on a phase 2 projection. That will expose the GFS in particular (it has a large bias to tropical convection in the longer range) to greater pressure to turn the jet northward over Iberia. This will be a false bias given that the GWO is in phase 8/1 - and this is the superior measure. That lobe of the pv cut off over NE Siberia also rolling around like the preverbial loose cannon.

GEFS H5 day 10 a reasonable depiction however (huge snow potential btw):

post-2478-0-92960500-1354783624_thumb.jpg

Substantive ridge between Greenland / Iceland / Svalbard. Tonight's CPC 8-14 dayer will pretty much look like this. That will keep the jet well to the south and only when the ridge pulls fsr enough west will it be able to come up from the south. Always the risk however of shortwaves, but these likely to maintain our cold pool in situ by advecting the cold air westwards.

Stick with your ensemble means!!

he then posted this the following day notice where he says the gefs has a large bias to tropical convection in the longer range i'm assuming he means the gefs wants to power up the atlantic more than it should be

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Hardly 'zonal' is it really, the low pressures barely reach our shores

To me it isn't zonal either however the meteorological definition of zonal is just" the the flow of air along a latitudinal component of existing flow, normally from west to east" so in that sense surely it is zonal. It certainly isn't meridonal.

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Buriedundersnow. We have Seen a ridge to Greenland but it was very weak with the jet running underneath. Looking for this is pointless.

We need to wait for upstream patterns to change perhaps courtesy of a SSW with any impact on these islands in 4 to 6 weeks or so

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av-2478.jpg?_r=0 Posted by Glacier Point on 06 December 2012 - 08:47 in Model Forum Archive

As if NWP didn't have enough on its plate with the disturbance to the PV, MJO forecasts consolidating on a phase 2 projection. That will expose the GFS in particular (it has a large bias to tropical convection in the longer range) to greater pressure to turn the jet northward over Iberia. This will be a false bias given that the GWO is in phase 8/1 - and this is the superior measure. That lobe of the pv cut off over NE Siberia also rolling around like the preverbial loose cannon.

GEFS H5 day 10 a reasonable depiction however (huge snow potential btw):

post-2478-0-92960500-1354783624_thumb.jpg

Substantive ridge between Greenland / Iceland / Svalbard. Tonight's CPC 8-14 dayer will pretty much look like this. That will keep the jet well to the south and only when the ridge pulls fsr enough west will it be able to come up from the south. Always the risk however of shortwaves, but these likely to maintain our cold pool in situ by advecting the cold air westwards.

Stick with your ensemble means!!

he then posted this the following day notice where he says the gefs has a large bias to tropical convection in the longer range i'm assuming he means the gefs wants to power up the atlantic more than it should be

I think this ship has sailed, has it not??

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Huh? I simply stated that the 12z is showing strong indications for high pressure formation over Europe which on this run sets in from around 120hrs through to 300hrs + so a week or more. Yes you can term it FI if you wish,but it a model discussion thread after all.

Yep it's the model discussion, which I guess would mean it's reasonable to assume we're discussing the models?

120 hours - a ridge into Portugal - not especially indicative of a euro high?

h500slp.png

144 hours, Spain under high pressure, rest of Europe, no..

h500slp.png

168 hours, western Europe high pressure

h500slp.png

192 hours, ridging into most of Europe by now, but pressure centre over Africa

h500slp.png

And by 240 hours (and beyond), regular troughing in to Europe..

h500slp.png

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We can see on both GFS and UKMO that the vortex is moving towards Siberia next week but leaves just enough energy our side to keep replenishing that Atlantic trough.

post-2026-0-17091700-1355330818_thumb.pnpost-2026-0-81756500-1355330829_thumb.gi

It doesn`t look as if the Siberian high will last much longer and the hope is that at some point with lower heights possibly dropping down into that region we get an opportunity for heights building on the Atlantic side as the weakness of the vortex is still apparent.

For the time being though it`s over to the Westerlies.

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I think this ship has sailed, has it not??

But our ship won't hit an iceburg, it looks much milder for the next 7-10 days then maybe a bit cooler, lots of rain, strong winds, flooding..not very christmassy.

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Buriedundersnow. We have Seen a ridge to Greenland but it was very weak with the jet running underneath. Looking for this is pointless.

We need to wait for upstream patterns to change perhaps courtesy of a SSW with any impact on these islands in 4 to 6 weeks or so

if u look at his post it is dated the sixth he then shows a hiehgt anomoly chart for 10 days that would make it this sunday now look at the models and around sunday we start to see hieghts in greenland and scandi try to link now who says without upgrades between now and then it wont happen maybe gp might just be right here

was ment to say with upgrades

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if u look at his post it is dated the sixth he then shows a hiehgt anomoly chart for 10 days that would make it this sunday now look at the models and around sunday we start to see hieghts in greenland and scandi try to link now who says without upgrades between now and then it wont happen maybe gp might just be right here

Yep, but I have a hunch if you spoke to him now, that would/may not be his outlook....but the sudden unforeseen turnaround just experienced [and it was staggering and for me they are very poor]...who knows ?

Friday neartime looks like bringing some awful conditions from the SW with strong winds and heavy rain. A feature that models seem to want to repeat for a while. Concerning where areas have just recovered from flood conditions and a WATCH should be on over coming 10 days.

BFTP

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the one part of the model run to run that we have seen upgrades is that part between greenland and scandi.

would really like to hear from gp if his thoughts then still stand now.

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