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Model Output Discussion - 31/10/2014 and Beyond


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Lots of talk about the Polar Vortex, but what is it? Nick's blogged with the answers:

 

http://www.netweather.tv/index.cgi?action=news;storyid=6291;sess=

That is a great article which I have shared on my facebook, explains the pv to my friends much better than I can.

this is the NOAA link to day 5 and 6 statistics re northern hemisphere and 500mb patterns

http://www.emc.ncep.noaa.gov/gmb/STATS/html/new_acz6.html

Is the prx the Parallel?

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Not strictly model output related as it is in the here and now but just a heads up on current media forecasts, especially if one is out travelling in it. On the BBC there was talk of 75mph gusts in exposure this afternoon in conjunction with the first rainband currently out West and the risk transferring across into cenrtal parts over the coming hours. Another bout of rain and strong winds is expected to cover most parts overnight too.

Edited by gottolovethisweather
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Not strictly model output related as it is in the here and now but just a heads up on current media forecasts, especially if one is out travelling in it. On the BBC there was talk of 75mph gusts in exposure this afternoon in conjunction with the first rainband currently out West and the transferring across into cenrtal parts over the coming hours. Another bout of rain and strong winds is expected to cover most parts overnight too.

 

link to UK Met warnings

http://www.metoffice.gov.uk/public/weather/warnings/#?tab=warnings&map=Warnings&zoom=5&lon=-3.50&lat=55.50&fcTime=1415836800&regionName=wl

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The wind certainly is very strong here, house shaking. Must be really rough further W.

 

Remarkable contrast in the winds over Ireland as the front passes through. Gales to nothing in a few minutes.

 

nmm_uk1-11-9-0_tns9.png

Edited by Bobby
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Quite interesting anomalies on the 06 GEFS. Quite a change from T168 out.

 

At T168 it has the Alaskan ridge but orientated NW with Scandinavian HP still into Greenland with the vortex slightly closer. Low Hudson Bay with Azores ridge mid Atlantic and a trough SW of the UK. Very strong jet between the Hudson low and Atlantic ridge.So surface depression south Greenland influencing the UK.

 

By T240 it's all change. Weakening Alaskan and Scandinavian HP, no mid Atlantic ridge and much more emphasis on the Pacific/Atlantic lows. Jet weakening and becoming more zonal So depression Iceland area dominating the Atlantic with the HP to the south just sneaking a look in to maybe influence the south of the UK.

 

Deep into the future a more zonal pattern and still the unsettled Atlantic and no PV.

 

Temps average or slightly above normal.

 

Charts courtesy WxBell

post-12275-0-20755200-1415883073_thumb.p

post-12275-0-02235500-1415883082_thumb.p

post-12275-0-34952500-1415883090_thumb.p

post-12275-0-42570900-1415883105_thumb.p

Edited by knocker
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Overall today the continued trend to bring the PV east and on the face of it a more mobile wet pattern.

 

However a few things to pick out that still leave some uncertainty, the angle of any Atlantic attack effected by both the amplitude of the upstream pattern and whether any positive anomalies to the ne survive to place some forcing on low pressure near the UK.

 

Aswell as this whether those low heights to the nw  phase with low pressure near the UK around T144 to T168hrs.

 

The models generally do phase that and the energy heads ne however this type of chart from the ECM still has me wondering in terms of whether we'll see a bit more fight from high pressure to the ne:

 

post-1206-0-69400100-1415884665_thumb.gi

 

 

 

 

 

 

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One of the main improvements on the ECM 12z run is the strength of the polar vortex, yesterday especially the 00z run had the polar vortex really getting going. While it is not very weak it is certainly a lot weaker than was projected yesterday. Ir was also forecasted to form over Greenland this never happens on todays run. If you look at day 8-10 you can see the vortex is all over the place, and certainly nowhere near as strong as it should be for the time of year. It is a complete waste of time looking at day 10-16 charts to 'prove' that the Polar Vortex is started to get together. These never make it into the reliable timeframe, the vortex has completely changed in 24 hours at just day 6.

 

ECH1-216.GIF?13-12ECH1-240.GIF?13-12

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One of the main improvements on the ECM 12z run is the strength of the polar vortex, yesterday especially the 00z run had the polar vortex really getting going. While it is not very weak it is certainly a lot weaker than was projected yesterday. Ir was also forecasted to form over Greenland this never happens on todays run. If you look at day 8-10 you can see the vortex is all over the place, and certainly nowhere near as strong as it should be for the time of year. It is a complete waste of time looking at day 10-16 charts to 'prove' that the Polar Vortex is started to get together. These never make it into the reliable timeframe, the vortex has completely changed in 24 hours at just day 6.

 

I'd suggest not taking charts at +240 literally whatever they show. They will always chop and change significantly from one run to the next. It's best to use the ensemble mean/anomalies at that range if looking for patterns in the vortex etc.

 

ECM ens mean 00z yesterday vs today, same time period

 

EDH1-240_kdv9.GIF  EDH1-216_vlq6.GIF

 

So todays run has the chunk of the PV somewhat stronger to the NW and much more influencing the UK than yesterday's.

Edited by Bobby
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In the space of a day we go from

 

http://www.wetterzentrale.de/pics/Recm1681.gif

 

to

 

http://www.wetterzentrale.de/pics/Recm1921.gif

 

That is ridiculous.

 

Indeed, proving once again that t+168 hours ahead is too far in the future, to form any judgement of actual synoptics over the UK by then. FI, at least according to the GEFS 6z ensembles spreads is currently around the 19th November but given that the UKMO only seemingly have greatest confidence in their five day forecasts, judging on their latest thoughts, perhaps an even earlier timeframe could be considered as FI.

 

Broadly speaking, all three options listed at the end of a previous post of mine as shown below, remain on the cards as we enter the final third of November IMHO.

 

https://forum.netweather.tv/topic/81718-model-output-discussion-31102014-and-beyond/?p=3068368

 

 

What I'm personally favouring isn't generally being shown in the NWP outputs right now aside from hints coming from the occasional ECM run.

 

With the much lauded state of affairs up above us in the troposphere and stratosphere, this should really be our focus of attention for any longer-term hints I would imagine.

 

The last third of November is by far a done deal and there will be plenty of fun and games to come over the coming days I feel.

Edited by gottolovethisweather
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I'd suggest not taking charts at +240 literally whatever they show. They will always chop and change significantly from one run to the next. It's best to use the ensemble mean/anomalies at that range if looking for patterns in the vortex etc.

 

ECM ens mean 00z yesterday vs today, same time period

 

EDH1-240_kdv9.GIF  EDH1-216_vlq6.GIF

 

So todays run has the chunk of the PV somewhat stronger to the NW and much more influencing the UK than yesterday's.

 

Mean or not it's still in FI, and will change. I bet the polar vortex isn't as strong as that once it gets into the reliable timeframe.

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Move towards colder options on the ensembles, hardly any below 0 yesterday (wish id saved it now) and a fair few more now.  though many more in the milder side too just a move towards the right area for a cold spell

 

 

MT8_Manchester_ens.png

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The output has gone much as I expected today with a slow erosion of blocking to our E/NE being modelled and the Atlantic getting in proper around day 10.

Yes there are still uncertainties how quickly this breakdown of the stubborn pattern we have been stuck in for some time but I really don't believe we are going to see another reversal with more undercutting around day 7/9 though it can't be dismissed.

In a way I hope the models are right with the breakdown because I think we need this shift East of the PV and I'm afraid a period of zonal conditions will be unavoidable if we achieve that.

 

As stated previously, although we can never predict how long an Atlantic dominated set up will last there is nothing in the output, be it SW or raw FI model output that suggests it will continue through Dec as with last year.

What I hope to happen is that we will get a nice clean exit West to east of the PV currently setting up home West of Greenland and after a relatively brief stormy period we get low pressure into Europe with a robust Atlantic ridge building behind.

 

Long timeframes I'm afraid. First the breakdown 9-12 days perhaps? Then the Atlantic driven weather which will be at least a week and very likely longer and then the building blocks for blocking again but this time to our West. 

So if all that crystal ball gazing were anywhere near we would be looking for blocking to reappear somewhere early Dec.

 

If the block holds on to our East this post will self destruct.

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Early days on the 12z GFS, but is this it attempting to undercut at T120? Negatively tilted low with heights trying to remain above...

 

gfs-0-120.png?12

 

GFS(P) has a similar idea, but the low does look stronger on it:

 

gfs-0-120.png?12

Edited by Winter Cold
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If you want proof that this slider saga is not over then compare the 138 hour chart from thr 06z to the 12z 132 hour chart! ! More of a split between iceland and Scandinavia and pressure slightly higher!!

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If you want proof that this slider saga is not over then compare the 138 hour chart from thr 06z to the 12z 132 hour chart! ! More of a split between iceland and Scandinavia and pressure slightly higher!!

 

 

Plus if you look at the Northern Hemisphere, you will see even till the 19th of November that the Polar Vortex is less organised than the 06z

Early days on the 12z GFS, but is this it attempting to undercut at T120? Negatively tilted low with heights trying to remain above...

 

gfs-0-120.png?12

 

GFS(P) hasnt got to the same time in the run yet to compare.

 

 

Its not undercutting on this run, just filling up in the Atlantic instead

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gfsnh-0-84.png?12

 

 

 

Very different NH profile to the 06z on this run the Pressure Gradients haven't really changed much in 150h till this point from where we are currently apart from the big low pressure near us in the Atlantic

 

 

 

gfsnh-0-6.png?12

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And another one!! The ukmo compare the 120 chart from 12z yesterday and the 96 from today! ! Yesterday had low pressure south of greenland but today its gone and instead we have higher pressure further west!! We are seeing the slow changes from the gfs that we have come accustomed to!!

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